scholarly journals From Quantum Entanglement to Spatiotemporal Distance

2021 ◽  
pp. 78-102
Author(s):  
Alyssa Ney
Keyword(s):  
Quantum Gravity ◽  
Quantum Entanglement ◽  
Research Program ◽  
Degrees Of Freedom ◽  
Entanglement Entropy ◽  
Quantum Theories ◽  
Spacetime Structure ◽  
Component Systems ◽  
Nonperturbative Theory ◽  
Entropy Distance

There is an influential research program in quantum gravity developing the connection between quantum entanglement and spatiotemporal distance. Through a series of well-confirmed results, it has been shown how these facts about the entanglement entropy of component systems may be connected to facts about spatiotemporal distance. Physicists are seeing these results as yielding promising methods for better understanding the emergence of (the dynamical) spacetime from more fundamental quantum theories, and for the development of a nonperturbative theory of quantum gravity. However, to what extent does the case for the entanglement entropy-distance link provide evidence that spacetime structure is nonfundamental and emergent from nongravitational degrees of freedom? I will show that a closer look at the results lends support only to a weaker conclusion: that the facts about quantum entanglement are constrained by facts about spatiotemporal distance, and not that they are the basis from which facts about spatiotemporal distance emerge.

scholarly journals Quantum gravity as a metaphysical problem

2017 ◽  
Vol 1 (5) ◽  
pp. 163-170
Author(s):  
Ilja Schmelzer
Keyword(s):  
Field Theory ◽  
Quantum Gravity ◽  
Degrees Of Freedom ◽  
Einstein Equations ◽  
Absolute Space ◽  
Quantum Theories ◽  
Approximation Techniques ◽  
Metaphysical Problem ◽  
Space And Time ◽  
Important Argument

The problem with quantum gravity is usually presented as if it would be difficult to construct even a single quantum theory of relativistic gravity. This is shown to be wrong. A straightforward approach using standard, well-studied methods allows to construct mathematically well-defined quantum theories which give, in a certain classical limit, the Einstein equations of GR: GR may be transformed into a field theory on a fixed background by breaking diffeomorphism symmetry using harmonic coordinates. The resulting field theory may be regularized using standard lattice approximation techniques. The result is a well-defined canonical theory with a finite number of degrees of freedom, which can be quantized without problems in a canonical way. Why such a straightforward way to quantize gravity is simply ignored? We identify missing explanation of relativistic symmetry as an important argument, and propose a solution. evaluate possible explanations why this simple possibility to construct a theory of quantum gravity is ignored. While a lot of different metaphysical and sociological reasons play a role, we identify as a main point a preference of the scientific community for the relational philosophy behind the spacetime interpretation of GR, in opposition to the Newtonian concept of absolute space and time (substantivalism). We conclude that the quantization of gravity is not a problem of physics, but a metaphysical problem. It is a problem of the relational philosophy of space and time in the tradition of Descartes and Leibniz, which is the base of the spacetime interpretation of GR, because this philosophy is incompatible with the known examples of theories of quantum gravity.

scholarly journals Entanglement entropy, scale-dependent dimensions and the origin of gravity

2017 ◽  
Vol 26 (12) ◽  
pp. 1743030 ◽  
Author(s):  
Michele Arzano ◽  
Gianluca Calcagni
Keyword(s):  
Quantum Gravity ◽  
Degrees Of Freedom ◽  
Entanglement Entropy ◽  
Boundary Surface ◽  
Gravitational Theory ◽  
Einstein Gravity ◽  
Entropy Density ◽  
Spectral Dimension ◽  
Quantum Geometry

We argue that the requirement of a finite entanglement entropy of quantum degrees of freedom across a boundary surface is closely related to the phenomenon of running spectral dimension, universal in approaches to quantum gravity. If quantum geometry hinders diffusion, for instance, when its structure at some given scale is discrete or too rough, then the spectral dimension of spacetime vanishes at that scale and the entropy density blows up. A finite entanglement entropy is a key ingredient in deriving Einstein gravity in a semi-classical regime of a quantum-gravitational theory and, thus, our arguments strengthen the role of running dimensionality as an imprint of quantum geometry with potentially observable consequences.

