Talk by Brajesh Gupt

Title: Some numerical and phenomenological studies in loop quantum cosmology
Time: Monday June 23 2014
Place: 241 Nicholson

Abstract:
A key feature of the singularity resolution in loop quantum cosmology (LQC) is the occurrence of the quantum bounce when the spacetime curvature becomes comparable to the Planck scale. The presence of quantum bounce greatly modifies the dynamics of the early universe and can have important implications for the observational signatures. Although the quantum bounce has been previously studied via numerical methods for initial conditions that correspond to large macroscopic universes at late times, a detailed study of the robustness of the quantum bounce for a generic class of initial condition has so far been missing due to severe computational challenges. I will talk about a numerical scheme, Chimera, which we have developed to tackle these computational challenges. I will also discuss some phenomenological implications on the quantum bounce in anisotropic spacetimes.

Talk by Brajesh Gupt (LSU)

Title: Non-singular AdS-dS transitions in a landscape scenario
Time: Wednesday April 2
Place: 241 Nicholson

Abstract:
In the multiverse scanario allowing eternal inflation, it is an important problem to understand transitions between different vacua, of which the ones from anti-deSitter to de-Sitter is forbidden in the classical theory. In this talk, we consider toy landscape potentials: a double well and a triple well potential allowing anti-deSitter and de-Sitter vacua, in the effective dynamics of loop quantum cosmology for the k
=−1 FRW model. We show that due to the non-perturbative quantum gravity effects as understood in loop quantum cosmology, non-singular anti-deSitter to de-Sitter transitions are possible. In the future evolution, an anti-deSitter bubble universe does not encounter a big crunch singularity but undergoes a big bounce occurring at a scale determined by the underlying quantum geometry. These non-singular transitions provide a mechanism through which a probe or a ``watcher,'' used to define a local measure, can safely evolve through the bounce and geodesics can be smoothly extended from anti-deSitter to de-Sitter vacua.

Talk by Anton Joe (LSU)

Title: Effective dynamics of Kantowski-Sachs spacetime in loop quantum cosmology
Time: Wednesday April 2
Place: 241 Nicholson

Abstract:
We study singularity resolution in Kantowski-Sachs spacetime in the effective loop quantum cosmology setting for various matter models such as dust, radiation, cosmic strings, cosmological constant and scalar fields. We find the inverse triad correction and bounds on energy density, shear scalar and expansion scalar. The evolution of universe after bounce is studied and found that a Nariai-like spacetime is obtained for different choices of matter. We analyze the stability of these quantum Nariai-like spacetimes with respect to homogeneous perturbations and find that unlike classical Nariai spacetimes, these are stable.

Talk by Jorge Pullin

Title: Spherical quantum vacua for quantum black holes in loop quantum gravity
Time: Wednesday November 19th 11:00am
Place: 241 Nicholson

Talk by Yifu Cai (McGill)

Title: Perturbation theory of bounce cosmology
Time: Monday November 11th 11:00am
Place: 241 Nicholson
Abstract:

I will focus on the understanding of big bang singularity and briefly review how we may avoid it from the approaches of effective field theory. This can be viewed as an important phenomenological step towards quantum gravity. I will talk about the corresponding perturbation theory of primordial cosmological perturbations within this frame and the predictions we could make for observations. Part of them have already been able to be constrained by the present CMB data, while more are expected in forthcoming data, namely the CMB polarization.

Talk by Emanuele Berti (OleMiss)

Title: Physics and astrophysics with gravitational-wave observations: opportunities and challenges
Time: Friday November 8th 10:00am
Place: 241 Nicholson
Abstract:
Future detections of compact binary mergers with Earth- and space-based gravitational-wave detectors may give us an opportunity to
test strong-field gravity in previously unexplored regimes, and to constrain the formation history of compact binaries. Building on the introduction from my departmental colloquium, I will give an informal (and more technical) discussion of the opportunities and challenges that await us. Can we really constrain alternative theories of gravity? Can we actually pin down the physical mechanism responsible for compact binary formation? What are the challenges that await gravitational-wave astronomy, given the current funding climate in the US and Europe?

Talk by Jorge Pullin

Title: Complete quantization of vacuum spherically symmetric gravity
Time: Wednesday October 23rd 11:00am
Place: 241 Nicholson