talks & meeting schedule 

Following the Big Bang, the universe underwent a period of exponential expansion known as inflation. This era left all matter and energy in the universe extremely diluted and cold. However, to account for the successes of the Standard Cosmological Model, it is necessary to assume that the universe in its early stages was extremely hot. Consequently, we need a transition phase that reheats the universe after inflation, enabling the Hot Big Bang.

Conventionally, reheating is done by adding a coupling between the field responsible for inflation and the particles to be created. In our work, we will start from a minimalist approach, where only gravitational interaction will be responsible for reheating the universe. We will address particle production in two ways: perturbatively, where amplitudes and transition rates are calculated using Quantum Field Theory in flat spaces; and non-perturbatively, where the effects of curved spacetime are taken into account.

Within the classical Maxwell-Chern-Simons limit of the Standard-Model Extension (SME), the emission of light by uniformly moving charges is studied confirming the possibility of a Cherenkov-type effect. In this context, the exact radiation rate for charged magnetic point dipoles is determined and found in agreement with a phase-space estimate under certain assumptions. 

Several pulsar timing array collaborations recently reported evidence of a stochastic gravitational wave background (SGWB) at nHz frequencies. Whilst the SGWB could originate from the merger of supermassive black holes, it could be a signature of new physics near the 100 MeV scale. Supercooled first-order phase transitions (FOPTs) that end at the 100 MeV scale are intriguing explanations, because they could connect the nHz signal to new physics at the electroweak scale or beyond. Here, however, we provide a clear demonstration that it is not simple to create a nHz signal from a supercooled phase transition, due to two crucial issues that should be checked in any proposed supercooled explanations.

    The stochastic gravitational-wave backgrounds (SGWBs) from the cosmological first-order phase transitions (FOPTs) serve as a promising probe for the new physics beyond the standard model of particle physics. When most of the bubble walls collide with each other long after they had reached the terminal wall velocity, the dominated contribution to the SGWBs comes from the sound waves characterized by the efficiency factor of inserting the released vacuum energy into the bulk fluid motions. However, the previous works of estimating this efficiency factor have only considered the simplified case of the constant sound velocities in both symmetric and broken phases, either for the bag model with equal sound velocities or ν-model with different sound velocities in the symmetric and broken phases, which is unrealistic from a viewpoint of particle physics. In this paper, we propose to solve the fluid EoM with an iteration method when taking into account the sound-velocity variation across the bubble wall for a general and realistic equation of state (EoS) beyond the simple bag model and ν-model. We have found a suppression effect for the efficiency factor of bulk fluid motions, though such a suppression effect could be negligible for the strong FOPT, in which case the previous estimation from a bag EoS on the efficiency factor of bulk fluid motions still works as a good approximation.

We report on the first search for nuclear recoils from dark matter in the form of weakly interacting massive particles (WIMPs) with the XENONnT experiment, which is based on a two-phase time projection chamber with a sensitive liquid xenon mass of 5.9 ton. During the ( 1.09 ± 0.03 ) ton yr exposure used for this search, the intrinsic 85 Kr and 222 Rn concentrations in the liquid target are reduced to unprecedentedly low levels, giving an electronic recoil background rate of ( 15.8 ± 1.3 ) events / ton yr keV in the region of interest. A blind analysis of nuclear recoil events with energies between 3.3 and 60.5 keV finds no significant excess. This leads to a minimum upper limit on the spin-independent WIMP-nucleon cross section of 2.58 × 10 − 47 cm 2 for a WIMP mass of 28 GeV / c 2 at 90% confidence level. Limits for spin-dependent interactions are also provided. Both the limit and the sensitivity for the full range of WIMP masses analyzed here improve on previous results obtained with the XENON1T experiment for the same exposure.

