Past seminars

The muon's anomalous magnetic moment, a_μ, holds special significance in the development of the Standard Model (SM). Precise calculations and measurements of this quantity provide a stringent test of the SM and a window to the physics beyond. The new Fermilab measurements from Run-1/2/3 increase the discrepancy with respect to the SM prediction obtained in the Muon g-2 Theory Initiative WP of 2020 at the 5σ level. However, recent results for the hadronic vacuum polarization (HVP) contribution, which dominates the overall uncertainty, are in tension with the previous estimation in the dispersive approach and predict a number closer to the experimental average. In this talk, I will discuss the use of hadronic tau decays as a supplementary tool for calculating the HVP integrals, and how they could help us address these tensions.

Strongly correlated impurities immersed in a Bose-Einstein condensate (BEC) can form a periodic structure of tightly localized single atoms due to competing inter- and intra-species interactions, leading to a self-organized pinned state. In this work, we show numerically that the impurities in the self-pinned state form a soliton-train, as a consequence of a BEC-mediated attractive self-interaction and ordering due to the exclusion principle. The dynamics of the impurities possess the characteristics of bright matter-wave soliton-trains as often seen in classical fields; however, in the few impurities cases, the detailed nature of collisions is determined by their quantum statistics.

Although quantum chromodynamics (QCD) is accepted as the theory of the strong force, there are still many properties of the theory which are not well understood. Perhaps the most elementary of these is the observed hadronic spectrum. In this talk, I discuss several different approaches to studying the hadronic spectrum predicted by QCD. In particular, I will discuss a lattice QCD determination of the nucleon-nucleon spectrum at unphysically heavy quark masses and explain how the results of this study contribute to the so-called "NN controversy". Secondly, I will summarize work done at the University of Barcelona developing a model of two-pion photoproduction, which is relevant for understanding the spectrum of light meson resonances.

The NAPLIFE fusion project is running already two tasks at ELI-ALPS. This project is unique in two aspects (i) it is using resonant plasmonic nano-antennas to achieve a simultaneous, rapid and stable ignition of fusion fuel and (2) to achieve a high-energy, non-thermal ignition mechanism in all dynamical stages of ignition and burning, until the start of nuclear fusion reactions. With the specific arrangements, orientations and scheduling we will be able to avoid thermalization and thermalization losses at all stages of the ignition process in contrast to all other present fusion energy schemes.

Classical simulations of quantum many-body systems are essential for both studying and understanding quantum technologies. In recent years, with the improvement and the development of several methods such as tensor networks and neural quantum states, classical simulations can reach outstanding results in both efficiency and accuracy. In this framework, we present a novel approach based on deep learning density functionals for quantum many-body systems. density functional theory can bypass the wavefunction approach for solving the many-body problem increasing the speed up and with good accuracies. By using deep learning, density functional can be easily provided without approximations and with adaptive functional forms. Here, we present the idea based on the deep learning density functional theory applied to continuous systems, with its limits and novel strategies to overcome them. We also show how the theory and the deep learning method can be extended to spin systems. Finally, we show how it is possible to extend the density functional for time dependent spin models and the application of DL-density functionals into that framework.

Core-collapse supernovae (CCSNe) host a large variety of thermodynamic conditions, from cold low-density regions in the external layers of the collapsing star to the hot and very dense nascent proto-neutron star (PNS). Nuclear physics is a key ingredient to determine the evolution of CCSNe. At high densities, the strong interaction governs the equation of state (EOS), which has large impact on the dynamics. Nevertheless, the EOS of dense matter is not fully understood. Numerical simulations are crucial to understand, and explore, the mechanisms involved in the explosion. We use CCSNe simulations as laboratories to study the impact of several nuclear matter properties on the dynamics of the PNS and the explosion. At low densities, nuclear reactions describe the nucleosynthesis that takes place in the events, which play an essential role in the chemical evolution of the universe. We investigate the impact of the composition and the energy released by nuclear reactions on the dynamics of the explosion and the nucleosynthesis.

One of the main issues posed by the presence of hadrons in any reaction is their final-state interactions, which are formally expressed in terms of the unitarity of the amplitude. In two-body scattering, unitarity is usually imposed in the direct channel only, as one is not sensitive to the details of the crossed channels. This is certainly not the case for a three-body decay, where the three possible two-hadron channels are physical, and one ideally wants to impose unitarity in all channels at once. The Khuri-Treiman formalism is a dispersive approach which indeed allows one to do so. In this talk, I will introduce such formalism and study various important applications, e.g. V→3π (V=ω,φ,J/ψ).

Basic questions such as the quantum nature of neutrinos or the origin of the matter-antimatter asymmetry in the universe, remain as big open challenges for physics. The yet undiscovered 0νββ decay is sensitive to the way of describing neutrinos and more fundamentally to the symmetries of nature. Due to this unique potential an eager experiental search is underway.

In order to plan these searches, reliable estimations for the decay lifetimes, which are known to exceed 10^26 yr, are crucial as well as to extract precise new physics parameters or constrains from these experiments. However, the nuclear matrix elements -a theory input that must be calculated- are not well known, as state-of-the-art nuclear structure methods disagree in their predictions.

In this seminar, I will revisit a physics process known since quite long ago, double-gamma decay (γγ), but from a new perspective: providing valuable insights into neutrinoless double-beta decay (0νββ) nuclear matrix elements.

Kinetic frustration is opening a new paradigm in cold atomic systems and two-dimensional moiré materials, since it induces nontrivial magnetic and spin-charge correlations at temperature scales of the order of the tunneling force, giving rise to so-called kinetic magnetism [1,2,3]. This phenomenon appears in the strongly interacting regime of doped Fermi-Hubbard Hamiltonians in non-bipartite lattices, such as the two-dimensional triangular lattice. In this talk I will discuss how kinetic magnetism and magnetic polarons emerge in these systems [4] and how recent experiments with cold atoms using quantum gas microscopes have been able to observe them experimentally [5,6].

[1]I. Morera, A. Bohrdt, W. W. Ho, E. Demler. arXiv:2106.09600. To be published in Phys. Rev. Res.

[2] Ivan Morera, Annabelle Bohrdt, Wen Wei Ho, Eugene Demler. Physical Review Research 5 (2), L022048.

[3] Livio Ciorciaro, T Smoleński, Ivan Morera, Natasha Kiper, Sarah Hiestand, Martin Kroner, Yang Zhang, Kenji Watanabe, Takashi Taniguchi, Eugene Demler, A İmamoğlu. Nature 623 (7987), 509-513.

[4] Ivan Morera, Eugene Demler. arXiv:2402.14074

[5] Martin Lebrat, Muqing Xu, Lev Haldar Kendrick, Anant Kale, Youqi Gang, Pranav Seetharaman, Ivan Morera, Ehsan Khatami, Eugene Demler, Markus Greiner. arXiv:2308.12269. To be published in Nature.

[6] Max L Prichard, Benjamin M Spar, Ivan Morera, Eugene Demler, Zoe Z Yan, Waseem S Bakr. arXiv:2308.12951. To be published in Nature.

Recently, Variational Monte Carlo (VMC) solutions to the quantum many-body problem have experienced tremendous progress in accuracy thanks to the use of neural quantum states (NQS). While more and more sophisticated ansätze have been designed to tackle a wide variety of many-body problems, little progress has been made on their optimization process.

In this talk, I will revisit the Kronecker Factored Approximate Curvature (KFAC), one of the main optimizers used for the most challenging many-body systems. After exposing how KFAC is fundamentally unfit for VMC with NQS, I will discuss the design of a novel optimization strategy based on decision geometry. As a test bench, I will consider a NQS modelling polarized fermions interacting in an harmonic trap. Preliminary results will be reported, showing how this new optimizer outperforms KFAC in terms of stability, accuracy and speed of convergence.

Beyond VMC, the versatility of this approach suggests that decision geometry could provide a solid foundation for accelerating a broad class of machine learning problems.

Neutrinoless double-beta decay is a hypothetical weak-interaction process in which two neutrons inside an atomic nucleus simultaneously transform into protons and only two electrons are emitted. Since the electrons are emitted without accompanying antiparticles, the process violates the lepton-number conservation and requires that neutrinos are Majorana particles, hence providing unique vistas in the physics beyond the Standard Model of particle physics. The potential to discover new physics drives ambitious experimental searches around the world. However, extracting interesting physics from the experiments relies on nuclear-theory predictions, which remain a major obstacle. 

I will talk about two approaches to tackle this problem. First, I will discuss the evaluation of recent effective-field-theory corrections to the operators and their effect on the theory predictions based on phenomenological nuclear many-body methods. Then, I will discuss first-principles calculations of muon capture in light nuclei, which have the potential to shed light on the high-momentum-exchange currents driving neutrinoless double-beta decay.

An anomaly in the energy differences of mirror nuclei, not yet well understood from a microscopic point of view, was found more than 50 years ago and is called the Okamoto-Nolen-Schiffer (ONS) anomaly. A systematic study from light to heavy nuclei within the framework of the independent-particle model finds that the theoretical values of the energy difference underestimate the experimental values by 3–9%. 

The aim of this research is to apply a quantum chromodynamics (QCD) sum rule approach to derive charge symmetry breaking (CSB) interaction by making a quantitative link between the Skyrme-type energy density functional (EDF) and the CSB effect due to the u-d quark mass difference and the chiral condensation in QCD. 

I will discuss application of QCD-based CSB to cure the ONS anomaly of mirror nuclei with mass A=16+/-1 and 40+/-1 nuclei. Further development of QCD sum rule approach for charge independence breaking (CIB) interaction and CSB interaction in hypernuclei will be also mentioned.

Reference

HS, T. Naito, X. Roca-Maza, and T. Hatsuda, Phys. Rev. C 109 L011302 (2024).

