Towards Inflation in String Theory
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Symmetries of String Theory and Early Universe Cosmology
String Cosmology R. Branden- berger Introduction Symmetries of String Theory and Early T-Duality: Key Symmetry of Universe Cosmology String Theory String Gas Cosmology Structure Robert Brandenberger Perturbations Overview Physics Department, McGill University Analysis DFT Conclusions Yukawa Institute, Kyoto University, Feb. 26, 2018 1 / 61 Outline String Cosmology 1 Introduction R. Branden- berger 2 T-Duality: Key Symmetry of String Theory Introduction T-Duality: Key 3 String Gas Cosmology Symmetry of String Theory String Gas 4 String Gas Cosmology and Structure Formation Cosmology Review of the Theory of Cosmological Perturbations Structure Perturbations Overview Overview Analysis Analysis DFT 5 Double Field Theory as a Background for String Gas Conclusions Cosmology 6 Conclusions 2 / 61 Plan String Cosmology 1 Introduction R. Branden- berger 2 T-Duality: Key Symmetry of String Theory Introduction T-Duality: Key 3 String Gas Cosmology Symmetry of String Theory String Gas 4 String Gas Cosmology and Structure Formation Cosmology Review of the Theory of Cosmological Perturbations Structure Perturbations Overview Overview Analysis Analysis DFT 5 Double Field Theory as a Background for String Gas Conclusions Cosmology 6 Conclusions 3 / 61 Inflation: the Standard Model of Early Universe Cosmology String Cosmology R. Branden- berger Introduction Inflation is the standard paradigm of early universe T-Duality: Key cosmology. Symmetry of String Theory Inflation solves conceptual problems of Standard Big String Gas Bang Cosmology. Cosmology Structure Inflation predicts an almost scale-invariant spectrum of Perturbations Overview primordial cosmological perturbations with a small red Analysis tilt (Chibisov & Mukhanov, 1981). DFT Conclusions Fluctuations are nearly Gaussian and nearly adiabatic. 4 / 61 Map of the Cosmic Microwave Background (CMB) String Cosmology R. -
Eternal Inflation and Its Implications
IOP PUBLISHING JOURNAL OF PHYSICS A: MATHEMATICAL AND THEORETICAL J. Phys. A: Math. Theor. 40 (2007) 6811–6826 doi:10.1088/1751-8113/40/25/S25 Eternal inflation and its implications Alan H Guth Center for Theoretical Physics, Laboratory for Nuclear Science, and Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA E-mail: [email protected] Received 8 February 2006 Published 6 June 2007 Online at stacks.iop.org/JPhysA/40/6811 Abstract Isummarizetheargumentsthatstronglysuggestthatouruniverseisthe product of inflation. The mechanisms that lead to eternal inflation in both new and chaotic models are described. Although the infinity of pocket universes produced by eternal inflation are unobservable, it is argued that eternal inflation has real consequences in terms of the way that predictions are extracted from theoretical models. The ambiguities in defining probabilities in eternally inflating spacetimes are reviewed, with emphasis on the youngness paradox that results from a synchronous gauge regularization technique. Although inflation is generically eternal into the future, it is not eternal into the past: it can be proven under reasonable assumptions that the inflating region must be incomplete in past directions, so some physics other than inflation is needed to describe the past boundary of the inflating region. PACS numbers: 98.80.cQ, 98.80.Bp, 98.80.Es 1. Introduction: the successes of inflation Since the proposal of the inflationary model some 25 years ago [1–4], inflation has been remarkably successful in explaining many important qualitative and quantitative properties of the universe. In this paper, I will summarize the key successes, and then discuss a number of issues associated with the eternal nature of inflation. -
String-Inspired Running Vacuum—The ``Vacuumon''—And the Swampland Criteria