We report multiple lines of evidence for a stochastic signal that is correlated among 67 pulsars from the 15-year pulsar-timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. The correlations follow the Hellings-Downs pattern expected for a stochastic gravitational-wave background. The presence of such a gravitational-wave background with a power-law-spectrum is favored over a model with only independent pulsar noises with a Bayes factor in excess of 1014, and this same model is favored over an uncorrelated common power-law-spectrum model with Bayes factors of 200-1000, depending on spectral modeling choices. We have built a statistical background distribution for these latter Bayes factors using a method that removes inter-pulsar correlations from our data set, finding p=10−3 (approx. 3σ) for the observed Bayes factors in the null no-correlation scenario. A frequentist test statistic built directly as a weighted sum of inter-pulsar correlations yields p=5×10−5−1.9×10−4 (approx. 3.5−4σ). Assuming a fiducial f−2/3 characteristic-strain spectrum, as appropriate for an ensemble of binary supermassive black-hole inspirals, the strain amplitude is 2.4+0.7−0.6×10−15 (median + 90% credible interval) at a reference frequency of 1/(1 yr). The inferred gravitational-wave background amplitude and spectrum are consistent with astrophysical expectations for a signal from a population of supermassive black-hole binaries, although more exotic cosmological and astrophysical sources cannot be excluded. The observation of Hellings-Downs correlations points to the gravitational-wave origin of this signal.

The question of whether classically conformal modifications of the standard model are consistent with experimental observations has recently been subject to renewed interest. The method of Gildener and Weinberg provides a natural framework for the study of the effective potential of the resulting multiscalar standard model extensions. This approach relies on the assumption of the ordinary loop hierarchy λs∼g2g of scalar and gauge couplings. On the other hand, Andreassen et al. recently argued that in the (single-scalar) standard model gauge invariant results require the consistent scaling λs∼g4g. In the present paper, we contrast these two hierarchy assumptions and illustrate the differences in the phenomenological predictions of minimal conformal extensions of the standard model.

The Standard Model of particle physics, despite its many triumphs, still has flaws that are yet to be convincingly addressed by new physics models. Among many other open questions, the nature of dark matter and the recently updated muon g-2 anomaly remain as some of the more pertinent examples. In this talk, I will review a possible explanation of these issues in light of a recently proposed effective field theory for higher spin particles. I will first highlight the problems of higher spin theories of the past and then explain how one can construct a theory avoiding these obstacles. After that I will explain the phenomenological features of the new theory in detail, covering issues related to dark matter, collider physics, the g-2 anomaly, and nuclear physics.

The scalar sector of the 3-3-1 model with an axionlike particle is studied in detail. In the model under consideration, there are two kinds of scalar fields: the bilepton scalars carrying lepton number two and the ordinary ones without lepton number. We show that there is no mixing among these two kinds of scalar fields.We analyze in detail the CP-odd scalar sector of the model to find the physical fields of the axionlike particle and a pseudoscalar with mass in the range 100 GeV to 1 TeV. The results are different from others which have been published before. The CP-even scalar sector of the model is analyzed as well. The results of our analysis of the scalar sector allow us to accommodate scalar masses in the 100 GeV–1 TeV region. Furthermore we analyze the implications of the model in several flavor changing neutral decays of the top quark as well as in rare top quark decays. Besides that, the leptonic decays of the SM like Higgs boson as well as the meson oscillations are also analyzed. Our numerical analysis show that the model under consideration is consistent with the experimental constraints imposed by these processes.

This talk will be about our study of the interaction between 't Hooft-Polyakov magnetic monopoles and SU(2) invariant vacuum layers within an SU(2) gauge theory. We observed that the collision leads to the erasure of the magnetic monopoles, as suggested by Dvali, Liu, and Vachaspati. We performed numerical simulations to analyze the collision during which electromagnetic radiation is emitted and moves away radially. The angular distribution of the emitted radiation depends only on the velocity of the monopole at the time of the collision.

We study some observational signatures of nonlinearities of the electromagnetic field. First to all we show the vital role played by nonlinearities in triggering a material behavior of the vacuum with (ε > 0,μ < 0), which corresponds to a ferrimagnetic material. Secondly, the permittivity and susceptibility induced by nonlinearities are considered in order to obtain the refractive index via the dispersion relation for logarithmic electrodynamics. Finally, we consider the electromagnetic radiation produced by a moving charged particle interacting with a medium characterized by nonlinearities of the electromagnetic field. To this end we consider logarithmic electrodynamics. The result shows that the radiation is driven by the medium through which the particle travels like the one that happens in the Cherenkov effect.

Studies of entanglement and other quantum information measures at colliders have recently been proposed to probe fundamental interactions at high energies. Inspired by these results, we examine tau pair productions at both lepton and hadron colliders, to probe dimension-6 dipole operators in the Standard Model Effective Field Theory (SMEFT).

