Publicações

Smooth reheating via non-Abelian dark sector | Colóquio DFMA

Data: 
quinta-feira, 19 Setembro, 2024 - 14:00 até 15:00
Palestrante: 
Dr. Simona Procacci (Universidade de Genebra)
Resumo: 

 

Abstract: We consider a model, where a single inflaton interacts weakly as an axion with Yang-Mills gauge bosons. As these rapidly thermalize, the friction felt by the inflaton field is increased, leading to a self-amplifying process. If the gauge bosons of the thermal bath represent a dark sector, the reheating of the Standard Model is then realised through portal interactions. The dark relic abundance in this scenario depends mostly on the departure from equilibrium after the universe cools down below the critical temperature, when the dark vectors confine into composite states. This constrains the confinement scale of the dark sector. Moreover, indirect detection and Big-Bang nucleosynthesis set bounds on the portal interactions, revealing a predictive parameter space.

 

 

Bootstrapping the relativistic two-body problem | Colóquio DFMA

Data: 
quinta-feira, 22 Agosto, 2024 - 16:00 até 17:00
Palestrante: 
Dr. Rafael Porto (DESY, Alemanha)
Resumo: 

Abstract: I review the state of the art of modern approaches to gravitational wave physics that leverage ideas and tools from scattering amplitudes and quantum field theory to tackle the gravitational binary problem in (classical) general relativity.

Emulators for beyond-LCDM models and photometric probes | Colóquio DFMA

Data: 
terça-feira, 20 Agosto, 2024 - 16:00 até 17:00
Palestrante: 
Dr. Guilherme Brando (Max Planck Institute for Astrophysics -- Munique. Alemanha)
Resumo: 

Abstract: In this talk, I will discuss the current effort of creating emulators for the non-linear power spectrum in beyond-LCDM models. I will present a pipeline that has been developed to model the matter power spectrum from large to small scales, with a focus on stage-IV photometric galaxy surveys. I will delve into the fundamental components of this pipeline, the consistency checks performed to validate it, and how effectively this new tool performs when conducting a full Bayesian parameter estimation analysis with a survey similar to LSST.
 

 

 

Post-Newtonian observables for aligned-spin binaries from gravitational self-force and Compton amplitudes | Colóquio DFMA

Data: 
quinta-feira, 15 Agosto, 2024 - 16:00 até 17:00
Palestrante: 
Dr. Yilber Fabian Bautista (IPhT-Saclay)
Resumo: 

Abstract: Accurate modeling of compact binaries is essential for gravitational-wave detection and parameter estimation, with spin being an important effect to include in waveform models. In this seminar, I will show how to derive new post-Newtonian (PN) results for the conservative aligned-spin dynamics at next-to-next-to-leading order for the spin3 and spin4 contributions, in addition to the next-to-leading order (NLO) spin5 and spin6 contributions. One approach we follow is the Tutti Frutti method, which relates PN and gravitational self-force (GSF) results through the redshift and spin-precession invariants, by making use of the simple dependence of the scattering angle on the binary mass ratio. However, an ambiguity arises at the NLO spin5 contribution, due to transcendental  functions of the Kerr spin in the redshift; this is also the order at which Compton amplitudes calculations are affected by spurious poles. Therefore, we discuss an additional approach to determine the NLO spin5 and spin6 dynamics: using on-shell Compton amplitudes dictated by homogeneous solutions of the Teukolsky equation, the later solved non-perturbative in terms of the Nekrasov-Shatashvili Function.

Dia 15/08/2024 (quinta-feira), às 16h, na Sala Jayme Tiomno

 

Distillation of quantum non-Markovianity | Colóquio DFMA

Data: 
quinta-feira, 15 Agosto, 2024 - 14:00 até 17:00
Palestrante: 
Profa. Nadja Bernardes - UFPE
Resumo: 

Resumo: Non-Markovianty of open quantum systems dynamics is a physically relevant property which is usually associated with the backflow of (quantum) information. Using this paradigmatic marker, we develop an operational framework to investigate how non-Markovianity for qubit dynamics can be distilled when many copies of the channels are used, possibly allowing for a stronger effect on the backflow of information.