universe Article String-Inspired Running Vacuum—The “Vacuumon”—And the Swampland Criteria Nick E. Mavromatos 1 , Joan Solà Peracaula 2,* and Spyros Basilakos 3,4 1 Theoretical Particle Physics and Cosmology Group, Physics Department, King’s College London, Strand, London WC2R 2LS, UK; [email protected] 2 Departament de Física Quàntica i Astrofísica, and Institute of Cosmos Sciences (ICCUB), Universitat de Barcelona, Av. Diagonal 647, E-08028 Barcelona, Catalonia, Spain 3 Academy of Athens, Research Center for Astronomy and Applied Mathematics, Soranou Efessiou 4, 11527 Athens, Greece; [email protected] 4 National Observatory of Athens, Lofos Nymfon, 11852 Athens, Greece * Correspondence: [email protected] Received: 15 October 2020; Accepted: 17 November 2020; Published: 20 November 2020 Abstract: We elaborate further on the compatibility of the “vacuumon potential” that characterises the inflationary phase of the running vacuum model (RVM) with the swampland criteria. The work is motivated by the fact that, as demonstrated recently by the authors, the RVM framework can be derived as an effective gravitational field theory stemming from underlying microscopic (critical) string theory models with gravitational anomalies, involving condensation of primordial gravitational waves. Although believed to be a classical scalar field description, not representing a fully fledged quantum field, we show here that the vacuumon potential satisfies certain swampland criteria for the relevant regime of parameters and field range. We link the criteria to the Gibbons–Hawking entropy that has been argued to characterise the RVM during the de Sitter phase. These results imply that the vacuumon may, after all, admit under certain conditions, a rôle as a quantum field during the inflationary (almost de Sitter) phase of the running vacuum. -
A Correspondence Between Strings in the Hagedorn Phase and Asymptotically De Sitter Space
A correspondence between strings in the Hagedorn phase and asymptotically de Sitter space Ram Brustein(1), A.J.M. Medved(2;3) (1) Department of Physics, Ben-Gurion University, Beer-Sheva 84105, Israel (2) Department of Physics & Electronics, Rhodes University, Grahamstown 6140, South Africa (3) National Institute for Theoretical Physics (NITheP), Western Cape 7602, South Africa [email protected], [email protected] Abstract A correspondence between closed strings in their high-temperature Hage- dorn phase and asymptotically de Sitter (dS) space is established. We identify a thermal, conformal field theory (CFT) whose partition function is, on the one hand, equal to the partition function of closed, interacting, fundamental strings in their Hagedorn phase yet is, on the other hand, also equal to the Hartle-Hawking (HH) wavefunction of an asymptotically dS Universe. The Lagrangian of the CFT is a functional of a single scalar field, the condensate of a thermal scalar, which is proportional to the entropy density of the strings. The correspondence has some aspects in common with the anti-de Sitter/CFT correspondence, as well as with some of its proposed analytic continuations to a dS/CFT correspondence, but it also has some important conceptual and technical differences. The equilibrium state of the CFT is one of maximal pres- sure and entropy, and it is at a temperature that is above but parametrically close to the Hagedorn temperature. The CFT is valid beyond the regime of semiclassical gravity and thus defines the initial quantum state of the dS Uni- verse in a way that replaces and supersedes the HH wavefunction. -
Punctuated Eternal Inflation Via Ads/CFT
BROWN-HET-1593 Punctuated eternal inflation via AdS/CFT David A. Lowe† and Shubho Roy†♮♯∗ †Department of Physics, Brown University, Providence, RI 02912, USA ♮Physics Department City College of the CUNY New York, NY 10031, USA and ♯Department of Physics and Astronomy Lehman College of the CUNY Bronx, NY 10468, USA Abstract The work is an attempt to model a scenario of inflation in the framework of Anti de Sit- ter/Conformal Field theory (AdS/CFT) duality, a potentially complete nonperturbative description of quantum gravity via string theory. We look at bubble geometries with de Sitter interiors within an ambient Schwarzschild anti-de Sitter black hole spacetime and obtain a characterization for the states in the dual CFT on boundary of the asymptotic AdS which code the expanding dS bubble. These can then in turn be used to specify initial conditions for cosmology. Our scenario naturally interprets the entropy of de Sitter space as a (logarithm of) subspace of states of the black hole microstates. Consistency checks are performed and a number of implications regarding cosmology are discussed including how the key problems or paradoxes of conventional eternal inflation are overcome. arXiv:1004.1402v1 [hep-th] 8 Apr 2010 ∗Electronic address: [email protected], [email protected] 1 I. INTRODUCTION Making contact with realistic cosmology remains the fundamental challenge for any can- didate unified theory of matter and gravity. Precise observations [1, 2] indicate that the current epoch of the acceleration of universe is driven by a very mild (in Planck units) neg- ative pressure, positive energy density constituent - “dark energy”. -