The SMEFT contributions are found to be sizable in some regions of parameter space, if quadratic contributions are considered, prompting a comparison with other known indirect constraints on the tau dipole operators. We also find interesting patterns of entanglement across the phase space, feeding into previous discussions on quantum information in the context of EFTs.

Terminal velocity reached by bubble walls in first order phase transitions is an important parameter determining both primordial gravitational-wave spectrum and production of baryon asymmetry in models of electroweak baryogenesis. We developed a numerical code to study the real-time evolution of expanding bubbles and investigate how their walls reach stationary states. Our results agree with profiles obtained within the so-called bag model with very good accuracy, however, not all such solutions are stable and realised in dynamical systems. Depending on the exact shape of the potential there is always a range of wall velocities where no steady state solutions exist. This behaviour in deflagrations was explained by hydrodynamical obstruction where solutions that would heat the plasma outside the wall above the critical temperature and cause local symmetry restoration are forbidden. For even more affected hybrid solutions causes are less straight forward, however, we provide a simple numerical fit allowing one to verify if a solution with a given velocity is allowed simply by computing the ratio of the nucleation temperature to the critical one for the potential in question.

We consider the direct s-channel gravitational production of dark matter during the reheating process. Independent of the identity of the dark matter candidate or its non-gravitational interactions, the gravitational process is always present and provides a minimal production mechanism. During reheating, a thermal bath is quickly generated with a maximum temperature Tmax, and the temperature decreases as the inflaton continues to decay until the energy densities of radiation and inflaton oscillations are equal, at TRH. During these oscillations, s-channel gravitational production of dark matter occurs. We show that the abundance of dark matter (fermionic or scalar) depends primarily on the combination T4max/TRHM3P. We find that a sufficient density of dark matter can be produced over a wide range of dark matter masses: from a GeV to a ZeV.

In this talk, Supersymmetry and Compositeness will be present as solutions to the hierarchy problem. We will also discuss how the 2 Higgs Doublet Models can separate the two models by the spectra of masses and couplings accessible at the Large Hadron Collider in the same way it is done in the reference paper.

We address the notorious metastability of the standard model (SM) Higgs potential and promote it to a model building task: What are the new ingredients required to stabilize the SM up to the Planck scale without encountering subplanckian Landau poles? Using the SM extended by vector-like fermions, we chart out the corresponding landscape of Higgs vacuum stability. We find that the gauge portal mechanism, triggered by new SM charge carriers, opens up sizeable room for stability in a minimally invasive manner. 

We also find models with Yukawa portals into Higgs stability opening up at stronger coupling. Several models allow for vector-like fermions in the TeV-range, which can be searched for at the LHC. For nontrivial flavor structure of Yukawa couplings severe FCNC constraints arise which complement those from stability, and push lower fermion masses up to a few hundred TeV.

The past decades were a great success story for precision cosmology. Still, at temperatures above the MeV-scale we lack experimental probes of our theories. To test new models for the Early Universe at times prior to Big Bang Nucleosynthesis (BBN) we need a new messenger that is able to pass the hot and dense plasma of elementary particles, the most promising one being gravitational waves. The pulsar timing array (PTA) NANOGrav has found evidence for a signal at frequencies that would correspond to temperatures just above the MeV scale, if it is from gravitational waves of a cosmic origin. In this talk, I will discuss the possibility whether the measured signal could be due to a dark sector phase transition when taking into account constraints from BBN and the cosmic microwave background.

In this talk I will introduce the Asymptotically Safe Standard Model, product of the unification of our knowledge of the Standard Model with Asymptotically Safe quantum gravity. The physics scales included range from the asymptotically safe trans-Planckian regime in the ultraviolet, the intermediate high-energy regime with electroweak symmetry breaking to strongly correlated QCD in the infrared. I will discuss their derivation by means of non-perturbative techniques provided by the Functional Renormalisation Group. The results presented take care of all physical threshold effects and the respective decoupling of ultraviolet degrees of freedom, for example the decoupling of gravity at the Planck scale or decoupling of massive particles in the Higgs broken phase. I will discuss how the matter part of the Asymptotically Safe Standard Model has the same number of relevant parameters as the Standard Model, and is asymptotically free. This result is based on the novel UV fixed point found in the present work: the fixed point Higgs potential is flat but has two relevant directions. Overall, I will emphasise how the picture here presented establishes a framework for the development and test of theories beyond the Standard Model which do not admit a perturbative treatment. I will conclude with some prospects in Gauge-Higgs unification and Composite Higgs theories.

