The INT has a new website! Please visit the S@INT Seminars page on our new site.

Please visit the above link to access information on recent and upcoming S@INT seminars.

Information on S@INT seminars that took place between April, 2018 and December, 2020 can be found below.

If you have questions or feedback about the INT website, please contact us at intmail@uw.edu

Online Seminar:

"Deconstructing General-Relativistic Viscous Fluid Dynamics"

Jorge Noronha, University of Illinois at Urbana-Champaign

Thursday, December 10, 2020, 10:30 AM Pacific Time

Abstract:

With the dawn of the multi-messenger astronomy era marked by the detection of a binary neutron star merger, it became imperative to understand how extremely dense fluids behave under very strong gravitational fields. In this talk I will critically review the foundations of relativistic viscous fluid dynamics and its formulation in curved spacetime. I will present the first set of fluid dynamic equations that satisfies all of the following properties: (a) the system when coupled to Einstein’s equations is causal and strongly hyperbolic (the initial value problem is well-posed); (b) equilibrium states are stable; (c) all leading dissipative contributions are present, i.e., shear viscosity, bulk viscosity, and thermal conductivity; (d) effects from non-zero baryon number are included; (e) entropy production is non-negative in the regime of validity of the theory. The properties above hold in the nonlinear regime without any simplifying symmetry assumptions and are mathematically rigorously established. This is achieved using a new formulation of relativistic fluid dynamics containing only the hydrodynamic variables and their first-order derivatives. The framework presented here provides the starting point for systematic investigations of general-relativistic viscous phenomena in neutron star mergers.

Zoom link will be available via announcement email, or by contacting: ikolbe[at]uw.edu

Online Seminar:

"Hot Neutrons From The Lattice" [PDF]

Neill C. Warrington, Institute for Nuclear Theory

Tuesday, November 24, 2020, 10:30 AM Pacific Time

Abstract:

I present a model-independent calculation of the structure factors of neutron matter using a lattice formulation of leading-order pionless effective field theory. I analyze conditions relevant to both neutron star mergers and supernovae, where precise knowledge of these quantities is valuable. Importing methods from lattice QCD, all errors, both systematic and statistical, are controlled for.

Zoom link will be available via announcement email, or by contacting: ikolbe[at]uw.edu

Online Seminar:

"Heavy-Quark Brownian Motion and sQGP"

Ralf Rapp, Texas A&M University

Thursday, October 22, 2020, 10:30 AM Pacific Time

Abstract:

The microscopic properties of the strongly coupled quark-gluon plasma (QGP) remain a topic of great current interest. We discuss a quantum many-body approach based on quark and gluon degrees of freedom that tries to address this challenge. Its starting point is the heavy-flavor sector where the large masses of the charm and bottom quarks enable substantial simplifications in the treatment of the in-medium one- and two-body correlation functions. The key ingredient is the in-medium two-body force which we constrain through lattice-QCD data for the heavy-quark free energy and euclidean quarkonium correlation functions. We apply this framework to compute transport parameters for heavy-quark diffusion and quarkonium kinetics and pertinent observables in heavy-ion collisions. Finally, based on a fit to the lattice-QCD equation of state using thermal quark and gluon masses, we proceed to analyze the spectral and transport properties of the QGP. Remnants of the confining force in the QGP are found to play a dual role of generating its strong-coupling behavior while also triggering a transition from melting-parton to broad hadronic-bound state degrees of freedom.

Zoom link will be available via announcement email, or by contacting: ikolbe[at]uw.edu

Online Seminar:

"Discrete Scale Invariance and Structure"

U. van Kolck, Centre National de la Recherche Scientifique and University of Arizona

Thursday, October 8, 2020, 10:30 AM Pacific Time

Abstract:

When nonrelativistic particles interact through short-range forces near the unitarity limit, the two-body system is approximately scale invariant. Renormalization for more-body systems requires a three-body force, which lies on a limit cycle and breaks the symmetry to a discrete subgroup. The remaining, approximate discrete scale invariance gives rise to nearly geometric towers of excited states, including the famous Efimov three-body spectrum. In leading order, all energies are related through the one dimensionful parameter of the three-body force, an example being the Tjon correlation between three- and four-body ground-state energies. I discuss the implications for larger systems, in particular saturation for bosons (such as certain atoms near Feshbach resonances) and clustering for (multi-component) fermions (such as nucleons).