String Theory and Pre-Big Bang Cosmology
IL NUOVO CIMENTO 38 C (2015) 160 DOI 10.1393/ncc/i2015-15160-8 Colloquia: VILASIFEST String theory and pre-big bang cosmology M. Gasperini(1)andG. Veneziano(2) (1) Dipartimento di Fisica, Universit`a di Bari - Via G. Amendola 173, 70126 Bari, Italy and INFN, Sezione di Bari - Bari, Italy (2) CERN, Theory Unit, Physics Department - CH-1211 Geneva 23, Switzerland and Coll`ege de France - 11 Place M. Berthelot, 75005 Paris, France received 11 January 2016 Summary. — In string theory, the traditional picture of a Universe that emerges from the inflation of a very small and highly curved space-time patch is a possibility, not a necessity: quite different initial conditions are possible, and not necessarily unlikely. In particular, the duality symmetries of string theory suggest scenarios in which the Universe starts inflating from an initial state characterized by very small curvature and interactions. Such a state, being gravitationally unstable, will evolve towards higher curvature and coupling, until string-size effects and loop corrections make the Universe “bounce” into a standard, decreasing-curvature regime. In such a context, the hot big bang of conventional cosmology is replaced by a “hot big bounce” in which the bouncing and heating mechanisms originate from the quan- tum production of particles in the high-curvature, large-coupling pre-bounce phase. Here we briefly summarize the main features of this inflationary scenario, proposed a quarter century ago. In its simplest version (where it represents an alternative and not a complement to standard slow-roll inflation) it can produce a viable spectrum of density perturbations, together with a tensor component characterized by a “blue” spectral index with a peak in the GHz frequency range. -
Yasunori Nomura
Yasunori Nomura UC Berkeley; LBNL Why is the universe as we see today? ― Mathematics requires — “We require” Dramatic change of the view Our universe is only a part of the “multiverse” … suggested both from observation and theory This comes with revolutionary change of the view on spacetime and gravity • Holographic principle • Horizon complementarity • Multiverse as quantum many worlds • … … implications on particle physics and cosmology Shocking news in 1998 Supernova cosmology project; Supernova search team Universe is accelerating! ≠ 0 ! Particle Data Group (2010) 2 2 4 4 … natural size of ≡ MPl (naively) ~ MPl (at the very least ~ TeV ) Observationally, -3 4 120 ~ (10 eV) Naïve estimates O(10 ) too large Also, ~ matter — Why now? Nonzero value completely changes the view ! 4 Natural size for vacuum energy ~ MPl 4 • 4 -MPl 0 -120 4 MPl ,obs ~10 MPl Unnatural (Note: = 0 is NOT special from theoretical point of view) Wait! Is it really unnatural to observe this value? • No observer0 No observer It is quite “natural” to observe ,obs, as long as different values of are “sampled” Weinberg (’87) Many universes ─ multiverse ─ needed • String landscape Compact (six) dimensins ex. O(100) fields with O(10) minima each → huge number of vacua → O(10100) vacua • Eternal inflation Inflation is (generically) future eternal → populate all the vacua Anthropic considerations mandatory (not an option) Full of “miracles” Examples: • yu,d,e v ~ QCD ~ O(0.01) QCD … otherwise, no nuclear physics or chemistry (Conservative) estimate of the probability: P « 10-3 • Baryon ~ DM …. Some of them anthropic (and some may not) Implications? • Observational / experimental (test, new scenarios, …) • Fundamental physics (spacetime, gravity, …) Full of “miracles” Examples: • yu,d,e v ~ QCD ~ O(0.01) QCD … otherwise, no nuclear physics or chemistry (Conservative) estimate of the probability: P « 10-3 • Baryon ~ DM …. -
Phenomenological Aspects of Type IIB Flux Compactifications
