DOCSLIB.ORG

Pregeometry of -Minkowski/-Poincaré Spacetime and Relative Locality For

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Pregeometry of -Minkowski/-Poincaré Spacetime and Relative Locality For Pregeometry of κ-Minkowski/κ-Poincar´espacetime and relative locality for fuzzy worldlines Giacomo Rosati Institute for Theoretical Physics, University of Wroc law July 3, 2019 Giovanni Amelino-Camelia, Valerio Astuti, G. R., arXiv:1206.3805, Eur.Phys.J. C73 (2013) 2521; arXiv:1304.7630, Phys.Rev. D87 (2013) 084023 One way of characterizing such a \quantum spacetime" is through a sort of \Heisenberg uncertainty principle for spacetime", where, similarly to position and momentum in quantum mechanics ([^p; x^] = i~ ) δpδ^ x^ & ~), spacetime coordinates µ ν µν do not commute among themeselves: [^x ; x^ ] = iΘ (^x) / `P (Doplicher+Fredenaghen+Roberts,Phys.Lett.B(1994)331) µ ν µν ρ µν Consider [^x ; x^ ] = iλρ x^ , with λρ = O(`P ). Is this a preferred-frame picture or still a fully relativistic picture? If λµν is the same for all inertial observers, one needs to modify (\deform") the relativistic laws of transformations between their coordinates. κ-Minkowski (c = ~ = 1) £ κ ∼ Mp = ~ = `P c ¢ ¡ q i ~c ∼ 1019GeV=c2 [xj ; x0] = xj [xj ; x ] = 0 G κ k κ-Poincar´e is the deformed (Hopf-)algebra of symmetries £ (See the talks of Gubitosi, (Lukierski,Ruegg,Majid,...'90) ¢ ¡ Amelino-Camelia,...) Several arguments suggest that, when both gravitational and quantum effects are considered, localization measurements in spacetime can be performed down to a minimum length scale, usually thought to be close to the Planck scale q ` = ~G ∼ 10−35 m. P c3 µ ν µν ρ µν Consider [^x ; x^ ] = iλρ x^ , with λρ = O(`P ). Is this a preferred-frame picture or still a fully relativistic picture? If λµν is the same for all inertial observers, one needs to modify (\deform") the relativistic laws of transformations between their coordinates. κ-Minkowski (c = ~ = 1) £ κ ∼ Mp = ~ = `P c ¢ ¡ q i ~c ∼ 1019GeV=c2 [xj ; x0] = xj [xj ; x ] = 0 G κ k κ-Poincar´e is the deformed (Hopf-)algebra of symmetries £ (See the talks of Gubitosi, (Lukierski,Ruegg,Majid,...'90) ¢ ¡ Amelino-Camelia,...) Several arguments suggest that, when both gravitational and quantum effects are considered, localization measurements in spacetime can be performed down to a minimum length scale, usually thought to be close to the Planck scale q ` = ~G ∼ 10−35 m. P c3 One way of characterizing such a \quantum spacetime" is through a sort of \Heisenberg uncertainty principle for spacetime", where, similarly to position and momentum in quantum mechanics ([^p; x^] = i~ ) δpδ^ x^ & ~), spacetime coordinates µ ν µν do not commute among themeselves: [^x ; x^ ] = iΘ (^x) / `P (Doplicher+Fredenaghen+Roberts,Phys.Lett.B(1994)331) κ-Minkowski (c = ~ = 1) £ κ ∼ Mp = ~ = `P c ¢ ¡ q i ~c ∼ 1019GeV=c2 [xj ; x0] = xj [xj ; x ] = 0 G κ k κ-Poincar´e is the deformed (Hopf-)algebra of symmetries £ (See the talks of Gubitosi, (Lukierski,Ruegg,Majid,...'90) ¢ ¡ Amelino-Camelia,...) Several arguments suggest that, when both gravitational and quantum effects are considered, localization measurements in spacetime can be performed down to a minimum length scale, usually thought to be close to the Planck scale q ` = ~G ∼ 10−35 m. P