Zoom link will be available via announcement email, or by contacting: ikolbe[at]uw.edu

Online Seminar:

"Relativistic Navier-Stokes equations" [PDF]

Pavel Kovtun, University of Victoria

Thursday, September 24, 2020, 10:30 AM Pacific Time

Abstract:

It has been widely believed that the relativistic Navier-Stokes equations violate the basic physical requirements of equilibrium stability and causality, and therefore can not be used for practical simulations of relativistic fluids. In this talk, I will discuss why this belief is unfounded. There is not one, but infinitely many Navier-Stokes equations because there are infinitely many conventions that can be used to define what one means by "fluid temperature", "fluid velocity" etc. out of equilibrium. The early works on relativistic hydrodynamics (Eckart, Landau-Lifshitz) have indeed adopted conventions that lead to unphysical predictions. On the other hand, when one adopts physically sensible conventions, the resulting relativistic Navier-Stokes equations are both stable and causal.

Zoom link will be available via announcement email, or by contacting: ikolbe[at]uw.edu

Online Seminar:

"Progress in nuclear quantum Monte Carlo" [PDF]

Alessandro Lovato, Argonne National Lab

Tuesday, September 15, 2020, 10:30 AM Pacific Time

Abstract:

The last decades have witnessed tremendous progress in nuclear many-body theory, aiming to understand how nuclei emerge from the individual interactions among protons and neutrons. Effective field theories exploit the symmetries of quantum chromo-dynamics to construct realistic nuclear potentials and consistent electroweak currents in a systematic fashion. They are the input to “ab-initio” many-body methods that solve the many-body Schrödinger equation with controlled approximations. Among them, quantum Monte Carlo approaches are known for their accuracy and capability to treat on the same footing long-range structure and short-range dynamics of nuclear systems. I will report on recent quantum Monte Carlo progresses towards a comprehensive description of the spectrum of light nuclei, their interactions with neutrinos, and the nucleonic matter equation of state. A novel representation of the nuclear many-body wave function in terms of artificial neural networks, suitable to extend the reach of quantum Monte Carlo to medium-mass nuclei, will also be discussed.

Online Seminar:

"r-process: from simulations to observations and back"

Almudena Arcones, Technische Universität Darmstadt

Thursday, September 3, 2020, 10:30 AM Pacific Time

Abstract:

Our understanding of the origin of heavy elements by the r-process has made great progress in the last years. In addition to the gravitational wave and kilonova observations for GW170817, there have been major advances in the hydrodynamical simulations of neutron star mergers and core-collapse supernovae, in the microphysics included in those simulations (neutrinos and high density equation of state (EoS)), in galactic chemical evolution models, in observations of old stars in our galaxy and in dwarf galaxies. This talk will discuss these new advances. First, we will explore the impact of the EoS in neutron star merger nucleosynthesis and kilonova. Investigation of the EoS in core-collapse supernovae demonstrates that the effective mass governs the neutron star contraction. We will then discuss the first magneto-rotational supernova simulations with detailed neutrino transport and their nucleosynthesis. Observations of old stars and meteorites can strongly constrain the astrophysical site of the r-process, once the nuclear physics uncertainties of extreme neutron-rich nuclei are reduced by experiments and by improved theoretical models.

Online Seminar:

"Quark matter in the cores of neutron stars"

Aleksi Kurkela, Stavanger University

Thursday, August 27, 2020, 10:30 AM Pacific Time

Abstract:

Neutron stars are the densest astrophysical objects in the universe. Cores of neutron stars reach densities that are as high as those realized in ultrarelativistic heavy-ion collisions where ordinary nuclear matter melts into a new phase of matter, the quark matter. This naturally raises the question: does quark matter also exist inside neutron stars? In my talk, I describe how recent advancements in theory of superdense matter and in observations of neutron stars—such as the LIGO/Virgo detection of gravitational waves arising from a merger of two neutron stars—can inform us about what lies in the centers of neutron stars. I discuss how the different constraints point to the existence of quark matter in the cores of most massive neutron stars.

