Joseph Conlon - Why String Theory?

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WHY STRING THEORY?

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WHY STRING THEORY?

Joseph Conlon

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CRC Press

Taylor & Francis Group

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Boca Raton, FL 33487-2742

2016 by Joseph Conlon

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Version Date: 20151020

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Contents

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Preface

This is a book about string theory. I started writing this book in 2010 with two motivations. The first was a desire to give back to those who have given to me it is an incredible privilege to be paid to think about science and fundamental physics, and those who pay the piper have a right to hear the tune. The second was an intent to heed advice passed on to me since childhood: learn as much by writing as by reading. Writing is fun, and I wanted to go beyond the technical prose of journal articles.

This book is written in response to the questions of What is string theory? and Why do you work on it then?, and it aims to answer them. String theory is, however, a large subject. Over its history, there have probably been over twenty thousand research papers on it. No one and certainly not myself! knows all of this work in detail. Writing a book requires an ordered account. In arranging material I have had to select topics, and in selecting I have aimed for the combination of intrinsic importance and personal familiarity.

To state the obvious, this is not a textbook. It does not have equations. It will not teach anyone either to do calculations in string theory or to perform research in the subject. There are many good textbooks that do precisely this, and I give references to some of them in the bibliography. What I hope the book does provide is a mental map of the subject, a tourists guide to those who want to come and see the sights before returning to their own pursuits. I also hope that it may allow those who aspire to a career in the area a chance to reconnoitre the lay of the land.

To these ends, I have aimed to describe the physics as accurately as possible consistent with the constraints. Accuracy is not a single standard. The geography of the British Isles can be accurately described either as two triangles or through a bookshelf full of Ordnance Survey maps. Neither is right or wrong; it depends on the desired level of description. I have aimed my account of string theory somewhere between these two extremes.

The book is written to be read sequentially, but this is not an absolute requirement. A reader already familiar with the big picture of known physics could skip over the first part with little loss. In the third part, on the different applications of string theory, the chapters can be read in any order. The twelfth chapter, on the different styles of scientist, stands alone by itself.

One of the joys of physics is that it is a connected subject. Ideas repeat themselves, and on occasion in this book the same idea comes up more than once. When this happens I have sometimes allowed myself to re-explain concepts rather than expect the reader to remember an explanation from a hundred pages earlier. It always takes me multiple attempts to understand any concept, and in seminars I find few things more annoying than the speaker who believes that a single mention of an idea allows them to deny the audience any further reminders or clarifications of the topic.

When quotations occur within the book, I have gathered the details of the original sources into the end-notes and bibliography. Those who require them can find them, and I wish to avoid the academic custom of battering the reader into submission through a fusillade of references to obscure journals.

Many people have helped bring this book to fruition. I should first thank those, too numerous to mention, who have helped me professionally in learning the subject over the years. I particularly thank my fellow PhD students in Cambridge from 2003 to 2006, my research collaborators, and especially my doctoral supervisor Fernando Quevedo.

In the early stages of this book a website http://whystringtheory.com was made during summer 2012, constructed by myself and two undergraduate physicists, Edward Hughes and Charlotte Mason, who are now doing PhD degrees at respectively Queen Mary University of London and the University of California at Santa Barbara. I have borrowed the title of the book from the website.

Two eyes good, many eyes better: I thank those who have read parts of this book in draft form and whose feedback has helped me both sharpen the text and remove errors of physics, grammar and style: Lucy Broomfield, Frank Close, Theresa Conlon, Marcus du Sautoy, Pedro Ferreira, Sven Krippendorf, Fernando Quevedo, Markus Rummel, Andrei Starinets, David Tong, Peter West, and particularly Thomas Conlon, David Marsh and the anonymous copyeditor. The mistakes that remain are my own.

I also want to thank both my colleagues in the Oxford physics department and the Warden, Fellows, staff and students of New College, Oxford, for providing a stimulating and inspirational environment during the writing of this book.

I thank my editor at CRC Press, Francesca McGowan, for all her hard work, unfailing enthusiasm, and her many precise and detailed emails.

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