General Relativity & Quantum Cosmology

Displaying 313 - 324 of 2001

Hearts of Darkness: Nonsingular Black Holes Beyond General Relativity

Francesco Di Filippo Kyoto University
October 26, 2023

PIRSA:23100013
General Relativity & Quantum Cosmology
Quantum hair and information loss paradox - VIRTUAL

Xavier Calmet University of Sussex
October 26, 2023

PIRSA:23100067
General Relativity & Quantum Cosmology
Open Discussion with today's speakers (Ashtekar, Surya, Vieira)
- Abhay Ashtekar Pennsylvania State University
- Sumati Surya Raman Research Institute
- Pedro Vieira Perimeter Institute for Theoretical Physics
October 25, 2023

PIRSA:23100012
General Relativity & Quantum Cosmology
Panel Discussion - Cosmological Puzzles (Ashtekar, Brandenberger, Geshnizjani, Sakellariadou, Yazdi)
- Abhay Ashtekar Pennsylvania State University
- Robert Brandenberger McGill University - Department of Physics
- Ghazal Geshnizjani Perimeter Institute for Theoretical Physics
- Mairi Sakellariadou King's College London
- Yasaman Kouchekzadeh Yazdi Dublin Institute For Advanced Studies
October 25, 2023

PIRSA:23100011
General Relativity & Quantum Cosmology
Where is String Theory

Pedro Vieira Perimeter Institute for Theoretical Physics
October 25, 2023

PIRSA:23100066
General Relativity & Quantum Cosmology
Glimpses into Loop Quantum Gravity

Abhay Ashtekar Pennsylvania State University
October 25, 2023

PIRSA:23100009
General Relativity & Quantum Cosmology
Panel Discussion - QFT vs beyond-QFT approaches (Buoninfante, Rejzner, Smolin, Vieira)
- Luca Buoninfante Nordic Institute for Theoretical Physics
- Benjamin Knorr Nordic Institute for Theoretical Physics
- Katarzyna Rejzner University of York
- Lee Smolin Perimeter Institute for Theoretical Physics
- Pedro Vieira Perimeter Institute for Theoretical Physics
October 24, 2023

PIRSA:23100008
General Relativity & Quantum Cosmology
Open Discussion with today's speakers (Buoninfante, Eichhorn, Holdom, Knorr, Loll)
- Luca Buoninfante Nordic Institute for Theoretical Physics
- Astrid Eichhorn Universität Heidelberg
- Bob Holdom University of Toronto
- Benjamin Knorr Nordic Institute for Theoretical Physics
- Renate Loll Radboud Universiteit Nijmegen
October 24, 2023

PIRSA:23100007
General Relativity & Quantum Cosmology
Form Factors - a unifying language for Quantum Gravity

Benjamin Knorr Nordic Institute for Theoretical Physics
October 24, 2023

PIRSA:23100087
General Relativity & Quantum Cosmology
The Case for Renormalizable Quantum Gravity: from local to nonlocal approaches (and back!)

Luca Buoninfante Nordic Institute for Theoretical Physics
October 24, 2023

PIRSA:23100064
General Relativity & Quantum Cosmology
UV complete 4-derivative scalar field theory

Bob Holdom University of Toronto
October 24, 2023

PIRSA:23100006
General Relativity & Quantum Cosmology
CDT as computational gateway to nonperturbative quantum gravity

Renate Loll Radboud Universiteit Nijmegen
October 24, 2023

PIRSA:23100062
General Relativity & Quantum Cosmology

Hearts of Darkness: Nonsingular Black Holes Beyond General Relativity

Francesco Di Filippo Kyoto University
October 26, 2023

PIRSA:23100013
General Relativity & Quantum Cosmology
Black holes contain, deep in their interior, theoretical evidence of the failure of general relativity. A series of fundamental results, starting from the 1965 Penrose singularity theorem, proved that physically realistic initial conditions will unavoidably produce a singular black hole spacetime. It is generally expected that a full theory of quantum gravity should remove the singularities that appear in general relativity. However, the lack of proper understanding of the dynamical laws dictating the evolution of spacetime and matter in these extreme situations hinders the extraction of predictions in specific models. I will discuss, in a model-independent manner, the different possibilities that singularity regularization may open. I will then focus on fundamental open issues that need to be addressed to obtain viable nonsingular black hole candidates.
Quantum hair and information loss paradox - VIRTUAL

Xavier Calmet University of Sussex
October 26, 2023

PIRSA:23100067
General Relativity & Quantum Cosmology
In this talk I present our solution to the information paradox published in Phys.Rev.Lett. 128 (2022) 11, 111301 and Phys.Lett.B 827 (2022) 136995 (see EPL 139 (2022) 4, 49001 for a review). Long wavelength quantum gravitational effects allow the interior state of the black hole to influence Hawking radiation, leading to unitary evaporation. I explain why the Mathur theorem is evaded due to the complex nature of the Hawking radiation superposition state. --- The presenter will be joining via Zoom for this talk.
Open Discussion with today's speakers (Ashtekar, Surya, Vieira)
- Abhay Ashtekar Pennsylvania State University
- Sumati Surya Raman Research Institute
- Pedro Vieira Perimeter Institute for Theoretical Physics
October 25, 2023