Online Seminar:

"Efficient emulators for scattering using eigenvector continuation" [PDF]

Xilin Zhang, The Ohio State University

Thursday, August 13, 2020, 10:30 AM Pacific Time

Abstract:

Bayesian inference is increasingly favored for uncertainty quantification in nuclear physics, but its parameter estimation generally requires Monte Carlo sampling of a model’s parameter space. Each evaluation of the model’s prediction may be so computationally expensive that the inference becomes infeasible. Eigenvector continuation (EC), as coupled with variational method, has recently shown that it can be used as an efficient and accurate emulator to ameliorate this problem for computing nuclear bound-state properties from chiral effective field theory (Chiral EFT) Hamiltonians [1909.08446, 1910.02922].

In this talk, I will discuss our extension [2007.03635] of this approach to two-body scattering, by combining Kohn variational method with the EC. Tests of the emulators will be presented for the scatterings from various potentials. The efficiency will also be discussed. I will briefly mention our ongoing generalization of the method to the three-body systems. These emulators would have a wide range of applications, such as fitting the Chiral EFT to nucleon-deuteron scattering data and nuclear optical potentials to nuclear scattering/reaction data. I will also speculate how this method could be applied to analyze the results from ab initio calculations, including Lattice QCD and a newly developed Luscher-type calculation [2004.13575] for low-energy nuclear scattering.

Online Seminar:

"Exotic Atoms and Molecules for Nuclear Science" [PDF]

Ronald Garcia Ruiz, MIT

Thursday, August 6, 2020, 10:30 AM Pacific Time

Abstract:

Precise knowledge of the interaction between the atomic nucleus and the surrounding electrons offers a complementary insight into the atomic nucleus and the fundamental particles and forces of nature. Exotic atoms and molecules - those containing nuclei with extreme proton-to-neutron ratios - can be made to investigate a particular nuclear structure or symmetry-violating effect. Thereby offering high sensitivity to explore diverse nuclear phenomena, to study the violation of fundamental symmetries, and to search for new physics. In this seminar, I will present recent highlights from laser spectroscopy experiments of these exotic species, containing isotopes produced in extreme regions of the nuclear chart. The relevance of these results to some of the pressing questions of nuclear science will be discussed.

Online Seminar:

"From quarks to nuclei: machine learning the structure of matter" [PDF]

Phiala Shanahan, MIT

Thursday, July 23, 2020, 10:30 AM Pacific Time

Abstract:

With advances in supercomputing, we are beginning to quantitatively understand nuclear structure and interactions directly from the fundamental quark and gluon degrees of freedom of the Standard Model. Recent studies provide insight into the neutrino-nucleus interactions relevant to long-baseline neutrino experiments, double beta decay, and nuclear sigma terms needed for theory predictions of dark matter cross-sections at underground detectors. The rapid progress in this field has been possible because of new algorithms, but challenges still remain to achieve full systematic control. I will describe the physics challenges, and outline how new machine learning tools have the potential to provide a revolutionary way to enable currently-intractable calculations to reveal the physics of nuclei from the Standard Model.

Online Seminar:

"Exotica and Heavy Ion Collision"

Su Houng Lee, Yonsei University

Thursday, July 9, 2020, 10:30 AM Pacific Time

Abstract:

Relativistic heavy ion collisions provide an excellent venue to produce some of the recently observed and theoretically proposed exotic states because they contain heavy quarks, which are profusely produced in these experiments. We first discuss the difference between a molecular configuration and a compact multiquark states from the view point of the short distance interaction between hadrons using a quark model. We then point out possible flavor exotic states and why heavy quarks are needed to make them more stable. We finally show how measurements in heavy ion can be used to discriminate the structure of exotic particles. Some comments are made about the recent measurements of X(3872) in heavy ion collision.

Online Seminar:

"Nucleon Electromagnetic Form Factors - Measurements, Meanings and Messages" [PDF]

Gerald A. Miller, University of Washington

Thursday, June 18, 2020, 10:30 AM Pacific Time

Abstract:

Electron scattering measurements at JLab, Mainz and Bates have led to substantial changes in our understanding of the proton and neutron. The key results and their interpretation will be reviewed. The essential findings are that the non-relativistic quark model is not accurate, the proton is not round, the charge density of the neutron is determined by the pion cloud, and the central charge density of the neutron is negative.

