scholarly journals Effective actions for Regge state-sum models of quantum gravity

2017 ◽  
Vol 21 (3) ◽  
pp. 631-653 ◽  
Author(s):  
Aleksandar Miković
Keyword(s):  
Models Of Quantum Gravity ◽  
Quantum Gravity

scholarly journals Comment on Coleman-DeLuccia instantons

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Thomas Banks ◽  
Bingnan Zhang
Keyword(s):  
Models Of Quantum Gravity ◽  
Quantum Gravity ◽  
Transition Probabilities ◽  
Detailed Balance ◽  
De Sitter Space ◽  
Positive Energy ◽  
De Sitter ◽  
Finite Area ◽  
Quantum Models

We complete an old argument that causal diamonds in the crunching region of the Lorentzian continuation of a Coleman-Deluccia instanton for transitions out of de Sitter space have finite area, and provide quantum models consistent with the principle of detailed balance, which can mimic the instanton transition probabilities for the cases where this diamond is larger or smaller than the causal patch of de Sitter space. We review arguments that potentials which do not have a positive energy theorem when the lowest de Sitter minimum is shifted to zero, may not correspond to real models of quantum gravity.

One-loop renormalization in quantum gravity

2021 ◽  
pp. 474-487
Author(s):  
Iosif L. Buchbinder ◽  
Ilya L. Shapiro
Keyword(s):  
General Relativity ◽  
Models Of Quantum Gravity ◽  
Quantum Gravity ◽  
Detailed Analysis ◽  
Polynomial Model ◽  
Similar Calculation ◽  
Higher Derivative ◽  
Gauge Fixing ◽  
Fourth Derivative ◽  
Detailed Derivation

This chapter demonstrates the basic methods of one-loop calculations in quantum gravity. Basing its discussion on the general results obtained in chapter 10, it first presents a detailed analysis of the gauge-fixing dependence of one-loop divergences in quantum general relativity and higher-derivative models of quantum gravity. After that, a detailed derivation of divergences in quantum general relativity is given, with the simplest parametrization of the quantum metric and minimal gauge fixing. One-loop divergences in the general (non-conformal) fourth-derivative quantum gravity are then derived in less detail. For a similar calculation in the superrenormalizable polynomial model (superrenormalizable gravity), the chapter just presents and discusses the final result.

scholarly journals GRAVITY AS BF THEORY PLUS POTENTIAL

2009 ◽  
Vol 24 (15) ◽  
pp. 2776-2782 ◽  
Author(s):  
KIRILL KRASNOV
Keyword(s):  
General Relativity ◽  
Models Of Quantum Gravity ◽  
Quantum Gravity ◽  
Alternative Formulation ◽  
Potential Term ◽  
Bf Theory ◽  
Spin Foam Models ◽  
Spin Foam ◽  
To Come

Spin foam models of quantum gravity are based on Plebanski's formulation of general relativity as a constrained BF theory. We give an alternative formulation of gravity as BF theory plus a certain potential term for the B-field. When the potential is taken to be infinitely steep one recovers general relativity. For a generic potential the theory still describes gravity in that it propagates just two graviton polarizations. The arising class of theories is of the type amenable to spin foam quantization methods, and, we argue, may allow one to come to terms with renormalization in the spin foam context.

scholarly journals TENSOR MODELS AND HIERARCHY OF n-ARY ALGEBRAS

2011 ◽  
Vol 26 (19) ◽  
pp. 3249-3258 ◽  
Author(s):  
NAOKI SASAKURA
Keyword(s):  
Models Of Quantum Gravity ◽  
Quantum Gravity ◽  
Matrix Models ◽  
Algebraic Structure ◽  
The Other ◽  
Invariant Form ◽  
Infinitesimal Symmetry ◽  
Tensor Models ◽  
Symmetry Transformations

Tensor models are generalization of matrix models, and are studied as models of quantum gravity. It is shown that the symmetry of the rank-three tensor models is generated by a hierarchy of n-ary algebras starting from the usual commutator, and the 3-ary algebra symmetry reported in the previous paper is just a single sector of the whole structure. The condition for the Leibnitz rules of the n-ary algebras is discussed from the perspective of the invariance of the underlying algebra under the n-ary transformations. It is shown that the n-ary transformations which keep the underlying algebraic structure invariant form closed finite n-ary Lie subalgebras. It is also shown that, in physical settings, the 3-ary transformation practically generates only local infinitesimal symmetry transformations, and the other more nonlocal infinitesimal symmetry transformations of the tensor models are generated by higher n-ary transformations.