c3 One way of characterizing such a \quantum spacetime" is through a sort of \Heisenberg uncertainty principle for spacetime", where, similarly to position and momentum in quantum mechanics ([^p; x^] = i~ ) δpδ^ x^ & ~), spacetime coordinates µ ν µν do not commute among themeselves: [^x ; x^ ] = iΘ (^x) / `P (Doplicher+Fredenaghen+Roberts,Phys.Lett.B(1994)331) µ ν µν ρ µν Consider [^x ; x^ ] = iλρ x^ , with λρ = O(`P ). Is this a preferred-frame picture or still a fully relativistic picture? If λµν is the same for all inertial observers, one needs to modify (\deform") the relativistic laws of transformations between their coordinates. Several arguments suggest that, when both gravitational and quantum effects are considered, localization measurements in spacetime can be performed down to a minimum length scale, usually thought to be close to the Planck scale q ` = ~G ∼ 10−35 m. P c3 One way of characterizing such a \quantum spacetime" is through a sort of \Heisenberg uncertainty principle for spacetime", where, similarly to position and momentum in quantum mechanics ([^p; x^] = i~ ) δpδ^ x^ & ~), spacetime coordinates µ ν µν do not commute among themeselves: [^x ; x^ ] = iΘ (^x) / `P (Doplicher+Fredenaghen+Roberts,Phys.Lett.B(1994)331) µ ν µν ρ µν Consider [^x ; x^ ] = iλρ x^ , with λρ = O(`P ). Is this a preferred-frame picture or still a fully relativistic picture? If λµν is the same for all inertial observers, one needs to modify (\deform") the relativistic laws of transformations between their coordinates. κ-Minkowski (c = ~ = 1) £ κ ∼ Mp = ~ = `P c ¢ ¡ q i ~c ∼ 1019GeV=c2 [xj ; x0] = xj [xj ; x ] = 0 G κ k κ-Poincar´e is the deformed (Hopf-)algebra of symmetries £ (See the talks of Gubitosi, (Lukierski,Ruegg,Majid,...'90) ¢ ¡ Amelino-Camelia,...) It turns out that in theories where relativistic symmetries are deformed in terms of a (inverse-) momentum invariant scale 1/κ (DSR theories (Amelino-Camelia,Kowalski-Glikman,Smolin,Magueijo ∼ 2000)) the notion of absolute spacetime locality is relaxed in favor of a relativity of locality (Amelino-Camelia+Matassa+Mercati+G.R.(2010)Phys.Rev.Lett.106), similarly to how, in the transition from Galilean to special relativity, the deformation of relativistic symmetries in terms of an invariant speed c, enforces relativity of simultaneity. 1 xB detector ℓb ∆p Bob | | 0 xB 1 xA p s p h emitter 0 Alice xA (Amelino-Camelia+Loret+G.R.,(2011)Phys.Lett.B700; Amelino-Camelia+Arzano+Kowalski-Glikman+G.R.+Trevisan(2011)Class.Quant.Grav.29; Amelino-Camelia+Freidel+Kowalski-Glikman+Smolin(2011)Phys.Rev.D84) What is the description of spacetime points in κ-Minkowski? One expect some kind of fuzziness. How can it be characterized? Is it possible to provide a quantum mechanical description of κ-Minkowski/κ-Poincar´e? In a \pregeometrical" interpretation, κ-Minkowski emerges from quantum gravity at some level of effective description, and non-commutativity is represented in terms of standard Heisenberg quantum mechanics introduced at some deeper level. Some previous attempts (Lukierski+Ruegg+Zakrzewski,Ann.Phys.243(1995)90) (Livine+Oriti,J.HighEnergyPhys.0406(2004)050) (Agostini,J.Math.Phys.48(2007)052305) (D'andrea,J.Math.Phys.47(2006)062105) (Ghosh+Pal,Phys.Rev.D75(2007)105021) (Dabrowski+Piacitelli,ArXiv:1004.5091) (Mignemi,Phys.Rev.D84(2011)025021) (Kovacevic+Meljanac,J.Phys.A45(2012)135208) κ-Poincar´ealgebra