scholarly journals BUILDING UP SPACE–TIME WITH QUANTUM ENTANGLEMENT

2010 ◽  
Vol 19 (14) ◽  
pp. 2429-2435 ◽  
Author(s):  
MARK VAN RAAMSDONK
Keyword(s):  
Quantum Gravity ◽  
Quantum Entanglement ◽  
Degrees Of Freedom ◽  
Space Time ◽  
Connected Space

In this essay, we argue that the emergence of classically connected space–times is intimately related to the quantum entanglement of degrees of freedom in a nonperturbative description of quantum gravity. Disentangling the degrees of freedom associated with two regions of space–time results in these regions pulling apart and pinching off from each other in a way that can be quantified by standard measures of entanglement.

Philosophy Beyond Spacetime

2021 ◽  
Keyword(s):  
Quantum Gravity ◽  
Philosophy Of Mind ◽  
Degrees Of Freedom ◽  
Loop Quantum Gravity ◽  
Quantum Theories ◽  
Philosophical Foundations ◽  
Naturalized Metaphysics ◽  
Theories Of Gravity ◽  
Methodological Aspects ◽  
Emergence Of Spacetime

The present volume collects essays on the philosophical foundations of quantum theories of gravity, such as loop quantum gravity and string theory. Central for philosophical concerns is quantum gravity's suggestion that space and time, or spacetime, may not exist fundamentally, but instead be a derivative entity emerging from non-spatiotemporal degrees of freedom. In the spirit of naturalized metaphysics, contributions to this volume consider the philosophical implications of this suggestion. In turn, philosophical methods and insights are brought to bear on the foundations of quantum gravity itself. For instance, the idea of functionalism, borrowed from the philosophy of mind and discussed by several chapters, exemplifies this mutual interaction the collection seeks to foster. The chapters of this collection cover three main subjects: first, the potential emergence of spacetime in various approaches to quantum gravity; second, metaphysical and epistemological considerations concerning the nature of this relation of emergence; and third, broader methodological aspects of the philosophy of quantum gravity.

scholarly journals QUANTUM GRAVITY AND HIGHER CURVATURE ACTIONS

2007 ◽  
Vol 04 (01) ◽  
pp. 25-52 ◽  
Author(s):  
MARTIN BOJOWALD ◽  
AURELIANO SKIRZEWSKI
Keyword(s):  
Quantum Gravity ◽  
Degrees Of Freedom ◽  
General Scheme ◽  
Hamiltonian Formalism ◽  
Classical Type ◽  
Physical Situation ◽  
Quantum Theories ◽  
Higher Derivative ◽  
Physical Information

Effective equations are often useful to extract physical information from quantum theories without having to face all technical and conceptual difficulties. One can then describe aspects of the quantum system by equations of classical type, which correct the classical equations by modified coefficients and higher derivative terms. In gravity, for instance, one expects terms with higher powers of curvature. Such higher derivative formulations are discussed here with an emphasis on the role of degrees of freedom and on differences between Lagrangian and Hamiltonian treatments. A general scheme is then provided which allows one to compute effective equations perturbatively in a Hamiltonian formalism. Here, one can expand effective equations around any quantum state and not just a perturbative vacuum. This is particularly useful in situations of quantum gravity or cosmology where perturbations only around vacuum states would be too restrictive. The discussion also demonstrates the number of free parameters expected in effective equations, used to determine the physical situation being approximated, as well as the role of classical symmetries such as Lorentz transformation properties in effective equations. An appendix collects information on effective correction terms expected from loop quantum gravity and string theory.

scholarly journals DO SUBLEADING CORRECTIONS TO BEKENSTEIN–HAWKING ENTROPY HOLD THE KEY TO QUANTUM GRAVITY?

