Quantum Gravity

Quantum gravity is concerned with unifying Einstein's general theory of relativity with quantum theory into a single theoretical framework. At Perimeter Institute, researchers are actively pursuing a number of approaches to this problem including loop quantum gravity, spin foam models, asymptotic safety, emergent gravity, string theory, and causal set theory. We are also particularly interested in experimental implications of these different proposals. As the aim is a unification of the laws of physics into a single theory, the search for quantum gravity overlaps with other areas such as cosmology, particle physics and the foundations of quantum theory.

Displaying 133 - 144 of 1382

A minimal SM/LCDM cosmology

Neil Turok University of Edinburgh
October 27, 2023

PIRSA:23100063
Quantum Gravity
String Theory and the Cosmological Constant

Fernando Quevedo University of Cambridge
October 27, 2023

PIRSA:23100069
Quantum Gravity
The simplicial Lorentzian path integral and spin foams

Bianca Dittrich Perimeter Institute for Theoretical Physics
October 27, 2023

PIRSA:23100068
Quantum Gravity
Balance Laws as Test of Gravity - VIRTUAL

Lavinia Heisenberg ETH Zurich
October 27, 2023

PIRSA:23100017
Quantum Gravity
Colloquium - Insights from Warped Extra Dimensions - VIRTUAL

Lisa Randall Harvard University
October 26, 2023

PIRSA:23100016
Quantum Gravity
Panel Discussion - Black hole puzzles (Di Filippo, Gregory, Holdom, Myers, Stelle)
- Francesco Di Filippo Kyoto University
- Ruth Gregory King's College London
- Bob Holdom University of Toronto
- Robert Myers Perimeter Institute for Theoretical Physics
- Kellogg Stelle Imperial College London
October 26, 2023

PIRSA:23100015
Quantum Gravity
Open Discussion with today's speakers (Calmet, di Filippo, Gregory)
- Xavier Calmet University of Sussex
- Francesco Di Filippo Kyoto University
- Ruth Gregory King's College London
October 26, 2023

PIRSA:23100014
Quantum Gravity
Holographic Thermodynamics: C-ing a Black Hole

Ruth Gregory King's College London
October 26, 2023

PIRSA:23100010
Quantum Gravity
Hearts of Darkness: Nonsingular Black Holes Beyond General Relativity

Francesco Di Filippo Kyoto University
October 26, 2023

PIRSA:23100013
Quantum Gravity
Quantum hair and information loss paradox - VIRTUAL

Xavier Calmet University of Sussex
October 26, 2023

PIRSA:23100067
Quantum Gravity
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
Quantum Gravity
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
Quantum Gravity

A minimal SM/LCDM cosmology

Neil Turok University of Edinburgh
October 27, 2023

PIRSA:23100063
Quantum Gravity
Recent observations point to a surprisingly economical description of the universe on both very small and very large scales. Stimulated by these findings, Boyle and I have proposed a new, potentially more complete theoretical framework than currently popular paradigms. Our search has so far led to 1) the simplest-yet explanation for the cosmic dark matter, soon to be tested by galaxy surveys, 2) a thermodynamic explanation for the large scale geometry of the cosmos, based on the concept of gravitational entropy à la Hawking, 3) a new account of the big bang singularity as a “mirror” enforcing CPT-symmetric boundary conditions, realising Penrose's "Weyl curvature hypothesis" and 4) a new mechanism for cancelling the divergent vacuum energy and the trace anomalies in the Standard Model (SM). The new mechanism successfully predicts the primordial density perturbations in terms of the SM’s gauge couplings. It also explains why there are 3 generations of elementary particles, each including a RH neutrino, one of which is stable and comprises the dark matter. I’ll outline the challenges the new picture faces and the opportunities it presents, ranging from solving the gauge hierarchy problem to an improved description of quantum gravity along with prospective observational tests.
String Theory and the Cosmological Constant

Fernando Quevedo University of Cambridge
October 27, 2023

PIRSA:23100069
Quantum Gravity
An overview is given on moduli stabilization in string theory with emphasis in obtaining de Sitter space solutions. Recent work on vacuum transitions will be emphasised.
The simplicial Lorentzian path integral and spin foams

