Lecture Notes in Physics 903 Makoto Natsuume AdS/CFT Duality User Guide Lecture Notes in Physics Volume 903 Founding Editors W. Beiglböck J. Ehlers K. Hepp H. Weidenmüller Editorial Board B.-G. Englert, Singapore, Singapore P. Hänggi, Augsburg, Germany M. Hjorth-Jensen, Oslo, Norway R.A.L. Jones, Sheffield, UK M. Lewenstein, Barcelona, Spain J.-M. Raimond, Paris, France A. Rubio, Donostia-San Sebastian, Spain S. Theisen, Golm, Germany D. Vollhardt, Augsburg, Germany H. von Löhneysen, Karlsruhe, Germany J.D. Wells, Ann Arbor, USA G.P. Zank, Huntsville, USA The Lecture Notes in Physics The series Lecture Notes in Physics (LNP), founded in 1969, reports new developmentsinphysicsresearchandteaching-quicklyandinformally,butwitha high quality and the explicit aim to summarize and communicate current knowledge in an accessible way. Books published in this series are conceived as bridging material between advanced graduate textbooks and the forefront of research and to serve three purposes: (cid:129) to be a compact and modern up-to-date source of reference on a well-defined topic (cid:129) to serve as an accessible introduction to the field to postgraduate students and nonspecialist researchers from related areas (cid:129) to be a source of advanced teaching material for specialized seminars, courses and schools Bothmonographsandmulti-authorvolumeswillbeconsideredfor publication. Editedvolumesshould,however,consistofaverylimitednumberofcontributions only. Proceedings will not be considered for LNP. Volumes published in LNP are disseminated both in print and in electronic formats, the electronic archive being available at springerlink.com. The series contentisindexed,abstractedandreferencedbymanyabstractingandinformation services, bibliographic networks, subscription agencies, library networks, and consortia. Proposals should be sent to a member of the Editorial Board, or directly to the managing editor at Springer: Christian Caron Springer Heidelberg Physics Editorial Department I Tiergartenstrasse 17 69121 Heidelberg/Germany [email protected] More information about this series at http://www.springer.com/series/5304 Makoto Natsuume AdS/CFT Duality User Guide 123 MakotoNatsuume Theory Center Instituteof Particle& Nuclear Studies HighEnergy Accelerator Research Organization (KEK) Tsukuba Japan TYOGENRIRON NOOYObyMakotoNatsuume. OriginalJapanese language edition publishedbySaiensu-sha Co.,Ltd. 1-3-25,Sendagaya, Shibuya-ku,Tokyo151-0051, Japan Copyright©2012, Saiensu-sha Co.,Ltd.AllRightsreserved. ISSN 0075-8450 ISSN 1616-6361 (electronic) Lecture Notesin Physics ISBN 978-4-431-55440-0 ISBN 978-4-431-55441-7 (eBook) DOI 10.1007/978-4-431-55441-7 LibraryofCongressControlNumber:2015931920 SpringerTokyoHeidelbergNewYorkDordrechtLondon ©SpringerJapan2015 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilarmethodologynowknownorhereafterdeveloped. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexempt fromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthis book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained hereinorforanyerrorsoromissionsthatmayhavebeenmade. Printedonacid-freepaper SpringerJapanKKispartofSpringerScience+BusinessMedia(www.springer.com) Preface This book describes “real-world” applications of the AdS/CFT duality for begin- ning graduate students in particle physics and for researchers in the other fields. The AdS/CFT duality is a powerful tool for analyzing strongly coupled gauge theories using classical gravitational theories. The duality originated from string theory, so it has been actively investigated in particle physics. In recent years, however,thedualityhasbeendiscussedbeyondtheoreticalparticlephysics.Infact, theoriginalAdS/CFTpaperbyMaldacenahasbeencitedinallphysicsarXivs.This is because the duality is becoming a powerful tool to analyze the “real world.” For example, it turns out that one prediction of AdS/CFT is indeed close to the experimental results of the real quark–gluon plasma. Since then, the duality has been applied to various fields of physics; examples are QCD, nuclear physics, nonequilibrium physics, and condensed matter physics. In order to carry out such researches, one has to know many materials such as string theory, general relativity, nuclear physics, nonequilibrium physics, and condensed matter physics. The aim of this book is to provide these background materials as well as some key applications of the AdS/CFT duality in a single volume. The emphasis throughout the book is on a pedagogical and intuitive approach focusing on the underlying physical concepts. Yet it also includes step- by-step computations for important results which are useful for beginners. Most of them are contained in the