Gerardo Urrutia Sanchez (Institute for Theoretical Physics, PAN, Warsaw)
Gamma-ray bursts (GRBs) are the most luminous explosions in the universe ( $L \sim 10^{50} - 10^{52}$~erg s$^{-1}$ ) originating from mergers of neutron stars or from the collapse of stripped-envelope massive stars. The first seconds of emission are dominated by gamma emission and high variability in its light curves, in addition, a long-lasting afterglow emission across a wide range of frequencies could be observed after the burst time. In this talk, I will present numerical simulations of collapsar GRBs, showing the propagation of a relativistic jet through the progenitor star and after its breakout. Since electromagnetic signals (the light curves) cannot fully reveal the physical properties of the jet within the stellar envelope, I will discuss GRBs as candidates for gravitational wave (GW) emission arising from the propagation of such ultra-relativistic jets. Our results indicate that key parameters of jet propagation can be inferred from this GW signal and detected by future instruments such as LISA, BBO, DECIGO, and ALIA. These results suggest that future GW detections associated with GRB jets could provide a complete picture of jet evolution together with electromagnetic counterparts.
Mariana Jaber (Center for Theoretical Physics, PAN, Warsaw)
The standard ΛCDM model, despite its remarkable success, remains incomplete, especially regarding the nature of cosmic acceleration. During the first part of the talk, I will discuss my work testing alternatives to the Cosmological Constant, including quintessence models and modifications to General Relativity using galaxy redshift surveys. The resulting catalogues contain a wealth of untapped information, particularly regarding galaxy motions and pairwise velocities. A key challenge in utilising this wealth of new data is understanding galaxy bias, which is essential for making accurate cosmological inferences. This motivates the second part of my talk, where I discuss my research on developing analytical models of galaxy pairwise dynamics based on the kinetic BBGKY theory describing the evolution of a system of particles interacting via gravity. This approach could lead to new methods to constrain cosmological parameters such as matter density, the Hubble parameter, and the growth rate. Combining these analytical models with the information about the large-scale environment and observational data, we could refine constraints on ΛCDM and extend our galaxy bias modelling to non-linear scales.
Deka Kishan (National Center for Nuclear Research, Warsaw)
Weak gravitational lensing remaps the primordial anisotropies in the Cosmic Microwave Background (CMB), introducing lensing induced B-mode polarisation. Estimating the lensing potential field and delensing the observed CMB maps are crucial for improving constrains on cosmological parameters. However, one of the main obstacles is the presence of polarised foreground emissions from our own Galaxy. In this talk, I will discuss about CMB weak lensing reconstruction methods and the impact of galactic foreground emissions in delensing. I will present my results on galactic foreground bias on the tensor-to-scalar ratio in the context of upcoming CMB Stage-4 survey.
