String Theory For Dummies

Title Page
Copyright Page
Table of Contents
Introduction
About This Book
Foolish Assumptions
Icons Used in This Book
Beyond the Book
Where to Go from Here
Part 1 Introducing String Theory
Chapter 1 So What Is String Theory Anyway?
String Theory: Seeing What Vibrating Strings Can Tell Us about the Universe
Using tiny and huge concepts to create a theory of everything
A quick look at where string theory has been
Introducing the Key Elements of String Theory
Strings and branes
Quantum gravity
Unification of forces
Supersymmetry
Extra dimensions
Understanding the Aim of String Theory
Quantizing gravity
Unifying forces
Explaining matter and mass
Defining space and time
Appreciating the Theory’s Amazing (and Controversial) Implications
Landscape of possible theories
The universe as a hologram
Why Is String Theory So Important?
Chapter 2 The Physics Road Dead-Ends at Quantum Gravity
Understanding Two Schools of Thought on Gravity
Newton’s law of gravity: Gravity as force
Einstein’s law of gravity: Gravity as geometry
Describing Matter: Physical and Energy-Filled
Viewing matter classically: Chunks of stuff
Viewing matter at a quantum scale: Chunks of energy
Grasping for the Fundamental Forces of Physics
Electromagnetism: Super-speedy energy waves
Nuclear forces: What the strong force joins, the weak force tears apart
Infinities: Why Einstein and the Quanta Don’t Get Along
Singularities: Bending gravity to the breaking point
Quantum jitters: Space-time under a quantum microscope
Unifying the Forces
Einstein’s failed quest to explain everything
A particle of gravity: The graviton
Supersymmetry’s role in quantum gravity
Chapter 3 Accomplishments and Failures of String Theory
Celebrating String Theory’s Successes
Predicting gravity out of strings
Explaining what happens to a black hole (sort of)
Explaining quantum field theory using string theory
String theory keeps making a comeback
Being the most popular theory in town
Considering String Theory’s Setbacks
The universe doesn’t have enough particles
Dark energy: The discovery string theory should have predicted
Where did all these “fundamental” theories come from?
Looking into String Theory’s Future
Theoretical complications: Can we figure out string theory?
Experimental complications: Can we prove string theory?
Part 2 The Physics Upon Which String Theory Is Built
Chapter 4 Putting String Theory in Context: Understanding the Method of Science
Exploring the Practice of Science
The myth of the scientific method
The need for experimental falsifiability
The foundation of theory is mathematics
The rule of simplicity
The role of objectivity in science
Understanding How Scientific Change Is Viewed
Precision and accuracy: Science as measurement
Old becomes new again: Science as revolution
Combining forces: Science as unification
What happens when you break it? Science as symmetry
Chapter 5 What You Must Know about Classical Physics
This Crazy Little Thing Called Physics
No laughing matter: What we’re made of
Add a little energy: Why stuff happens
Symmetry: Why some laws were made to be broken
All Shook Up: Waves and Vibrations
Catching the wave
Getting some good vibrations
Newton’s Revolution: How Physics Was Born
Force, mass, and acceleration: Putting objects into motion
Gravity: A great discovery
Optics: Shedding light on light’s properties
Calculus and mathematics: Enhancing scientific understanding
The Forces of Light: Electricity and Magnetism
Light as a wave: The ether theory
Invisible lines of force: Electric and magnetic fields
Maxwell’s equations bring it all together: Electromagnetic waves
Two dark clouds and the birth of modern physics
Chapter 6 Revolutionizing Space and Time: Einstein’s Relativity
What Waves Light Waves? Searching for the Ether
No Ether? No Problem: Introducing Special Relativity
Unifying space and time
Unifying mass and energy
Changing Course: Introducing General Relativity
Gravity as acceleration
Gravity as geometry
Testing general relativity
Surfing the gravitational waves
Applying Einstein’s Work to the Mysteries of the Universe
Kaluza-Klein Theory — String Theory’s Predecessor
Chapter 7 Brushing Up on Quantum Theory Basics
Unlocking the First Quanta: The Birth of Quantum Physics
Fun with Photons: Einstein’s Nobel Idea of Light
Waves and Particles Living Together
Light as a wave: The double slit experiment
Particles as a wave: The de Broglie hypothesis
Quantum physics to the rescue: The quantum wavefunction
Why We Can’t Measure It All: The Uncertainty Principle
Dead Cats, Live Cats, and Probability in Quantum Physics
Does Anyone Know What Quantum Theory Means?