and κ-Minkowski spacetime (1+1D) Lukierski,Ruegg,Majid,...'90 κ-Minkowski Xκ is the homogeneous space of the κ-Poincar´eHopf algebra Pκ i [x1; x0] = x1 κ [P1;P0] = 0 [N; P0] = iP1 1 1 κ 2 i ∆ (xµ) = xµ ⊗ + ⊗ xµ − P0 2 [N; P1] = i 1 − e κ − P 2 2κ 1 S (xµ) = −xµ (xµ) = 0 ∆P0 = P0 ⊗ 1 + ⊗P0 P − 0 ∆P1 = P1 ⊗ 1 + e κ ⊗ P1 P − 0 ∆N = N ⊗ 1 + e κ ⊗ N P0 P0 S (P0) = −P0 S (P1) = −e κ P1 S(N) = −e κ N1 P 2 2 P0 0 2 2κ = (2κ) sinh − e κ P~ 2κ Translations and differential calculus Coproduct ∆ =) action . : Pκ ⊗ Xκ !Xκ £ ¢ ¡ P − 0 P1 . f(x)g(x) = (P1 . f(x)) g(x) + e κ . f(x) (P1 . g(x)) Leibniz i P1 . [x1; x0] = P1 . x1 κ 0 0 0 i 0 Translations: xµ = xµ − aµ () x1; x0 = κ x1 κ i κ κ κ a ; x0 = a a ; x1 = 0 a ; x0 = 0 § 1 κ 1 µ 0 ¤ ¦ 1 κ µ ¥ T = + d d = −iaµP differential calculus df(x)g(x) = (df(x)) g(x) + f(x)dg(x) Woronowicz,Majid,Oeckl,...'90 Pregeometry of κ-Minkowski/κ-Poincar´e Covariant quantum mechanics Pregeometry spacetime noncommutativity arises from a more fundamental theory £ ¢ Ordinary Heisenberg¡ algebra () κ-Minkowski/κ-Poincar´e pregeometric representation But what framework? κ-Minkowski Quantum Mechanics time coordinate = noncommutative time coordinate = evolution parameter observable + Covariant formulation of ordinary quantum mechanics Reisenberger,Rovelli Phys.Rev.D65(2002) The spatial coordinates£ and the time coordinate play the same type of role. Both operators on¢ a \kinematical Hilbert space" ¡ (ordinary Hilbert space of normalizable wave functions) (See also the talks of Hoehn, Giacomini) Covariant quantum mechanics Reisenberger,Rovelli,Phys.Rev.D65(2002) Kinematical Hilbert space 2 2 Space of (1+1D) \spacetime regions" L (R ; dq0; dq1) Standard multiplicative operators q^0; q^1 and derivative operators π^ ≡ i @ ; π^ ≡ i @ 0 @q0 1 @q1 Standard commutator algebra [^π0; q^0] = i [^π0; q^1] = 0 [^π1; q^0] = 0 [^π1; q^1] = −i \Regions of spacetime" hq^0i ; hq^1i, δq0; δq1 Covariant quantum mechanics Reisenberger,Rovelli,Phys.Rev.D65(2002) Dynamics There is no \evolution" £ ¢ ¡ Kinematical Hilbert space () Physical Hilbert space Hamiltonian constraint H = 0 relationships between the properties of the (partial) observables for ) dynamics = £ spatial coordinates and the properties of the time (partial) observable ¢ ¡ −! \fuzzy worldlines" "Geometrical interpretation\ (Classical) Special Relativity: Covariant Quantum Mechanics arena = Minkowski spacetime arena = kinematical Hilbert space H = 0 H = 0 + + dynamics of relativistic classical dynamics of relativistic quantum particles unfolds particles unfolds Geometrical interpretation Minkowski spacetime classical particles \spacetime observables" physically observable experiment property =) properties kinematical Hilbert space quantum particles \spacetime observables" physically observable experiment property =) (physical Hilbert space) Pregeometry of κ-Minkowski/κ-Poincar´e Pregeometric representations [^π0; q^0] = i [^π0; q^1] = 0 Amelino-Camelia,Astuti,G.R.,arXiv:1206.3805,Eur.Phys.J.C73(2013) [^π1; q^0] = 0 [^π1; q^1] = −i x^0 =q ^0 i π^0 ) [^x1; x^0] = x^1 x^1 =q ^1e κ κ π^0 P P0 . f(^x0; x^1) ! [^π0; f(^q0; q^1e κ )] − 0 ) P1.fg = (P1 .f) g+ e κ .f (P1 .g) π^ π^ − 0 0 P1 .