I will discuss our recent quantum simulations of the Schwinger model using IBM's Eagle and Heron processors. The Schwinger model is quantum electrodynamics in 1+1D, and shares features with quantum chromodynamics in 3+1D that describes strong interaction physics. We have prepared the quantum vacuum on lattices using more than 100 qubits, and prepared and time-evolved a hadronic wavepacket for up to 14 Trotter steps, clearly identifying a hadronic light cone. The largest quantum volume we used involved 112 qubits and depth 370, the largest quantum simulation to date. To make this possible, we introduced new algorithms, centered around scalable circuits that take advantage of the discrete translational invariance of the lattice system,  and exponentially converging truncations of long-range interactions. Classical simulations using small and modest lattices were sufficient to exponentially converge parameters of the quantum circuits for simulations on much larger lattices. We performed a suite of simulations utilizing more than one trillion CNOT gates on IBM's Torino quantum computer. These developments take us close to being able to collide hadrons, with the potential of a quantum advantage in the near-term simulations of 1+1D systems. These techniques and results are generally applicable to other confining theories. 

References:

1) Scalable Circuits for Preparing Ground States on Digital Quantum Computers: The Schwinger Model Vacuum on 100 Qubits,

Roland C. Farrell, Marc Illa, Anthony N. Ciavarella, Martin J. Savage. e-Print: 2308.04481 [quant-ph]

2) Quantum Simulations of Hadron Dynamics in the Schwinger Model using 112 Qubits

Roland C. Farrell, Marc Illa, Anthony N. Ciavarella, Martin J. Savage. e-Print: 2401.08044 [quant-ph]

The era of quantum computing has arrived with a wide range of implementation proposals. While there are different models of quantum computation, the quantum ecosystem is mainly focusing on the development of the digital or gate-based model. This is one of the most explored approaches to quantum computation but it is not unique. In fact, an alternative candidate to bring closer the era of practical quantum computers relies on a different but equivalently universal computing paradigm: the adiabatic model of computation, an analog architecture that shows up strong due to its promises to bypass the demanding error-correction requirements of its counterpart. In this talk we explore the basics of this alternative quantum computing paradigm, its advantages, applications and challenges as well as the efforts in Qilimanjaro towards this new promising technology. 

The continuum-discretized coupled-channels (CDCC) method [1] was developed in the 80s to study nuclear reactions for three-body systems, composed by a two-body projectile plus a target nucleus. In the 2000s the CDCC formalism was extended to four-body systems [2-6] in order to study reactions induced by the two-neutron halo Borromean nuclei 6He(4He+n+n) and 11Li (9Li +n+n). Two different approaches were used to build the states of the three-body projectile: Pseudo-State (PS) methods [2,3,7,8] and the binning procedure [4]. The four-body CDCC can be also applied to other three-body projectiles such as the stable, although weakly-bound, Borromean nucleus 9Be(α+α+n) [7,9,10,11] and the Borromean p-rich nucleus 17Ne(15O+p+p) (in progress). Also, we have applied the formalism to reactions induced by the Brunnian nucleus 10C(α+α+p+p) [12], adopting a three-body model 10C(8Be+p+p) that assumes 8Be is in its ground state (a very narrow resonance only 92 keV over the α-α threshold). A comparison between methods to build the projectile states will be shown, along with the comparison with experimental data. The reaction dynamics, as the binding energy of the projectile increases, will be discussed. 

[1] M. Yahiro et al., Prog. Theor. Phys. Suppl. 89, 32 (1986); N. Austern et al., Phys. Rep. 154, 125 (1987).

[2] T. Matsumoto, T. Egami, K. Ogata, Y. Iseri, M. Kamimura, M. Yahiro, Phys. Rev. C (2006) 73, 051602(R).

[3] M. Rodríguez-Gallardo, J. M. Arias, J. Gómez-Camacho, R. C. Johnson, A. M. Moro, I. J.

Thompson,  J. A. Tostevin, Phys. Rev. C 77 (2008) 064609.

[4] M. Rodríguez-Gallardo, J. M. Arias, J. Gómez-Camacho, A. M. Moro, I. J. Thompson, J. A. Tostevin, Phys. Rev. C 80, (2009) 051601(R).

[5] M. Cubero, J. P. Fernández-García, M. Rodríguez-Gallardo et al., Phys. Rev. Lett. 109 (2012)  262701.

[6] J. P. Fernández-García, M. Cubero, M. Rodríguez-Gallardo et al., Phys. Rev. Lett. 110 (2013)  142701.

[7] P. Descouvemont, T. Druet, L.F. Canto,  M.S. Hussein, Phys. Rev. C 91 (2015) 024606.

[8] J. Casal, M. Rodríguez-Gallardo, and J.M. Arias, Phys. Rev. C 88 (2013) 014327.

[9] J. Casal, M. Rodríguez-Gallardo, and J.M. Arias, Phys. Rev. C 92 (2015) 054611.

[10] A. Arazi, J. Casal, M. Rodríguez-Gallardo et al, Phys. Rev. C 97 (2018) 044609.

[11] V. Soukeras, O. Sgouros, A. Pakou et al., Phys. Rev. C 102 (2020) 064622.

[12] R. Linares, Mandira Sinha, E.N. Cardozo et al., Phy. Rev. C 103 (2021) 044613.

The coalescence of a binary system of neutron stars represents a perfect scenario to study hot and ultra-dense matter. Under these extreme conditions, exotic species such as hyperons may be present too. In this seminar I will speak about the influence that the appearance of hyperons have on the equation of state, and consequently, the signatures they may leave in the observables measured from the astrophysical phenomena. In particular, I will focus on the signatures that come from the thermal behaviour of hyperons in matter. The presence of hyperons produces a significant drop of the thermal pressure. This effect consequently induces a characteristic increase of the dominant postmerger gravitational-wave frequency by up to ∼ 150 Hz compared to purely nucleonic EoS models.

The Gravitational Form Factors (GFFs) give access to the internal distributions of mass, pressure and shear force inside the proton. They were considered experimentally unmeasurable for decades due to the very weak gravitational interaction [1]. However, the Generalized Parton Distributions (GPDs), which describe the correlations between the longitudinal momentum and the transverse position of the partons inside the nucleon, have lately been related to the GFFs. For the first time, this relation gives the opportunity to extract GFFs experimentally.  In this talk, I will present two ways to access GFFs using data taken in 2018 by the CLAS12 detector at Jefferson Lab with a 10.6 GeV electron beam impinging on a liquid-hydrogen target. First, I will present the first measurement of the Timelike Compton Scattering reaction (the hard photoproduction of a lepton pair), that gives access to the quark GFFs via the angular asymmetry of the electron/positron pair. I will then present the current effort to extract the near-threshold J/ψ photoproduction cross section using the same dataset. This later measurement is expected to provide direct insight on the gluons GFFs of the proton. 

[1] H. PAGELS. Energy-Momentum Structure Form Factors of Particles. Phys.Rev. 144 (1966) 1250-1260 

In ab-initio electronic structure simulations, fermion-to-qubit mappings represent the initial encoding step of the fermionic problem into qubits. Here, a physically-inspired method is presented for constructing mappings that significantly simplify entanglement requirements when simulating states of interest. The presence of electronic excitations drives the construction of the mappings, reducing correlations for target states in the qubit space. Ultimately, ground state simulation of small molecules offers enhanced performance when compared to prior research employing conventional mappings, both in the frameworks of quantum computing and tensor networks.

Neutron stars are the universe’s best natural laboratories to study dense nuclear matter. At high densities and low temperatures inaccessible in terrestrial collider experiments, neutron stars host the most extreme matter in the universe. Different regions of neutron stars will probe different physics, with some observables dominated by the poorly understood physics at supranuclear densities, while others can be used to constrain properties of nucleonic matter, such as the nuclear symmetry energy. I will discuss our latest work on Resonant Shattering Flares, multimessenger signatures which can be used as a powerful constraint on nuclear physics. Studying the spectrum of asteroseismic modes in a neutron stars can provide probes at different densities, and hence of different physics. 

We discuss the application of van der Waals-type models in describing hadronic systems in extreme conditions, such as the high density regime. For this purpose, we modify the attractive and repulsive parts of the nucleon–nucleon interaction by making them density-dependent functions. More specifically, we adopt the Carnahan–Starling (CS) method for the latter, and a suitable expression for the former in order to reproduce the structure of a real gas model. The phenomenology of short-range correlations (SRCs) are also taken into account. The parametrizations of the resulting models are shown to be capable of reproducing the flow constraint at the high-density regime of symmetric nuclear matter for incompressibility values inside the range of K0 = (240 ± 20) MeV. In the context of stellar matter, our findings point out a good agreement with recent astrophysical observational data, namely, mass–radius contours and dimensionless tidal deformability regions and values, coming from gravitational waves data related to the GW170817 and GW190425 events, and from the NASA’s Neutron star Interior Composition Explorer mission.

We explore how data from low-energy nuclear physics can impact the properties of neutron stars, such as mass, radius, and deformability, in the absence of phase transitions in dense matter. We use different nuclear interactions to analyze how they describe the ground state binding energies, charge radii, and giant monopole resonances of a set of spherical nuclei and use these results to estimate the symmetry energy of nuclear matter. These estimates help us predict the properties of neutron stars, but we find that the predominant uncertainty still lies in the density dependence of the equations used, which remains unknown for extremely high densities.

Some paradigms are known for nuclear structure, and are indeed working well.  However, many of them were obtained six or seven decades ago, and may not be sufficient. Those includes the paradigms of fundamental properties such as shell structure, shape deformation and alpha clustering. Recent studies starting from basic features of nuclear forces sometimes lead us to different pictures, and I would like to present such cases with certain emphasis on the effects of tensor force or more ab initio forces.