appendices. Following conventions of many textbooks, I often do not refer to original researchpapersandreferonlytotheothertextbooksandreviewsthatmaybemore useful to readers. Also, the choice of references reflects my knowledge, and I apologize in advance for possible omissions. Initially, this project was begun for a book that was published in Japanese (Saiensu-sha Co., Ltd, 2012), and this is the “translated” one. But I used this opportunitytoimprovemanyexplanationsandtoaddmorematerialstotheJapanese edition. So, this book isthe“second edition” in this sense. Iwouldlike tothank many people who helped mewiththis book.This book is based on review talks at various conferences and on courses I taught at various v vi Preface graduateschools(TohokuUniversity,OchanomizuUniversity,GraduateUniversity of Advanced Studies, and Rikkyo University). I thank the organizers and the par- ticipantsoftheconferencesandthecourses.IalsoliketothankElenaCáceres,Koji Hashimoto, Tetsuo Hatsuda, Gary Horowitz, and Joe Polchinski for encouraging me to write this English edition. I also thank Tetsufumi Hirano, Akihiro Ishibashi, andTakeshiMoritaforusefulcommentsanddiscussion.Iespeciallywouldliketo thankTakashiOkamurawhoclarifiedmyunderstandingofthesubjectsinthisbook through collaboration for many years. He also gave many suggestions for improvement.IthankmyeditorHisakoNikoatSpringerJapanandthestaffofthe LectureNotesinPhysics.Ofcourse,theresponsibilityforanyremainingmistakeis solelymine.Iwillbehappytoreceivecommentsonthisbook.Pleasesendthemto [email protected]. An updated list of corrections will be posted on my website. The tentative address is http://research.kek.jp/people/natsuume/ads-real-world.html. Even if the address changes in future, you can probably easily search the website because my family name is rather rare. I hope that this book will help readers to explore new applications of the AdS/ CFT duality. Contents 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Overview of AdS/CFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 AdS/Real-World. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4 Notation and Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.5 Some Useful Textbooks. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2 General Relativity and Black Holes. . . . . . . . . . . . . . . . . . . . . . . 9 2.1 Particle Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2 Einstein Equation and Schwarzschild Metric. . . . . . . . . . . . . . 14 2.3 Physics of the Schwarzschild Black Hole. . . . . . . . . . . . . . . . 15 2.3.1 Gravitational Redshift . . . . . . . . . . . . . . . . . . . . . . . 15 2.3.2 Particle Motion. . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4 Kruskal Coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Appendix: Review of General Relativity. . . . . . . . . . . . . . . . . . . . . 21 3 Black Holes and Thermodynamics. . . . . . . . . . . . . . . . . . . . . . . . 25 3.1 Black Holes and Thermodynamics . . . . . . . . . . . . . . . . . . . . 25 3.1.1 Zeroth Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.1.2 Surface Gravity (cid:1) . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.1.3 First Law. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.2 From Analogy to Real Thermodynamics . . . . . . . . . . . . . . . . 29 3.2.1 Hawking Radiation. . . . . . . . . . . . . . . . . . . . . . . . . 29 3.2.2 Hawking Temperature and Euclidean Formalism. . . . . 31 3.2.3 On the Origin of Black Hole Entropy (cid:1). . . . . . . . . . . 33 3.3 Other Black Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 3.3.1 Higher-Dimensional Schwarzschild Black Holes. . . . . 35 3.3.2 Black Branes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 3.3.3 Charged Black Holes. . . . . . . . . . . . . . . . . . . . . . . . 38 vii viii Contents 3.4 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Appendix: Black Holes and Thermodynamic Relations (cid:1). . . . . . . . . . 41 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4 Strong Interaction and Gauge Theories. . . . . . . . . . . . . . . . . . . . 43 4.1 Strong Interaction and QCD. . . . . . . . . . . . . . . . . . . . . . . . . 43 4.1.1 Overview of QCD . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.1.2 Phase Structure of QCD . . . . . . . . . . . . . . . . . . . . . 44 4.1.3 Heavy-Ion Experiments. . . . . . . . . . . . . . . . . . . . . . 45 4.1.4 “Unexpected Connection Between String Theory and RHIC Collisions”. . . . . . . . . . . . . . . . . . 46 4.2 Large-Nc Gauge Theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.3 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 5 The Road to AdS/CFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 5.1 String Theory: Prehistory. . . . . . . . . . . . . . . . . . . . . . . . . . . 