Load more

Recommended publications
  • 1. Introduction 2. Pregeometry
    Hidezumi Terazawa 219 218 Proceedings of BGL-4 SPECIAL INCONSTANCY IN PREGEOMETRY for 0.2 < z < 3. 7, which is consistent with a time-varying a . Note, however, that in 1976 Shylakhter f81 obtained the very restrictive limit of 16.a/al < 10- 7 or, more precisely, Hidezumi Terazawa 6.Œ/a6.t = (-0.2 ± 0.8) x 10-17 yr-1 for z ,...., 0.16 (but over a. narrower and latest range of epochs betwcen now and about 1.8 Instu.te of ?article and Nuclear St11dies 1 H'igh Energy Accelemtor Research Organization, billion years ago) from the "Oklo natural reactor". Very lately, Srianand et al. [9] have made Japan a detailed many-multiplet analysis performcd on a new sample of Mg II systems observed in high quality quasar spectra obtained using the Very Large Telescope and found a null result Midlands Acaderny of Bnsiness ël Technology (MABT), 5 United Kingdom of 6.a/cr. = (-0.06 ± 0.06) x 10- for the fractional change in Œ or a 3ri constraint of 16 1 16 1 -2.5 x 10- yr-- -:; (6.a./a6.t) -:; +1.2 x 10- yr- A thcory of spccial inconstancy, in which some fondamental physical constants such as the for 0.4-:; z -:; 2.3, which seems to be inconsistent with the result of Webb et al. [7]. However, fine-structure and grnvitational constants may vary, is proposed Ill pregcometry. In thf~ the­ a careful comparison of thesc different rcsults [7-9] indicates that thcy are ail consistent with ory, the alpha-G relation of a = 3n /[16 ln( 471' /5CM~ )] between the varyin~ fine~structure ;;i,r~d gravitational constants (where Mw is the charged weak Loso.n mass) 1s denved frorn a tirne-varying l~ as the hypothesis that Loth of these constants arc related to the same fu11damcnt:l1 ~en~t~1 ~cale in nature.
    [Show full text]
  • Philip Gibbs EVENT-SYMMETRIC SPACE-TIME
    Event-Symmetric Space-Time “The universe is made of stories, not of atoms.” Muriel Rukeyser Philip Gibbs EVENT-SYMMETRIC SPACE-TIME WEBURBIA PUBLICATION Cyberspace First published in 1998 by Weburbia Press 27 Stanley Mead Bradley Stoke Bristol BS32 0EF [email protected] http://www.weburbia.com/press/ This address is supplied for legal reasons only. Please do not send book proposals as Weburbia does not have facilities for large scale publication. © 1998 Philip Gibbs [email protected] A catalogue record for this book is available from the British Library. Distributed by Weburbia Tel 01454 617659 Electronic copies of this book are available on the world wide web at http://www.weburbia.com/press/esst.htm Philip Gibbs’s right to be identified as the author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved, except that permission is given that this booklet may be reproduced by photocopy or electronic duplication by individuals for personal use only, or by libraries and educational establishments for non-profit purposes only. Mass distribution of copies in any form is prohibited except with the written permission of the author. Printed copies are printed and bound in Great Britain by Weburbia. Dedicated to Alice Contents THE STORYTELLER ................................................................................... 11 Between a story and the world ............................................................. 11 Dreams of Rationalism .......................................................................