We discuss a nonrelativistic version of Georgi’s "unparticle physics". An "unparticle" is a field in a nonrelativistic conformal field theory characterized by a mass and a scaling dimension. It is realized approximately in high-energy nuclear reactions involving emission of a few neutrons with relative energies between about 0.1 MeV and 5 MeV. Conformal symmetry predicts a universal power law behavior of the inclusive cross section in this kinematic regime and relates it to the energy levels of spin-1/2 fermions in a harmonic trap. Certain bosonic systems may also show unparticle behavior. We argue that it may be possible to create unparticles of neutral D mesons in short-distance reactions at the LHC.

HWH, D.T. Son, Proc. Nat. Acad. Sci. 118, e2108716118 (2021) [arXiv:2103.12610]

Braaten, HWH, Phys. Rev. Lett. 128, 032002 (2022) [arxiv:2107.02831]

Braaten, HWH, Phys.Rev. D 107, 034017 (2023) [arXiv:2301.04399]

Quantum electrodynamics in 1+1 dimensions (the Schwinger model) exhibits a number of features similar to quantum chromodynamics in 3+1D (SU(3) Yang-Mills gauge theory plus quarks), including confinement and a fermion condensate. A new algorithm to prepare the ground state of such gapped translationally-invariant systems is discussed, Scalable Circuits ADAPT- VQE. This algorithm uses the exponential decay of correlations between distant regions of the ground state, together with ADAPT-VQE, to construct quantum circuits for state preparation that can be scaled to arbitrarily large systems.  We will discuss how using scalable circuits defined on 28 qubits are used to prepare the analogous states on up to 100 qubits, made possible by using a modified decoherence renormalization procedure.

I will present our first findings on D-meson femtoscopy by using the TROIA framework. Our analysis employs unitarized effective hadron interactions derived from an off-shell T-matrix calculation in a coupled-channel basis. We have obtained correlation functions of heavy-light mesons accounting for Coulomb interaction in the relevant channels, and have analyzed the impact of inelastic processes. I will present a set of results that can be directly compared to experimental data from the ALICE experiment. Our study also encompasses predictions involving novel channels, including strange mesons and their vector siblings. Our original research contributes to a deeper understanding of heavy meson-light meson interactions via femtoscopy measurements in proton-proton collisions.

Since 2003, when the $D^*_{s0}(2317)$ and the $X(3872)$ states where discovered, a wealth of states or resonances with charm quark content have been discovered in modern hadron colliders and/or detectors, many of which do not fit into conventional constituent quark models. In this seminar I will discuss several examples in which a coherent picture can be drawn for some of these states, starting from the use of Effective Field Theories and unitarity. 

Neutrino oscillation programs are soon entering the precision era, in which the uncertainties of neutrino-nucleus cross-sections will have to be well under control to ensure future discoveries. Motivated by this need, we started a program which employs the ab initio coupled cluster theory, to give prediction in the range of medium-mass nuclei (16O, 40Ar) important for the future experiments (DUNE, HyperK), up to the quasi-elastic peak.

In my talk I will present various aspects of the endeavour.  In particular, I will present a consistent calculation of nuclear responses via Lorentz integral transform, benchmarking our results with available electron scattering data on 4He and 40Ca. I will also show our strategies to assess the theoretical uncertainties, stemming both from the expansion of chiral Hamiltonians and from the many-body method. Lastly, I will discuss how the nuclear calculations can be used in the relativistic regime, which is an essential step to make a connection to neutrino oscillation experiments.

The existence of pentaquarks with strangeness content zero (S=0) and one (S=-1) are major discoveries of the latest years in hadron physics. Most of these states can be understood as hadronic molecules and were predicted prior to their discovery within a model based on unitarized meson-baryon amplitudes obtained from vector-meson exchange interactions. Contrary to earlier statements, we show this model to also predict the existence of pentaquarks with double strangeness (S=-2), at about 4500 and 4600 MeV, which are generated in a very specific and unique mechanism, via an attraction induced by a strong coupling between the two heaviest meson-baryon states. 

Based on: J. A. Marsé-Valera, V. K. Magas, and A. Ramos, Phys. Rev. Lett. 130, 091903 (2023)

Before the advent of duality (late 60s) two disconnected phenomena were studied in the dynamics of strong interactions: low-energy resonances and high-energy smooth asymptotic behavior. With the discovery of duality and its realization by the Veneziano model that unified the low- and high-energy regions the situation changed drastically. Various versions of dual models and their practical applications were proposed and applied to describe physical reactions. An important virtue of dual models is the possibility of their multiparticle generalizations. Duality also stimulated the birth of new ideas, including supersymmetry.

On the other hand, progress in further development and practical applications of dual models was limited by problems with unitarity, partially resolved by a group of theorists at the Bogolubov Institute for Theoretical Physics (Kiev, Ukraine), in the so-called Dual Amplitude with Mandelstam Analyticity (DAMA) by use of non-linear, complex Regge trajectories. A further development was related to off-mass-shell modifications of DAMA, known as MDAMA (V. Magas et al.). Recently we are witnessing a revival of the ideas of duality, partly in formal mathematical constructions such as q-deformed dual amplitude. 

The basic idea and goal remain topical and timely: understanding and unified description of various elastic and inelastic reactions in a wide range of kinematical variables. 

Ordinary muon capture is a nuclear-weak process in which a negatively charged muon, initially bound on an atomic orbit, is captured by the atomic nucleus, resulting in atomic number reduction by one and emission of a muon neutrino. Thanks to the high momentum transfer involved in the process, it is one of the most promising probes for the hypothetical neutrinoless double-beta decay. With the recent renaissance of muon-capture experiments, reliable theory estimates are now of paramount importance. In my talk, I will discuss my recent studies on muon capture on light nuclei, 6Li, 12C, 16O and 24Mg, using two different ab initio nuclear techniques.

Hadronic physics in general, and the quark and gluon structure of protons, mesons, and nuclei in particular, has witnessed recent impressive progress. Hadronic science is driven both by the goal of achieving a deeper understanding of Quantum Chromodynamics, addressing key questions such as the origin of mass and spin of hadrons, and by the need of precise knowledge of hadronic structure for theory predictions in high-energy proton- and lepton-scattering experiments, from the Large Hadron Collider (LHC) to the Electron-Ion Collider (EIC) and neutrino facilities such as IceCube and the Forward Physics Facility (FPF).

In this talk I provide a pedagogical overview of our current understanding of the quark and gluon substructure of protons and nuclei, what we have conclusively learned about them in the past years, and what are the big questions that will be studied in the near future. Specifically, I present evidence for intrinsic charm quarks in the proton wave function; demonstrate the rich pattern of nuclear effects such as shadowing unravelled by proton-lead collisions; and highlight how searches for physics beyond the Standard Model at the high-energy frontier can be severly biased without a robust understanding of proton structure

In the past years increasing effort has been devoted to re-examining quantum many-body systems from a quantum information point of view.  In particular, there has been renewed interest in understanding the phenomenon of entanglement due to its essential role in quantum computing and potential guidance in formulating the many-body problem. 

In this talk we investigate entanglement properties of nuclear systems obtained from calculations with effective model spaces. These include exactly solvable models as well as ab-initio calculations of light nuclei. We study how entanglement structures rearrange into localized regions of the Hilbert space through Hamiltonian transformation, and the relation to physical phenomena. We also explore how entanglement localization can be utilized to develop quantum algorithms that efficiently leverage the potential of quantum computers. To this aim, we introduce a “Hamiltonian-Learning Variational Quantum Eigensolver” to simultaneously determine the Hamiltonian and ground-state wave function in effective model spaces, which we apply to simple models. 

References: C. Robin, M. J. Savage and N. Pillet, PRC 103, 034325 (2021), C. E.P. Robin and M. J. Savage, arXiv:2301.05976 [quant-ph] (2023).

In 1999, Hampton and Zanette revealed the first synchronization concept for coupled Hamiltonian systems, known as measure synchronization (MS). Since then, there are continued efforts to explore synchronization occurring in Hamiltonian systems, in particular, MS. In this talk, I will briefly overview our research on MS in three different categories of coupled Hamiltonian systems: i) Coupled classical Hamiltonian systems; ii) Coupled quantum Hamiltonian systems; iii) Coupled quantum-classical hybrid systems.

DFT is a powerful and versatile method in nuclear structure theory [1]. The predictive power of DFT is tied to the accuracy of the nuclear energy density functional (EDF). Current In this talk, I will discuss how machine learning tools can be employed to solve the quantum many-fermion problem. I will specifically look at proof-of-principle simulations for the ground-state properties of fully polarized (or spinless), trapped, one-dimensional fermionic systems interacting through a gaussian potential. I will clarify how to construct antisymmetric variational artificial neural network ansätze for the wavefunction, and how to exploit the method to minimize the energy of systems from 2 to 6 particles. I will describe the emergence of two distinct physical phases depending on the sign of the interaction. Attractive systems show clear signs of bosonization, whereas repulsive systems display crystalline order. Extensive benchmarks with other methods, including exact diagonalization and the Hartree-Fock approximation, will also be discussed. 

DFT is a powerful and versatile method in nuclear structure theory [1]. The predictive power of DFT is tied to the accuracy of the nuclear energy density functional (EDF). Current phenomenological EDFs are rather successful in reproducing stable nuclei, but to overcome their known shortcomings that are visible e.g. when they are applied to nuclei far from the stability valley, new strategies are called for. In this talk, I will describe our approach to constructing EDFs constrained by ab initio calculations of the equation of state (EOS) and the static response of infinite nuclear matter [2,3]. Then, I will show ongoing developments of the ab initio Self-consistent Green’s functions method [4] for the nuclear matter EOS.

References

[1] G. Colò, Advances in Physics: X 5, 1740061 (2020)

[2] F. Marino, C. Barbieri, A. Carbone, G. Colò, A. Lovato, F. Pederiva, X. Roca-Maza, and E. Vigezzi, Phys. Rev. C 104, 024315 (2021)

[3] F. Marino, G. Colò, X. Roca-Maza, and E. Vigezzi, arXiv:2211.07986 (2022)

[4] C. Barbieri and A. Carbone, in An Advanced Course in Computational Nuclear Physics (Springer International Publishing, Cham, 2017) 

The nuclear shell model is one of the prime many-body methods to study the structure of atomic nuclei, but it is hampered by an exponential scaling on the basis size as the number of particles increases. We present a shell-model quantum circuit design strategy to find nuclear ground states that circumvents this limitation by exploiting an adaptive variational quantum eigensolver algorithm. Our circuit implementation is in excellent agreement with classical shell-model calculations for a dozen of light and medium-mass nuclei, including neon and calcium isotopes. We quantify the circuit depth, width and number of gates to encode realistic shell-model wavefunctions. Our simulated circuits approach the benchmark results exponentially with a polynomial scaling in quantum resources for each nucleus and configuration space. This work paves the way for quantum computing shell-model studies across the nuclear chart.

In the presence of spin-orbit coupling and a linear Zeeman field, an interacting Fermi gas exhibits a topological phase transition from a regular superfluid phase to a topological superfluid phase, where the latter phase supports Majorana zero modes. These modes are long sought objects by solid state experiments, since they can show a non-Abelian exchange  statistics with promising potential for applications. Such a motivation has also triggered the search for Majorana zero modes in ultra-cold Fermi gases. They can be found when the fermionic pairing vanishes locally, and thus they are associated either with the system boundary, as edge states, or with internal defects that locally destroy superfluidity, as pinned modes. 

A particularly interesting example of the latter phenomenon in quasi one dimensional gases is the dark soliton, which was theoretically shown to exhibit novel dynamics in the topological phase, qualitatively distinct from the regular behavior of solitons. We have studied this topological excitation and found that there is not only one, but two types of dark solitons in spin-orbit-coupled Fermi gases. The existence of two Fermi surfaces, with different characteristic energy and length scales that feature distinct condensation peaks of fermionic pairs, allows for the emergence of two different types of dark solitons in the regular superfluid phase, while only one type has continuation into the topological phase, where it hosts Majorana zero modes at the core. The detection and identification of the two types of solitons in ultracold-gas experiments requires probing both the fermionic density and the order parameter. 

It is commonly believed that simple cubic lattices are mechanically unstable due to softening of the shear modulus. Similarly, two-dimensional square lattices are commonly unstable, and instead, the typical triangular lattice is formed instead. We provide counterexamples and provide a simple stability analysis in terms of the sign of the second derivative of the interaction potential and the lattice spacing. As an example, we consider a two-dimensional lattice of Rydberg atoms and find densities at which the usual triangular lattice is unstable. As a result, a variety of unusual lattice packings is observed in classical Monte Carlo simulations. As an additional check for stability, we perform normal mode analysis. The proposed mechanism for instability might be relevant to other systems leading to curios effects (pairing, large elementary cells, supersolidity, etc).

I will discuss recent progress of optical lattice emulators of the Fermi Hubbard model, specifically the new availability of snapshots of many-body states with single particle resolution. I will review new insights from these experiments on the properties of doped Mott insulators, including the demonstration of magnetically mediated pairing. I will also present the idea of using quantum simulators to perform inference of NMR spectra for biological molecules. I will review a recent experimental realization of this algorithm on a quantum computer using trapped ions. Prospects for scaling this approach to solving practically relevant problems will be discussed.

In this talk I am going to present one of the most novel structures that has been experimentally observed: supersolids. The supersolid phase is a state of matter that simultaneously presents superfluidity and solid order (by breaking translational invariance). This dual behavior opens the door to many intriguing phenomena both from the static and the dynamic perspective, since supersolids display solid and non dissipative fluid features at the same time.

I am going to provide an overview about what has been found already in the topic of supersolids, paying special attention to excitation of collective modes, the still ongoing studies on the characterization of the superfluidity of a supersolid and the role of the dimensionality and an external confinement.

After that, I will comment about one of the main future perspectives of supersolids: binary dipolar gases.Two-component systems present richer properties, since features such as miscibility and polarization (under the presence of Rabi coupling) play now a crucial role. The possibility to excite independently the density and the spin chanel in a two-component supersolid paves the way to the study of magnetic effects in supersolids and to the eventual nucleation of novel domains.

In this talk I will present a new project that we are starting together with the University of Caen and the University of Milano-Bicocca. The aim of the project is to build an Equation of State (EoS) for neutron star merger simulations. Specifically, in my presentation, I will focus on the motivation of the first part of the project that consists in building a reliable EoS up to about two times nuclear saturation density (ρ₀). For that purpose, the development of new nuclear effective models is instrumental. State-of-the-art nuclear physics models used as input for neutron star merger simulations nowadays are not able to describe at the same time the electric nuclear dipole polarizability and the parity violating asymmetry recently measured in different nuclei [1,2]. The connection of these two observables with specific properties of the neutron matter EoS will be discussed and current results will be presented. As a conclusion, a nuclear physics theoretical effort is needed in the near future not only for nuclear structure and reaction studies but also for reliable applications in nuclear astrophysics. 

[1] Information content of the parity-violating asymmetry in 208Pb P.-G. Reinhard, X. Roca-Maza, W. Nazarewicz, Phys. Rev. Lett. 127 232501 (2021)

[2] Combined theoretical analysis of the parity-violating asymmetry for 48Ca and 208Pb, P.-G. Reinhard, X. Roca-Maza, W. Nazarewicz, Phys. Rev. Lett. (2022) – Accepted 

Recently, the JPAC collaboration has developed and benchmarked a systematic approach to use Deep Neural Networks as a model-independent tool to analyze and interpret experimental data and to determine the nature of an exotic hadron. Specifically, we studied the line shape of the Pc(4312) signal reported by the LHCb collaboration. This novel method presents great potential and can be applied to other near-threshold resonance candidates.

More than 20 years ago at the beginning of the RHIC era, a new nucleus-nucleus initial state was proposed, based on the longitudinal Effective String Rope Model for further 3+1D relativistic fluid dynamical evolution. The big advantage of this initial state, in comparison to others available at that time, was that it reflected correctly not only the energy-momentum, but also angular momentum conservation laws. Consequently, such an initial state for non-central ultra-relativistic heavy ion collisions may lead to overall rotation of the reaction volume or/and to a large vorticity of the collective flow, which can manifest itself via polarization of emitted particles. This is supported by the observations of global polarization of Lambda and anti-Lambda hyperons at non-zero impact parameter in Au+Au collisions at RHIC reported by STAR collaboration.

In the last two decades with the construction of high energy colliders, such as the Large Hadron Collider at CERN, as well as with the development of new detectors and new data storing and analyzing methods, the study of heavy ion collisions event-by-event has become possible. In order to perform an analysis of the simulated collisions in a

modern "event-by-event" mode such an initial state model has to be modified.

I will present the Generalized Effective String Rope Model in which the fluctuations in the initial state are taken into account following the Glauber Monte Carlo approach. I will analyze how such fluctuations lead to principal differences in the initial state not only for a single (random) event, but also if we perform an averaging over many events. I will also compare the results obtained in this model for symmetric Au+Au collisions at different impact parameters with those for asymmetric A+Au head on collisions.

The Generator Coordinate Method (GCM) provides a general framework to give variational solutions to the many-body problem. It is based on the definition of the variational trial wave functions as the linear mixing of different intrinsic configurations defined along the so-called generating coordinates. This beyond-mean-field method can give ground and excitation energies, decay probabilities, and interpretations of the results in terms of collective and single-particle degrees of freedom. In nuclear physics, the most common (and involved) realizations of the GCM formalism nowadays is the mixing of symmetry-restored (particle-number, parity and angular momentum projected) intrinsic quasi-particle states obtained from self-consistent mean-field calculations, the so-called Projected-GCM (PGCM).

In this seminar I will present some technical aspects of the PGCM method related to the proper orthogonalization of the original set of states used to defined the trial wave functions. In addition, I will show some recent results obtained with the PGCM method that can be compared with experimental data (shape evolution/coexistence/mixing in atomic nuclei, weak decays nuclear matrix elements, etc.).

The light-cone distribution amplitude (LCDA) of the pion carries information about the parton momentum distribution and is an important theoretical input into various predictions of exclusive measurements at high energy, including the pion electromagnetic form factor. In this talk, I will discuss a lattice determination of the second Mellin moment of the pion LCDA and the progress towards a lattice determination of the fourth Mellin moment of the LCDA, both using the heavy quark operator product expansion (HOPE) method.

In an attempt to tackle systematically the complexity of strongly correlated quantum many-body systems, modern ab initio approaches have grown more and more sophisticated, both formally and numerically. One standard strategy consists in combining several pre-existing many-body schemes such as symmetry-breaking mean-field calculations with non-perturbative corrections. In this particular case, the additional formal complexity appears as anomalous propagators and/or anomalous vertices in the diagrammatic.

In this talk, I will show how the introduction of a specific tensorial structure enables the reformulation of many-body approximations, such as Self-consistent Green’s Functions (SCGFs), in a way that is explicitly invariant with respect to any Bogoliubov transformation. As a result, symmetry-breaking extensions of many-body approximations become formally as simple as their symmetric counterpart.

To illustrate the simplifications that occur, I will showcase the set of equations formulating the self-consistent ladder approximation of symmetry-breaking Green’s functions at finite temperature, in a general basis. Application of such general expression for a many-body system of interest will then be presented by considering the example of superfluid polarized asymmetric nuclear matter in a plane-wave basis.

Finally, I will revisit the celebrated Thouless’ criterion linking the convergence of the series of ladder diagrams at vanishing energy with the stability of the Bardeen-Cooper-Schrieffer (BCS) self-energy for homogeneous matter. Taking advantage of the Nambu-covariant formalism, I will show how Thouless’ criterion trivially extends to the case of a complex general Hartree-Fock-Bogoliubov (HFB) self-energy when one considers a general many-body system. Last, as an attempt to make up for the shortcoming of Thouless’ criterion, I will introduce a new condition on the stability of the HFB self-energy which is sufficient to ensure the convergence of the series of ladder diagrams at any energy.

