São Paulo Research Group meetings in Astro & Cosmo
Next meeting: May 9, 2025
São Paulo, Brazil
Venue: Instituto Principia
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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.
The activity will be transmitted online by Zoom.
Next Meetings:
May 09, 2025
June 13, 2025
If you want to receive mailings about the meetings, click HERE.
Organizers:
- Raul Abramo (IFUSP)
- Chee Sheng Fong (UFABC)
- Rogério Rosenfeld (IFT-UNESP)
- Riccardo Sturani (IFT-UNESP)
Announcement:
Invited Speakers May 9, 2025
10:00 Pedro Bittar (USP)
Baryogenesis just around the corner: Generating the matter asymmetry at or below the weak scale
The origin of the asymmetry between matter and antimatter is one of the main drivers for new physics beyond the Standard Model.
Many models assume this asymmetry is generated very early in the cosmic evolution, at temperatures much higher than the scales
of physics we probe in terrestrial laboratories like the Large Hadron Collider (LHC).
While well-motivated, these scenarios are hard to test given the high energy scales involved.
In this talk, I focus on models where the observed matter-antimatter asymmetry is generated much later comparatively – during or after the electroweak (EW) phase transition.
Because they involve lower energy scales, these models offer a rich phenomenology for collider and cosmological experiments.
In the first part of the talk, I focus on the connection between low-temperature baryogenesis and signals for long-lived particles at the LHC.
In the second part, I cover the role of a first-order EW phase transition in EW baryogenesis,
highlight methods to improve the precision of the effective potential calculation, and explore the implications for the gravitational wave spectrum.
The origin of the asymmetry between matter and antimatter is one of the main drivers for new physics beyond the Standard Model.
Many models assume this asymmetry is generated very early in the cosmic evolution, at temperatures much higher than the scales
of physics we probe in terrestrial laboratories like the Large Hadron Collider (LHC).
While well-motivated, these scenarios are hard to test given the high energy scales involved.
In this talk, I focus on models where the observed matter-antimatter asymmetry is generated much later comparatively – during or after the electroweak (EW) phase transition.
Because they involve lower energy scales, these models offer a rich phenomenology for collider and cosmological experiments.
In the first part of the talk, I focus on the connection between low-temperature baryogenesis and signals for long-lived particles at the LHC.
In the second part, I cover the role of a first-order EW phase transition in EW baryogenesis,
highlight methods to improve the precision of the effective potential calculation, and explore the implications for the gravitational wave spectrum.
11:15 Rodrigo Voidovic (Donostia Int. Physics Cent. San Sebastian & IFT-UNESP)
Likelihoods
Even with a perfect theory or simulator, one must properly compare predictions to observations. This crucial connection is established through the likelihood. In this talk, I will demonstrate how to compute the likelihood from a perturbative prediction of a given observable. In addition, I will explore how to utilize the implicit likelihood from a simulator using E(3)-steerable continuous normalizing flows. As an example, I will determine the posterior distribution of cosmological parameters using a simplified field observation.
14:00 Gustavo Henrique dos Santos (UFABC)
ACT Constraints on Low Scale Inflation and a Mechanism for Vector Dark Matter Production
Recent observations from the Atacama Cosmology Telescope (ACT DR6) provide updated constraints on the inflationary parameter space, enabling a reassessment of the viability of low scale inflationary models. In this study, we investigate the consistency of single-field inflation scenarios with inflationary Hubble scales in light of the ACT data, focusing on models that reproduce the observed scalar spectral index and amplitude. We also examine the possibility of generating the observed dark matter abundance in these scenarios through the tachyonic production of heavy vector bosons coupled to the inflaton via a Chern-Simons interaction. The parameter space for successful dark matter generation is analyzed numerically, highlighting the regimes where low scale inflation and heavy vector dark matter are simultaneously viable.
Previous Meetings
April 04, 2025
10:00 Parth Bambhaniya (USP): Are We Sure It’s a Supermassive Black Hole at the Heart of Our Galaxy? – Video
Recent observations of Sagittarius A* (Sgr A*) at the heart of our galaxy have garnered significant interest, prompting investigations of its properties. In particular, through studies of its shadow imaging, accretion dynamics, and the orbits of S-stars. The classical Oppenheimer-Snyder-Dutt (OSD) model predicts black hole formation from gravitational collapse, while Penrose’s cosmic censorship conjecture (CCC) extends this idea and suggests that the singularity must remain hidden within an event horizon. However, Penrose’s CCC remains unproven and more realistic gravitational collapse models challenge these assumptions, raising the possibility of naked singularities or supermassive compact objects. In this talk, we discuss the generalized shadow formation conditions by supermassive compact objects and how precise astrometric data from the GRAVITY and UCLA Galactic Center groups provide insights into the spacetime geometry of Sgr A*. Finally, we discuss observational tests that could distinguish a black hole from alternative supermassive compact objects, improving our understanding of the core of the Milky Way.