Bianca Dittrich Perimeter Institute for Theoretical Physics
October 27, 2023

PIRSA:23100068
Quantum Gravity
I will discuss two versions of the simplicial Lorentizian path integral, namely the (Lorentzian) quantum Regge and the spin foam version. I will do so in the simple context of de Sitter cosmology. This simple example will reveal the important role of light cone irregular configurations in the simplicial path integral — I will show that these can either lead to an exponentially enhanced or an exponentially suppressed amplitude. I will then highlight an important difference between the spin foams and quantum Regge path integral, which affects the probability for the creation of the (de Sitter) universe.
Balance Laws as Test of Gravity - VIRTUAL

Lavinia Heisenberg ETH Zurich
October 27, 2023

PIRSA:23100017
Quantum Gravity
I will discuss how one can use balance laws in full non-linear general relativity in order to test waveform models (arXiv:2309.12505) --- The presenter will be joining via Zoom for this talk.
Colloquium - Insights from Warped Extra Dimensions - VIRTUAL

Lisa Randall Harvard University
October 26, 2023

PIRSA:23100016
Quantum Gravity
Warped extra dimensions were originally introduced as a way of addressing the hierarchy problem. But insights from these scenarios have extended to black hole physics, cosmology, and even mechanisms for addressing issues in purely four dimensions. We investigate this scenario and some compelling lessons. The presenter will be joining via Zoom for this talk.
Panel Discussion - Black hole puzzles (Di Filippo, Gregory, Holdom, Myers, Stelle)
- Francesco Di Filippo Kyoto University
- Ruth Gregory King's College London
- Bob Holdom University of Toronto
- Robert Myers Perimeter Institute for Theoretical Physics
- Kellogg Stelle Imperial College London
October 26, 2023

PIRSA:23100015
Quantum Gravity
Open Discussion with today's speakers (Calmet, di Filippo, Gregory)
- Xavier Calmet University of Sussex
- Francesco Di Filippo Kyoto University
- Ruth Gregory King's College London
October 26, 2023

PIRSA:23100014
Quantum Gravity
Holographic Thermodynamics: C-ing a Black Hole

Ruth Gregory King's College London
October 26, 2023

PIRSA:23100010
Quantum Gravity
One of the fascinating things about Black Hole Thermodynamics is how we often approach it in a very classical fashion, yet - if real - it is an intrinsically quantum phenomenon. I'll use the illustration of thermodynamics of an accelerating black hole to highlight some of these issues, and I'd like to raise questions on how we derive the First Law, and how unique this derivation is.
Hearts of Darkness: Nonsingular Black Holes Beyond General Relativity

Francesco Di Filippo Kyoto University
October 26, 2023

PIRSA:23100013
Quantum Gravity
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
Quantum Gravity
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
Quantum Gravity
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
Quantum Gravity

Title	Speaker(s)	Date	Talk Type	Info link
A minimal SM/LCDM cosmology	Neil Turok	2023-10-27	Conference	View details
String Theory and the Cosmological Constant	Fernando Quevedo	2023-10-27	Conference	View details
The simplicial Lorentzian path integral and spin foams	Bianca Dittrich	2023-10-27	Conference	View details
Balance Laws as Test of Gravity - VIRTUAL	Lavinia Heisenberg	2023-10-27	Conference	View details
Colloquium - Insights from Warped Extra Dimensions - VIRTUAL	Lisa Randall	2023-10-26	Conference	View details
Panel Discussion - Black hole puzzles (Di Filippo, Gregory, Holdom, Myers, Stelle)	Francesco Di Filippo, Ruth Gregory, Bob Holdom, Robert Myers, Kellogg Stelle	2023-10-26	Conference	View details
Open Discussion with today's speakers (Calmet, di Filippo, Gregory)	Xavier Calmet, Francesco Di Filippo, Ruth Gregory	2023-10-26	Conference	View details
Holographic Thermodynamics: C-ing a Black Hole	Ruth Gregory	2023-10-26	Conference	View details
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

Quantum Gravity

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