Phenomenological Aspects of Type IIB Flux Compactifications Enrico Pajer Munchen¨ 2008 Phenomenological Aspects of Type IIB Flux Compactifications Enrico Pajer Dissertation an der Fakult¨at fur¨ Physik der Ludwig–Maximilians–Universit¨at Munchen¨ vorgelegt von Enrico Pajer aus Venedig, Italien Munchen,¨ den 01. Juni 2008 Erstgutachter: Dr. Michael Haack Zweitgutachter: Prof. Dr. Dieter Lust¨ Tag der mundlichen¨ Prufung:¨ 18.07.2008 Contents 1 Introduction and conclusions 1 2 Type IIB flux compactifications 9 2.1 Superstring theory in a nutshell . 10 2.2 How many string theories are there? . 13 2.3 Type IIB . 15 2.4 D-branes . 17 2.5 Flux compactifications . 18 2.5.1 The GKP setup . 19 2.6 Towards de Sitter vacua in string theory . 21 3 Inflation in string theory 27 3.1 Observations . 27 3.2 Inflation . 29 3.2.1 Slow-roll models . 32 3.3 String theory models of inflation . 35 3.3.1 Open string models . 35 3.3.2 Closed string models . 36 3.4 Discussion . 37 4 Radial brane inflation 39 4.1 Preliminaries . 40 4.2 The superpotential . 42 4.3 Warped Brane inflation . 44 4.3.1 The η-problem from volume stabilization . 44 4.3.2 F-term potential for the conifold . 46 4.4 Critical points of the potential . 47 4.4.1 Axion stabilization . 48 4.4.2 Volume stabilization . 48 4.4.3 Angular moduli stabilization . 50 4.4.4 Potential with fixed moduli . 51 4.5 Explicit examples: Ouyang vs Kuperstein embedding . 52 4.5.1 Ouyang embedding . 52 4.5.2 Kuperstein embedding . -
The Kavli Prize in Astrophysics 2014
THE KAVLI PRIZE IN ASTROPHYSICS 2014 The Norwegian Academy of Science and Letters has decided to award the Kavli Prize in Astrophysics for 2014 to Alan H. Guth Massachusetts Institute of Technology, Cambridge, MA, USA Andrei D. Linde Stanford University, CA, USA Alexei A. Starobinsky Landau Institute for Theoretical Physics, Russian Academy of Sciences, Moscow, Russia “for pioneering the theory of cosmic inflation” The theory of cosmic inflation, proposed astounding success, the Big Bang theory These two fundamental problems were and developed by Alan Guth, Andrei suffers from two major shortcomings: the elegantly solved in one fell swoop by Alan Linde and Alexei Starobinsky, has revo- “horizon” and the “flatness” problems. Guth in a paper entitled “Inflationary lutionized our thinking about the uni- Cosmic inflation solves them both. universe: A possible solution to the hori- verse. This theory extends our physical zon and flatness problems” published in description of the cosmos to the earliest As the universe expanded it cooled. Today 1981. Guth hypothesized that the uni- times, when the universe was only a tiny it is bathed in a sea of microwave radia- verse was initially trapped in a peculiar fraction of a second old. According to this tion, the heat left over from the Big Bang. state (the “false vacuum”) from which it theory, very soon after our universe came At first sight, the near uniformity of this decayed, in the process expanding expo- into existence it underwent a short-lived microwave background across the sky nentially and liberating the energy pres- phase of exponential expansion. During implies a disturbing contradiction: oppo- ent in our universe today. -
Brief Answers to the Big Questions
Copyright © 2018 by Spacetime Publications Limited Foreword copyright © 2018 by Eddie Redmayne Introduction copyright © 2018 by Kip Thorne Afterword copyright © 2018 by Lucy Hawking All rights reserved. Published in the United States by Bantam Books, an imprint of Random House, a division of Penguin Random House LLC, New York. BANTAM BOOKS and the HOUSE colophon are registered trademarks of Penguin Random House LLC. Published in the United Kingdom by John Murray (Publishers), a Hachette UK Company. Photograph of the adult Stephen Hawking © Andre Pattenden Hardback ISBN 9781984819192 Ebook ISBN 9781984819208 randomhousebooks.com Text design by Craig Burgess, adapted for ebook Cover design: Dan Rembert Cover image: © Shutterstock v5.3.2 ep Contents Cover Title Page Copyright A Note from the Publisher Foreword: Eddie Redmayne An Introduction: Kip Thorne Why We Must Ask the Big Questions Chapter 1: Is There a God? Chapter 2: How Did It All Begin? Chapter 3: Is There Other Intelligent Life in the Universe? Chapter 4: Can We Predict the Future? Chapter 5: What Is Inside a Black Hole? Chapter 6: Is Time Travel Possible? Chapter 7: Will We Survive on Earth? Chapter 8: Should We Colonise Space? Chapter 9: Will Artificial Intelligence Outsmart Us? Chapter 10: How Do We Shape the Future? Afterword: Lucy Hawking Acknowledgements By Stephen Hawking About the Author A Note from the Publisher Stephen Hawking was regularly asked for his thoughts on the “big questions” of the day by scientists, tech entrepreneurs, senior business figures, political leaders and the general public. Stephen maintained an enormous personal archive of his responses, which took the form of speeches, interviews and essays. -