Recent observations of Sagittarius A* (Sgr A*) at the heart of our galaxy have garnered significant interest, prompting investigations of its properties. In particular, through studies of its shadow imaging, accretion dynamics, and the orbits of S-stars. The classical Oppenheimer-Snyder-Dutt (OSD) model predicts black hole formation from gravitational collapse, while Penrose’s cosmic censorship conjecture (CCC) extends this idea and suggests that the singularity must remain hidden within an event horizon. However, Penrose’s CCC remains unproven and more realistic gravitational collapse models challenge these assumptions, raising the possibility of naked singularities or supermassive compact objects. In this talk, we discuss the generalized shadow formation conditions by supermassive compact objects and how precise astrometric data from the GRAVITY and UCLA Galactic Center groups provide insights into the spacetime geometry of Sgr A*. Finally, we discuss observational tests that could distinguish a black hole from alternative supermassive compact objects, improving our understanding of the core of the Milky Way.
11:15 Natalia Villa Rodrigues (USP) : Modeling halo bias with neural networks – Video
Understanding the relation between the distribution of dark matter halos and the underlying dark matter field, known as halo bias, is of paramount importance for testing cosmological and galaxy formation models against observations. In this work, we investigate how to model halo bias as a probability distribution for the number of halos in a certain volume, conditioned to a set of properties from the underlying dark matter field. In particular, we explore the connection between these properties and the cosmic web classification. We exploit the power of neural networks and related models to handle high dimensional parameter spaces, their flexibility in modeling probability distributions with complex shapes, and the ability of deep learning to extract informative features from the dark matter field.
14:00 Vitor Sampaio (UNICID): Disks and Spheroids across cosmic time: Morphological and Star Formation Evolution of Galaxies from z = 2.4 to z = 0.2 – Video
In this presentation, I will explore the morphological and star formation evolution of galaxies across cosmic time using a sample of ~14,000 galaxies from the CANDELS fields. I start by introducing a hybrid unsupervised-supervised morphological classification method based on non-parametric indices, carefully tailored to narrow redshift bins to account for galaxy evolution and observational effects. Comparison shows that significant biases may arise from adopting a single model across wide redshift ranges, particularly leading to a higher uncertainty in the fraction of disk galaxies. Then, by combining morphology with star formation properties, I will show that disk galaxies maintain high sSFRs but show a decreasing average stellar mass, while massive spheroids grow and quench, likely through mergers of massive disk systems. I will discuss our findings in the context of the downsizing scenario and cosmic noon. Throughout the talk, I will highlight how redshift-aware, automated classification methods challenge long-standing results based on visual inspection, providing relevant contributions for the already-here JWST era.
March 14, 2025
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10:00 Jorge Luiz Meléndez Moreno (IAG, USP): Solar Twins and their implications for Planets, Stars and the Galaxy – Video
Participants List: Here
2024
November 8, 2024
- 10:00 Abdias Aires (IFT-UNESP): Mitigation of nonlinear galaxy bias with theoretical-error likelihood – Video
- 11:00 Giorgio Torrieri (Unicamp): Non-local effective field theory in general relativity – Video
- 14:00 Daniel Lopez-Cano (IF-USP): Machine Learning Applications in Cosmology: Past, Present, and Future – Video
Participants List: Here
October 11, 2024
- 10:00 Walter Riquelme (IFT/UNESP): Unveiling the initial conditions of the universe with galaxy surveys – Video
- 11:00 Yago Porto (UFABC): Flavor Matters, but Matter Flavors: Matter Effects on Flavor Composition of Astrophysical Neutrinos – Video
- 14:00 Lilianne Nakazono (USP): Searching for quasars in the era of large multi-wavelength datasets – Video
Participants List: Here
September 13, 2024
- 10:00 – João Victor Silva (IFT UNESP): Dynamical Dark Energy and Massive Neutrinos in Light of DESI 2024 BAO – Video
- 11:00 – Lia Doubrawa (IAG USP): Galaxy clusters in photometric surveys: detection and analysis – Video
Participants List: Here
August 16, 2024
- 10:00 – Edivaldo Moura Santos (USP): The ultra-high energy cosmic ray sky – Video
- 11:00 – João Vitor Dinarte Ferri (USP): A cosmic standard ruler from the cross-correlations of galaxies and dark sirens – Video
- 14:00 – Natali de Santi (USP São Carlos): Cosmology with graph neural networks – Video
Participants List: Here
June 14, 2024
- 10:00 – Nickolas de Aguiar Alves (UFABC): Don’t forget about the memory
- 11:00 – Reinaldo de Carvalho (UNICID): Studies on Galaxy Morphology: Diving into the Primordial Era
- 14:00 – Isabela Santiago de Matos (IFT-UNESP): Cosmological tests with bright and dark standard sirens
Participants List: Here
May 10, 2024
- 10:00 – Lucas Gabriel Silva (IAG USP): Galaxy cluster mass estimation using the splashback radius
- 11:00 – Adriana Valio (Mackenzie): Exoplanetas: atmosferas e habitabilidade
- 14:00 – Carol Guandalin (Institute for Astronomy (IfA), University of Edinburgh): I see bispectrum everywhere
April 12, 2024
- 10:00 – Rodrigo Voivodic (Donostia Intl. Phys. Ctr., San Sebastian): The Hybrid Lagrangian Perturbation Theory
- 11:00 – Louis Legrand (ICTP-SAIFR): Next generation galaxy and CMB surveys: optimal estimators and cross-correlations
- 14:00 – Chee Sheng Fong (UFABC): How much baryon asymmetry and dark matter can be generated from primordial black holes?
Announcement:
Photos
Additional Information
How to reach the Principia Institute: The meeting will be held in the first-floor auditorium of the Science Center at Principia Institute located at Rua Pamplona, 145 near the Trianon-Masp metro station.