The Little Book of String Theory (Science Essentials) - Hardcover

Gubser, Steven S.

Hardcover

ISBN 10: 0691142890 ISBN 13: 9780691142890

Verlag: Princeton University Press, 2010

Inhaltsangabe

The essential beginner's guide to string theory

The Little Book of String Theory offers a short, accessible, and entertaining introduction to one of the most talked-about areas of physics today. String theory has been called the "theory of everything." It seeks to describe all the fundamental forces of nature. It encompasses gravity and quantum mechanics in one unifying theory. But it is unproven and fraught with controversy. After reading this book, you'll be able to draw your own conclusions about string theory.

Steve Gubser begins by explaining Einstein's famous equation E = mc2, quantum mechanics, and black holes. He then gives readers a crash course in string theory and the core ideas behind it. In plain English and with a minimum of mathematics, Gubser covers strings, branes, string dualities, extra dimensions, curved spacetime, quantum fluctuations, symmetry, and supersymmetry. He describes efforts to link string theory to experimental physics and uses analogies that nonscientists can understand. How does Chopin's Fantasie-Impromptu relate to quantum mechanics? What would it be like to fall into a black hole? Why is dancing a waltz similar to contemplating a string duality? Find out in the pages of this book.

The Little Book of String Theory is the essential, most up-to-date beginner's guide to this elegant, multidimensional field of physics.

Über diesen Titel

Über die Autorin bzw. den Autor

Steven S. Gubser (1972–2019) was professor of physics at Princeton University.

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"This is an engaging and concise introduction to the main ideas in string theory. Gubser gives us a quick tour of the basic laws of physics as we understand them today, and then demonstrates how string theory seeks to go beyond them. He serves as an artful and attentive guide, as the reader explores the mysteries of quantum mechanics, black holes, strings, branes, supersymmetry, and extra dimensions in the pages of this book."--Juan Maldacena, Institute for Advanced Study

"Steve Gubser has written an engaging and thought-provoking account of what was achieved in physics in the last century and how physicists are seeking to go farther in the ambitious framework known as string theory. This is one of the most thoughtful books on this much-discussed topic, and readers will find much to ponder."--Edward Witten, Institute for Advanced Study

"This book offers a very nice short introduction to some of the basic ideas and implications of string theory. Gubser knows his subject."--John H. Schwarz, coauthor ofSpecial Relativity: From Einstein to Strings

Aus dem Klappentext

"This is an engaging and concise introduction to the main ideas in string theory. Gubser gives us a quick tour of the basic laws of physics as we understand them today, and then demonstrates how string theory seeks to go beyond them. He serves as an artful and attentive guide, as the reader explores the mysteries of quantum mechanics, black holes, strings, branes, supersymmetry, and extra dimensions in the pages of this book."--Juan Maldacena, Institute for Advanced Study

"Steve Gubser has written an engaging and thought-provoking account of what was achieved in physics in the last century and how physicists are seeking to go farther in the ambitious framework known as string theory. This is one of the most thoughtful books on this much-discussed topic, and readers will find much to ponder."--Edward Witten, Institute for Advanced Study

"This book offers a very nice short introduction to some of the basic ideas and implications of string theory. Gubser knows his subject."--John H. Schwarz, coauthor ofSpecial Relativity: From Einstein to Strings

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the LITTLE BOOK of STRING THEORY

By Steven S. Gubser

PRINCETON UNIVERSITY PRESS

Copyright © 2010 Steven S. Gubser
All right reserved.
ISBN: 978-0-691-14289-0

Contents

Introduction..........................................................1CHAPTER ONE energy...................................................11CHAPTER TWO Quantum Mechanics........................................19CHAPTER THREE gravity and Black holes................................34CHAPTER FOUR String Theory...........................................49CHAPTER FIVE Branes..................................................69CHAPTER SIX String Dualities.........................................99CHAPTER SEVEN Supersymmetry and the LHC..............................117CHAPTER EIGHT heavy ions and the fifth Dimension.....................140Epilogue..............................................................159Index.................................................................163

Chapter One

ENERGY

The aim of this chapter is to present the most famous equation of physics: E = mc². This equation underlies nuclear power and the atom bomb. It says that if you convert one pound of matter entirely into energy, you could keep the lights on in a million American households for a year. E = mc² also underlies much of string theory. In particular, as we'll discuss in chapter 4, the mass of a vibrating string receives contributions from its vibrational energy.

What's strange about the equation E = mc² is that it relates things you usually don't think of as related. E is for energy, like the kilowatt-hours you pay your electric company for each month; m is for mass, like a pound of flour; c is for the speed of light, which is 299,792,458 meters per second, or (approximately) 186,282 miles per second. So the first task is to understand what physicists call "dimensionful quantities," like length, mass, time, and speed. Then we'll get back to E = mc² itself. Along the way, I'll introduce metric units, like meters and kilograms; scientific notation for big numbers; and a bit of nuclear physics. Although it's not necessary to understand nuclear physics in order to grasp string theory, it provides a good context for discussing E = mc². And in chapter 8, I will come back and explain efforts to use string theory to better understand aspects of modern nuclear physics.

