Collection Number S004
Collection Type Series
This series consists of talks in the area of Cosmology and Gravitation.

Primordial SU(2), a new paradigm for Particle Cosmology

Azadeh Maleknejad Max-Planck-Institut für Astrophysik (MPA), Garching

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

Unitarization from geometry

James Bonifacio Case Western Reserve University

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.

Cosmology and cosmography from peculiar velocities in the nearby Universe

Mike Hudson University of Waterloo

Maps of the mass density field can be used to predict peculiar velocities point-by-point. The comparison of these predictions to peculiar velocity data can be used to determine the cosmological parameter combination f sigma_8. I will briefly discuss the history of this field, present some of our recent results as well as other applications to calibrating the Hubble constant via SNe and gravitational waves, and discuss ongoing work to improving these measurements, through better modelling and, more importantly, acquiring more peculiar velocity data.

Cosmology from Condensed Matter Physics: A study of out-of-equilibrium physics

Sayantan Choudhury Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)

 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.

Neutrino mass and cosmic flows

Hong-Ming Zhu National Astronomical Observatories, Chinese Academy of Sciences

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.

New probes of fundamental physics: Utilising small-scale signatures in the Universe.

Selim Hotinli Imperial College London

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.

Cosmology with Massive Neutrinos

Jia Liu University of California

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.

Inelastic dark matter revives the dark photon explanation of the muon g-2 anomaly.

Gopolang Mohlabeng Brookhaven National Laboratory

A massive U(1)' gauge boson known as a “dark photon” or A', has long been proposed as a potential explanation for the muon g − 2 anomaly. Recently, experimental results have excluded this possibility for a dark photon decaying visibly and invisibly. I revisit this idea and consider a model where A' couples to inelastic dark matter, leading to a semi-visible decay mode. I show that for large mass splittings between the dark sector states this decay mode is enhanced, weakening the invisibly decaying dark photon bounds.