Astrophysics

Displaying 697 - 708 of 2079

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 Koehn AI
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 Canadian Institute for Theoretical Astrophysics (CITA)
June 26, 2017

PIRSA:17060097
Astrophysics
Bounce in Loop Quantum Cosmology and its Implications

Abhay Ashtekar Pennsylvania State University
June 26, 2017

PIRSA:17060095
Astrophysics
Welcome and Opening Remarks
- Steffen Gielen University of Sheffield
- Neil Turok University of Edinburgh
June 26, 2017

PIRSA:17060094
Astrophysics

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 Koehn AI
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 Canadian Institute for Theoretical Astrophysics (CITA)
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.
Bounce in Loop Quantum Cosmology and its Implications

Abhay Ashtekar Pennsylvania State University
June 26, 2017

PIRSA:17060095
Astrophysics
There is a huge body of work in Loop Quantum Cosmology comprising of several thousand journal articles. I will provide an overview of conclusions, focusing on the difficult conceptual and mathematical issues that accompany the notion of a bounce and opening the way for phenomenological implications that will be discussed by Ivan Agullo.
Welcome and Opening Remarks
- Steffen Gielen University of Sheffield
- Neil Turok University of Edinburgh
June 26, 2017

PIRSA:17060094
Astrophysics

Title	Speaker(s)	Date	Talk Type	Info link
Loop Quantum Cosmology, Non-Gaussianity, and CMB anomalies	Ivan Agullo	2017-06-28	Conference	View details
Discussion Session 4	Latham Boyle, Job Feldbrugge, Neil Turok	2017-06-27	Conference	View details
A Bouncing Universe approach to Fine Tuning	Stephon Alexander	2017-06-27	Conference	View details
Space(-time) structure in models of loop quantum gravity	Martin Bojowald	2017-06-27	Conference	View details
Quantum cosmological instabilities - with and without boundaries	Jean-Luc Lehners	2017-06-27	Conference	View details
Unitary Cosmological Bounces	Claudia de Rham	2017-06-27	Conference	View details
Discussion Session 2	Angelika Fertig, Steffen Gielen, Elizabeth Gould	2017-06-26	Conference	View details
Emergent bouncing cosmology from quantum gravity condensates	Edward Wilson-Ewing	2017-06-26	Conference	View details
Challenges for Bouncing Cosmologies	Robert Brandenberger	2017-06-26	Conference	View details
Observable Consequences of a Bounce	Ue-Li Pen	2017-06-26	Conference	View details
Bounce in Loop Quantum Cosmology and its Implications	Abhay Ashtekar	2017-06-26	Conference	View details
Welcome and Opening Remarks	Steffen Gielen, Neil Turok	2017-06-26	Conference	View details

Supported by

Format results

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

Bounce in Loop Quantum Cosmology and its Implications

Welcome and Opening Remarks

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

Bounce in Loop Quantum Cosmology and its Implications

Welcome and Opening Remarks