Online Seminar:

"Asymptotically Free Quantum Fields from Dimensional Reduction of Discrete Variables"

Uwe-Jens Wiese, Institute for Theoretical Physics,

Albert Einstein Center for Fundamental Physics, Bern University

Thursday, June 4, 2020, 10:30 AM Pacific Time

Abstract:

Quantum Chromodynamics (QCD) --- the (3+1)-d asymptotically free SU(3) gauge theory that describes the strong interaction --- is usually formulated in terms of fundamental quark and gluon fields. CP(N-1) models in (1+1)-d have a global SU(N) symmetry and share many features with QCD. They are also asymptotically free, have a non-perturbatively generated mass gap, and non-trivial theta-vacuum states. CP(N-1) models can be regularized unconventionally by using discrete SU(N) quantum spins forming a (2+1)-d spin ladder that consists of n transversely coupled quantum spin chains. The (1+1)-d asymptotically free CP(N-1) fields then emerge from dimensional reduction when n is increased. Even n leads to the vacuum angle theta = 0, while odd n leads to theta = pi. In a similar way, gluon fields emerge naturally from the dimensional reduction of (4+1)-d quantum links, which are discrete gauge variables that generalize quantum spins. In this formulation quarks arise as domain wall fermions. In contrast to the usual quantum fields, quantum spins and quantum links realize asymptotically free field theories with finite-dimensional local Hilbert spaces. This is advantageous in the context of quantum simulation experiments. Both CP(N-1) models and QCD can be quantum simulated with ultra-cold alkaline-earth atoms in optical super-lattices. When CP(N-1) models are studied at non-zero chemical potential, non-trivial condensed matter physics arises in these quantum field theories. In particular, there are Bose-Einstein condensates, with or without ferromagnetism.

Zoom link will be available via announcement email, or by contacting: stroberg[at]uw.edu

Online Seminar:

"Effective Field Theory Approach to Neutrinoless Double Beta Decay" [PDF]

Vincenzo Cirigliano, Los Alamos National Lab

Tuesday, May 26, 2020, 10:30 AM Pacific Time

Abstract:

In this talk I will discuss neutrinoless double beta decay and lepton number violation (LNV).

I will describe an end-to-end effective field theory (EFT) framework connecting the possibly very high scale at which LNV originates to the nuclear scale. Such a framework is crucial to assess the discovery potential and model diagnosing power of neutrinoless double beta decay searches. At the high-energy end, the EFT allows one to classify the various sources of LNV. At the low-energy end, the EFT allows one to organize contributions to hadronic and nuclear matrix elements in a systematic expansion, which is the basis to reach controlled uncertainties in the near future. I will discuss recent developments in the EFT approach and illustrate the framework through explicit examples, such as the high-scale seesaw and the TeV scale left-right-symmetric model.

Zoom link will be available via announcement email, or by contacting: stroberg[at]uw.edu

Online Seminar:

"Quantified Nuclear Structure Theory" [PDF]

Witold Nazarewicz

Department of Physics & Astronomy, and Facility for Rare Isotope Beams

Michigan State University

Thursday, May 14, 2020, 10:30 AM Pacific Time

Abstract:

To an increasing extent, theoretical nuclear physics involves statistical inference on computationally-demanding theoretical models that often combine heterogeneous datasets. Advanced statistical approaches can enhance the quality of nuclear modeling in many ways. First, the statistical tools of uncertainty quantification can be used to estimate theoretical errors on computed observables. Second, they can help to assess the information content of measured observables with respect to theoretical models and assess the information content of present-day theoretical models with respect to measured observables. Importantly, they can be used to understand a model's structure through parameter estimation and model reduction. Finally, statistical tools can improve predictive capability and optimize knowledge extraction by extrapolating beyond the regions reached by experiments to provide meaningful input to applications and planned measurements.

