scholarly journals BORN'S PROPHECY LEAVES NO SPACE FOR QUANTUM GRAVITY

2012 ◽  
Vol 09 (06) ◽  
pp. 1261001 ◽  
Author(s):  
GIOVANNI AMELINO-CAMELIA
Keyword(s):  
Quantum Gravity ◽  
Momentum Space ◽  
Physical Content ◽  
Emergent Gravity ◽  
Max Born ◽  
Emergent Spacetime

I stress that spacetime is a redundant abstraction, since describing the physical content of all so-called "spacetime measurements" only requires timing (by a physical/material clock) of particle detections (at a physical/material detector). It is interesting then to establish which aspects of our current theories afford us the convenient abstraction of a spacetime. I emphasize the role played by the assumed triviality of the geometry of momentum space, which makes room for an observer-independent notion of locality. This is relevant for some recent studies of the quantum-gravity problem that stumbled upon hints of a nontrivial geometry of momentum space, something which had been strikingly envisaged for quantum gravity already in 1938 by Max Born. If indeed momentum space has nontrivial geometry then the abstraction of a spacetime becomes more evidently redundant and less convenient: one may still abstract a spacetime but only allowing for the possibility of a relativity of spacetime locality. I also provide some examples of how all this could affect our attitude toward the quantum-gravity problem, including some for the program of emergent gravity and emergent spacetime. And in order to give an illustrative example of possible logical path for the "disappearance of spacetime" I rely on formulas inspired by the κ-Poincaré framework.

scholarly journals Quantum gravity, dynamical phase-space and string theory

2014 ◽  
Vol 23 (12) ◽  
pp. 1442006 ◽  
Author(s):  
Laurent Freidel ◽  
Robert G. Leigh ◽  
Djordje Minic
Keyword(s):  
Quantum Theory ◽  
Phase Space ◽  
String Theory ◽  
Quantum Gravity ◽  
Momentum Space ◽  
Symplectic Geometry ◽  
Complex Geometry ◽  
Hamiltonian Dynamics ◽  
Natural Extension ◽  
Dynamical Phase

In a natural extension of the relativity principle, we speculate that a quantum theory of gravity involves two fundamental scales associated with both dynamical spacetime as well as dynamical momentum space. This view of quantum gravity is explicitly realized in a new formulation of string theory which involves dynamical phase-space and in which spacetime is a derived concept. This formulation naturally unifies symplectic geometry of Hamiltonian dynamics, complex geometry of quantum theory and real geometry of general relativity. The spacetime and momentum space dynamics, and thus dynamical phase-space, is governed by a new version of the renormalization group (RG).

A NEW FORMULATION OF QUANTUM FIELD THEORY ON S4

1994 ◽  
Vol 09 (18) ◽  
pp. 3245-3282 ◽  
Author(s):  
B.A. HARRIS ◽  
G.C. JOSHI
Keyword(s):  
Field Theory ◽  
Angular Momentum ◽  
Quantum Gravity ◽  
Momentum Space ◽  
Space Representation ◽  
Fundamental Constants ◽  
Spherical Space ◽  
Recent Developments ◽  
New Formulation ◽  
Constants Of Nature

Recent developments in quantum gravity suggest that wormholes may influence the observed values of the constants of nature. The Euclidean formulation of quantum gravity predicts that wormholes induce a probability distribution in the space of possible fundamental constants. In particular, the effective action on a large spherical space may lead to the vanishing of the cosmological constant and possibly determine the values of other constants of nature. The ability to perform calculations involving interacting quantum fields, particularly non-Abelian models, on a four-sphere is vital if one is to investigate this possibility. In this paper we present a new formulation of field theory on a four-sphere using the angular momentum space representation of SO(5). We give a review of field theory on a sphere and then show how a matrix element prescription in angular momentum space and a new summation technique based on the complex l plane, overcome previous limitations in calculational techniques. The standard one-loop graphs of QED are given as examples.

scholarly journals DARK ENERGY AND EMERGENT SPACETIME

2011 ◽  
Vol 01 ◽  
pp. 266-271
Author(s):  
HYUN SEOK YANG
Keyword(s):  
Dark Energy ◽  
Symplectic Geometry ◽  
Cosmological Constant Problem ◽  
Geometric Framework ◽  
Emergent Gravity ◽  
Flat Spacetime ◽  
Darboux Theorem ◽  
Noncommutative Spacetime ◽  
Emergent Spacetime ◽  
Planck Energy

A natural geometric framework of noncommutative spacetime is symplectic geometry rather than Riemannian geometry. The Darboux theorem in symplectic geometry then admits a novel form of the equivalence principle such that the electromagnetism in noncommutative spacetime can be regarded as a theory of gravity. Remarkably the emergent gravity reveals a noble picture about the origin of spacetime, dubbed as emergent spacetime, which is radically different from any previous physical theory all of which describe what happens in a given spacetime. In particular, the emergent gravity naturally explains the dynamical origin of flat spacetime, which is absent in Einstein gravity: A flat spacetime is not free gratis but a result of Planck energy condensation in a vacuum. This emergent spacetime picture, if it is correct anyway, turns out to be essential to resolve the cosmological constant problem, to understand the nature of dark energy and to explain why gravity is so weak compared to other forces.