    [Show full text]
  • “Algebraic Quantum Mechanics and Pregeometry”. B
    Quantum Space-Times: An Introduction to “Algebraic Quantum Mechanics and Pregeometry”. B. J. Hiley1 Theoretical Physics Research Unit, Birkbeck, University of London, Malet Street, London, WC1E 7HK Abstract. This is an introductory note to the paper, “Algebraic Quantum Mechanics and Pregeometry”, written by D.J. Bohm, P.G. Davies and B.J. Hiley in 1982, and previously unpusblished. Keywords: Quantum pre-space, non-locality, non-commutative geometry PACS: 03.65.Ud,04.60.Nc There is now a growing realisation that some of the problems in quantum mechanics seem to have their origins in the deeper meaning of space-time. To date the classical Minkowskian view has dominated physics, but the pioneering work of Wheeler [1] and the advent of string theory, M-branes etc [2]. have accelerated our thinking as to the role space-time plays in the quantum domain. Normally one thinks that these questions are only relevant on the very small scale where it is common to talk about notions such as the fluctuations in the metric tensor. But we should be cautious about limiting our discussions to small space-time distances. For example, quantum entangled states already exhibit non-locality on the macroscopic scale and such a notion is completely foreign to our traditional concepts of space-time with its insistence on a notion of absolute locality. What is called for, in my view, is a radical re-consideration of our views of space-time as a whole and the role it plays in the quantum domain. This debate is gaining momentum and in this conference Thomas Filk [3] presents a paper raising some of the deep questions that have to be considered.
    [Show full text]
  • Information, Physics, Quantum: the Search for Links
    19 INFORMATION, PHYSICS, QUANTUM: THE SEARCH FOR LINKS John Archibald Wheeler * t Abstract This report reviews what quantum physics and information theory have to tell us about the age-old question, How come existence? No escape is evident from four conclusions: (1) The world cannot be a giant machine, ruled by any preestablished continuum physical law. (2) There is no such thing at the microscopic level as space or time or spacetime continuum. (3) The familiar probability function or functional, and wave equation or functional wave equation, of standard quantum theory provide mere continuum idealizations and by reason of this circumstance conceal the information-theoretic source from which they derive. (4) No element in the description of physics shows itself as closer to primordial than the elementary quantum phenomenon, that is, the elementary device-intermediated act of posing a yes-no physical question and eliciting an answer or, in brief, the elementary act of observer-participancy. Otherwise stated, every physical quantity, every it, derives its ultimate significance from bits, binary yes-or-no indications, a conclusion which we epitomize in the phrase, it from bit. 19.1 Quantum Physics Requires a New View of Reality Revolution in outlook though Kepler, Newton, and Einstein brought us [1-4], and still more startling the story of life [5-7] that evolution forced upon an unwilling world, the ultimate shock to preconceived ideas lies ahead, be it a decade hence, a century or a millenium. The overarching principle of 20th-century physics,
    [Show full text]
  • 1 Uniform Spaces in the Pregeometric Modeling of Quantum Non
    Uniform Spaces in the Pregeometric Modeling of Quantum Non-Separability W.M. Stuckey, Dept of Physics Michael Silberstein, Dept of Philosophy, Elizabethtown College Elizabethtown, PA 17022 Abstract We introduce a pregeometry employing uniform spaces over the denumerable set X of spacetime events. The discrete uniformity DX over X is used to obtain a pregeometric model of macroscopic spacetime neighborhoods. We then use a uniformity base generated by a topological group structure over X to provide a pregeometric model of microscopic spacetime neighborhoods. Accordingly, quantum non-separability as it pertains to non-locality is understood pregeometrically as a contrast between microscopic spacetime neighborhoods and macroscopic spacetime neighborhoods. A nexus between this pregeometry and conventional spacetime physics is implied per the metric induced by DX. A metric over the topological group Z2 x … x Z2 is so generated. Implications for quantum gravity are enumerated. Keywords: Uniform spaces, pregeometry, quantum non-separability, quantum non-locality, quantum gravity 1 1. INTRODUCTION Uniform spaces lie between topological spaces and metric spaces in structural sophistication. Unlike the open sets of topological spaces, one may compare sizes of the entourages of a uniform space, although the size of an entourage needn’t be specified via a mapping to ú as with a metric space. In some sense, a metric space is a uniform space with ‘choice of gauge’. Therefore, uniform spaces provide a reasonable mathematics for pregeometry (Bergliaffa et al., 1998). Herein, we employ the discrete uniformity DX over the denumerable set X of spacetime events as a discrete, pregeometric model of macroscopic spacetime neighborhoods, i.e., spacetime neighborhoods compatible with the locality implicit in the construct of trans-temporal objects (Stuckey, 2000).
