Talks

8605 - 8616 of 20132 Results

Cosmological implications of quantum gravity proposals

Mairi Sakellariadou King's College London

June 28, 2017

PIRSA:17060108

Astrophysics
Loop quantum gravity and bounces : cosmology and black holes

Aurelien Barrau Laboratoire de Physique Subatomique et de Cosmologie (LPSC Grenoble)

June 28, 2017

PIRSA:17060106

Astrophysics
Loop Quantum Cosmology, Non-Gaussianity, and CMB anomalies

Ivan Agullo Louisiana State University

June 28, 2017

PIRSA:17060105

Astrophysics
Discussion Session 4

Latham Boyle University of Edinburgh

Job Feldbrugge Perimeter Institute for Theoretical Physics

Neil Turok University of Edinburgh

June 27, 2017

PIRSA:17060104

Astrophysics
A Bouncing Universe approach to Fine Tuning

Stephon Alexander Brown University

June 27, 2017

PIRSA:17060103

Astrophysics
Space(-time) structure in models of loop quantum gravity

Martin Bojowald Pennsylvania State University

June 27, 2017

PIRSA:17060102

Astrophysics
Quantum cosmological instabilities - with and without boundaries

Jean-Luc Lehners Self Employed

June 27, 2017

PIRSA:17060100

Astrophysics
Unitary Cosmological Bounces

Claudia de Rham Imperial College London

June 27, 2017

PIRSA:17060099

Astrophysics
Discussion Session 2

Angelika Fertig TotalEnergies (France)

Steffen Gielen University of Sheffield

Elizabeth Gould Arthur B. McDonald Canadian Astroparticle Physics Research Institute

June 26, 2017

PIRSA:17060101

Astrophysics
Emergent bouncing cosmology from quantum gravity condensates

Edward Wilson-Ewing University of New Brunswick

June 26, 2017

PIRSA:17060098

Astrophysics
Challenges for Bouncing Cosmologies

Robert Brandenberger McGill University - Department of Physics

June 26, 2017

PIRSA:17060096

Astrophysics
Observable Consequences of a Bounce

Ue-Li Pen University of Toronto

June 26, 2017

PIRSA:17060097

Astrophysics

Cosmological implications of quantum gravity proposals

Mairi Sakellariadou King's College London

June 28, 2017

PIRSA:17060108

Astrophysics

I will highlight cosmological consequences of Group Field theory Condensate Cosmology and Emergent Gravity on Non-commutative Spaces, two cosmological models based on a top-down and a bottom-up, respectively, approaches to quantum gravity. In particular, I will show that the initial singularity of the standard cosmology is replaced by a bounce, while there is an inflation-like phase with a graceful exit, driven by a purely geometrical mechanism which does not require the introduction of an ad-hoc scalar field.
Loop quantum gravity and bounces : cosmology and black holes

Aurelien Barrau Laboratoire de Physique Subatomique et de Cosmologie (LPSC Grenoble)

June 28, 2017

PIRSA:17060106

Astrophysics

In his talk I will review some recent results concerning the cosmological bounce in loop quantum gravity. In particular I will show how the predicted duration of inflation in affected by the choices of initial conditions, amount of shear and inflaton potential shape. Then I will show how those ideas can be used in black holes physics and comment on the associated phenomenology?
Loop Quantum Cosmology, Non-Gaussianity, and CMB anomalies

Ivan Agullo Louisiana State University

June 28, 2017

PIRSA:17060105

Astrophysics

Loop quantum cosmology has become a robust framework to describe the highest curvature regime of the early universe. In this theory, inflation is preceded by a bounce replacing the big bang singularity. I will summarize the theoretical framework, and explore the corrections to the inflationary predictions for the primordial spectrum of cosmological perturbations that this pre-inflationary, quantum gravity phase of the universe introduces. The impact of the bounce on non-Gaussianity and the exciting relation to the observed large scale anomalies in the CMB will be discussed.
Discussion Session 4

Latham Boyle University of Edinburgh

Job Feldbrugge Perimeter Institute for Theoretical Physics

Neil Turok University of Edinburgh

June 27, 2017

PIRSA:17060104

Astrophysics
A Bouncing Universe approach to Fine Tuning

Stephon Alexander Brown University

June 27, 2017

PIRSA:17060103

Astrophysics
Space(-time) structure in models of loop quantum gravity

Martin Bojowald Pennsylvania State University

June 27, 2017

PIRSA:17060102

Astrophysics

Loop quantum gravity has suggested modifications of the dynamics of cosmological models that could lead to a bounce at large curvature. However, the same modifications may alter the gauge structure of the theory, which is related to the structure of space-time. In a large class of examples the space-time structure has been derived and shown to imply signature change just in the bounce region. The picture of a cyclic universe with a deterministic bounce then has to be replaced by the scenario of a non-singular beginning some finite time ago.
Quantum cosmological instabilities - with and without boundaries

