São Paulo Research Group meetings in Astro & Cosmo

ICTP-SAIFR is promoting monthly one-day meetings of the São Paulo community working in the related areas of Cosmology/Astrophysics/Astroparticles/Gravity to be held at the Instituto Principia. The idea is to have a light schedule, with a couple of talks and plenty of time for discussion. The main purpose is to explore synergies of the different groups.

Next Meetings: March 30

• 10:00 Alan Muller (IFT-UNESP): An effective field theory approach to post-Newtonian binary dynamics

Compact binary coalescences are among the most important sources of gravitational waves and require increasingly precise theoretical predictions for their dynamics and radiation. In the post-Newtonian regime, the 2-body problem exhibits a clear hierarchy of length scales: the size of the compact objects; the orbital separation; and the wavelength of the emitted radiation. This hierarchy allows the system to be described within an effective field theory framework. In this talk, I will review the effective field theory approach to post-Newtonian binary dynamics known as nonrelativistic general relativity (NRGR), in which the separation of scales provides a natural distinction between conservative and radiative effects. I will discuss how this framework can be used to compute contributions to the binary dynamics and to the emitted gravitational radiation, with particular attention to radiation and hereditary effects. I will then present recent developments in this program, including results from our works and ongoing efforts to compute high-order contributions to the conservative dynamics arising from angular-momentum tail effects.

• 11:15 Alexandre Le Tiec (Obs. Meduon, France & IFT-UNESP): What is the shape of a spinning black hole?

In his classical monographs Ellipsoidal Figures of Equilibrium and The Mathematical Theory of Black Holes*, Subrahmanyan Chandrasekhar developed, respectively, the theory of self-gravitating fluid configurations and the mathematical structure of black hole spacetimes in general relativity. Bringing these two lines of thought into dialogue raises a seemingly simple but in fact subtle question: What is the shape of a spinning black hole, and in what sense can such a notion even be defined in general relativity? We will offer three complementary answers, based on optical (ray-tracing / shadow), asymptotic (multipole moments), and quasi-local (horizon geometry) characterizations of Kerr black holes, and then consider their extension to weakly tidally perturbed configurations, where the notion of shape becomes dynamical and is captured either by asymptotic (field) or horizon (surficial) tidal Love numbers.

• 14:00 Manuel Cubides Pérez (UFABC): Cosmic evolution of lepton and baryon flavour charges

We study the evolution of baryon and lepton asymmetries including the full Standard Model flavour structure and spectator processes. Since physical observables must be basis independent, the asymmetries of the SU(2)_L doublets and singlets are formulated in terms of flavour-space density matrices. Within this framework we construct Boltzmann equations for the number asymmetries of all SM fermion species — namely the lepton and quark SU(2)_L doublets and their corresponding singlets—together with the constraint imposed by hypercharge conservation. This leads to a closed linear system relating conserved charges to the baryon number across the temperature range 10^{15} GeV − 100 GeV, providing a consistent flavour-covariant description of baryogenesis. The resulting relations determine how charge asymmetries are distributed among particle species and supply the physical input for the subsequent dynamical analysis. We apply this framework to leptogenesis in the Type-I and Type-II seesaw scenarios, finding controlled deviations arising from spectator processes and flavour correlations that are missed in treatments without a full flavour-covariant description.

• 10:00 Rainer Menote (UFES): CosmoDC2_BCO: A Gateway to Multi-Messenger Cosmology – Video
• 11:15 Tabata Aira (INPE): Exploring the Origins of Glitches in the LIGO Detectors Using Machine Learning Techniques – Video
• 14:00 Germán Lugones (UFABC): New Stable Branches of Compact Stars Beyond the Maximum-Mass Turning Point – Video

• 11:15 Pedro Henrique Rossetto (USP): Continuous Gravitational Waves from Neutron Stars Magnetic Mountains – Video

• 14:00 Joaquin Armijo (USP): Cosmological constraints from the first year data of the Hyper Suprime-Cam – Video

• 11:00 Alexandre Le Tiec (IFT-UNESP — CNRS): What’s in a Name: the Anthropocene – Video
• 14:00 Fernanda Lima (IF-USP): Ultra-light dark matter and power spectra emulators – Video
• 15:15 João Ferri (IF-USP): What can we gain from small scales in shear analysis? A comparison between Fourier and Real spaces. – Video