    [Show full text]
  • Cognitive Constructivism and the Epistemic Significance Of
    Cognitive Constructivism and the Epistemic Significance of Sharp Statistical Hypotheses in Natural Sciences Julio Michael Stern IME-USP Institute of Mathematics and Statistics of the University of S~aoPaulo Version 2.31, May 01, 2013. arXiv:1006.5471v8 [stat.OT] 26 Oct 2020 2 3 A` Marisa e a nossos filhos, Rafael, Ana Carolina, e Deborah. 4 5 \Remanso de rio largo, viola da solid~ao: Quando vou p'ra dar batalha, convido meu cora¸c~ao." Gentle backwater of wide river, fiddle to solitude: When going to do battle, I invite my heart. Jo~aoGuimar~aesRosa (1908-1967). Grande Sert~ao,Veredas. \Sert~ao´eonde o homem tem de ter a dura nuca e a m~aoquadrada. (Onde quem manda ´eforte, com astucia e com cilada.) Mas onde ´ebobice a qualquer resposta, ´ea´ıque a pergunta se pergunta." \A gente vive repetido, o repetido... Digo: o real n~aoest´ana sa´ıdanem na chegada: ele se disp~oempara a gente ´eno meio da travessia." Sertao is where a man's might must prevail, where he has to be strong, smart and wise. But there, where any answer is wrong, there is where the question asks itself. We live repeating the reapeated... I say: the real is neither at the departure nor at the arrival: It presents itself to us at the middle of the journey. 6 Contents Preface 13 Cognitive Constructivism . 14 Basic Tools for the (Home) Works . 16 Acknowledgements and Final Remarks . 16 1 Eigen-Solutions and Sharp Statistical Hypotheses 19 1.1 Introduction . 19 1.2 Autopoiesis and Eigen-Solutions .
    [Show full text]
  • Semiclassical Length Measure from a Quantum-Gravity Wave Function
    technologies Technical Note Semiclassical Length Measure from a Quantum-Gravity Wave Function Orchidea Maria Lecian DIAEE—Department for Astronautics Engineering, Electrical and Energetics, Sapienza University of Rome, Via Eudossiana, 18, 00184 Rome, Italy; [email protected] Received: 7 July 2017; Accepted: 23 August 2017; Published: 8 September 2017 Abstract: The definition of a length operator in quantum cosmology is usually influenced by a quantum theory for gravity considered. The semiclassical limit at the Planck age must meet the requirements implied in present observations. The features of a semiclassical wave-functional state are investigated, for which the modern measure(ment)s is consistent. The results of a length measurement at present times are compared with the same measurement operation at cosmological times. By this measure, it is possible to discriminate, within the same Planck-length expansion, the corrections to a Minkowski flat space possibly due to classicalization of quantum phenomena at the Planck time and those due to possible quantum-gravitational manifestations of present times. This analysis and the comparison with the previous literature can be framed as a test for the verification of the time at which anomalies at present related to the gravitational field, and, in particular, whether they are ascribed to the classicalization epoch. Indeed, it allows to discriminate not only within the possible quantum features of the quasi (Minkowski) flat spacetime, but also from (possibly Lorentz violating) phenomena detectable at high-energy astrophysical scales. The results of two different (coordinate) length measures have been compared both at cosmological time and as a perturbation element on flat Minkowski spacetime.