PIRSA:23100012
General Relativity & Quantum Cosmology
Panel Discussion - Cosmological Puzzles (Ashtekar, Brandenberger, Geshnizjani, Sakellariadou, Yazdi)
- Abhay Ashtekar Pennsylvania State University
- Robert Brandenberger McGill University - Department of Physics
- Ghazal Geshnizjani Perimeter Institute for Theoretical Physics
- Mairi Sakellariadou King's College London
- Yasaman Kouchekzadeh Yazdi Dublin Institute For Advanced Studies
October 25, 2023

PIRSA:23100011
General Relativity & Quantum Cosmology
Where is String Theory

Pedro Vieira Perimeter Institute for Theoretical Physics
October 25, 2023

PIRSA:23100066
General Relativity & Quantum Cosmology
Glimpses into Loop Quantum Gravity

Abhay Ashtekar Pennsylvania State University
October 25, 2023

PIRSA:23100009
General Relativity & Quantum Cosmology
The organizers requested an overview of Loop Quantum Gravity (LQG). However, this is an impossible task, especially for a 30 minute talk, given that the subject is over three decades old with tens of thousands of papers. Instead, I will outline some of the key distinguishing features of LQG and discuss an illustrative application. Hopefully these topics will complement those that will be covered by Bianca Dittrich and Lee Smolin, without too much of an overlap.
Panel Discussion - QFT vs beyond-QFT approaches (Buoninfante, Rejzner, Smolin, Vieira)
- Luca Buoninfante Nordic Institute for Theoretical Physics
- Benjamin Knorr Nordic Institute for Theoretical Physics
- Katarzyna Rejzner University of York
- Lee Smolin Perimeter Institute for Theoretical Physics
- Pedro Vieira Perimeter Institute for Theoretical Physics
October 24, 2023

PIRSA:23100008
General Relativity & Quantum Cosmology
Open Discussion with today's speakers (Buoninfante, Eichhorn, Holdom, Knorr, Loll)
- Luca Buoninfante Nordic Institute for Theoretical Physics
- Astrid Eichhorn Universität Heidelberg
- Bob Holdom University of Toronto
- Benjamin Knorr Nordic Institute for Theoretical Physics
- Renate Loll Radboud Universiteit Nijmegen
October 24, 2023

PIRSA:23100007
General Relativity & Quantum Cosmology
Form Factors - a unifying language for Quantum Gravity

Benjamin Knorr Nordic Institute for Theoretical Physics
October 24, 2023

PIRSA:23100087
General Relativity & Quantum Cosmology
QFT's remarkable success lies in its ability to yield precise predictions through e.g. scattering amplitudes, capturing the essence of running couplings in a gauge-invariant manner. However, the introduction of gravity disrupts this straightforward notion of momentum dependence, posing a significant challenge to our theoretical framework. Enter form factors—an ingenious concept that extends the idea of momentum dependence to the curved spacetime of quantum gravity. They form the central ingredient when discussing quantum gravity in a QFT language. Furthermore, within an effective action, form factors offer a unifying language, allowing us to compare and contrast different quantum gravity approaches apples-to-apples. I will give an overview of the ideas underlying form factors, their application to scattering problems, and their potential to put different approaches on the same footing.
The Case for Renormalizable Quantum Gravity: from local to nonlocal approaches (and back!)

Luca Buoninfante Nordic Institute for Theoretical Physics
October 24, 2023

PIRSA:23100064
General Relativity & Quantum Cosmology
In the context of perturbative quantum field theory (QFT), the addition of quadratic-curvature invariants to the Einstein-Hilbert action makes it possible to achieve strict renormalizability in four dimensions. This theory exhibits unusual features due to an additional massive spin-2 ghost which, in general, may cause instabilities. In the first part of this talk, we focus on the possibility of giving up locality as a way to avoid ghost-like degrees of freedom and provide a critical assessment on open questions in nonlocal theories of gravity, such as the uniqueness problem. In the second part of the talk, we take a step back and argue that, despite the presence of the ghost and actually thanks to it, Quadratic Gravity can still provide a consistent local perturbative QFT description of the gravitational interaction and explain new physics beyond Einstein's general relativity, e.g., it offers a natural explanation for the inflationary phase. Finally, we argue that a type of nonlocality in gravity can still occur non-perturbatively and show that a new lower bound on scattering amplitudes indicates that the gravitational interaction is intrinsically nonlocal if black holes form.
UV complete 4-derivative scalar field theory

Bob Holdom University of Toronto
October 24, 2023

PIRSA:23100006
General Relativity & Quantum Cosmology
A scalar field theory with 4-derivative kinetic terms and 4-derivative cubic and quartic couplings is presented as a proxy for quadratic gravity. Unitarity and positivity appear as the key issues in the scalar field theory, just as they do in quadratic gravity. We have extended some calculations to show how these issues are resolved in the high energy limit of the theory. The results also show how it is that differential cross sections can have good high energy behaviour.
CDT as computational gateway to nonperturbative quantum gravity