Quantum Units of Nature: Planck Units
Chapter 8 The Standard Model of Particle Physics
Atoms, Atoms, Everywhere Atoms: Introducing Atomic Theory
Popping Open the Atomic Hood and Seeing What’s Inside
Discovering the electron
The nucleus is the thing in the middle
Watching the dance inside an atom
The Quantum Picture of the Photon: Quantum Electrodynamics
Dr. Feynman’s doodles explain how particles exchange information
Discovering that other kind of matter: Antimatter
Sometimes a particle is only virtual
Digging into the Nucleus: Quantum Chromodynamics
The pieces that make up the nucleus: Nucleons
The pieces that make up the nucleon’s parts: Quarks
Looking into the Types of Particles
Particles of force: Bosons
Particles of matter: Fermions
Gauge Bosons: Particles Holding Other Particles Together
Exploring the Theory of Where Mass Comes From
What is the Higgs field?
Discovering the Higgs boson at the LHC
From Big to Small: The Hierarchy Problem in Physics
Chapter 9 Physics in Space: Considering Cosmology and Astrophysics
The Enlightened Universe and the Birth of Modern Astrophysics
Everything doesn’t revolve around Earth
Beholding the movements of heavenly bodies
Introducing the Idea of an Expanding Universe
Discovering that energy and pressure have gravity
Hubble drives it home
Finding a Beginning: The Big Bang Theory
Going to bat for the big bang: Cosmic microwave background radiation
Understanding where the chemical elements came from
Using Inflation to Solve the Universe’s Problems of Flatness and Horizon
The universe’s issues: Too far and too flat
Rapid expansion early on holds the solutions
Dark Matter: The Source of Extra Gravity
Dark Energy: Pushing the Universe Apart
Stretching the Fabric of Space-Time into a Black Hole
What goes on inside a black hole?
What goes on at the edge of a black hole?
Part 3 Building String Theory: A Theory of Everything
Chapter 10 Early Strings and Superstrings: Unearthing the Theory’s Beginnings
Bosonic String Theory: The First String Theory
Explaining the scattering of particles with early dual resonance models
Exploring the first physical model: Particles as strings
Bosonic string theory loses out to the Standard Model
Why Bosonic String Theory Doesn’t Describe Our Universe
Massless particles
Tachyons
No electrons allowed
25 space dimensions, plus 1 of time
Supersymmetry Saves the Day: Superstring Theory
Fermions and bosons coexist . . . sort of
Double your particle fun: Supersymmetry hypothesizes superpartners
Some problems get fixed, but the dimension problem remains
Supersymmetry and Quantum Gravity in the Disco Era
The graviton is found hiding in string theory
The other supersymmetric gravity theory: Supergravity
String theorists don’t get no respect
A Theory of Everything: The First Superstring Revolution
But We’ve Got Five Theories!
Type I string theory
Type IIA string theory
Type IIB string theory
Two strings in one: Heterotic strings
How to Fold Space: Introducing Calabi-Yau Manifolds
String Theory Loses Steam
Chapter 11 M-Theory and Beyond: Bringing String Theory Together
Introducing the Unifying Theory: M-Theory
Translating one string theory into another: Duality
Using two dualities to unite five superstring theories
The second superstring revolution begins: Connecting to the 11-dimensional theory
Branes: Stretching Out a String
The discovery of D-branes: Giving open strings something to hold on to
Creating particles from p-branes
Deducing that branes are required by M-theory
Uniting D-branes and p-branes into one type of brane
Using branes to explain black holes
Getting stuck on a brane: Brane worlds
Matrix Theory as a Potential M-Theory
Chapter 12 Exploring Strings and Their Landscape
Strings and Fields: String Field Theory
String Theory Gets Surprised by Dark Energy
Considering Proposals for Why Dimensions Sometimes Uncurl
Measurable dimensions
Infinite dimensions: Randall-Sundrum models
Understanding the Current Landscape: A Multitude of Theories
The anthropic principle requires observers
Disagreeing about the principle’s value
Chapter 13 Gaining Insights from the Holographic Principle
What’s a Hologram?
Creating optical holograms
More bang for your buck: Encoding information in fewer dimensions
Using Holograms to Understand Black Holes
Going down a black hole
Black holes and entropy
If it works for black holes, it works for me
Considering AdS/CFT Correspondence
Checking the predictions
AdS space, or living in an M. C. Escher painting
CFTs: conformal, but nonconformist
Understanding quantum gravity through AdS/CFT correspondence
Turning the Tables: Using Holography to Study Strongly Interacting Matter
The force is strong when using AdS/CFT
Cooking up a soup of quarks and gluons
Chapter 14 Putting String Theory to the Test
Understanding the Obstacles
Testing an incomplete theory with indistinct predictions
Testing versus proof
Analyzing Supersymmetry
Finding the missing sparticles
Testing implications of supersymmetry
Testing Gravity from Extra Dimensions
Checking the inverse-square law
Searching for gravity waves to understand inflation
Disproving String Theory Sounds Easier Than It Is
Violating relativity
Could proton decay spell disaster?