Dilaton and Off-Shell (Non-Critical String) Effects in Boltzmann Equation for Species Abundances AB Lahanas1, NE Mavromatos2 and DV Nanopoulos3,4,5
Research article Open Access Dilaton and off-shell (non-critical string) effects in Boltzmann equation for species abundances AB Lahanas1, NE Mavromatos2 and DV Nanopoulos3,4,5 Address: 1University of Athens, Physics Department, Nuclear and Particle Physics Section, GR157 71, Athens, Greece., 2King's College London, University of London, Department of Physics, Strand WC2R 2LS, London, UK., 3George P. and Cynthia W. Mitchell Institute for Fundamental Physics, Texas A&M University, College Station, TX 77843, USA., 4Astroparticle Physics Group, Houston Advanced Research Center (HARC), Mitchell Campus, Woodlands, TX 77381, USA. and 5Academy of Athens, Division of Natural Sciences, 28 Panepistimiou Avenue, Athens 10679, Greece. Email: AB Lahanas - [email protected]; NE Mavromatos - [email protected]; DV Nanopoulos - [email protected] Published: 2 October 2007 Received: 3 June 2007 Accepted: 2 October 2007 PMC Physics A 2007, 1:2 doi:10.1186/1754-0410-1-2 This article is available from: http://www.physmathcentral.com/1754-0410/1/2 © 2007 Lahanas et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/ licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract In this work we derive the modifications to the Boltzmann equation governing the cosmic evolution of relic abundances induced by dilaton dissipative-source and non-critical-string terms in dilaton-driven non-equilibrium string Cosmologies. We also discuss briefly the most important phenomenological consequences, including modifications of the constraints on the available parameter space of cosmologically appealing particle physics models, imposed by recent precision data of astrophysical measurements. -
Qnas with Alan Guth
QNAS QNAS QnAs with Alan Guth Paul Gabrielsen Science Writer The announcement in March 2014 that a few minutes of the history of the universe. telescope near the South Pole had detected Inflation comes before all that. possible evidence of gravitational waves PNAS: Whatwasyourreactiontothe brought renewed attention to inflationary results of the BICEP2 experiment, suggesting theory, which describes the earliest moments evidence of gravitational waves? of the universe. According to inflationary Guth: I was incredibly impressed that they theory, exotic matter present at the birth of had discovered what, at that time, appeared to the universe exerted repulsive gravitational be a completely unambiguous signal of gravi- effects, driving extremely rapid expansion of tational radiation coming from the early uni- the universe and leaving behind traces of verse, presumably from inflation. Since then gravitational waves in the cosmic background things have changed. The observations were radiation. National Academy of Sciences certainly a tour de force, but when other people member Alan Guth, a physicist at the Mas- looked more carefully at the ways the experi- sachusetts Institute of Technology, first out- ment could go wrong, the possibility that the lined inflationary theory in 1981 and has since signal could have been entirely due to dust been working out the details and implications couldnotberuledout.SorightnowIthink Alan Guth. Image courtesy of Jenny Guth. of the theory with his colleagues. The South it is waiting to be confirmed. I still hope that it Pole experiment, called BICEP2 (Background willturnouttobereal,butatthispointIthink ImagingofCosmicExtragalacticPolarization we don’tknowifitwasarealsignalofgravita- Henry Tye got himself interested in a class of 2), is undergoing further scrutiny to assess tional radiation from the early universe or not.