In this presentation, after presenting a brief summary of machine learning applications to low-energy nuclear theory, I will employ Bayesian machine learning tools to assess the predictive power of global mass models towards more unstable nuclei and provide uncertainty quantification of predictions. The proposed robust statistical approach to extrapolations can be useful for assessing the impact of current and future experiments in the context of model developments.

Zoom link will be available via announcement email, or by contacting: stroberg[at]uw.edu

Online Seminar:

"Advances in coupled-cluster computations of nuclei" [PDF]

Gaute Hagen, Oak Ridge National Laboratory

Thursday, April 30, 10:30 AM Pacific Time

Abstract:

In this talk I will report on recent advances in ab-initio coupled-cluster computations of nuclei starting chiral Hamiltonians with two- and three-nucleon forces. Using high precision coupled-cluster methods we addressed the quenching puzzle of β-decays in nuclei. We showed that this quenching can be explained from two-body currents and many-body correlations. In particular, we made predictions for the Gamow-Teller decay of the heavy nucleus ¹⁰⁰Sn [1,2], and our result is consistent with the recent high precision measurement at RIKEN [3]. I will also show very recent results for medium-mass nuclei and nuclear matter using optimized chiral interactions with explicit delta degrees of freedom. Binding energies, radii, and saturation properties in nuclear matter are improved compared to existing chiral Hamiltonians. We have also started computations of deformed nuclei using a coupled-cluster approach starting from a deformed Hartree-Fock reference state with promising results for nuclei up to mass A~50. Last, but not least, I will present a new method that allows for the computation of bulk properties of an atomic nucleus for a million of different model parameters in less than one hour on a standard laptop. The equivalent set of ab-initio coupled-cluster computations would require about 20 years. This speedup enables statistical computing of the chiral nuclear Hamiltonian, and entirely new ways to use experimental data across the nuclear chart to generate new knowledge about the strong nuclear interaction [4].

[1] T. D. Morris, et al, Phys. Rev. Lett. 120, 152503 (2018)

[2] P. Gysbers, et al, Nature Physics 15, 428–431 (2019)

[3] D. Lubos et al., Phys. Rev. Lett. 122, 222502 (2019)

[4] A. Ekström and G. Hagen, Phys. Rev. Lett. 123, 252501 (2019)

Zoom link will be available via announcement email, or by contacting: stroberg[at]uw.edu

Online Seminar:

"Light at the end of the tunnel: The Electron-Ion Collider and QCD at high energies" [PDF]

Raju Venugopalan, Brookhaven National Lab

Thursday, April 16, 10:30 AM Pacific Time

Abstract:

I will outline the science and status of the EIC. I will then discuss some of my on-going research on the infrared structure of QCD at high energies, with emphasis on the potential insight provided by new theory techniques and from unanticipated interdisciplinary connections.

Online Seminar:

"Surprises in large N Thermodynamics" [PDF]

Tom Cohen, University of Maryland

Thursday, April 2, 10:00 AM Pacific Time

Abstract:

The thermodynamic behavior of QCD at large N has been studied for decades. Despite this, there are a number of features that are not widely appreciated and are quite surprising. I this talk we note a few of these under the assumption that QCD has a generic first-order phase transition at large N as one sees for pure gauge theory. The existence of a first-order transition implies metastable phases. One surprise is that under this assumption large N QCD has a supercooled metastable plasma phase with negative absolute pressure---that is a pressure below that of the vacuum. Another surprise concerns the region beyond the endpoint of the superheated hadronic which, though both globally and locally unstable is never-the-less parametrically long lived at large N.

"Delineating the properties of neutron star matter in cold, dense QCD"

Toru Kojo, Central China Normal University

Thursday, February 27, 2020, 2:30 PM, PAT C421

All interested graduate students and faculty are invited to attend.

"Exact representations of many body interactions from Restricted Boltzmann Machine neural networks"

Ermal Rrapaj, University of Berkeley, University of Minnesota

Thursday, February 6, 2020, 2:30 PM, PAT C421

Abstract:

In recent decades, machine learning in the form of deep neural networks, has been effectively used in diverse industrial applications. In physics, deep learning has been used to analyse particle accelerator data, discover phases of matter, represent ground states of quantum many body systems, and accelerate numerical algorithms. This talk will focus on the Restricted Boltzmann Machine and how it can be used to derive exact representations of many body forces with applications in quantum Monte Carlo simulations and quantum annealing. I conclude with implications for training this type of architecture based on its connection to physical systems.