Simple scalar-singlet extensions of the Standard Model with a (spontaneously broken) Z2 symmetry allow for a strong first order electroweak phase transition, as sought in order to realize electroweak baryogenesis. However they generically also lead to the emergence of phenomenologically problematic domain walls. Here we present a framework with a real scalar singlet that features a different thermal history that avoids this problem by never restoring the Z2 symmetry in the early universe. This is accomplished by considering D>4 operators that emerge on general grounds, understanding the model as the low energy tail of a more complete theory, like for example in composite Higgs scenarios. Sticking to the latter framework, we present a concrete SO(6)/SO(5) composite realization of the idea. To this end, we additionally provide a complete classification of the structure of the Higgs potential (and the Yukawa couplings) in SO(6)/SO(5) models with fermions in the 1,6,15 or 20′ of SO(6). 

There are at least two open problems in elementary particle physics that challenge our understanding of the composition and fundamental interactions in the universe. The first is evidence for the existence of a different type of matter, known as Dark Matter, and the second is the disagreement between the experimental and theoretical predicted value of the muon’s magnetic moment, known as the g − 2 muon anomaly. Both problems can be solved by considering an extension of the gauge symmetry group of electroweak interactions of the Standard Model to the symmetry SU(2)L⊗U(1)L⊗U(1)Lμ−Lτ . The key ingredient to solve these two problems is that the considered model has a neutral and stable fermionic particle, which produces an abundance of dark matter relics according to the experiments. This particle couples to the Standard Model particles through a gauge boson Z′ that makes an extra contribution to the muon’s g − 2 anomaly. In this way, both problems are connected in this model. In this thesis we study how couplings and model masses can be fixed using recent experimental results. In doing so, we conclude that the masses of dark matter and boson Z′ are in the range of 1 − 50 MeV, which gives us a minimal solution to these puzzling problems. Finally, the model also gives us a contribution to ∆Neff that can relieve the tension on the Hubble constant.

Nowadays there are many problems in physics that can be solved  with optimization through Machine Learning. Topics like bariogenese and gravitational waves are relevant in particle physics to understand the electroweak phase transition in the early universe. Therefore, solving differential equations that describe the dynamic in this period is essential, but solving these equations analytically isn't possible or simple in some situations, then employing Machine Learning methods to get a numerical solution that allows citaded topics to be studied can be useful.

The first interferometers are dated from 1880-1890 with contributions from Michelson and Morley and later improved by Fabry and Perot to allow the creation of sophisticated devices capable of measuring gravitational waves (LIGO-VIRGO-KAGRA). These measurements, when made on land, carry interference that impairs accuracy. 

Let's talk a little about the noise of these measurements in LIGO and what are the advantages of putting the Laser Interferometer Space Antenna into orbit, which offers a new way to investigate the universe and gravitational waves.

The CDF II detector has made an incredible measurement of the W mass, with great accuracy. The value obtained was not in agreement with the prediction by the Standard Model (SM), leading to a possible new physics beyond the SM.

In this meeting, we will talk about the new measurement of the boson W mass, how this mass is predicted theoretically predicted at the tree level, and the consequences for the SM.

In this Masters dissertation, will be investigated topological solitons in the classical theory of fields, more specifically, kinks, vortices, monopoles and instantons. These objects emerge in the theory after a symmetry breaking pattern, in wich we are able to create a non-trivial map between the vacuum manifold and the spacial manifold analysed at the infinity. Firstly, the kink solution will be found in the λφ^4 and sine-Gordon model, his classical energy will be derived and calculated and, after that, the appropriate quantum corrections, for the masses of these structures, will be done. Following a natural process, more degrees of freedom will be added to the system, and it will lead us to global vortices, endowed with an infinite energy. To solve this issue, one uses Derrick's theorem, in wich a gauge term is added to the Lagrangian, permitting one to find a topological soliton with finite energy, also known as Nielsen-Olesen vortex. Inspired by Dirac's monopole, the same previous process will be applied to derive the 't Hooft-Polyakov monopole solution, that possesses a finite energy configuration. However, the orders of magnitude are way above what modern colliders can detect. We will continue searching for this particle in the Glashow-Weinberg-Salam theory, also known as Cho-Maison monopole, and an extension in the hipercharge sector U(1)Y will be done, in order to estimate this particle's mass. Lastly, we will conclude this dissertation addressing the instantons, topological defects that arise in the pure Yang-Mills theory, and it will be shown how this structure solve de U(1)-problem in QCD.