Laser Induced Inertial Confinement Fusion has some obstacles and we proposed some new ideas recently. In the Nanoplasmonic Laser Induced Fusion Energy (NAPLIFE) project our aim is to circumvent some of these by using results from ultra-relativistic heavy ion reactions and nanotechnology. We aim for time-like detonation to avoid instabilities and slow spreading of the burning front and regulate the light absorption in the target by implanted nano-antennas. Along with initial theoretical modeling, we started validation experiments of the amplification of laser light absorption at the Wigner RCP in Budapest, which will be presented. The next step of validation experiments will aim for simultaneous ignition of the whole target. Then the Full energy ignition experiments will be performed at the ELI-ALPS, European Laser Infrastructure in Szeged.

Predicting the ground-state properties of quantum many-body systems using classical computers is, in the most general case, an intractable computational problem. Also predicting the output of gate-based quantum computers is computationally prohibitive for classical computers. However, it was recently shown that classical machine-learning algorithms trained on databases of solved instances can predict ground-state properties with rigorous accuracy guarantees. 

In this talk, I will discuss the use of deep neural networks — trained via supervised learning — to predict the ground-state properties of disordered quantum systems, as well as the output expectation values of random quantum circuits. Special attention is devoted to the scalability property. This allows us training neural networks on (computationally accessible) small systems, to predict properties of (computationally challenging) larger systems with more particles or more qubits. If time permits, I will also briefly discuss the development of energy-density functionals for density functional theory via deep neural networks with tailored architectures.  

References

P. Mujal, À. Martínez Miguel, A. Polls, B. Juliá-Díaz, S. Pilati, Supervised learning of few dirty bosons with variable particle number, SciPost Physics 10, 073 (2021).

S. Cantori, D. Vitali, S. Pilati, Supervised learning of random quantum circuits via scalable neural networks, arXiv:2206.10348 (2022).

E. Costa, G. Scriva, R. Fazio, S. Pilati, Deep learning density functionals for gradient descent optimization, arXiv:2205.08367 (2022).

In the light of the recent experimental results on the muon g-2, we would like to scrutinize the Standard Model contributions, comment about its weak and strong points, and openly discuss with the UB experts about possible avenues to follow for the year to come.

I will argue that if black holes represent one the most fascinating implications of Einstein's theory of gravity, neutron stars in binary system are arguably its richest laboratory, where gravity blends with astrophysics and particle physics. I will discuss the rapid recent progress made in modelling these systems and show how the gravitational signal can provide tight constraints on the equation of state and sound speed for matter at nuclear densities, as well as on one of the most important consequences of general relativity for compact stars: the existence of a maximum mass. Finally, I will discuss how the merger may lead to a phase transition from hadronic to quark matter. Such a process would lead to a signature in the post-merger gravitational-wave signal and open an observational window on the production of quark matter in the present Universe.

Quantum computers promise to allow quasi-exact solutions of quantum many-body problems in chemistry and physics without the exponential scaling that plagues classical methods. Among the many ways of exploiting quantum computers, hybrid algorithms known as Variational Quantum Eigensolvers (VQEs) which are based on the variational principle of quantum mechanics, are being developed particularly intensively. These algorithms allocate optimization of wave functions to classical computers, using their quantum counterparts only to realize the parameterized state that the optimization scheme calls for. The result is fewer quantum operations at the expense of more measurements, leading to the hope that near-term quantum circuits, which are noisy, can implement the procedures without becoming too inaccurate. We use the Lipkin-Meshkov-Glick (LMG) model and the valence-space nuclear shell model to examine the likely performance of variational quantum eigensolvers in nuclear-structure theory.

Bose-Einstein condensates (BECs) constitute fertile physical platforms for investigating the existence, dynamics and interactions of solitons or multicomponent and multidimensional variants thereof. Solitons are fundamental excitations that arise in nonlinear media from the balance between dispersion and the nonlinearity. In 1D BECs, these macroscopic nonlinear excitations can have the form of local density suppressions (dark solitons) or local density humps (bright solitons) depending on whether the nonlinear interaction is repulsive or attractive, respectively.

In this talk, we will focus on the generation of solitonic structures of the dark-bright (DB) type in a repulsive two-component BEC. By means of matter-wave interference and conunter-flow processes, trains of DB solitons dynamically emerge upon choosing suitable box-type configurations for each component wave function. First, we will solve the direct scattering problem for the defocusing vector nonlinear Schrödinger equation with nonzero boundary conditions and obtain analytical expressions for the spectrum of DB soliton solutions resulting from the box-type configuration. Then, we will compare the analytically obtained DB soliton solutions with direct numerical simulations of the Gross-Pitaevskii equation, in the absence and in the presence of external confinement, showcasing an excellent agreement between the two.

While universal quantum computation is essential in the quest to simulate Standard Model physics, the near-term devices that define the NISQ era, without high-fidelity qubits and error correction, will be challenged to provide results that can be quantitatively compared with experiment. Much of the current research in this area is performed on gate-based quantum computers, and the alternative, adiabatic quantum computing, has not been explored with as much detail. We explore the potential of D-Wave’s quantum annealers for computing basic components required for quantum simulations of Standard Model physics. By implementing a basic multigrid (including “zooming”) and specializing Feynman-clock algorithms, D-Wave’s Advantage is used to study harmonic and anharmonic oscillators relevant for lattice scalar field theories and effective field theories, the time evolution of a single plaquette of SU(3) Yang-Mills lattice gauge field theory, and the dynamics of flavor entanglement in four neutrino systems.

Quarkonium has been used as a probe of the quark-gluon plasma (QGP) in heavy ion collisions for decades. To understand the experimental data on quarkonium production, it is important to study the time evolution of quarkonium states inside the plasma. Most phenomenological studies replied on classical rate equations which neglect quantum effects and introduce model dependence in recombination. In this talk, I will review the application of the open quantum system framework to study quarkonium in the QGP. I will explain how the open quantum system framework treats Debye screening, dissociation and recombination in the same theoretical ground and thus removing model dependence in recombination. I will then discuss recent calculations of the chromoelectric field correlators that encode the essential information of the QGP in the quarkonium in-medium dynamics. Finally, I will briefly mention some initial efforts for the quantum simulation of open quantum systems in heavy ion collisions.

The determination of eigensolutions of quantum N-body Hamiltonians in D dimensions can be a really hard problem, especially for large number of particles. The envelope theory and its improvements provide reliable and easy-to-implement approximations for the spectrum of a very large class of Hamiltonian. These methods, that were built for systems of N identical particles, have been recently generalized to systems with one particle different from the others. The main goal of this seminar is to give the audience the key points to concretely use these two methods. The origin of the equations will be quickly discussed too.

The recent developments mainly in nuclear interaction and many-body techniques allow us to compute the properties of finite nuclei. The applicability of the ab initio calculations is expanding to the mass number ~ 100 [1]. However, it becomes difficult to find a reliable result for further heavy nuclei, primarily due to the memory expensive three-nucleon interaction. To overcome the limitation and make the computation of the heavier nuclei feasible, we proposed a new storage scheme of the 3N matrix elements [2]. This new scheme enables us to compute the heavier nuclei well beyond the previous limitation. In this talk, I will present our results and predictions for lead 208, the known heaviest doubly magic nucleus [3].

References

[1] S. R. Stroberg, J. D. Holt, A. Schwenk, and J. Simonis, Phys. Rev. Lett. 126, 022501 (2021).

[2] T. Miyagi, S. R. Stroberg, P. Navrátil, K. Hebeler, and J. D. Holt, Phys. Rev. C 105, 014302 (2022).

[3] B. Hu, W. Jiang, T. Miyagi, Z. Sun, A. Ekström, C. Forssén, G. Hagen, J. D. Holt, T. Papenbrock, S. R. Stroberg, and I. Vernon, arXiv:2112.01125

We have studied the many-body physics of D mesons in a thermal medium by applying an effective field theory based on chiral and heavy-quark spin symmetries. Relying on unitarity constraints and diagrammatic self-consistency, we have analyzed the in-medium properties (masses and decay widths) of charmed mesons and developed a kinetic theory approach. Given the separation of scales in the problem, we were able to derive an off-shell Fokker-Planck equation for these states. I will report our findings on dynamically generated states and their thermal evolution, in-medium modifications including off-shell effects, and the heavy-flavor transport coefficients below the chiral restoration temperature.

The Gogny interaction was established by D. Gogny forty years ago [1] aimed to describe simultaneously the mean  eld and the pairing  eld with the same interaction. This type of forces consists of a finite-range part and a zero-range density dependent term together with a spin-orbit interaction, which is also of zero-range. The finite-range contribution consists of the sum of two Gaussian form-factors of different ranges, which simulate the short- and long-range parts of the interaction. The Gogny force D1S [2] have been used in large-scale Hartree-Fock-Bogoliubov calculations along the whole periodic table [3]. This force, as well as the improved parametrizations D1N [4] and D1M [5], are, actually, benchmarks of the deformation and pairing properties of the ground-state of finite nuclei.

The Gogny forces are effective interactions and therefore extrapolations to different scenarios from the one where the forces were fitted is not evident a priori and shall be carefully checked. In this talk, I will review the extrapolation of Gogny forces to describe neutron stars and nucleon-nucleus elastic scattering. The standard Gogny forces of the D1 family, namely D1S, D1N and D1M, suffer of too soft symmetry energy and fail in predicting the maximum mass of two solar masses (2M⦿), as required by recent astronomical observations. To overcome these limitations, we have proposed a reparametrization of the Gogny D1M force by increasing the slope of the symmetry energy, and therefore reaching the maximum mass of 2M⦿, and at the same time, providing a description of  finite nuclei with a global quality similar to that found using the original D1M force. This new force, named D1M, has been used to build up a global Equation of State from the outer crust to the core, able to reproduce the physics of neutron stars reasonably well as has been reported recently in a review article [6].

