Friday Seminar

Date: 1/19/2024

Speaker: Albin Joseph

Institution: ASU

Faculty Host: Simon Foreman 

Title: Dynamics of Dark Energy: Cosmological Trackers

Abstract: Two decades have passed since the groundbreaking discovery of cosmic acceleration, yet the mysteries surrounding the laws of physics on the largest scales persist. This remarkable phenomenon, initially revealed through the observation of type 1a supernovae, has revolutionized our comprehension of cosmology and serves as a paradigm shift in our understanding of the Universe. In this talk, I will discuss the cosmological models exhibiting tracker properties that have great significance in the context of dark energy as they can reach the present value of dark energy density from a wide range of initial conditions, thereby alleviating both the fine-tuning and the cosmic coincidence problem. In particular, I will discuss the Oscillatory Tracker Model, which belongs to the family of tracker dark energy models and their effect on various observational probes.

Date: 3/22/24

Speaker: Tarun Souradeep

Institution: Raman Research Institute

Faculty Host: Tanmay

Title:  Validating the Cosmological principle

Abstract: The Cosmological Principle, a fundamental tenet of the 'standard model of cosmology',   predicates a statistically isotropic distribution of fluctuations in the measured Cosmic Microwave Background (CMB)  temperature and polarisation sky maps. Enigmatic anomalies claimed in the WMAP and Planck CMB sky maps, and some other recent observations could  challenge the standard model. However, these claims need to be cast in an objective mathematical framework and established with statistical rigour. Bayesian inference of the underlying covariance structure of random fields on the sphere in the Bipolar Spherical Harmonic  (BipoSH) representation developed in our research program provides such a framework.  We review the recent inferences drawn from Planck data and dwell on the future prospects with proposed CMB observations.

Date: 3/29/24

Speaker: Damien Easson

Institution: ASU

Faculty Host: Matt

Title: Solving the initial singularity problem: eternal inflation and a world without end

Abstract: 

We discuss the possibility an eternal universe, a universe with no first moment and no end. 

The talk will focus on eternal inflation and the key role that inflation plays in resolving the initial big-bang singularity.

Along the way we, will describe how proposed no-go theorems, such as the famous theorem of Borde, Guth and Vilenkin (BGV)

are circumvented or obviated. Our exploration encompasses eternal inflating, loitering, and bouncing models, shedding light on 

the critical aspects that underpin geodesic completeness. This will include a detailed analysis of the classical energy conditions in General Relativity. 

Ignoring the intractable subtleties introduced by quantum considerations, such as rare tunneling events and

Boltzmann brains, we will argue that the universe need not have a beginning or an end.

Date: 4/12/24

Speaker: Yosef Verbin

Institution:

Faculty Host: Damien

Title: Palatini Nonlinear Electrodynamics

Abstract: The general subject of this talk is the formulation of electrodynamics and its non-linear generalizations, in an analogy with the Palatini formalism of General Relativity and its extensions and modifications. As in GR, the first order formulation of Maxwell theory is equivalent to the second order standard formulation since the field equations are identical. Moreover, for theories of nonlinear electrodynamics, the situation is similar to that of gravity and in certain cases, the first and second order formulations yield different field equations. Some of the initial results of the most basic implications of these Palatini non-linear electrodynamics (PNLED for short) will be presented – mainly as compact objects like solitons and black holes. If time permits, cosmological implications will be mentioned briefly.

Date: 4/19/24

Speaker: Francesc Ferrer 

Institution:

Faculty Host: Tanmay

Title: 

Abstract: