Why String Theory? 1st Edition by Joseph Conlon (PDF)

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Physics World’s ‘Book of the Year’ for 2016 An Entertaining and Enlightening Guide to the Who, What, and Why of String Theory, now also available in an updated reflowable electronic format compatible with mobile devices and e-readers.During the last 50 years, numerous physicists have tried to unravel the secrets of string theory. Yet why do these scientists work on a theory lacking experimental confirmation?Why String Theory? provides the answer, offering a highly readable and accessible panorama of the who, what, and why of this large aspect of modern theoretical physics. The author, a theoretical physics professor at the University of Oxford and a leading string theorist, explains what string theory is and where it originated. He describes how string theory fits into physics and why so many physicists and mathematicians find it appealing when working on topics from M-theory to monsters and from cosmology to superconductors.

User’s Reviews

Reviews from Amazon users which were colected at the time this book was published on the website:

⭐Most books on string theory concentrate on the desire for a single, unifying Theory of Everything (ToE) and give the impression that string theorists are all of a single mind in this regard. This book is different. It does not pit string theory against quantum theory, and it delves into the multitude of reasons why physicists with different interests concern themselves with string theory. The short answer is that string theory solves a plethora of problems in various fields of interest.You will also enjoy what Americans would call the playful word choices of our friends across the pond. The author teaches at Oxford and has the typical English propensity for using one $10 word where several $1 words would be more economical. This is not a criticism, since anyone who reads this book will have long ago succumbed to the joy of learning. Most Americans will have need to look up words like “peregrination” and “myrmecology” on their smart phone, but will enjoy adding such words to their personal lexicon.The author also has a playful way of dealing with the subject matter. One example should suffice. When talking about the Big Bang, Conlon says, “What did happen earlier than one second [after the Big Bang]? We do not know. In this epoch, all is speculation. There is good speculation and bad speculation. … Much has been said or written about what may have happened before the Big Bang, including anthropic landscapes of different laws of physics and eternally reproducing multiverses of many possible universes. It is not that the ideas are necessarily wrong. It is rather that the extravagance of these conjectures is matched only by the paucity of either rigorous calculation or observational motivation. The danger is that this replaces physics’ long-standing chaste marriage of solid theory and careful experiment with a form of scientific soft porn best suited for the pages of glossy magazines.”As a result, the book is serious but fun to read.I particularly enjoyed the chapter entitled, “What Was String Theory”, which is a detailed recounting of string theory history from 1968 to 1996. This is followed by, “What Is String Theory”, which brings us up to 2014 and a bit of 2015. All solid stuff peppered with periodic recollections of who was in the White House, a Top 40 song or band, together with notable sporting and other events from each important era in physics that – once again – make the book fun to read. Along the way we learn why and how string theory morphed from a “Theory of Everything” into a powerful problem-solving tool for other branches of physics and for mathematics as well, while the author quickly recognizes the community of physicists still laboring on an all-encompassing String ToE.Subsequent chapters elaborate on the use of string theory in quantum physics – particularly in strong coupling situations – and mathematics, cosmology, particle physics and even quantum gravity. In the latter Chapter, the author notes that we need to be able to observe physics at the Planck length – either directly or indirectly – to validate quantum gravity. In other parts of the book, he correctly infers the same for quantum field theory and string theory. But then he goes on to say, “The absence of direct probes of quantum gravity does not preclude indirect probes, where physics present at the Planck length can bubble up to produce observable effects in doable experiments.” And the book contains examples of such experiments in more than one Chapter.Chapter 13 – “Criticisms of String Theory” – is poorly titled. A much more complete title for this Chapter would be “Refuting String Theory Criticisms”. Much can be learned from this Chapter alone.A book like this – the quality of which does not come along very often – allows us to sit back in our easy chairs and ponder where the world of physics has been, how we got here, and where we’re going. Since the storyteller is accurate and detailed, the story cannot help but spark new thoughts about possible new avenues of investigation. It’s that kind of book, with only enough math to clarify the subject matter, never veering off on a tedious math tangent.I discovered this book by searching for “String Theory” in the “Books” category at Amazon – just to see if there was something new on the subject – and I am very glad that I did. This is the best overall grasp I’ve read.

⭐I thought that Prof. Conlon’s book was excellent for providing a perspective on string theory, and why it has retained enduring interest among physicists and mathematicians. He presents a number of different points of view, mostly helping to show the importance of string theory, and some background on its history and evolution. The theory is not currently experimentally accessible, and its claims, such as the existence of extra dimensions, which are to a certain extent empirically testable, have universally resulted in negative results. Nevertheless, there is a richness about string theory, in that it has led to interesting physical models, to methods in physics which are quite novel, and almost bound to have significance beyond string theory in other areas of physics and science generally, and to some extremely significant results in modern mathematics. As an indicator of this latter point, Prof. Witten, a principal string theorist, won the Fields Medal, which is a very prestigious award in mathematics. In addition, due to its obvious beauty and rich results, it has attracted numerous mainstream physicists who work in quantum field theory. Due to the achievements of its proponents, string theory has retained considerable interest, despite its tenuous connection to experiments. Prior to reading this book, I was aware of a number of aspects of string theory, but I thought that this book is extremely well-written and helps one with the “big picture” for string theory. I recommend this book highly as one that speaks broadly about this field, to all who have an interest in knowing and understanding string theory better, but have little direct knowledge of the field. My personal view is that string theory is one of the most important physical theories of our times, whether or not it describes nature correctly. I recommend this book highly for the outsider to gain a better appreciation.

⭐Why String Theory? is a very interesting book that brings the topic up to date as a nice complement to older overviews such as those of Brian Green and Lee Smolin. It is rated as “five stars” and is even recommended by Peter Woit (perhaps because it is lacking in commonly found string theory hyperbole). It admits that, “there is no direct experimental evidence for string theory!” And, indeed, most string theorists are little concerned with verification by experiment. The subject instead has other redeemable aspects such as wonderfully rich “physical mathematics” and a world of insight into physical possibilities as well as food for pure mathematicians. Theoretical work on the AdS/CFT correspondence by Starinets and Son predicted that quark-gluon plasma might be lacking in viscosity (and that turned out to be true). Calabi-Yau spaces became a rich field of study. The book is well written, and the language is rich and colorful: “in Einstein’s theory, geometry is dynamical. If you strike it, it rings.” One can have the choice of “an atlas of charts rather than a globe.” “M-theory is known from its boundaries. The Picts and Numidians could infer the existence of Rome from their battles with its legions, but could never know that it has seven hills.” “Gauge symmetries are to the Standard Model of particle physics what carbon is to organic molecules…”I took many notes and learned things such as: there could have been an early cosmological era of “moduli;” string theory predicts a new possible “dark radiation” in the universe; calculations can often avoid singularities and give finite answers; dualities enable some hard problems to become much easier calculations; there is fashion in physics; strings and branes are equally important; tachyons signal an instability (versus being hyper-luminal); and “axion-like particles arise ubiquitously in string theory.” I recommend this book; and since it doesn’t show any math, the kindle version is adequate.

⭐The title suggests that Joseph Conlon’s book is a defence of string theory against its detractors; it is so much more than that.He begins by reviewing the strengths and limitations of the Standard Model. The Standard Model is a somewhat ramshackle construction which, to the surprise of its constructors, has proven extraordinarily successful and resilient over the decades, culminating in the recent discovery of the predicted Higgs boson at the LHC. We know, however, that the Standard Model is wrong because it assumes a fixed spacetime (i.e. no gravity) – it has proved impossible to successfully quantise gravity within the framework of the Standard Model.Conlon’s approach is historical. The first inklings of string theory came about through attempts to understand the strong nuclear force in the 1970s, where string harmonics emerged mathematically from observed scattering patterns. It later transpired that the ‘strings’ were an epiphenomenon of the correct quantum field theory – quantum chromodynamics – where the force lines did indeed tend to bunch up into strings. The glory years of QFT saw string theory relegated to a backwater.The end of the seventies saw attempts to quantise gravity under the assumptions of supersymmetry. It turned out that these ‘supergravity’ theories had severe problems which string theory seemed to solve in a very natural way. Suddenly people began to take notice and the string community rapidly expanded. These were the years of five different string theories, and the realisation that they were all different limits of one underlying theory – M-theory – an insight due to Ed Witten.The author reviews quantum field theories, string theory and the AdS/CFT correspondence in his characteristically clear way. But after all this work, is there any direct experimental evidence for string theory? Chapter 7 is very short, consisting of this one sentence: ‘There is no direct experimental evidence for string theory.’Having got that out of the way, Conlon now explains how the complex and sophisticated toolkit of string theory has led to insights across physics. He discusses the use of string theory in facilitating calculations in quantum field theories in their strong coupling regime via the AdS/CFT correspondence; the modelling of heavy ion collisions; applications in mathematics (relating to ‘monstrous moonshine’); predictions of dark matter candidates such as axions; predictions of dark radiation resulting from the theory’s extra spatial dimensions; and of course the opportunity to model black hole microstates, entropy and spacetime topology changes in what is presumed to be string theory’s core competence, quantum gravity.The author now moves on to mini-portraits of the main kinds of scientists he see in the community around him. We hear about the revolutionaries who wish to kick over the applecart (not so easy). We hear about the worker ants whose slogan is ‘Vorsprung durch Technik’ – those researchers who kick the can of science up the road with their calculations so that experimentation can progress – little chance of glory but employment prospects are good. Under ‘Stockholm or Bust’ we meet the model builders, those hoping to call nature right and get to Sweden – and those who game the system. There are the super-theorists, like Witten, members of the ‘Most Sublime Brahminate of Princeton’, and those who appreciate that ‘il faut cultiver notre jardin’ – who look for unfashionable areas which to their eyes show great promise and are able to deliver.Conlon’s final two chapters address (in a fair and even-handed manner) the well-known criticisms of string theory and provide rebuttals. He then explains why string theory remains so dominant in the field and hazards some guesses as to its future.Understanding the state-of-the-art in fundamental physics is of course hard, the subject is inaccessible for most physicists let alone the broader community. Conlon writes (p. 198):“Undergraduate physics is an unparalleled intellectual experience: it is a smorgasbord of the deepest and most powerful thoughts that have ever been thunk. You learn physics at a rate of a Nobel Prize a week, and the resulting frisson of the mind is at a level that is never experienced again. Four years takes you from Newtonian gravity through the laws of heat and energy, past Maxwell’s synthesis of electromagnetism and into the laws of special and general relativity, from the basics of quantum mechanics to the Standard Model and quantum field theory. It is wonderful and magnificent.”Sadly, beyond these well-explored paths there is the slog of the new, where progress slows to a crawl. In this book Professor Conlon has provided – as he promises in his preface – an astonishingly clear tour of modern physics. It is hard to think of a better, clearer or wittier review, and one which will be particularly useful to science undergraduates curious as to where their field is heading. School students who have done some reading around the subject (e.g. who have read books by Brian Greene) might also find this work of great value. It’s highly recommended.

⭐I would love to read the Kindle version of this book but the text is tiny and cannot be increased in size by the usual methods. This is not what a kindle book should be. Guess I will have to buy the paperback

⭐The kindle version is not in a kindle friendly format. It is very expensive.As I can’t read it I cant give a more though review

⭐Very clear description of the thoughts that arrived at the concept

⭐String Theorie gehört zu den kontroversen Themen, die seit etlichen Jahren immer wieder populär wissenschaftlich diskutiert wurden, Autoren wie Brian Green oder Michio Kaku propagieren sie als ‘Theory of Everything’ und argumentieren sogar, dass die Vielzahl der gefundenen möglichen Konfigurationen, Evidenz für ein Multiversum liefern könnte. Auf der anderen Seite kritisieren Lee Smolin und Peter Woit, dass trotz Jahrzehnte langer Forschung zur String Theorie weder experimentelle Belege für diese Theorie in Sicht sind, noch konnten bisher auch nur die ihr zugrunde liegenden Prinzipien gefunden werden.Joseph Conlon ist Theoretischer Physiker an der Universität Oxford, sein Interesse gilt hauptsächlich der String Phänomenologie, d.h. der Verwendung von Ideen und Methoden der String Theorie in anderem Gebieten der Physik. In seinem vorliegenden Buch “Why String Theory?” versucht er, einen unvoreingenommenen Überblick über die wechselvolle Geschichte der String Theorie, ihren Inhalt, ihre überraschenden Beziehung zu anderen Gebiete der Physik und Mathematik, und über verschiedene Anlässe ihres Studiums, zu liefern – in vier Abschnitten geht der Autor den Fragen des ‘What?’, ‘What For?’, ‘Who?’ und ‘Why?’ der String Theorie nach.Um Licht ins Dunkel der seltsamen Eigenschaften der starken Wechselwirkungen (WW) zu bringen, betrachtete Gabriele Veneziano 1968 am CERN Beta- Funktionen zur Beschreibung von Streuamplituden von Resonanzen; daraus entwickelte die Forschergruppe um Daniele Amati Anfang der 1970iger Jahre das Duale Resonanzmodel, Claud Lovelance konnte zeigen, dass dieses Model mit der Quantenmechanik in 26 Dimensionen vereinbar ist. Schließlich kamen Y. Nambu, H. Bech Nielsen und L. Susskind 1970/71 unabhängig voneinander auf die Idee, dass das Duale Resonanzmodel nichts weiter beschrieb, als Streuamplituden von relativistischen Strings.Die Theorie wurde im Laufe der 70iger Jahre fast verworfen, nachdem die starke WW im Rahmen der Quanten Chromodynamik ihre Erklärung fand.P. Ramond, A. Neveu und J. Schwarz kombinierten Supersymmetrie mit String Theorie, damit ließ sich die Zahl der notwendigen Dimensionen auf 10 reduzieren, und diese Theorie enthielt auf natürliche Weise ein masseloses Spin 2 Teilchen; T. Yoneda, J. Scherk und J, Schwarz zeigten, dass dieses Partikel tatsächlich dem Graviton der Allgemeinen Relativitätstheorie entspricht.Damit avancierte die Theorie zu einer möglichen Theorie der Quanten Gravitation – ihre natürliche Größenskala schrumpfte auf die Planck Länge. Nachdem Michael Green und John Schwarz Anomalien in der Superstring Theorie ausschließen konnten, fand man fünf konsistente Versionen; von denen Edward Witten 1995 zeigt, dass diese nur verschiedene Sichten einer noch allgemeineren Theorie, der