The application of Gogny forces to nuclear reactions has been discussed in a recent paper [7]. We have obtained the optical potential in a semi-microscopic nuclear matter approach, which allows to obtain its real and imaginary parts as the first and second-order terms of the Taylor expansion of the mass operator, computed in the Brueckner-Hartree-Fock method, using the reaction G-matrix built up with the Gogny force instead of the microscopic interaction. This relatively simple approach allows to obtain the optical potential without any additional paramter and, therefore, to explore the ability of this force to describe the phenomenology of the elastic nucleon-nucleus scattering along the periodic table. Our calculation shows that the differential cross sections and analyzing powers describe, qualitatively, the experimental data. However, a more accurate description, similar to that found using global optical model parametrizations fitted to the data [8], requires a renormalization of both, real and imaginary, parts of the optical model computed with our approximation using Gogny forces. It is also interesting to point out that our optical potential without any renormalization is also able to reproduce, at least at qualitative level, elastic cross-section of composite particles by nuclei and quasi-elastic charge exchange reactions A(p,n)B.

[1] J. Dechargé and D. Gogny; Phys. Rev. C21, 1568 (1980).

[2] J.F. Beger, M. Girod and D. Gogny; Comp. Phys. Comm. 63, 365 (1991).

[3] S. Hilaire and M. Girod, AMEDEE database.

[4] F. Chappert, M. Girod and S. Hilaire; Phys. Lett. B668, 420 (2008).

[5] S. Goriely, S. Hilaire, M. Girod and S. Peru; Phys. Rev. Lett. 102, 242501 (2009).

[6] X. Viñas, C. Gonzalez-Boquera, M. Centelles, C. Mondal and L.M. Robledo; Symmetry 13, 1621 (2021).

[7] J. Lopez-Moraña and X. Viñas; J. Phys. G48, 036104 (2021).

[8] A.J. Koning and J.P. Delaroche; Nucl. Phys. A713, 231 (2003)

The numerical modeling of the magnetic field evolution in astrophysical scenarios is essential for the understanding of systems such as magnetars and highly magnetic pulsars. The governing equation of the magnetic field evolution in the crust of a neutron star is the Hall induction equation. In this equation, the relative contribution of the Hall term and Ohmic dissipation varies depending on the local conditions of temperature and magnetic field strength. Besides, the strong magnetic field of neutron stars is coupled to the observed temperature, spectral properties, as well as timing properties. In this work, we present the results of 2D magneto-thermal simulations varying different parameters: initial magnetic field, equation of state and mass. A comparison of models to the data obtained from X-ray observations is discussed, for a better understanding of different classes of neutron stars.

Mixed fermion-boson stars are equilibrium solutions of the coupled Einstein Klein-Gordon-Euler system. While isolated neutron stars and boson stars are uniquely determined by their central energy density, mixed configurations conform an extended parameter space that depends on the combination of the number of fermions and (ultra- light) bosons. The wider possibilities offered by fermion-boson stars could help explain the tension in the measurements of neutron star masses and radii reported in recent multi-messenger observations (e.g. LVC gravitational wave observations and NICER/XMM-Newton measurements) and nuclear-physics experiments (PREX2). 

Quantum sensing is one of the four pillars of the European roadmap on quantum technologies. In particular, atomic sensors, including magnetometers, clocks, gyroscopes and gravimeters, are of interest to many areas of physics and they are useful in many applications.

Optically-pumped magnetometers (OPMs), in which an atomic ensemble is optically pumped and its spin-dynamics optically detected, are the most sensitive devices to measure low-frequency magnetic fields. This is a paradigmatic quantum sensing technology, which applies to medical diagnosis, geophysics, navigation and searches beyond the standard model.

In this talk, after giving a general overview on optical magnetometry [1], I will describe a number of experiments [2, 3] that I performed as postdoctoral research associate at Princeton University. This is a class of scalar optically-pumped magnetic gradiometers that reach femtotesla sensitivity over a broad dynamic range, including Earth’s field magnitude, and led to the first detection of human biomagnetism in unshielded environment [2].

In the second part, I will describe the quantum noise contributions to the sensitivity of OPMs. Once atomic sensors reach fundamental sensitivity, the only way to improve their performance is to use quantum resources as optical and atomic spin squeezing or entanglement, which is one of the major goals in atomic quantum sensing. In particular, I will describe the first quantum enhancement of high-density atomic sensors by using squeezed-light, first applied to an unpolarized ensemble, i.e. to spin noise spectroscopy (SNS) [4], secondly to a high sensitivity OPM, thanks to the evasion of quantum backaction [5].     

Finally, I will give an overlook on two current projects I am leading at ICFO towards miniaturization of atomic sensors by using MEMS technology, within the EU quantum flagship project macQsimal [6], as well as a new class of vapour cells written by a femtosecond laser.

[1] D. Budker and M. Romalis “Optical Magnetometry”, Nature Physics 3, 227–234 (2007)

[2] M. E. Limes et al. “Portable magnetometry for detection of biomagnetism in ambient environments”, Phys. Rev. Applied 14, 011002 (2020)

[3] V. G. Lucivero et al. “Femtotesla direct magnetic gradiometer using a single multipass cell”, Phys. Rev. Applied 15, 014004 (2021)

[4] V. G. Lucivero et al. “Squeezed- light spin noise spectroscopy”, Phys. Rev. A 93, 053802 (2016)

[5] C. Troullinou et al. “Squeezed-light enhancement and backaction evasion in a high-sensitivity optically pumped magnetometer”, Phys. Rev. Lett. 127, 193601 (2021)

[6] https://www.macqsimal.eu/

By means of energy and orthogonality considerations we optimize the computation of nuclear matrix elements for neutrinoless double-β (0νββ), calculated using the generator-coordinate method with symmetry-restored constrained mean-field states. A selection mechanism is proposed to choose the most relevant mean-field states, giving the major contributions to the NME. We calculate the NME of the 76Ge→76Se transition using the quadrupole deformations and the isoscalar pairing coordinate as relevant constrained degrees of freedom. Our results show that not all states are necessary to be included in the GCM calculation, reducing the computational cost of solving the Hill-Wheeler-Griffin equation.

The study of the alternative energy source is one of the absolutely imperative research topics in the world as our present energy sources such as fossil fuels are limited. This work is dedicated to the nuclear fusion physics research in close collaboration with existing experimental fusion devices and the ITER organization (www.iter.org) which is an huge international nuclear fusion R&D project. The goal of the ITER project is to demonstrate a clean and safe energy production by nuclear fusion which is the reaction that powers the sun. One of the ideas of the nuclear fusion on the earth is that the very high temperature ionized particles, forming a plasma can be controlled by a magnetic field, called magnetically confined plasma. This is essential, because no material can be sustained against such high temperature reached in a fusion reactor. Tokamak is a device which uses a powerful magnetic field to confine a hot plasma in the shape of a torus. It is a demanding task to achieve a sufficiently good confinement in a tokamak for a ‘burning plasma’ due to various kinds of plasma instabilities.

One of the critical unsolved problems is MHD (MagnetoHydroDynamics) instabilities in the fusion plasmas. The MHD instabilities at the plasma boundary damages the plasma facing component of the fusion reactor. One of techniques to control the MHD instabilities is injection of pellets (small deuterium ice bodies). The physics of the interaction between pellet ablation and MHD dynamics is very complex, and uncertainties still remain regarding the theoretical physics as well as the numerical modelling point of view. The simulation of the plasma physics, which includes wide range of spatio-temporal scales, especially, the non-linear interaction of plasma particles and magnetic fields requires significantly large computing resources within highly sophisticated numerical scheme. Numerical modelling of MHD instabilities and the control by pellet injection for existing fusion experiment machines has been carried out with the non-linear MHD code JOREK (www.jorek.eu) using supercomputers. JOREK is one of the recognized codes in the fusion community as it allows to determine the consequences caused by the MHD instabilities in fusion plasmas. The numerical experiment of the pellet injection studies contributes the design and the optimization of the pellet injector and the injection conditions in the fusion devices.

In this seminar, our recently published work which shows good agreement in qualitative and quantitative comparison between JOREK simulation and experimental observation will be presented [S. Futatani et al., Nucl. Fusion 60 026003 (2020); S. Futatani et al., Nuclear Fusion 61, 046043 (2021)].

In parallel to the numerical modellings of fusion plasmas in tokamaks, the simulations of stellarator which is alternative fusion device to tokamak, have been carried out. Stellarator exploits strangely-shaped magnets that is hard to build but potentially easier to operate, so it is considered as an alternative promising future fusion device. Non-linear MHD simulations of stellarator plasma have been carried out with Japanese-made simulation code, MIPS. In this seminar, the MHD simulation results of stellarator plasma obtained by MIPS code which has been published in these years will be presented [Shimpei Futatani and Yasuhiro Suzuki 2019 Plasma Phys. Control. Fusion 61 095014].

I worked on cold atomic and optical systems and investigated non-classical properties of these systems during my PhD. In this talk, I will start with very brief introduction of cold atoms and present two projects of my work. The project I will talk about first is about spin-orbit coupling in ultracold gases. Spin-obit coupled (SOC) systems have become an interesting laboratory for exploring new physics in ultracold gases. However, as condensates are only weakly correlated, the influence of interactions on the spin-orbit coupling is only weak. In the project, we have explored the influence of strong contact interactions on a SOC quantum system, using exact solutions to the paradigmatic two particle model. Several distinct effects that are not present in the mean-field limit can be identified. Even though the system we consider is bosonic, we find that a regime exists in which the competition between the contact and spin-orbit interactions results in the emergence of a ground state that contains a significant contribution from the anti-symmetric spin state. 