Length, mass, time, and speed

Length is the easiest of all dimensionful quantities. It's what you measure with a ruler. Physicists generally insist on using the metric system, so I'll start doing that now. A meter is about 39.37 inches. A kilometer is 1000 meters, which is about 0.6214 miles.

Time is regarded as an additional dimension by physicists. We perceive four dimensions total: three of space and one of time. Time is different from space. You can move any direction you want in space, but you can't move backward in time. In fact, you can't really "move" in time at all. Seconds tick by no matter what you do. At least, that's our everyday experience. But it's actually not that simple. If you run in a circle really fast while a friend stands still, time as you experience it will go by less quickly. If you and your friend both wear stopwatches, yours will show less time elapsed than your friend's. This effect, called time dilation, is imperceptibly small unless the speed with which you run is comparable to the speed of light.

Mass measures an amount of matter. We're used to thinking of mass as the same as weight, but it's not. Weight has to do with gravitational pull. If you're in outer space, you're weightless, but your mass hasn't changed. Most of the mass in everyday objects is in protons and neutrons, and a little bit more is in electrons. Quoting the mass of an everyday object basically comes down to saying how many nucleons are in it. A nucleon is either a proton or a neutron. My mass is about 75 kilograms. Rounding up a bit, that's about 50,000,000,000, 000,000,000,000,000,000 nucleons. It's hard to keep track of such big numbers. There are so many digits that you can't easily count them up. So people resort to what's called scientific notation: instead of writing out all the digits like I did before, you would say that I have about 5x10²⁸ nucleons in me. The 28 means that there are 28 zeroes after the 5. Let's practice a bit more. A million could be written as 1x10⁶, or, more simply, as 106. The U.S. national debt, currently about $10,000,000,000,000, can be conveniently expressed as 10¹³ dollars. Now, if only I had a dime for every nucleon in me ...

Let's get back to dimensionful quantities in physics. Speed is a conversion factor between length and time. Suppose you can run 10 meters per second. That's fast for a person—really fast. In 10 seconds you can go 100 meters. You wouldn't win an Olympic gold with that time, but you'd be close. Suppose you could keep up your speed of 10 meters per second over any distance. How long would it take to go one kilometer? Let's work it out. One kilometer is ten times 100 meters. You can do the 100-meter dash in 10 seconds flat. So you can run a kilometer in 100 seconds. You could run a mile in 161 seconds, which is 2 minutes and 41 seconds. No one can do that, because no one can keep up a 10m/s pace for that long.

Suppose you could, though. Would you be able to notice the time dilation effect I described earlier? not even close. Time would run a little slower for you while you were pounding out your 2:41 mile, but slower only by one part in about 1015 (that's a part in 1,000,000,000,000,000, or a thousand million million). In order to get a big effect, you would have to be moving much, much faster. Particles whirling around modern accelerators experience tremendous time dilation. Time for them runs about 1000 times slower than for a proton at rest. The exact figure depends on the particle accelerator in question.

The speed of light is an awkward conversion factor for everyday use because it's so big. Light can go all the way around the equator of the earth in about 0.1 seconds. That's part of why an American can hold a conversation by telephone with someone in India and not notice much time lag. Light is more useful when you're thinking of really big distances. The distance to the moon is equivalent to about 1.3 seconds. you could say that the moon is 1.3 light-seconds away from us. The distance to the sun is about 500 light-seconds.

A light-year is an even bigger distance: it's the distance that light travels in a year. The Milky Way is about 100,000 light-years across. The known universe is about 14 billion light-years across. That's about 1.3x10²⁶ meters.

E = mc²

The formula E = mc² is a conversion between mass and energy. it works a lot like the conversion between time and distance that we just discussed. But just what is energy? The question is hard to answer because there are so many forms of energy. Motion is energy. Electricity is energy. Heat is energy. Light is energy. Any of these things can be converted into any other. For example, a lightbulb converts electricity into heat and light, and an electric generator converts motion into electricity. A fundamental principle of physics is that total energy is conserved, even as its form may change. in order to make this principle meaningful, one has to have ways of quantifying different forms of energy that can be converted into one another.

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Details zur Ausgabe

• Verlag: Princeton University Press
• Erscheinungsdatum: 2010
• Sprache: Englisch
• ISBN 10: 0691142890
• ISBN 13: 9780691142890
• Einband: Gebundene Ausgabe
• Anzahl der Seiten: 184
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Nicht verfügbar