Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session S6: Loop Quantum Gravity and CosmologyFocus

Hide Abstracts 
Sponsoring Units: DGRAV Chair: Jorge Pullin, Louisana State University Room: Virginia C 
Monday, January 30, 2017 1:30PM  2:06PM 
S6.00001: Loop Quantum Cosmology and the CMB Invited Speaker: Ivan Agullo This talk will provide an uptodate summary of phenomenological explorations in loop quantum cosmology. The possibility of a quantum gravity origin of the anomalies observed in the cosmic microwave background at large angular scales will be discussed. The talk will also provide some background material for subsequent contributions in the same session. [Preview Abstract] 
Monday, January 30, 2017 2:06PM  2:18PM 
S6.00002: Evolution of perturbations in anisotropic loop quantum cosmology Sreenath Vijayakumar, Ivan Agullo, Javier Olmedo In loop quantum cosmology the big bang singularity is replaced by a quantum bounce. The evolution of primordial perturbations through such a bounce in a Friedmann–Lema\^{i}tre–Robertson–Walker universe has been studied in great detail. However, it is well known that any tiny anisotropy will grow (up to an upper bound) as the universe contracts and undergoes a bounce. Anisotropies will then decrease and eventually dilute in the expanding branch, but quantum perturbations may retain memory of the anisotropic bounce. In this talk, we present our efforts in understanding the effect of anisotropies ( of BianchiI type ) on the evolution of primordial perturbations in loop quantum cosmology, and in exploring its phenomenological implications. [Preview Abstract] 
Monday, January 30, 2017 2:18PM  2:30PM 
S6.00003: Loop quantum cosmology: confronting the hybrid quantization approach with observations Javier Olmedo, Daniel Martin de Blas In loop quantum cosmology there are several approaches for the confrontation of the theory with observations. Here, we focus on the hybrid quantization approach. We provide an exhaustive analysis including scalar and tensor perturbations on effective (quantummechanically corrected) homogeneous and isotropic cosmologies coupled to a massive scalar field. We compute the primordial power spectrum of the perturbations at the end of inflation for a set of initial vacuum states defined at the deep quantum regime of the cosmological model. We then analyze the tensortoscalar ratio and the consistency relation between this quantity and the spectral index of the tensor power spectrum. Eventually, we compute the temperaturetemperature, electricelectric, temperatureelectric and magneticmagnetic correlation functions predicted by this approach and compare them with present observations. [Preview Abstract] 
Monday, January 30, 2017 2:30PM  2:42PM 
S6.00004: The JWKB approximation in loop quantum cosmology David Craig, Parampreet Singh We explore the JWKB approximation in loop quantum cosmology in a flat universe with a scalar matter source. Exact solutions of the quantum constraint are studied at small volume in the JWKB approximation in order to assess the probability of tunneling to small or zero volume. Novel features of the approximation are discussed which appear due to the fact that the model is effectively a twodimensional dynamical system. Based on collaborative work with Parampreet Singh. [Preview Abstract] 
Monday, January 30, 2017 2:42PM  2:54PM 
S6.00005: Spinfoam Cosmology with the Proper Vertex Ilya Vilensky A modification of the EPRL vertex amplitude in the spinfoam framework of quantum gravity  socalled "proper vertex amplitude"  has been developed to enable correct semiclassical behavior to conform to the classical Regge calculus. The proper vertex amplitude is defined by projecting to the single gravitational sector. The amplitude is recast into an exponentiated form and we derive the asymptotic form of the projector part of the action. This enables us to study the asymptotics of the proper vertex by applying extended stationary phase methods. We use the proper vertex amplitude to investigate transition amplitudes between coherent quantum boundary states of cosmological geometries. In particular, HartleHawking noboundary states are computed in the proper vertex framework. We confirm that in the classical limit the HartleHawking wavefunction satisfies the Hamiltonian constraint. [Preview Abstract] 
Monday, January 30, 2017 2:54PM  3:06PM 
S6.00006: Squeezed vacua in loop quantum gravity Lucas Hackl, Eugenio Bianchi, Jonathan Guglielmon, Nelson Yokomizo Semiclassical states in quantum gravity are expected to exhibit long range correlations. In order to describe such states within the framework of loop quantum gravity, it is important to parametrize states in terms of their correlations. In this talk, I will introduce a new class of states with prescribed correlations, called squeezed vacua. They can be naturally understood in the bosonic Hilbert space representation where they are generated in two steps. First, we squeeze the AshtekarLewandowski vacuum via the action of a quadratic exponential and second, we project the resulting states onto the kinematical Hilbert space of Loop quantum gravity. I will give explicit examples on how to construct states that are peaked on some classical geometry, but whose quantum fluctuations exhibit long range correlations. [Preview Abstract] 
Monday, January 30, 2017 3:06PM  3:18PM 
S6.00007: Emergence of spacelike correlations in loop quantum gravity Eugenio Bianchi Vacuum states of a quantum field in a curved spacetime have nontrivial correlations at spacelike separation. The stretching and squeezing of such correlations plays a crucial role in inflationary cosmology. In this talk I discuss a preinflationary scenario where spacelike correlations of quantum perturbations arise from an initially unentangled state in loop quantum gravity. This scenario relies on recent results on squeezed vacua and entanglement in loop quantum gravity. [Preview Abstract] 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2020 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700