All interested graduate students and faculty are invited to attend.

"Constraining the equation of state of dense nuclear matter from multimessenger observations of binary neutron stars"

Collin Capano, Max Planck Institute for Gravitational Physics (Albert Einstein Institute) Hannover

Thursday, November 14, 2019, 2:30 PM, PAT C421

Abstract:

The first direct detection of a gravitational wave from a binary neutron star merger, GW170817, was also the first event to be observed both by gravitational-wave detectors and telescopes. These “multimessenger” observations provided an opportunity to constrain the equation of state of the dense nuclear matter inside of neutron stars. The equation of state determines the size of the stars, as well as how much they are tidally deformed as they spiral into each other. The stars' tidal deformability is encoded in the emitted gravitational wave. However, the gravitational wave is only weakly dependent on the these parameters, making the equation of state difficult to infer from gravitational-wave data alone. I will show how combining chiral effective field theory with multimessenger observations of GW170817 yields the most stringent constrains on neutron-star radii to date. I will also discuss the implications of this measurement for future detections.

All interested graduate students and faculty are invited to attend.

"Chiral charge dynamics in Abelian gauge theories at finite temperature "

Adrien Florio

Ecole Polytechnique Federale de Lausanne

Thursday, October 17, 2019, 2:00 PM, C421

Abstract:

The chiral anomaly present in the standard model can have important phenomenological consequences, especially in cosmology and heavy-ions physics. In this talk, I will focus on the contribution from the Abelian gauge fields. Despite an absence of topologically distinct sectors, they have a surprisingly rich vacuum dynamics, partly because of the chiral anomaly. I will present results obtained from real-time classical lattice simulations of a U(1) gauge field in the presence of a chiral chemical potential. They account for short distance fluctuations, contrary to effective descriptions such as Magneto-Hydrodynamics (MHD). I will discuss various phenomena, like inverse magnetic cascade, which occur in this system. In particular, in presence of a background magnetic field, the chemical potential exponentially decays. The associated chiral decay rate is related to the diffusion of the Abelian Chern-Simons number in a magnetic background, in the absence of chemical potential. The rate obtained from the simulations is an order of magnitude larger than the one predicted by MHD. If this result is shown to be robust under corrections such as Hard Thermal Loops, it will call for a revision of the implications of fermion number and chiral number non-conservation in Abelian theory at finite temperature.

All interested graduate students and faculty are invited to attend.

"Fission and lanthanide production in r-process nucleosynthesis"

Nicole Vassh

University of Notre Dame

Thursday, June 6, 2019, 3:00 PM, C421

Abstract:

The observations of the GW170817 electromagnetic counterpart suggested lanthanides were produced in this neutron star merger event. Lanthanide production in heavy element nucleosynthesis is subject to large uncertainties from nuclear physics and astrophysics unknowns. Specifically, the rare-earth abundance peak, a feature of enhanced lanthanide production at A~164 seen in the solar r-process residuals, is not robustly produced in r-process calculations. The proposed dynamical mechanism of peak formation requires the presence of a nuclear physics feature in the rare-earth region which may be within reach of experiments performed at, for example, the CPT at CARIBU and the upcoming FRIB. To take full advantage of such measurements, we employ Markov Chain Monte Carlo to "reverse engineer" the nuclear masses capable of producing a peak compatible with the observed solar r-process abundances and compare directly with experimental mass data. Here I will present our latest results and demonstrate how the method may be used to the learn which astrophysical conditions are consistent with both observational and experimental data. Uncertainties in the astrophysical conditions also make it difficult to know if merger events are responsible for populating the heaviest observed nuclei, the actinides. Here I will discuss a potential direct signature of actinide production in merger environments. However, an r process which reaches the actinides is also likely to host fission, which is largely experimentally uncharted for neutron-rich nuclei. The influence of fission on lanthanide abundances, and the potential for future experimental and theoretical efforts to refine our knowledge of fission in the r process, will be discussed. The question of where nature primarily produces the heavy elements can only be answered through such collaborative efforts between experiment, theory, and observation.