scholarly journals Quantum-gravity-induced dual lensing and IceCube neutrinos

2017 ◽  
Vol 26 (08) ◽  
pp. 1750076 ◽  
Author(s):  
Giovanni Amelino-Camelia ◽  
Leonardo Barcaroli ◽  
Giacomo D’Amico ◽  
Niccoló Loret ◽  
Giacomo Rosati
Keyword(s):  
Quantum Gravity ◽  
Energy Dependence ◽  
Momentum Space ◽  
Travel Times ◽  
Space Curvature

Momentum-space curvature, which is expected in some approaches to the quantum-gravity problem, can produce dual redshift, a feature which introduces energy dependence of the travel times of ultrarelativistic particles, and dual lensing, a feature which mainly affects the direction of observation of particles. In our recent paper [Phys. Lett. B 761 (2016) 318, arXiv:1605.00496 .], we explored the possibility that dual redshift might be relevant in the analysis of IceCube neutrinos, obtaining results which are preliminarily encouraging. Here, we explore the possibility that also dual lensing might play a role in the analysis of IceCube neutrinos. In doing so, we also investigate issues which are of broader interest, such as the possibility of estimating the contribution by background neutrinos and some noteworthy differences between candidate “early neutrinos” and candidate “late neutrinos”.

scholarly journals Emergent spacetime for quantum gravity

2016 ◽  
Vol 25 (13) ◽  
pp. 1645010 ◽  
Author(s):  
Hyun Seok Yang
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Quantum Gravity ◽  
Theoretical Physics ◽  
Hierarchy Problem ◽  
Cosmological Constant Problem ◽  
Cosmic Inflation ◽  
Thought Patterns ◽  
Emergent Spacetime ◽  
New Perspective

We emphasize that noncommutative (NC) spacetime necessarily implies emergent spacetime if spacetime at microscopic scales should be viewed as NC. In order to understand NC spacetime correctly, we need to deactivate the thought patterns that we have installed in our brains and taken for granted for so many years. Emergent spacetime allows a background-independent formulation of quantum gravity that will open a new perspective to resolve the notorious problems in theoretical physics such as the cosmological constant problem, hierarchy problem, dark energy, dark matter and cosmic inflation.

scholarly journals Thinking about Spacetime

2021 ◽  
pp. 129-153
Author(s):  
David Yates
Keyword(s):  
Quantum Gravity ◽  
Philosophy Of Mind ◽  
Fundamental Theory ◽  
True Nature ◽  
Fundamental Ontology ◽  
Fundamental Structure ◽  
Space And Time ◽  
Spacetime Structure ◽  
Research Programmes ◽  
Emergent Spacetime

Several different quantum gravity research programmes suggest, for various reasons, that spacetime is not part of the fundamental ontology of physics. This gives rise to the problem of empirical coherence, which I frame in terms of entailment: how could a non-spatiotemporal fundamental theory entail spatiotemporal evidence propositions? Solutions to this puzzle can be classified as realist or antirealist, depending on whether or not they posit a non-fundamental spacetime structure grounded in or caused by the fundamental structure. These approaches place different constraints on our everyday concepts of space and time. Applying lessons from the philosophy of mind, I argue that only realism is both conceptually plausible and suitable for addressing the problem at hand. I suggest a role-functionalist version of realism, which is consistent with both grounding and causation, and according to which our everyday concepts reveal something of the true nature of emergent spacetime.

scholarly journals Planck-Scale Dual-Curvature Lensing and Spacetime Noncommutativity

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Giovanni Amelino-Camelia ◽  
Leonardo Barcaroli ◽  
Stefano Bianco ◽  
Laura Pensato
Keyword(s):  
Quantum Gravity ◽  
Momentum Space ◽  
Planck Scale ◽  
Neutrino Telescope ◽  
Space Curvature ◽  
Noncommutative Spacetime ◽  
Gray Areas

It was recently realized that Planck-scale momentum-space curvature, which is expected in some approaches to the quantum-gravity problem, can produce dual-curvature lensing, a feature which mainly affects the direction of observation of particles emitted by very distant sources. Several gray areas remain in our understanding of dual-curvature lensing, including the possibility that it might be just a coordinate artifact and the possibility that it might be in some sense a by-product of the better studied dual-curvature redshift. We stress that data reported by the IceCube neutrino telescope should motivate a more vigorous effort of investigation of dual-curvature lensing, and we observe that studies of the recently proposed “ρ-Minkowski noncommutative spacetime” could be valuable from this perspective. Through a dedicated ρ-Minkowski analysis, we show that dual-curvature lensing is not merely a coordinate artifact and that it can be present even in theories without dual-curvature redshift.

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