Jean-Luc Lehners Self Employed

June 27, 2017

PIRSA:17060100

Astrophysics

The big bang singularity might be avoided by replacing it with a theory of initial conditions, or by considering a bounce from an earlier contracting phase. I will describe how both proposals can run into difficulties with instabilities when the spacetime must be treated semi-classically (i.e. when bounces occur due to a quantum tunneling transition rather than as classically non-singular solutions). The absence of such instabilities places new restrictions on the available theories, implying a selection criterion whose consequences remain to be explored.
Unitary Cosmological Bounces

Claudia de Rham Imperial College London

June 27, 2017

PIRSA:17060099

Astrophysics

A non-singular cosmological bounce in the Einstein frame can only take place if the Null Energy Condition (NEC) is violated. I will explore the constraints imposed by demanding tree level unitarity on a cosmological background in single scalar field theories before focusing on the explicit constraints that arise in P(X) theories. In that context, perturbative unitarity makes it impossible for the NEC violation to occur within the region of validity of the effective field theory but I will show explicitly how unitarity may be restored by involving irrelevant operators that arise at a higher scale.
Discussion Session 2

Angelika Fertig TotalEnergies (France)

Steffen Gielen University of Sheffield

Elizabeth Gould Arthur B. McDonald Canadian Astroparticle Physics Research Institute

June 26, 2017

PIRSA:17060101

Astrophysics
Emergent bouncing cosmology from quantum gravity condensates

Edward Wilson-Ewing University of New Brunswick

June 26, 2017

PIRSA:17060098

Astrophysics

I will explain how cosmological dynamics emerge from the hydrodynamics of isotropic group field theory condensate states in the Gross-Pitaevskii approximation. The correct Friedmann equations are recovered in the classical limit for some choices of the parameters in the action for the group field theory, and quantum gravity corrections arise in the high-curvature regime causing a bounce which generically resolves the big-bang and big-crunch singularities.
Challenges for Bouncing Cosmologies

Robert Brandenberger McGill University - Department of Physics

June 26, 2017

PIRSA:17060096

Astrophysics

I will review various approaches to bouncing cosmologies and will discuss challenges which the different approaches face.
Observable Consequences of a Bounce

Ue-Li Pen University of Toronto

June 26, 2017

PIRSA:17060097

Astrophysics

I discuss potentially observable signatures of scalar and tensor decaying modes, which do not exist in inflation, and could be a probe of a bouncing universe.

Title	Date	Collection	Type	Info
Cosmological implications of quantum gravity proposals	2017‑06‑28	Bounce Scenarios in Cosmology	Conference	View details
Loop quantum gravity and bounces : cosmology and black holes	2017‑06‑28	Bounce Scenarios in Cosmology	Conference	View details
Loop Quantum Cosmology, Non-Gaussianity, and CMB anomalies	2017‑06‑28	Bounce Scenarios in Cosmology	Conference	View details
Discussion Session 4	2017‑06‑27	Bounce Scenarios in Cosmology	Conference	View details
A Bouncing Universe approach to Fine Tuning	2017‑06‑27	Bounce Scenarios in Cosmology	Conference	View details
Space(-time) structure in models of loop quantum gravity	2017‑06‑27	Bounce Scenarios in Cosmology	Conference	View details
Quantum cosmological instabilities - with and without boundaries	2017‑06‑27	Bounce Scenarios in Cosmology	Conference	View details
Unitary Cosmological Bounces	2017‑06‑27	Bounce Scenarios in Cosmology	Conference	View details
Discussion Session 2	2017‑06‑26	Bounce Scenarios in Cosmology	Conference	View details
Emergent bouncing cosmology from quantum gravity condensates	2017‑06‑26	Bounce Scenarios in Cosmology	Conference	View details
Challenges for Bouncing Cosmologies	2017‑06‑26	Bounce Scenarios in Cosmology	Conference	View details
Observable Consequences of a Bounce	2017‑06‑26	Bounce Scenarios in Cosmology	Conference	View details

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Format results

Cosmological implications of quantum gravity proposals

Loop quantum gravity and bounces : cosmology and black holes

Loop Quantum Cosmology, Non-Gaussianity, and CMB anomalies

Discussion Session 4

A Bouncing Universe approach to Fine Tuning

Space(-time) structure in models of loop quantum gravity

Quantum cosmological instabilities - with and without boundaries

Unitary Cosmological Bounces

Discussion Session 2

Emergent bouncing cosmology from quantum gravity condensates

Challenges for Bouncing Cosmologies

Observable Consequences of a Bounce

Cosmological implications of quantum gravity proposals

Loop quantum gravity and bounces : cosmology and black holes

Loop Quantum Cosmology, Non-Gaussianity, and CMB anomalies

Discussion Session 4

A Bouncing Universe approach to Fine Tuning

Space(-time) structure in models of loop quantum gravity

Quantum cosmological instabilities - with and without boundaries

Unitary Cosmological Bounces

Discussion Session 2

Emergent bouncing cosmology from quantum gravity condensates

Challenges for Bouncing Cosmologies

Observable Consequences of a Bounce