Month: April 2019

Graduate Seminar, 15th April

Speaker: Artur Miroszewski

Title: Early universe cosmology and the coherent states

Abstract: The theory of General Relativity seems to be a well chosen tool to describe the evolution of the universe. Starting from very simplified model of the universe, Friedmann-Lemaître-Robertson-Walker spacetime, we are able to explain most of the observable phenomena on the cosmic scale. On the other hand the cosmological solutions in GR tend to contain past-incomplete geodesics, also know as singularities. The singularities occur in the very early universe regimes, where apart from the GR we should take into account quantum effects. Although the theory of Quantum Gravity seems to be far from invented and understood, the semi-classical approach may be able to point us to some features of it. During my talk I will present the semi-classical approach based on the coherent states, leading to the Big Bang singularity avoidance scenario- the Big Bounce.

Graduate Seminar, 8th April

Speaker: Chetan Bavdhankar

Title: Peculiar Velocities – a very important probe of cosmology

Abstract: Peculiar velocity of galaxies is one of the very important probes of the cosmological model (Strauss and Willick (1995)). Since peculiar velocities are induced by gravity only, they can be used to obtain various cosmological parameters such as mean matter density or the growth of structure (Nusser and Davis (2011)). The large-scale fluctuations of the matter distribution can be determined using bulk flows where a given volume of the sample shows the net peculiar motion of galaxies. To study these velocity dependent properties, I have started with estimating observers motion using the radial peculiar velocities of the galaxies in observers frame. In this analysis, I have simulated 1000 galaxies in a volume of a sphere of radius 350Mpc. These galaxies have peculiar velocities in random directions with gaussian magnitudes. Then we try to recover the observer’s motion from the observer frame updated data using chi-squared analysis. With real data, this type of analyses can be used to estimate the motion of the Local Group, bulk flows in at different scales, local voids, etc.