This series consists of talks in the areas of Cosmology, Gravitation and Particle Physics.
Cosmologists wish to explain how our universe, in all its complexity, could ever have come about. This is the problem of initial conditions and the first step towards its solution is the assessment of the universe’s entropy today. It is widely agreed upon that the entropy of vacuum energy, given by the Bekenstein bound, makes up the bulk of the current entropy budget, dominating over that of gravity and over thermal motions of the cosmic radiation background.
In this talk, I will outline the forward model approach to reconstruct cosmological fields in a Bayesian framework. I will focus on two examples - galaxy clustering and neutral hydrogen intensity mapping.
Primordial SU(2) gauge fields and axions can contribute to the physics of
inflation. In this class of models, both the gauge field and axion acquire
a VEV, which is P and CP breaking and enriches the phenomenology of
particles with spin. Their multifaceted phenomenology and unique
observational signatures, e.g., chiral primordial gravitational waves and
gravitational leptogenesis, turned this class of models to a hot topic of
research in the past nine years. In this talk, first, I will briefly
Thus far, the non-linear regime of structure formation is only accessible through expensive numerical N-body simulations since the conventional ana-
Scattering amplitudes of massive spin-2 particles generically grow with energy and lead to violations of perturbative unitarity. One way to partially soften such amplitudes is with the infinite towers of particles present in Kaluza-Klein theories. In this talk I will discuss in detail this mechanism of unitarization for general dimensional reductions of pure gravity and show that it leads to some interesting constraints on the eigenfunctions and eigenvalues of the scalar Laplacian on closed manifolds.
In this work, our prime focus is to study the one to one correspondence between the conduction phenomena in electrical wires with impurity and the scattering events responsible for particle production during stochastic inflation and reheating implemented under a closed quantum mechanical system in early universe cosmology.
Neutrinos are established to be massive and the mass differences have been measured, but the absolute neutrino mass values remain unknown. Cosmic neutrinos with finite mass slightly suppress the matter power spectrum below their free-streaming scale and this effect can be applied to constrain neutrino masses. However, the challenge of this method is to disentangle the complex and poorly understood baryonic effects and to obtain better optical depth measurements from the cosmic microwave background experiments.
The influx of new and high-quality cosmological data from upcoming cosmic microwave background (CMB) and large-scale structure surveys will provide unique and exciting opportunities to study the fundamental constituents of the Universe in the upcoming few years. In particular, measurements of second-order effects in the CMB will become observationally significant for the fist time as surveys will achieve the necessary precision.
Ghostly neutrino particles continue to bring surprises to fundamental physics, from their existence to the phenomenon of neutrino oscillation which implies that their masses are nonzero. Their exact masses, among the most curious unknowns beyond the Standard Model of particle physics, can soon be probed by the joint analysis of upcoming cosmological surveys including LSST, Euclid, WFIRST, Simons Observatory, and CMB-S4. In this talk, I will first discuss ongoing work studying the effects of massive neutrinos.