    [Show full text]
  • "The Quantum Universe"
    Classical and Quantum Causality in Quantum Field Theory or The Quantum Universe by Jonathan Simon Eakins, M.Sci. Thesis submitted to the University of Nottingham for the degree of Doctor of Philosophy, April 2004 Abstract Based on a number of experimentally verified physical observations, it is argued that the standard principles of quantum mechanics should be applied to the Universe as a whole. Thus, a paradigm is proposed in which the entire Universe is represented by a pure state wavefunction contained in a factorisable Hilbert space of enormous dimension, and where this statevector is developed by successive applications of operators that correspond to unitary rotations and Hermitian tests. Moreover, because by definition the Universe contains everything, it is argued that these operators must be chosen self-referentially; the overall dynamics of the system is envisaged to be analogous to a gigantic, self-governing, quantum computation. The issue of how the Universe could choose these operators with- out requiring or referring to a fictitious external observer is addressed, and this in turn rephrases and removes the traditional Measurement Problem inherent in the Copenhagen interpretation of quantum mechanics. The processes by which conventional physics might be recovered from this fundamental, mathematical and global description of reality are particularly investigated. Specifically, it is demonstrated that by considering the changing properties, separabilities and factori- sations of both the state and the operators as the Universe proceeds though a sequence of discrete computations, familiar notions such as classical distinguishability, particle physics, space, time, special relativity and endo-physical experiments can all begin to emerge from the proposed picture.
    [Show full text]
  • Pregeometry and Euclidean Quantum Gravity
    Available online at www.sciencedirect.com ScienceDirect Nuclear Physics B 971 (2021) 115526 www.elsevier.com/locate/nuclphysb Pregeometry and euclidean quantum gravity Christof Wetterich Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, D-69120 Heidelberg, Germany Received 7 May 2021; received in revised form 6 August 2021; accepted 24 August 2021 Available online 26 August 2021 Editor: Stephan Stieberger Abstract Einstein’s general relativity can emerge from pregeometry, with the metric composed of more fundamen- tal fields. We formulate euclidean pregeometry as a SO(4) - Yang-Mills theory. In addition to the gauge fields we include a vector field in the vector representation of the gauge group. The gauge -and diffeo- morphism -invariant kinetic terms for these fields permit a well-defined euclidean functional integral, in contrast to metric gravity with the Einstein-Hilbert action. The propagators of all fields are well behaved at short distances, without tachyonic or ghost modes. The long distance behavior is governed by the composite metric and corresponds to general relativity. In particular, the graviton propagator is free of ghost or tachy- onic poles despite the presence of higher order terms in a momentum expansion of the inverse propagator. This pregeometry seems to be a valid candidate for euclidean quantum gravity, without obstructions for analytic continuation to a Minkowski signature of the metric. © 2021 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3. 1. Introduction In a modern view, quantum field theories are defined by functional integrals.
    [Show full text]
  • Waves on Noncommutative Spacetime and Gamma-Ray Bursts
    CERN-TH/99-213 DAMTP/99-83 hep-th/9907110 July 1999 WAVES ON NONCOMMUTATIVE SPACETIME AND GAMMA-RAY BURSTS Giovanni AMELINO-CAMELIA1 Theory Division, CERN, CH-1211, Geneva, Switzerland Shahn MAJID2 Department of Applied Mathematics & Theoretical Physics University of Cambridge, Cambridge CB3 9EW Abstract Quantum group Fourier transform methods are applied to the study of processes on noncommutative Minkowski spacetime [xi,t]=ıλxi.Anaturalwave equation is derived and the associated phenomena of in vacuo dispersion are dis- cussed. Assuming the deformation scale λ is of the order of the Planck length one finds that the dispersion effects are large enough to be tested in experimental inves- tigations of astrophysical phenomena such as gamma-ray bursts. We also outline a new approach to the construction of field theories on the noncommutative spacetime, with the noncommutativity equivalent under Fourier transform to non-Abelianness of the ‘addition law’ for momentum in Feynman diagrams. We argue that CPT violation effects of the type testable using the sensitive neutral-kaon system are to be expected in such a theory. 1 Introduction Quantum groups and their associated noncommutative geometry have been proposed as a can- didate for the generalisation of geometry needed for Planck scale physics in [1, 2]. Using such methods there were provided models exhibiting the unification of quantum and gravity-like ef- fects into a single system with a flat space quantum limit when a parameter G 0andaclassical → but curved space limit when ~ 0. Radically new phenomena at the Planck scale were also → proposed, notably an extension of wave-particle duality between position and momentum via Fourier theory to a novel duality between quantum observables and states in which their roles 1Marie Curie Fellow (permanent address: Dipartimento di Fisica, Universit´a di Roma \La Sapienza", Piazzale Moro 2, Roma, Italy) 2Royal Society University Research Fellow and Fellow of Pembroke College, Cambridge 1 could be interchanged.