 
 
 

 

Strings as arrays of particles | Colóquio DFMA

Data: 
terça-feira, 13 Agosto, 2024 - 14:00 até 16:00
Palestrante: 
Dr. Renann Lipinski Jusinskas (CEICO)
Resumo: 
 
Abstract: In this talk I will informally discuss a recent proposal in which the Polyakov action emerges as a sort of low energy limit of an interacting array of relativistic particles. The model is relatively simple and is still under investigation. No previous knowledge on string theory is required.

"Explosões de Buracos Negros?" por S. Hawking: Cinquenta Anos de Legado | Colóquio DFMA

Data: 
terça-feira, 2 Julho, 2024 - 16:00 até 17:00
Palestrante: 
Dr. Bruno Arderucio (UNAM)
Resumo: 

   

ResumoHá cinquenta anos, um trabalho seminal de Stephen Hawking foi publicado na revista Nature. Nele, foi-se anunciada a radição emitida por buracos negros que levaria o nome do autor. Desde então, o fenômeno foi intensamente estudado por inúmeros autores e influenciou diversos campos da física teórica. Neste colóquio, exploramos a relevância da descoberta e algumas das repercussões que ainda hoje são estudadas. Daremos ênfase a avanços recentes na termodinâmica de buracos negros, ao chamado "paradoxo da informação" e ao relacionado "paradoxo do tempo de Page".

Defect RG flows in 3d Chern-Simons-matter theory | Colóquio DFMA

Data: 
terça-feira, 23 Abril, 2024 - 16:00
Palestrante: 
Dra. Márcia Tenser
Resumo: 

Abstract: In this talk I would like to discuss the defect renormalization group flows recently found in ABJM theory. In such a setting, we find RG flow trajectories that may or may not preserve some subset of the original N=6 supersymmetry. The $\beta$-functions have a rich spectrum of fixed points representing (super)conformal defects that provide a rich arena to study quantum effects in 2+1 dimensional theories. This sheds new light on universal information about the theory, such as the Bremsstrahlung function, and possibly on the holographic dual setting of strings in AdS4xCP3.

 

Probes of ultralight dark matter and primordial black holes with gravitational-wave detectors | Colóquio DFMA

Data: 
sexta-feira, 1 Março, 2024 - 16:00 até 17:30
Palestrante: 
Dr. Andrew Miller
Resumo: 

Resumo: Gravitational-wave interferometers can be used to probe the existence of dark matter. Different types of dark matter, such as sub-solar primordial black holes, axions and dark photons, could leave different imprints on gravitational-wave detectors. While arising from physically different sources, such signals share common traits, and can be searched for with similar methods. In this talk, I will explain how persistent, quasi-monochromatic signals in ground-based detectors could arise from each of the aforementioned dark matter candidates. I also describe some of our search methods and summarize results from the most recent observing runs of Advanced LIGO, Virgo, and KAGRA. 

 

The observer-dependence of the Hubble parameter: a covariant perspective | Colóquio DFMA

Data: 
quarta-feira, 29 Novembro, 2023 - 16:00 até 17:00
Palestrante: 
Dra. Jessica Santiago
Resumo: 

Resumo: Given the exponential growth on the upcoming supernovae data available, the possibilities of rigorously testing the cosmological principle becomes ever more real. One of the ways to do so is by measuring the multipole decomposition of the Hubble and deceleration parameters. In this presentation, I will discuss the observational-theoretical approach, initially introduced by Kristian & Sachs, which allows for the interpretation of data in non-homogeneous and anisotropic universes. I will also explore the effects introduced by the relative motion between the observer and the reference frame defined by galaxies (the matter frame), demonstrating that the luminosity distance should be corrected in such cases.

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