The second topic is about proposing a new condition for quantum simulation. If one aims to perform quantum simulation, one usually designs a system such that its Hamiltonian or time evolution operator is the same as the target system. This often requires quantum simulators to be quite complex setups. In this work, we have proposed a way to relax the requirement by not only designing the Hamiltonian but also considering the initial state. As an example, we showed that one-axis twisting, which is the dynamics governed by infinite range interactions, can be simulated by using a nearest-neighbour interaction system (Heisenberg XXX model) with an external field.

The recent revolution of lasers with increased power and shorter pulse length opens new possibilities for fusion for energy. Two ideas are taken from recent research. One is from high energy heavy ion research, that Quark Gluon Plasma (QGP) may burn (hadronize) simultaneously, i.e. across a hyper-surface with time-like normal, without Rayleigh-Taylor instabilities. The other new idea comes from nano-technology, that nano-antennas embedded in the target, may modify the laser light absorption in a way that this simultaneous ignition can be achieved. The way to do this was patented in 2017 by L.P. Cs., N. Kroo & I. Papp. 

The experimental verification of these ideas are in progress at the Wigner R.C.P. at lower, mJ, energies. Amplification of laser light absorption is already verified. The verification of simultaneous transition in the whole volume is coming soon. Expectedly in November, the near 30 J short pulse laser will be installed and become available at ELI-APLS in Szeged, Hungary.

Recent development in multi-messenger astronomy leading to a wealth of new observational results through gravitational waves (LIGO/VIRGO) and X-ray spectra (NICER) have opened new possibilities to understand hadronic matter at densities at and beyond our terrestrial reach. They provide new constraints to the theories of nuclear physics, where an absolute  energy density functional from ab-initio modelling is still not available.

General relativity guarantees that there is a unique one-to-one correspondence between static observables of neutron stars such as mass-radius relation or tidal deformability and equation of state (EoS) of beta equilibrated matter. However, these static properties are not enough to predict the composition of the interiors of neutron stars. In this talk, I will present EoS meta-modelling technique which was developed in our group, particularly to emphasize that even within pure nucleonic assumption, there is a big room for ambiguity in the composition. I will also demonstrate how recent observational data put bounds on the high density nucleonic matter using this (nucleonic) meta-modelling approach.

The interacting conditional wavefunction approach is a recently introduced method for performing quantum dynamics simulations that is multiconfigurational by construction, and hence that is able to capture quantitative accuracy for situations where mean-field theory fails. The technique is highly parallelizable and reformulates the traditional "curse of dimensionality" by using a stochastic wavefunction ansatz that is based on an interacting set of single-particle conditional wave functions. Despite the successes of the method to describe non-equilibrium quantum processes in model systems, the efficiency of the method for describing the dynamics of real systems is yet to be proven. A particular drawback of the method is the lack of a consistent solution of the time-independent Schrödinger equation, which makes the applicability of the method limited to systems for which, e.g., the ground state can be exactly calculated. We have recently filled this gap by putting forth an imaginary-time variation of the method. I will provide a throughout revision of the real- and imaginary-time versions of the method and show the ability of the method for capturing static and dynamic properties in model systems made of interacting electrons, nuclei and photons.

We report on our calculation of the hypertriton partial decay rate Γ(Hyp --> 3He + π^-). Our calculation uses full three-body hypertriton and 3He wave functions, computed with the no-core shell model (NCSM) and taking as input the NNLOsim NN+NNN and LO YN effective field theory Hamiltonians. 

The hypertriton wave function includes Σ-Λ admixtures, and we consider both weak vertices in the matrix element, Λ→N + π and Σ→N+π. The small Sigma probability in the hypertriton, P<0.5%, enhances the decay rate by about 10%. This effect is more than countered when the Coulomb distortion of the outgoing pion wave is considered, which decreases the rate by ~15%. 

Considering both effects, the decay rate evaluates to Γ=1.265 GHz. Γ is found to be strongly correlated with the Lambda separation energy B(Λ), not precisely determined by the state of the art nuclear Hamiltonians. This can be tracked down to the main contribution to the matrix element, coupling the deuteron-baryon components of hypertriton and ^3He amplitudes. Using the world average ratio R_3=Γ(Hyp --> 3Ηe+ π^-)/Γ_{π^-}(Hyp)=0.35 ± 0.04 and the isospin ΔI=1/2 rule, we derive a value for the hypertriton lifetime and show how it correlates with B(Λ).

Over the past decade, ab initio methods for finite nuclei have expanded their reach towards heavier nuclei and gained both in precision and complexity. With further progress and developments to be expected, the formal work is bound to take increasingly more time and errors to happen. This can hopefully be circumvented by developing safe and fast automated tools to generate the necessary expressions for the final numerical codes.

In this seminar, after introducing recent progress in ab initio methods [1,2], I will present the automated diagram generator ADG [3,4], focusing on its use for the recently-proposed Bogoliubov In-Medium Similarity Renormalization Group (BIMSRG) approach [5]. By generating automatically the diagrams and associated expressions at arbitrary orders in a given formalism in a safe way, such a tool can help fast-track the development of new formalisms or the implementation of older ones at higher precision, reducing the time to high-precision physical results.

[1] H. Hergert, Front. Phys. 8, 379 (2020), https://doi.org/10.3389/fphy.2020.00379

[2] P. Arthuis, C. Barbieri, M. Vorabbi and P. Finelli, Phys. Rev. Lett. 125 18, 182501 (2020), https://doi.org/10.1103/PhysRevLett.125.182501

[3] P. Arthuis, T. Duguet, A. Tichai, R.-D. Lasseri and J.-P. Ebran, Comput. Phys. Commun. 240, 202-227 (2019), https://doi.org/10.1016/j.cpc.2018.11.023

[4] P. Arthuis, A. Tichai, J. Ripoche and T. Duguet, Comput. Phys. Commun. 261, 107677 (2021), https://doi.org/10.1016/j.cpc.2020.107677

[5] A. Tichai, P. Arthuis, H. Hergert and T. Duguet, arXiv:2102.10889 [nucl-th] (2021), https://arxiv.org/abs/2102.10889

In this seminar, I will discuss the recent progress in connecting the symmetry-projected Generator Coordinate Method (PGCM) [1,2], which has been used for decades in the context of energy density functional (EDF) calculations, to the ab initio project. First, I will present the new numerical suite TAURUS [3] that is under development at the Universidad Autónoma de Madrid and that can perform very general variational calculations exploring the space of symmetry-projected Bogoliubov quasiparticle states and using state-of-the-art chiral interactions. Then, I will present the newly proposed In-Medium Generator Coordinate Method (IMGCM) that merges the PGCM with the In-Medium Similarity Renormalization Group (IMSRG) approach into a single consistent many-body technique. Finally, I will show first results concerning the calculation of the nuclear matrix elements for the neutrinoless double beta decay from first principles [4].

[1] J. J. Griffin and J. A. Wheeler, Phys. Rev. 108, 311 (1957). https://doi.org/10.1103/PhysRev.108.311

[2] B. Bally and M. Bender, Phys. Rev. C 103, 024315 (2021). https://doi.org/10.1103/PhysRevC.103.024315

[3] B. Bally, A. Sánchez-Fernández, and T. R. Rodríguez, Eur. Phys. J. A 57, 69 (2021). https://doi.org/10.1140/epja/s10050-021-00369-z

[4] J. M. Yao, B. Bally, J. Engel, R. Wirth, T. R. Rodríguez, and H. Hergert, Phys. Rev. Lett. 124, 232501 (2020). https://doi.org/10.1103/PhysRevLett.124.232501

Neutron stars unite many extremes of physics which cannot be recreated on Earth, making them excellent cosmic laboratories to study dense matter. One exciting characteristic is the presence of superfluid and superconducting components in mature neutron stars. Albeit created under very different circumstances, such macroscopic quantum behaviour exhibits many similarities with terrestrial condensates such as superfluid phases in helium, ultra-cold atomic gases, heavy-ion collisions or superconducting transitions in metals. In this talk, I will focus on the last relationship and discuss how we can describe the interiors of neutron stars by means of a two-component Ginzburg-Landau model, a framework well-known from the study of laboratory superconductors. By adapting this description to the neutron star interior and connecting it with realistic superfluid parameters and equations of state (specifically the Skyrme functional), we are able to determine the equilibrium properties of the superconducting component throughout the entire neutron star core. I will present the phase diagrams resulting from these analyses and discuss how our new approach can provide insights into the microphysical magnetic flux distribution in neutron star interiors.

The difference in the level of understanding between baryonic systems containing strangeness and the usual nuclear matter is so large due to the scarcity of experimental data. This limits the constraints that can be put on the low-energy coefficients appearing in the effective field theory (EFT) Lagrangian describing the interaction between two non-relativistic octet baryons. Trying to bridge this gap is lattice QCD, a demanding numerical approach to solve the complex dynamics of strongly-interacting systems. In this talk, I will present the results obtained by the NPLQCD collaboration for two octet-baryon systems, with strangeness ranging from 0 to -4, at two sets of quark masses that are heavier than those in nature [1,2]. In particular, I will present their scattering parameters and binding energies, as well as the constraints on the relevant EFT coefficients. The findings point to interesting symmetries observed in hypernuclear forces as predicted in the limit of QCD with a large number of colors.

[1] M. L. Wagman et al. (NPLQCD) Baryon-Baryon Interactions and Spin-Flavor Symmetry from Lattice Quantum Chromodynamics, Phys. Rev. D 96, 114510 (2017); arXiv:1706.06550 [hep-lat]

[2] M. Illa et al. (NPLQCD) Low-energy Scattering and Effective Interactions of Two Baryons at mπ ∼ 450 MeV from Lattice Quantum Chromodynamics; arXiv:2009.12357 [hep-lat]

The present knowledge of particle physics is based on the Standard Model (SM), which is an acknowledged theory of fundamental interactions and all known elementary particles. However, recent solar-neutrino experiments have proved that neutrinos have a non-zero mass, which conflicts with the SM as we know it. This signifies that the SM's perception of neutrinos is not accurate, making the search of new physics Beyond the Standard Model (BSM) most intriguing. Currently, the most practical way to access the yet-to-be-determined properties of neutrinos is observing neutrinoless double-beta (0νββ)  decay.

In this seminar, I will introduce my dissertation research in which I studied probing 0νββ decay by exploiting available data on charge-exchange reactions and ordinary muon capture. I studied the strength distributions of these processes in the isobaric triplets corresponding to ββ-decay of the key 0νββ-decay candidates in the pnQRPA framework. By studying these strength distributions we can not only probe the intermediate states 0νββ decay (see the figure), but also eventually shed light on the unknown effective values of the couplings in wide excitation-energy and momentum-exchange regions relevant for 0νββ decay. 

I will also cover some future directions for my postdoctoral research period at the University of Barcelona. The main aim is to extend the recent large-scale nuclear shell-model calculations of coherent elastic neutrino-nucleus scattering to inelastic scattering, heading up to high energies utilising pnQRPA.

[The dissertation study has been published in the University of Jyväskylä's dissertation series JYU Dissertations, number 288, Jyväskylä 2020. ISBN 978-951-39-8304-8 (PDF), URN: ISBN: 978-951-39-8304-8, ISSN 2489-9003. The publication is available in  the JYX publication archive at: https://jyx.jyu.fi/handle/123456789/71822]

Beside quark-antiquark meson and three-quark baryons, quantum chromodynamics predicts that other types of quark and gluon configurations could bind into hadron resonances. During the last decade, a lot of theoretical and experimental efforts have been devoted to the  search of tetraquark, pentaquark and hybrid mesons. Several candidates have been observed by experimental collaborations but the interpretation of these signals requires a joint collaboration between phenomenologists and experimentalists. In this talk, I'll review the challenges of discovering and interpreting exotic hadrons, with a particular attention to the lightest hybrid meson.

Density Functional Theory (DFT) and the so called ab initio methods constitute two different and complementary approaches to the nuclear many-body problem. While the latter encounter computational limitations, the former is currently the only available method that can be applied to the whole nuclear chart. DFT allows the study of both ground state properties and nuclear excitations, and finds successful applications in nuclear structure and nuclear astrophysics. 

I will briefly introduce the strong synergy between “heaven and earth” which is instrumental in the study of the nuclear Equation of State (EoS). That is, the relevance of ground experiments as well as accurate astronomical observations on neutron stars and gravitational waves to shed light into one of the most challenging problems of our times: how does subatomic matter organize itself.

On the basis of DFT, I will present our recent proposed solution to the apparent inconsistency between our current knowledge of the EoS, the energy of the isobaric analog state (IAS) in a heavy nucleus such as ²⁰⁸Pb (see a simple example in the figure for ⁹⁰Zr), and the isospin symmetry breaking forces in the nuclear medium [1]. This is achieved by performing state-of-the-art IAS calculations that include all isospin symmetry breaking contributions. To this aim, we propose a new energy density functional that is successful in reproducing the IAS excitation energy without compromising other properties of finite nuclei. Applications to the mass radius relation of a cold non-accreting neutron star will be briefly discussed. 

Future perspectives on the efforts of building more accurate nuclear energy density functionals will be also given.   

[1] X. Roca-Maza, G. Colò, and H. Sagawa, Phys. Rev. Lett. 120, 202501 (2018); arXiv:1803.09120

Neutrinoless double-beta (0νββ) decay is a proposed nuclear decay which turns out to be the most promising process to observe lepton number violation in the laboratory, and to establish whether neutrinos are its own antiparticle. Due to this unique potential, several international collaborations are actively searching for this rare decay, among them the NEXT experiment running at the Canfranc Underground Laboratory, in the Spanish Pyrenees. In order to plan these searches, estimations for the decay lifetimes, which are known to exceed 10^26 years, are crucial. However, the decay rate depends quadratically on nuclear matrix elements (NMEs) which are not well known, as state-of-the-art nuclear structure methods predict NMEs disagreeing by factors 2-3. An alternative avenue to learn about 0νββ NMEs is to find other observables correlated with 0νββ decay that may be easier to access experimentally. In this seminar, I will discuss results for double dipole magnetic (M1M1) transitions, which show a good correlation with 0νββ decay. This could be used to constrain 0νββ NMEs from measurements of nuclear 2γ M1M1 decays.

The realization of efficient and controlled interactions between photons and atomic media, or other quantum emitters, is a central goal within quantum optics. Photon loss — re-scattering of a photon into unwanted directions — represents a fundamental limitation to this aim. In typical atomic ensemble models, the atoms are assumed to emit independently and in an uncorrelated fashion. This paradigm however, is expected to break down for dense and ordered atomic arrays, where interference between emitted photons from different atoms becomes relevant, and can give rise to exciting phenomena such as the well known "super-" and "sub-radiance", with a strong modification of the atomic collective photon emission.

In this talk, we will provide a comprehensive treatment of this problem, and show through several examples that it is possible to take advantage of cooperative light-scattering in dense atomic ensembles. This includes a dramatic suppression of the error in single photon storage and retrieval [1, 2], the enhancement of excitation transport between two ring-shaped nano-structures [3], or an enhanced single-photon absorption by one of these rings when a single absorptive emitter is placed at its center [4].

[1] A. Asenjo-Garcia, M. Moreno-Cardoner, A. Albrecht, H. J. Kimble, and D. E. Chang, Phys. Rev. X 7, 031024 (2017).

[2] M. T. Manzoni, M. Moreno-Cardoner, A. Asenjo-Garcia, J. V. Porto, A. V. Gorshkov, and D. E. Chang, New Journal of Physics 20, 083048 (2018).

[3] M. Moreno-Cardoner, D. Plankensteiner, L. Ostermann, D. E. Chang, and H. Ritsch, Phys. Rev. A 100, 023806 (2019).

[4] M. Moreno-Cardoner, D. Holzinger, and H. Ritsch, arXiv:2010.09771 (2020).

The modeling of nuclear structure properties of neutron-rich nuclei is a crucial ingredient for understanding the production of heavy elements during the rapid neutron capture process (or r process). In order to properly interpret future kilonova observations, sensitivity studies addressing the impact of nuclear theoretical uncertainties are required. In this talk, I will present some recent network calculations based on nuclear input obtained within the Density Functional Theory (DFT) framework. In particular, I will focus in the role of nuclear masses and fission properties in the production of translead nuclei, and the possible implications for the electromagnetic counterparts produced during neutron star mergers. In the second part of this talk, I will introduce some recent advances regarding the large-scale DFT calculation of fission fragments distributions and the estimation of theoretical uncertainties using Bayesian machine-learning techniques.

The quark-gluon plasma (QGP) is expected to be produced with heavy-ion collisions at RHIC and LHC at very high temperatures and vanishing baryon densities. Due to the large mass and relaxation time of the c quark, charmed mesons are a powerful probe of the QGP and a proper theoretical understanding of their propagation in a hot medium is required. While lattice QCD is becoming an increasingly important tool in this regime, we employ a complementary theoretical approach that allows us to reach the QGP transition from the hadronic phase. In particular, we study the modification of open-charm mesons in a hot mesonic medium below Tc  within an effective field theory based on chiral and heavy-quark spin-flavor symmetries within the imaginary-time formalism [1,2]. The in-medium unitarized amplitudes of the scattering of the heavy mesons with the pseudoscalar light mesons and the ground-state self-energies are calculated self-consistently. I will show that the  D(*) and D_s(*) mesons acquire a substantial width and their masses drop with increasing temperatures, and that the excited mesonic states generated dynamically in our heavy-light molecular model (D_0^*(2300),  D_1^*(2430), D_{s0}^*(2317) and D_{s1}^*(2460)) are also modified in a thermal medium. Besides, from the thermal ground-state spectral functions, we have computed for the first time open-charm Euclidean correlators that can be compared with those obtained with lattice QCD [3].

[1] G. Montaña, A. Ramos, L. Tolos and J. M. Torres-Rincon, Phys. Lett. B 806 (2020), 135464 doi:10.1016/j.physletb.2020.135464 [arXiv:2001.11877].

[2] G. Montaña, A. Ramos, L. Tolos and J. M. Torres-Rincon, (Submitted to Phys.Rev.D) [arXiv:2007.12601].

[3] G. Montaña, O. Kaczmarek, L. Tolos and A. Ramos, (Submitted to Eur.Phys.J.A) [arXiv:2007.15690].

Machine learning techniques are ubiquitous in science, and nuclear physics is not an exception. Neural networks have found a variety of nuclear physics applications in the past, including capturing systematic trends in data. Recently, machine learning tools have also been used to solve directly for the properties of quantum many-body fermionic and bosonic systems. These developments open the door for a first-principles machine learning description of atomic nuclei. I will discuss the embryonic applications of these techniques to few-body nuclear systems, and lay down some of the challenges ahead. 

Keeble & Rios, Physics Letters B 809 135743 (2020); arxiv:1911.13092

By means of energy and orthogonality considerations we optimize the computation of nuclear matrix elements for neutrinoless double-β (0νββ), calculated using the generator-coordinate method with symmetry-restored constrained mean-field states. A selection mechanism is proposed to choose the most relevant mean-field states, giving the major contributions to the NME. We calculate the NME of the 76Ge→76Se transition using the quadrupole deformations and the isoscalar pairing coordinate as relevant constrained degrees of freedom. Our results show that not all states are necessary to be included in the GCM calculation, reducing the computational cost of solving the Hill-Wheeler-Griffin equation.