    [Show full text]
  • Models of Pregeometry
    Models of Pregeometry Frank Antonsen The Niels Bohr Institute Blegdamsvej 17, DK-2100 Copenhagen 0 Denmark Abstract We discuss an approach to the quantization of gravity, known as pregeometry, a notion going back to J .A. Wheeler and A.Sakharov. Over the past twenty years many different pregeometrical models have been proposed and we give a (very) short summary of the most important ones. The emphasis, however, is put on a model due to the author, which is based on random graphs. The predictions of that particular model is discussed, as are its relationship with other approaches to quantum gravity. Introduction Modern physics consists essentialy of two different theories, which are both very elegant and powerful. The one is quantum field theory, dealing with subnuclear length-scales, while the second is general relativity, which deals with stellar and galactical scales. Quantum field theory provides a succeaful description of three of the four fundamental forces, namely electromagne­ tism and the strong and weak interactions, it even allows a unification of these into one grand unified theory. General relativity is a classical theory of gravitational phenomena, and has sofar defied quantization: we have no consistent theory of quantum gravity. A lot of work is carried out trying to unite general relativity and quantum theory, this truely unified theory would then work for all length scales· (at least in principle). To get an idea of the complexities involved in quantizing gravity, it is worthwile to note the level of mathematical abstraction involved in the 287 288 Frank Antonsen Models of Pregeometry 289 formulation of the theory.
    [Show full text]
  • Quantum Gravity Quantum Gravity
    QUANTUM GRAVITY QUANTUM GRAVITY Edited by M. A. Markov Academy of Sciences of the USSR Moscow, USSR and P. C. West King's College London, England PLENUM PRESS • NEW YORK AND LONDON Library of Congress Cataloging in Publication Data Seminar on Quantum Gravity (2nd: 1981: Moscow, R.S.F.S.R.) Quantum gravity. "Proceedings of the Second Seminar on Quantum Gravity, held I October B-15, 1981, in Moscow, USSR"-T.p. verso. Includes bibliographical references and index. l. Quantum gravity-Congresses. 2. Cosmology-Congresses. 3. Black holes (Astronomy)-Congresses. I. Markov, M. A. (Moisei Aleksandrovich), 1908- II. West, P. C. (Peter C.) Ill. Title. QC178.S455 1981 530.1 83-24446 ISBN-13: 978-1-4612-9678-2 e-ISBN-13: 978-1-4613-2701-1 DOl: 10.1007/978-1-4613-2701-1 Proceedings of the second Seminar on Quantum Gravity, held October 13-15, 1981, in Moscow, USSR ©1984 Plenum Press, New York Softcover reprint of the hardcover 1st edition 1984 A Division of Plenum Publishing Corporation 233 Spring Street, New York, N.Y. 10013 All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical. photocopying, microfilming, recording, or otherwise, without written permission from the Publisher ORGANIZING COMMITTEE Markov M.A. Chairman Frolov V.P. Scientific Secretary Zlobina K.K. Secretary Berezin V.A. Ogievetsky V.I. Tavkhelidze A.N. Fradkin E.S. EDITORIAL BOARD Markov M.A. Chief Editor Berezin V.A. Frolov V.P. PREFACE Three years have passed after the First Moscow Seminar on Quantum Gravity.
    [Show full text]