All interested graduate students and faculty are invited to attend.

"Scattering Observables from Lattice QCD: progress in three-particle channels"

Steve Sharpe

University of Washington

Thursday, March 21, 2019, 3:00 PM, C421

Abstract:

Lattice QCD calculations have made great strides towards calculating resonance properties and decay amplitudes in cases where only two-particle channels are present. This required development of both theoretical formalism and simulation methods. However, many problems of interest involve three-particle channels, e.g. the Roper resonance and K -> 3 pion decays and for these, the theoretical formalism to relate the finite-volume lattice results to infinite-volume scattering quantities has been lacking.

After reviewing methods and results involving two particles, I describe recent work with Raul Briceno and Max Hansen in which we have developed the needed formalism in a generic relativistic field theory of identical scalar particles, and present results from a numerical implementation of the formalism in the isotropic approximation.

I close with a discussion of work with Tyler Blanton and Fernando Romero-López in which we go beyond the isotropic approximation and include d-wave interactions.

All interested graduate students and faculty are invited to attend.

"Effective field theory of (magneto) hydrodynamics and its gravity dual"

Paolo Glorioso

University of Chicago

Thursday, February 28, 2019, 3:30 PM, C421

Abstract:

In the first part I will review our work on formulating hydrodynamics as an effective field theory (EFT), which is based on the Schwinger-Keldysh formalism and is implemented in terms of a suitable set of degrees of freedom and symmetries. I will then show how this leads to a well-defined systematic framework to compute loop corrections around the equations of motion of hydrodynamics. I will also show how the formalism extends to magnetohydrodynamics by adding suitable degrees of freedom associated to a magnetic 1-form U(1) symmetry. Finally, I will outline the holographic construction of the EFT of diffusion, which is a baby version of the EFT of hydrodynamics. A crucial ingredient in the holographic derivation is a new analytic continuation in a double-sided black brane geometry.

All interested graduate students and faculty are invited to attend.

"Direct Detection of Composite Dark Matter"

Dorota Grabowska

University of California, Berkeley

Thursday, February 7, 2019, 3:00 PM, C421

Abstract:

Strongly interacting theories generically give rise to composite bound states; a strongly interacting dark sector is no different. These bound states may be comprised of just a few constituents or an exponentially large number, depending on factors such as other forces present in the sector and the mass of the constituents themselves. I will first present several possible mechanisms for the formations of these Dark Matter bound states in the Early Universe. I will then discuss various avenues for detection, focusing particularly on their detectability using both current and near future direct detection experiments.

All interested graduate students and faculty are invited to attend.

"Spectroscopy on the lattice"

Raul Briceno

Jefferson Lab

Thursday, January 10, 2019, 2:00 PM, C421

Abstract:

In order to decipher the underlying rules governing the non-perturbative behavior of quarks and gluons inside the bound states of QCD, we must first determine and understand the spectrum of the theory. In recent years we have seen increased interest in hadron spectroscopy, triggered primarily by the experimental discovery of states that challenged previous existing conventions. Experimental data alone is not sufficient to confirm the existence of a state or provide a detailed picture of its nature. As a result, it is necessary to carry a parallel theoretical program, and lattice QCD is the natural tool to base this effort on. In this talk, I review the progress in determining and understanding the QCD spectrum using lattice QCD.

All interested graduate students and faculty are invited to attend.

"Nuclear response at finite temperature "

Elena Litvinova

Western Michigan University

National Superconducting Cyclotron Laboratory

Thursday, November 15, 2018, 2:00 PM, C421

Abstract:

Recent developments of the relativistic nuclear field theory on the finite-temperature response will be presented. The general non-perturbative framework, which advances the nuclear response theory beyond the random phase approximation (RPA), is formulated in terms of a closed system of non-linear equations for the two-body Green’s functions. This provides a direct link to ab initio theories and allows for controlled approximate solutions.