In this paper the authors propose a new approach for the spontaneous breaking and restoration of the SU(3)C color symmetry in the framework of electroweak symmetry non-restoration (EWSNR) at high temperature, which provides an alternative approach for the Baryogenesis. Due to the exotic high vacuum expectation value (VEV) of the SM Higgs doublet in EWSNR, the color symmetry can be spontaneous broken succeeding the electroweak phase transition whenever there is a negative quartic coupling between the SM Higgs and a scalar color triplet. The color symmetry is then restored at low temperature as the VEV of SM Higgs evolving to small value. The authors show that the phase transitions related to color breaking and restoration can be first order, and the stochastic gravitational wave (GW) signals are smoking-gun of these processes.

We revisit the computation of bubble wall friction during a cosmological first-order phase transition, using an extended fluid Ansatz to solve the linearized Boltzmann equation. A singularity is found in the fluctuations of background species as the wall approaches the speed of sound. Using hydrodynamics, we argue that a discontinuity across the speed of sound is expected on general grounds, which manifests itself as the singularity in the solution of the linearized system. We discuss this result in comparison with alternative approaches proposed recently, which find a regular behaviour of the friction for all velocities. 

The standard vacuum bounce formalism suffers from inconsistencies when applied to thermal bubble nucleation, for which ad hoc workarounds are commonly adopted. Identifying the length scales on which nucleation takes place, we demonstrate how the construction of an effective description for these scales naturally resolves the problems of the standard vacuum bounce formalism. Further, by utilizing high-temperature dimensional reduction, we make a connection to classical nucleation theory. This offers a clear physical picture of thermal bubble nucleation, as well as a computational framework which can then be pushed to higher accuracy. We demonstrate the method for three qualitatively different quantum field theories.

In this article, as a follow up from previous studies, the authors discuss on the phenomenology of a non-linear hypercharge sector. Specifically, on the decay of Z-boson into three photons, the electron-positron annihilation into three photons and scattering processess involving exclusively neutral gauge bosons.

In this article the authors examine the possibility of using the Higgs mechanism to remove such catastrophic infrared singularities in non-Abelian gauge theories that are asymptotically free. He sees in detail how theories based on the SU(N) and O(N) gauge groups with scalar fields in various representations. The authors conclude that, for these theories, an S matrix, in the perturbative sense, and asymptotic freedom cannot coexist. 

We investigate a novel interplay between the decay and annihilation of a particle whose mass undergoes a large shift during a  rst order phase transition, leading to the particles becoming trapped in the false vacuum and enhancing their annihilation rates as the bubbles of true vacuum expand. This opens up a large region of the parameter space where annihilations can be important. We apply this scenario to baryogenesis, where we  nd that annihilations can be enhanced enough to generate the requires baryon asymmetry even for relatively tiny annihilation cross sections with modest CP asymmetries.

The article works with two, nowadays, famous problems inside particle physics beyond the standard model. The first one is the it topic of the moment, the g-2 anomaly. And the other one is the old and more famous, dark matter abundance problem. Mixing the two problems in one single model gives us a good frame with parameters given by the data of the g-2 anomaly and the observed dark matter abundance. In the end we have some perspectives for future experiments, observations and a relation with other problems as the Hubble Tension.

We re-evaluate the status of supersonic electroweak baryogenesis using a generalized fluid Ansatz for the non-equilibrium distribution functions. Instead of truncating the expansion to first order in momentum, we allow for higher order terms as well, including up to 21 fluctuations. The collision terms are computed analytically at leading-log accuracy. We also point out inconsistencies in the standard treatments of transport in electroweak baryogenesis, arguing that one cannot do without specifying an Ansatz for the distribution function. We present the first analysis of baryogenesis using the fluid approximation to higher orders. Our results support the recent findings that baryogenesis may indeed be possible even in the presence of supersonic wall velocities. 