55 5.2 String Theory as the Unified Theory. . . . . . . . . . . . . . . . . . . 58 5.2.1 String Oscillations and Elementary Particles. . . . . . . . 58 5.2.2 D-brane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 5.2.3 Why Open and Closed Strings? . . . . . . . . . . . . . . . . 61 5.2.4 String Interactions. . . . . . . . . . . . . . . . . . . . . . . . . . 62 5.2.5 Supergravity: Classical Gravity Approximation of String Theory. . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3 Reexamine String Theory as the Theory of Strong Interaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 5.3.1 Comparison of Partition Functions . . . . . . . . . . . . . . 66 5.3.2 Scale Invariance and Its Consequences . . . . . . . . . . . 68 5.3.3 AdS/CFT, Finally. . . . . . . . . . . . . . . . . . . . . . . . . . 72 5.4 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Appendix 1: Scale, Conformal, and Weyl Invariance (cid:1) . . . . . . . . . . . 75 Appendix 2: D-brane and AdS/CFT (cid:1). . . . . . . . . . . . . . . . . . . . . . . 77 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6 The AdS Spacetime. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 6.1 Spacetimes with Constant Curvature . . . . . . . . . . . . . . . . . . . 85 6.1.1 Spaces with Constant Curvature . . . . . . . . . . . . . . . . 85 6.1.2 Spacetimes with Constant Curvature . . . . . . . . . . . . . 87 6.1.3 Relation with Constant Curvature Spaces. . . . . . . . . . 89 6.1.4 Various Coordinate Systems of AdS Spacetime . . . . . 89 6.1.5 Higher-Dimensional Cases. . . . . . . . . . . . . . . . . . . . 91 6.2 Particle Motion in AdS Spacetime (cid:1) . . . . . . . . . . . . . . . . . . . 94 6.3 Remarks on AdS/CFT Interpretations . . . . . . . . . . . . . . . . . . 98 6.4 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Contents ix 7 AdS/CFT—Equilibrium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 7.1 The AdS Black Hole. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 7.2 Thermodynamic Quantities of AdS Black Hole. . . . . . . . . . . . 102 7.2.1 Thermodynamic Quantities. . . . . . . . . . . . . . . . . . . . 102 7.2.2 Free Gas Computation. . . . . . . . . . . . . . . . . . . . . . . 106 7.3 The AdS Black Hole with Spherical Horizon. . . . . . . . . . . . . 108 7.4 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Appendix: AdS Black Hole Partition Function (cid:1) . . . . . . . . . . . . . . . 110 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 8 AdS/CFT—Adding Probes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 8.1 Basics of Wilson Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 8.2 Wilson Loops in AdS/CFT: Intuitive Approach . . . . . . . . . . . 120 8.3 String Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 8.4 Wilson Loops in AdS/CFT: Actual Computation . . . . . . . . . . 129 8.5 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 Appendix: A Simple Example of the Confining Phase . . . . . . . . . . . 132 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 9 Basics of Nonequilibrium Physics . . . . . . . . . . . . . . . . . . . . . . . . 135 9.1 Linear Response Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 9.1.1 Ensemble Average and Density Matrix . . . . . . . . . . . 135 9.1.2 Linear Response Theory . . . . . . . . . . . . . . . . . . . . . 137 9.1.3 Transport Coefficient: An Example. . . . . . . . . . . . . . 140 9.2 Thermodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 9.3 Hydrodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 9.3.1 Overview of Hydrodynamics . . . . . . . . . . . . . . . . . . 144 9.3.2 Example: Diffusion Problem . . . . . . . . . . . . . . . . . . 145 9.3.3 Perfect Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 9.3.4 Viscous Fluid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 9.3.5 When a Current Exists (cid:1) . . . . . . . . . . . . . . . . . . . . . 155 9.3.6 Kubo Formula for Viscosity. . . . . . . . . . . . . . . . . . . 157 9.3.7 Linearized Hydrodynamic Equations and Their Poles . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 9.4 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 10 AdS/CFT—Non-equilibrium . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 10.1 GKP-Witten Relation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 10.2 Example: Scalar Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 10.3 Other Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 10.3.1 Maxwell Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 10.3.2 Massive Scalar Field. . . . . . . . . . . . . . . . . . . . . . . . 174 10.3.3 Gravitational Field . . . . . . . . . . . . . . . . . . . . . . . . . 176