The response theory beyond RPA is extended to the case of finite temperature. For this purpose, the time blocking approximation to the time-dependent part of the in-medium nucleon-nucleon interaction amplitude is adopted for the thermal Green’s function formalism. The method is implemented in a parameter-free way on the base of Quantum Hadrodynamics with effective meson-nucleon coupling adjusted on the mean-field level. In this framework, we investigate the temperature dependence of dipole spectra in the even-even medium-heavy nuclei with a special focus on the giant dipole resonance’s width problem and on the low-energy dipole strength distribution. Its behavior, together with the temperature dependence of the charge-exchange resonances, are studied for their potential impact on the r-process nucleosynthesis.

All interested graduate students and faculty are invited to attend.

"Hadronic corrections to the anomalous magnetic moment of the muon"

Peter Stoffer

University of California, San Diego

Thursday, September 27, 2018, 2:30 PM, C421

Abstract:

The anomalous magnetic moment of the muon g-2 has been measured and computed to very high precision of about 0.5 ppm. For more than a decade, a discrepancy has persisted between experiment and Standard Model prediction, now of about 3-4 sigma. The main uncertainty of the theory prediction is due to strong-interaction effects, the hadronic vacuum polarisation (HVP) and hadronic light-by-light (HLbL) contributions.

While the most precise HVP evaluation is based on dispersion relations and data input, HLbL is currently plagued by uncontrolled model uncertainties. Within a dispersive framework based on unitarity and analyticity, we scrutinize the uncertainty estimates for the two-pion HVP channel and we calculate model-independently two-pion contributions in HLbL, which shows an avenue towards a data-driven evaluation of g-2 of the muon.

All interested graduate students and faculty are invited to attend.

"Many-Body Perturbation Theory for Nuclear Matter at High Orders"

Christian Drischler

University of California, Berkeley

Thursday, June 21, 2018, 2:00 PM, C421

Abstract:

Nuclear matter is an ideal testbed for nuclear interactions with important consequences for nuclear astrophysics as well as finite nuclei. In particular, recent ab initio calculations of medium-mass to heavy nuclei have demonstrated the importance of realistic saturation properties of infinite matter for nuclear forces. We present an efficient Monte-Carlo framework for perturbative calculations of infinite nuclear matter based on two-, three-, and four-nucleon forces derived within chiral effective field theory. It enables to incorporate all many-body contributions in a transparent and also straightforward way, making it well-suited for pushing the limits of current state-of-the-art calculations to high orders in both the chiral as well as the many-body expansion. Furthermore, uncertainty estimates can be systematically extracted by order-by-order calculations, which provides important insights into the rate of convergence of each of the two expansions. After demonstrating its versatility, we make use of this novel framework to explore new chiral interactions up to next-to-next-to-next-to-leading order (N3LO) and study the equation of state of neutron and symmetric nuclear matter. Remarkably, simultaneous fits to the triton and to saturation properties can be achieved with natural 3N low-energy couplings. Taking advantage of the framework's efficacy, future chiral potentials may be optimized with respect to empirical saturation properties.

All interested graduate students and faculty are invited to attend.

"Chiral vortical effect for higher spin particles"

Andrey Sadofyev

Los Alamos National Laboratory

Thursday, May 17, 2018, 2:00 PM, C421

Abstract:

In a medium of massless fermions rotation can source a polarization current known as chiral vortical effect (CVE). Within a semi-classical description this phenomenon originates in the Berry phase and can be seen as a 3d analogue of the spin-Hall effect. It is well known that the spin-Hall effect takes place also for photons indicating a more general nature of topological polarization effects. In this talk we will discuss how CVE can be generalized to a system of massless particles with an arbitrary spin.

All interested graduate students and faculty are invited to attend.

"The Photon PDF"

Aneesh Manohar

University of California, San Diego

Thursday, April 26, 2018, 2:00 PM, C421

Abstract:

The photon PDF of the proton is needed for precision comparisons of LHC cross sections with theoretical predictions. A new approach allows the photon PDF to be computed in terms of proton deep-inelastic structure functions, reducing the uncertainty over previous methods by about a factor of 40. W and Z PDFs can be computed by similar methods. The talk discusses the determination of the photon and electroweak gauge boson PDFs.

All interested graduate students and faculty are invited to attend.