scholarly journals A RENORMALIZATION PROCEDURE FOR TENSOR MODELS AND SCALAR-TENSOR THEORIES OF GRAVITY

2010 ◽  
Vol 25 (23) ◽  
pp. 4475-4492 ◽  
Author(s):  
NAOKI SASAKURA
Keyword(s):  
General Relativity ◽  
Models Of Quantum Gravity ◽  
Quantum Gravity ◽  
Matrix Models ◽  
Dynamical Variable ◽  
Renormalization Procedure ◽  
Emergent Phenomena ◽  
Tensor Models ◽  
Theories Of Gravity

Tensor models are more-index generalizations of the so-called matrix models, and provide models of quantum gravity with the idea that spaces and general relativity are emergent phenomena. In this paper, a renormalization procedure for the tensor models whose dynamical variable is a totally symmetric real three-tensor is discussed. It is proven that configurations with certain Gaussian forms are the attractors of the three-tensor under the renormalization procedure. Since these Gaussian configurations are parametrized by a scalar and a symmetric two-tensor, it is argued that, in general situations, the infrared dynamics of the tensor models should be described by scalar-tensor theories of gravity.

scholarly journals Finite Groups for the Kummer Surface: the Genetic Code and a Quantum Gravity Analogy

2021 ◽  
Author(s):  
Michel Planat --- ◽  
David Chester ◽  
Raymond Aschheim ◽  
Marcelo Amaral ◽  
Fang Fang ◽  
...  
Keyword(s):  
Finite Group ◽  
Models Of Quantum Gravity ◽  
Quantum Gravity ◽  
Genetic Code ◽  
Finite Groups ◽  
Vital Role ◽  
Recent Model ◽  
Biological Functions ◽  
Kummer Surface ◽  
Octahedral Group

The Kummer surface was constructed in 1864. It corresponds to the desingularisation of the quotient of a 4-torus by 16 complex double points. Kummer surface is kwown to play a role in some models of quantum gravity. Following our recent model of the DNA genetic code based on the irreducible characters of the finite group G5:=(240,105)≅Z5⋊2O (with 2O the binary octahedral group), we now find that groups G6:=(288,69)≅Z6⋊2O and G7:=(336,118)≅Z7⋊2O can be used as models of the symmetries in hexamer and heptamer proteins playing a vital role for some biological functions. Groups G6 and G7 are found to involve the Kummer surface in the structure of their character table. An analogy between quantum gravity and DNA/RNA packings is suggested.

scholarly journals SPIN-CUBE MODELS OF QUANTUM GRAVITY

2013 ◽  
Vol 25 (10) ◽  
pp. 1343008 ◽  
Author(s):  
A. MIKOVIĆ
Keyword(s):  
Models Of Quantum Gravity ◽  
Quantum Gravity ◽  
Path Integral ◽  
Classical Limit ◽  
Edge Length ◽  
The State ◽  
Regge Model ◽  
Bf Theory ◽  
Spin Foam Models ◽  
Spin Foam

We study the state-sum models of quantum gravity based on a representation 2-category of the Poincaré 2-group. We call them spin-cube models, since they are categorical generalizations of spin-foam models. A spin-cube state sum can be considered as a path integral for a constrained 2-BF theory, and depending on how the constraints are imposed, a spin-cube state sum can be reduced to a path integral for the area-Regge model with the edge-length constraints, or to a path integral for the Regge model. We also show that the effective actions for these spin-cube models have the correct classical limit.

scholarly journals NEW SPIN FOAM MODELS OF QUANTUM GRAVITY

2005 ◽  
Vol 20 (17n18) ◽  
pp. 1305-1313
Author(s):  
A. MIKOVIĆ
Keyword(s):  
General Relativity ◽  
Models Of Quantum Gravity ◽  
Quantum Gravity ◽  
Path Integral ◽  
Critical Review ◽  
Loop Quantum Gravity ◽  
Spin Networks ◽  
Spin Foam Models ◽  
Spin Foam Model ◽  
Spin Foam

We give a brief and a critical review of the Barret-Crane spin foam models of quantum gravity. Then we describe two new spin foam models which are obtained by direct quantization of General Relativity and do not have some of the drawbacks of the Barret-Crane models. These are the model of spin foam invariants for the embedded spin networks in loop quantum gravity and the spin foam model based on the integration of the tetrads in the path integral for the Palatini action.

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