# Quantum Gravity

This series consists of talks in the area of Quantum Gravity.

## Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

## Ultraviolet Complete Quantum Gravity

Thursday Oct 28, 2010
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An ultraviolet complete quantum gravity theory is formulated in which vertex functions in Feynman graphs are entire functions and the propagating graviton is described by a local, causal propagator. A scalar-tensor action describes classical gravity theory. The cosmological constant problem is investigated in the context of the ultraviolet complete quantum gravity. Also investigated are black holes and cosmology.

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## A New Perspective on Quantum Field Theory

Wednesday Oct 20, 2010
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The Exact Renormalization Group (ERG) is a technique which can be fruitfully applied to systems with local interactions that exhibit a large number of degrees of freedom per correlation length. In the first part of the talk I will give a very general overview of the ERG, focussing on its applications in quantum field theory (QFT) and critical phenomena. In the second part I will discuss how a particular extension of the formalism suggests a new understanding of correlation functions in QFTs, in general, and gauge theories in particular.

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## Proposal for Divergence-Free Quantization of Covariant Scalar Fields

Wednesday Oct 06, 2010
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Guided by idealized but soluble nonrenormalizable models, a nontraditional proposal for the quantization of covariant scalar field theories is advanced, which achieves a term-by-term, divergence-free perturbation analysis of interacting models expanded about a suitable pseudofree theory [differing from a free theory by an $O(\hbar^2)$ term].

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## An apology for DRS

Wednesday Sep 22, 2010

In my talk I would like to discuss the present status of Doubly Special Relativity. DSR is an extension of Special Relativity aimed at describing kinematics of particles and fields in the regime where (quantum) gravity effects might become relevant. I will discuss an interplay between DSR physics and mathematics of Hopf algebras.

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## Cosmological constant, q-theory, and new TeV-scale physics

Wednesday Sep 08, 2010
Speaker(s):

A brief introduction to the notorious "cosmological constant problem" is given. Then, a particular approach is discussed, which has been developed by Volovik and the present speaker over the last years and which goes under the name of q-theory. This approach provides a possible solution of the main cosmological constant problem, why is |Lambda|^(1/4) negligible compared to the energy scales of the electroweak standard model (not to mention the Planck energy)?

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## Gravity: A different Perspective

Wednesday Jun 02, 2010
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Combining the principles of general relativity and quantum theory still remains as elusive as ever. Recent work, that concentrated on one of the points of contact (and conflict) between quantum theory and general relativity, suggests a new perspective on gravity. It appears that the gravitational dynamics in a wide class of theories - including, but not limited to, standard Einstein's theory - can be given a purely thermodynamic interpretation. In this approach gravity appears as an emergent phenomenon, like e.g., gas or fluid dynamics.

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## Fun from none: deformed Fock space and hidden entanglement

Wednesday May 19, 2010
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Attempts to go beyond the framework of local quantum field theory include scenarios in which the action of external symmetries on the quantum fields Hilbert space is deformed. A common feature of these models is that the quantum group symmetry of their Hilbert spaces induces additional structure in the multiparticle states which in turns reflects a non-trivial momentum-dependent statistics.

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## Loop Quantum Cosmology and Spin Foams

Thursday May 13, 2010
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Loop quantum gravity and spin foams are two closely related theories of quantum gravity. There is an expectation that the sum over histories or path integral formulation of LQG will take the form of a spin foam, although a rigorous connection between the two is available only in 2+1 gravity. Understanding the relation between them will resolve many open questions of both theories. We probe the connection through an exactly soluble model of loop quantum cosmology. Beginning from the canonical theory we construct a spin foam like expansion of LQC.

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## Deformations of General Relativity

Wednesday May 05, 2010
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I will describe a very special (infinite-parameter) family of gravity theories that all describe, exactly like General Relativity, just two propagating degrees of freedom. The theories are obtained by generalizing Plebanski's self-dual (chiral) formulation of GR. I will argue that this class of gravity theories provides a potentially powerful new framework for testing the asymptotic safety conjecture in quantum gravity.

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## Geometro-kinematics and dynamics in a discrete setting

Thursday Mar 25, 2010
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A quantum theory of gravity implies a quantum theory of geometries. To
this end we will introduce different phases spaces and choices for the
space of discretized geometries. These are derived through a canonical
analysis of simplicity constraints - which are central for spin foam
models - and gluing constraints. We will discuss implications for
spin foam models and map out how to obtain a path integral
quantization starting from a canonical quantization.

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## RECENT PUBLIC LECTURE

### Rob Moore: Stanford Institute for Materials and Energy Sciences

Speaker: Rob Moore