TBA

TBA

TBA

TBA

In stellar evolution, one of the fundamental ingredients is the chemical composition. At the stellar surface, the chemical abundances change during the life of the stars due to the presence of the chemical transport mechanisms. One of these processes is atomic diffusion. This process presents great success in simulating solar-type star evolution.
However, for F-type stars, the inclusion of atomic diffusion shows unrealistic chemical variations at the stellar surface, indicating the need for competing transport processes. In this talk, we present the possibility of parameterizing the effects of the competing processes using the turbulent mixing. We successfully found that it is possible to avoid the chemical over-variations at the stellar surface. We also found that the effects of radiative acceleration in F-type stars can be reproduced using turbulent mixing.
Then, we explored the performance of using the parameterised turbulent mixing in the inference of the global properties from a sample of observed Kepler stars. We also compared its results with the current models that neglect atomic diffusion in F-type stars. We found that considering turbulent mixing and atomic diffusion induce a difference in the inferred age up to 20%.

The deformability properties of a self-gravitating object immersed in a gravitational field are encoded in its Love numbers.
For vacuum four dimensional black holes solutions of General Relativity (GR), their Love numbers vanish, a feature which is not present in higher dimension or in modified gravity in general. It has been argued that this peculiar feature descends from a hidden symmetry of black hole perturbations dubbed the Love symmetry. However, several proposals exist and the origin of these symmetries is still debated. In this talk, I will discuss a specific set of symmetries (in relation to the ones found by L. Hui and collaborators in arXiv:2105.01069) for the static black hole perturbations and explain how they can used to explain the vanishing of the Love numbers. Then, I will discuss the relation between this Love symmetry and new non-standard symmetries of black hole mechanics.

Based on: arXiv:2202.12828 [gr-qc]
arXiv:2110.01455 [gr-qc]
arXiv:2302.07644 [gr-qc]

The redshifted 21 cm signal from neutral hydrogen is a very useful probe of the cosmic evolution. A particularly interesting phase of this evolution is the Epoch of Reionization (EoR), when the first ionizing sources were born in the early universe. The current and the upcoming low frequency radio telescopes, like the upgraded GMRT (Giant Metrewave Radio Telescope) or the Square Kilometre Array (SKA), are expected to play a crucial role in studying cosmic evolution during the EoR and the post-EoR era, and thus addressing many important but unresolved issues. One of the challenging aspects in this regard is the fast and efficient data processing necessary for detecting the weak cosmological signal in presence of the strong, confusing foreground. However, the foreground is interesting on its own right. In this talk, I will share some of our recent efforts to study the low radio frequency foreground using data from the uGMRT, an SKA pathfinder, as stepping stones towards constraining the 21 cm signal. This work may help us to understand the near-future pathways of studying the atomic hydrogen power spectrum from the EoR/post-EoR era; it also allows us to study, in details, the properties of a large population of extragalactic sources as well as of the interstellar medium of the Milky Way.

Reconciling the standard model's theoretical predictions with precision measurements from multiple probes stands as one of the most pressing challenges of modern cosmology. During the last decade, increasing evidence for persistent discrepancies in the value of cosmological parameters when inferred from model-dependent and -independent probes opened the door for a new paradigm. In this talk, I will address whether (part of) the cosmological tensions can be attributed to missing physics in the standard model. In particular I will focus on tests of different models with interactions between dark energy and dark matter.