sogenannten M- Theorie, sind. Das schürte die Hoffnung, dass eine eindeutige ‘Theory of Everything’ in greifbarer Nähe sein könnte. Allerdings fand man kurz darauf eine unermessliche Zahl möglicher Kompaktifizierungen — man schätzt etwa 10^500, die dieses hehre Ziel wieder in weite Ferne rücken ließen. Zur ‘Rettung’ der Theorie wurden u.a. Multiversen und das anthropische Prinzip bemüht. Diese, und das weitere Fehlen jeglicher experimentellen Belege, sind wichtige Angriffspunkte der Kritiker der String Theorie, die sie für gescheitert erklären.Der Autor versucht hingegen der String Theorie gerecht zu werden, in dem er Gründe zusammenträgt, weswegen sich auch weiterhin Forschen mit dieser Theorie befassen.Juan Maldacena fand mit der AdS/CRF Korrespondenz eine Äquivalenz von Stringtheorien in einem Anti-de-Sitter Raum und konformer Feldtheorie auf dem Rand dieses Raumes (holographisches Prinzip).Die Stringtheorie lieferte auch neue Ideen für die Lösung rein mathematischer Probleme: so bewies Richard Borcherds die Moonshine Vermutung, ein Zusammenhang der Dimensionen von Darstellungen der Monster Gruppen mit den Koeffizienten einer Modulfunktion, dazu setzte er Methoden der ursprünglich 26 dimensionalen bosonischen Stringtheorie ein. Der Mirror Symmetrie liegt die Beobachtung zu Grunde, dass einer Kompaktifizierung der String je zwei verschiedene Theorie (vom Typ IIA bzw. IIB) entsprechen, daraus entwickelte sich schließlich ein eigenes Gebiet der Algebraischen Geometrie.Ferner werden Ideen und Methoden der Stringtheorie heute auch in anderen Bereichen der Physik angewandt, dazu geht der Autor kurz auf seine eigenen Untersuchungen zu ‘dark radiation’ und Axion- artigen Teilchen ein.Die Stringtheorie hat also in ihrer über vierzig jährigen Geschichte bereits mehrere Wandel durchgemacht, und obwohl es sich eigentlich gar nicht um eine Theorie im eigentliche Sinne handelt, mit Grundprinzipien, Bewegungsgleichungen und daraus abgeleiteten Folgerungen, sondern eher um eine Sammlung von Ansätzen, Einsichten und faszinierenden Zusammenhängen, die es aber immer wieder schaffen über sich hinaus zu weisen. Ob die Stringtheorie tatsächlich eine fundamentale Theorie für alle vier WW ist, kann sogar fraglich sein, Gründe, sie weiter zu erforschen gibt es aber offenbar zahlreiche. Wohltuend wirkt auch, dass der Autor es vermeidet, Spekulationen zu folgen, die die Stringtheorie zum Anlass nehmen, alternative Paradigmen zur Verifikation/ Falsifikation wissenschaftlicher Theorien (etwa Bayesian reasoning) zu ästimieren.Die Darstellung von Conlon zählt zu den besten allgemein verständlichen Büchern ÜBER String Theorie, die dabei erfreulich überschaubar bleibt, denn der Autor verzichtet auf die epische Breite mancher populären Texte, die vor ihrem eigentlichen Thema zunächst die Geschichte der Physik von der Antike, über Galilei, Newton, etc. etc. abhandeln.Wer eine (elementare) Einführung in die Stringtheorie sucht, die vor Formeln nicht halt macht, sei noch auf einen Video- Kurs von Leonard Susskind verwiesen, den er im Rahmen seiner ‘Theoretical Minimum’ Vorlesungen an der Stanford Universität hielt.

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