In this article, the authors P. de Fabritiis and JA Helayël-Neto present the whole construction of the monopole in the Electroweak Theory, starting from Cho and Maison dyons. Also, they make a non-linear extension in the weak hypercharge sector based on logarithmic and exponential versions of the Electromagnetism. Finally, they estimate the monopole’s mass and calculate its BPS limit.

• 12/08: Deivide Kenede - Solutions to the Dirac's Equation and the Hole Theory (PDF File)

• 19/08: Gabriel Cruz - Quantum Electrodynamics Pt. 1 (PDF File)

• 26/08: Bruno Avellar - Poincaré Group and the Nature of Spin (PDF File)

• 09/09: Gabriel Fontenele - Gauge Fields (Not Available)

• 16/09: Guilherme Fontenele - Scalar and Dirac Fields (Not Available)

• 23/09: Álvaro Louzi - SU(2) (Not Available)

• 30/09: Deivide Kenede - Standard Model of Cosmology (PDF File)

• 07/10: Gabriel Cruz - Quantum Electrodynamics Pt. 2: Casimir Trick and Renormalization (PDF File)

• 14/10: Bruno Avellar - Homotopy and Fundamental Group (PDF File)

• 21/10: Gabriel Fontenele - Aharonov-Bohm Effect (Not Available)

• 28/11: Gabriel Cruz - Neutrino Oscillations (PDF File)

• 04/11: Guilherme Fontenele - Gravitational Fields (PDF File)

• 09/12: Álvaro Louzi - Applications of SU(2) (Not Available)

• 16/12: Deivide Kenede - Effective Potential (PDF File)

• 06/01: João Pedro - Early Universe Thermodynamics (PDF File)

• 13/01: Gabriel Cruz - Dark Matter (PPT File)

• 27/01: Bruno Avellar - Dirac's Monopoles (PDF Files)

• 03/02: Bruce Vega - Axion Dark Matter (PPT File)

• 10/02: Gabriel Fontenele - Path Integrals (Not Available)

• 24/02: Guilherme Fontenele - Matrix S Expansion (PPT File)

• 03/03: Álvaro Louzi - SU(3) (Not Available)

• 10/03: Deivide Kenede - Field Theory at Finite Temperature (PDF File)

• 17/03: Paula Ferreira - Gauge Symmetry and its Interpretations  (PPT File)

• 24/03: João Pedro - Electroweak Interactions for Leptons (PDF File) 

• 31/03: Bruno Avellar - Instantons and the U(1) Problem (PDF File) 

• 27/03: Gabriel Cruz - Klein-Gordon Equation (PDF File)

• 03/04: Bruno Avellar - Canonical Quantization of the Klein-Gordon Field (PDF File)

• 10/04: Gabriel Fontenele - Special Relativity: A Recall (Not Available)

• 17/04: Guilherme Fontenele - Transformations (PDF File)

• 01/05: Álvaro Louzi - Finite groups: Representations Pt. 1 (PDF File)

• 15/05: Gabriel Cruz - Tools for calculations in elementary particle of physics (PDF File)

• 22/05: Bruno Avellar - Derivation of Dirac's equation via group theory (PDF File)

• 29/05: Gabriel Fontenele - Introduction to Classical Fields (Not Available)

• 05/06: Guilherme Fontenele - General Formalism of Classical Fields (PDF File)

• 12/06: Álvaro Louzi - Finite Groups: Representations Pt. 2 (PDF File)

• 19/06: Deivide Kenede - Relativistic Quantum Mechanics and Dirac's Equation (PDF File)

• 26/06: Gabriel Cruz - The Feynman Calculus (PDF File)

• 09/07: Bruno Avellar - Calculus of Soliton's Mass (PDF File)

• 16/07: Guilherme Fontenele - Noether's Theorem (PDF File)

• 23/07: Gabriel Fontenele - Vector and Electromagnectic Fields (Not Available)

• 30/07: Álvaro Louzi - Hilbert Space (PDF File)