Renate Loll Radboud Universiteit Nijmegen
October 24, 2023

PIRSA:23100062
General Relativity & Quantum Cosmology
Based on quantitative results on quantum observables in a Planckian regime, I will argue that using dynamical lattices `a la CDT to construct and explore the nonperturbative path integral over Lorentzian geometries is a bona-fide quantum field-theoretic "method" rather than an "approach" to quantum gravity. Its most important features are universality, unitarity and the presence of powerful numerical tools to directly simulate and measure a chunk of quantum spacetime of about 20 Planck lengths across. This small observational window is a preferred place to look for clues to what quantum gravity is all about. Despite the diffeomorphism-invariant and nonlocal character of the observables, qualitatively new and surprising UV properties have already been discovered, and compatibility checks with semiclassical expectations for several cosmological observables ("classical limit") have been performed successfully. The underlying new mathematics is that of random geometry and beyond-Riemannian geometry.

Title	Speaker(s)	Date	Talk Type	Info link
Hearts of Darkness: Nonsingular Black Holes Beyond General Relativity	Francesco Di Filippo	2023-10-26	Conference	View details
Quantum hair and information loss paradox - VIRTUAL	Xavier Calmet	2023-10-26	Conference	View details
Open Discussion with today's speakers (Ashtekar, Surya, Vieira)	Abhay Ashtekar, Sumati Surya, Pedro Vieira	2023-10-25	Conference	View details
Panel Discussion - Cosmological Puzzles (Ashtekar, Brandenberger, Geshnizjani, Sakellariadou, Yazdi)	Abhay Ashtekar, Robert Brandenberger, Ghazal Geshnizjani, Mairi Sakellariadou, Yasaman Kouchekzadeh Yazdi	2023-10-25	Conference	View details
Where is String Theory	Pedro Vieira	2023-10-25	Conference	View details
Glimpses into Loop Quantum Gravity	Abhay Ashtekar	2023-10-25	Conference	View details
Panel Discussion - QFT vs beyond-QFT approaches (Buoninfante, Rejzner, Smolin, Vieira)	Luca Buoninfante, Benjamin Knorr, Katarzyna Rejzner, Lee Smolin, Pedro Vieira	2023-10-24	Conference	View details
Open Discussion with today's speakers (Buoninfante, Eichhorn, Holdom, Knorr, Loll)	Luca Buoninfante, Astrid Eichhorn, Bob Holdom, Benjamin Knorr, Renate Loll	2023-10-24	Conference	View details
Form Factors - a unifying language for Quantum Gravity	Benjamin Knorr	2023-10-24	Conference	View details
The Case for Renormalizable Quantum Gravity: from local to nonlocal approaches (and back!)	Luca Buoninfante	2023-10-24	Conference	View details
UV complete 4-derivative scalar field theory	Bob Holdom	2023-10-24	Conference	View details
CDT as computational gateway to nonperturbative quantum gravity	Renate Loll	2023-10-24	Conference	View details

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General Relativity & Quantum Cosmology

Format results

Hearts of Darkness: Nonsingular Black Holes Beyond General Relativity

Quantum hair and information loss paradox - VIRTUAL

Open Discussion with today's speakers (Ashtekar, Surya, Vieira)

Panel Discussion - Cosmological Puzzles (Ashtekar, Brandenberger, Geshnizjani, Sakellariadou, Yazdi)

Where is String Theory

Glimpses into Loop Quantum Gravity

Panel Discussion - QFT vs beyond-QFT approaches (Buoninfante, Rejzner, Smolin, Vieira)

Open Discussion with today's speakers (Buoninfante, Eichhorn, Holdom, Knorr, Loll)

Form Factors - a unifying language for Quantum Gravity

The Case for Renormalizable Quantum Gravity: from local to nonlocal approaches (and back!)

UV complete 4-derivative scalar field theory

CDT as computational gateway to nonperturbative quantum gravity

Hearts of Darkness: Nonsingular Black Holes Beyond General Relativity

Quantum hair and information loss paradox - VIRTUAL

Open Discussion with today's speakers (Ashtekar, Surya, Vieira)

Panel Discussion - Cosmological Puzzles (Ashtekar, Brandenberger, Geshnizjani, Sakellariadou, Yazdi)

Where is String Theory

Glimpses into Loop Quantum Gravity

Panel Discussion - QFT vs beyond-QFT approaches (Buoninfante, Rejzner, Smolin, Vieira)

Open Discussion with today's speakers (Buoninfante, Eichhorn, Holdom, Knorr, Loll)

Form Factors - a unifying language for Quantum Gravity

The Case for Renormalizable Quantum Gravity: from local to nonlocal approaches (and back!)

UV complete 4-derivative scalar field theory

CDT as computational gateway to nonperturbative quantum gravity