2008 ◽  
Vol 23 (24) ◽  
pp. 1975-1980 ◽  
Author(s):  
S. SHANKARANARAYANAN
Keyword(s):  
Black Holes ◽  
Models Of Quantum Gravity ◽  
Quantum Gravity ◽  
Quantum Entanglement ◽  
Event Horizon ◽  
Power Law ◽  
Degrees Of Freedom ◽  
Canonical Ensemble ◽  
Microscopic Origin

Black-holes are considered to be theoretical laboratories for testing models of quantum gravity. It is usually believed that any candidate for quantum gravity must explain the microscopic origin of the Bekenstein–Hawking (S BH ) entropy. In this letter, we argue (i) the requirement for a candidate approach to go beyond S BH and provide generic subleading corrections, and (ii) the importance to disentangle and identify the degrees of freedom leading to S BH and its subleading corrections. Using the approach of entanglement of modes across the horizon, we show that the microscopic degrees of freedom that lead to S BH and subleading corrections are different. We further show, using microcanonical and canonical ensemble approaches, that the quantum entanglement predicts generic power-law corrections to S BH and that the corrections can be identified with the kinematical properties of the event-horizon.

scholarly journals Quantum information probes of charge fractionalization in large-N gauge theories

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Brandon S. DiNunno ◽  
Niko Jokela ◽  
Juan F. Pedraza ◽  
Arttu Pönni
Keyword(s):  
Degrees Of Freedom ◽  
Gauge Theories ◽  
Entanglement Entropy ◽  
Coarse Grained ◽  
Strongly Coupled ◽  
Information Theoretic ◽  
Large N ◽  
Wide Range ◽  
Charge Fractionalization ◽  
Electric Flux

Abstract We study in detail various information theoretic quantities with the intent of distinguishing between different charged sectors in fractionalized states of large-N gauge theories. For concreteness, we focus on a simple holographic (2 + 1)-dimensional strongly coupled electron fluid whose charged states organize themselves into fractionalized and coherent patterns at sufficiently low temperatures. However, we expect that our results are quite generic and applicable to a wide range of systems, including non-holographic. The probes we consider include the entanglement entropy, mutual information, entanglement of purification and the butterfly velocity. The latter turns out to be particularly useful, given the universal connection between momentum and charge diffusion in the vicinity of a black hole horizon. The RT surfaces used to compute the above quantities, though, are largely insensitive to the electric flux in the bulk. To address this deficiency, we propose a generalized entanglement functional that is motivated through the Iyer-Wald formalism, applied to a gravity theory coupled to a U(1) gauge field. We argue that this functional gives rise to a coarse grained measure of entanglement in the boundary theory which is obtained by tracing over (part) of the fractionalized and cohesive charge degrees of freedom. Based on the above, we construct a candidate for an entropic c-function that accounts for the existence of bulk charges. We explore some of its general properties and their significance, and discuss how it can be used to efficiently account for charged degrees of freedom across different energy scales.

scholarly journals ENTROPY AND AREA IN LOOP QUANTUM GRAVITY

2005 ◽  
Vol 14 (12) ◽  
pp. 2301-2305
Author(s):  
JOHN SWAIN
Keyword(s):  
Black Hole ◽  
Quantum Gravity ◽  
Maximum Entropy ◽  
Degrees Of Freedom ◽  
Loop Quantum Gravity ◽  
Black Hole Entropy ◽  
Black Hole Thermodynamics ◽  
Three Dimensions ◽  
Spin Network

Black hole thermodynamics suggests that the maximum entropy that can be contained in a region of space is proportional to the area enclosing it rather than its volume. We argue that this follows naturally from loop quantum gravity and a result of Kolmogorov and Bardzin' on the the realizability of networks in three dimensions. This represents an alternative to other approaches in which some sort of correlation between field configurations helps limit the degrees of freedom within a region. It also provides an approach to thinking about black hole entropy in terms of states inside rather than on its surface. Intuitively, a spin network complicated enough to imbue a region with volume only lets that volume grow as quickly as the area bounding it.

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