Seeking mathematical inconsistencies
Bootstrapping Our Way into String Theory
Looking for Evidence in the Cosmic Laboratory: Exploring the Universe
Using outer space rays to amplify small events
Analyzing dark matter and dark energy
Detecting cosmic superstrings
Looking for Evidence Closer to Home: Using Particle Accelerators
Accelerating heavy ions at the RHIC
Colliders of the future
LHC finds a boson, but no superpartners yet
Discovering the Higgs boson
Looking for superpartners
Part 4 The Unseen Cosmos: String Theory on the Boundaries of Knowledge
Chapter 15 Making Space for Extra Dimensions
What Are Dimensions?
2-Dimensional Space: Exploring the Geometry of Flatland
Euclidean geometry: Think back to high school geometry
Cartesian geometry: Merging algebra and Euclidean geometry
Three Dimensions of Space
A straight line in space: Vectors
Twisting 2-dimensional space in three dimensions: The Mobius strip
More twists in three dimensions: Non-Euclidean geometry
Four Dimensions of Space-Time
Adding More Dimensions to Make a Theory Work
Sending Space and Time on a Bender
Are Extra Dimensions Really Necessary?
Offering an alternative to multiple dimensions
Weighing fewer dimensions against simpler equations
Chapter 16 Our Universe — String Theory, Cosmology, and Astrophysics
The Start of the Universe with String Theory
What was before the bang?
What banged?
Explaining Black Holes with String Theory
String theory and the thermodynamics of a black hole
String theory and the black hole information paradox
The Evolution of the Universe
The swelling continues: Eternal inflation
The hidden matter and energy
The Undiscovered Country: The Future of the Cosmos
A universe of ice: The big freeze
From point to point: The big crunch
A new beginning: The big bounce
Exploring a Finely Tuned Universe
Chapter 17 Have Time, Will Travel
Temporal Mechanics 101: How Time Flies
The arrow of time: A one-way ticket
Relativity, worldlines, and worldsheets: Moving through space-time
Hawking’s chronology protection conjecture: You’re not going anywhere
Slowing Time to a Standstill with Relativity
Time dilation: Sometimes even the best watches run slow
Black hole event horizons: An extra-slow version of slow motion
General Relativity and Wormholes: Doorways in Space and Time
Taking a shortcut through space and time with a wormhole
Overcoming a wormhole’s instability with negative energy
Crossing Cosmic Strings to Allow Time Travel
A Two-Timing Science: String Theory Makes More Time Dimensions Possible
Adding a new time dimension
Reflecting two-time physics onto a one-time universe
Does two-time physics have any real applications?
Sending Messages through Time
Part 5 What the Other Guys Say: Criticisms and Alternatives
Chapter 18 Taking a Closer Look at the String Theory Controversy
The String Wars: Outlining the Arguments
50 years and counting: Framing the debate from the skeptic’s point of view
A rise of criticisms
Is String Theory Scientific?
Argument No. 1: String theory explains nothing
Argument No. 2: String theory explains too much
Turning a Critical Eye on String Theorists
Hundreds of physicists just can’t be wrong
Holding the keys to the academic kingdom
Does String Theory Describe Our Universe?
Making sense of extra dimensions
Space-time should be fluid
The ever-elusive superpartners
How finite is string theory?
A String Theory Rebuttal
What about the extra dimensions?
Space-time fluidity?
Does string theory need to be finite?
Trying to Make Sense of the Controversy
Chapter 19 Loop Quantum Gravity: String Theory’s Biggest Competitor
Taking the Loop: Introducing Another Road to Quantum Gravity
The great background debate
What is looping anyway?
Making Predictions with Loop Quantum Gravity
Gravity exists (Duh!)
Black holes contain only so much space
Gamma ray burst radiation travels at different speeds
Finding Favor and Flaw with Loop Quantum Gravity
The benefit of a finite theorem
Spending some time focusing on the flaws
So Are These Two Theories the Same with Different Names?
Chapter 20 Considering Other Ways to Explain the Universe
Taking Other Roads to Quantum Gravity
CDT: If you’ve got the time, I’ve got the space
Quantum Einstein gravity: Too small to tug
Quantum graphity: Disconnecting nodes
Tensor models: gluing the space-time together
Newton and Einstein Don’t Make All the Rules: Modifying the Law of Gravity
DSR: Twice as many limits as ordinary relativity
MOND: Disregarding dark matter
VSL: Light used to travel even faster
MOG: The bigger the distance, the greater the gravity
Massive gravity and bimetric theory: making the graviton heavy
Rewriting the Math Books and Physics Books at the Same Time
Compute this: Quantum information theory
Looking at relationships: Twistor theory
Uniting mathematical systems: Noncommutative geometry
Mathematics All the Way Down: Are We Living in a Simulation?
Part 6 The Part of Tens
Chapter 21 Ten Tests for a Theory of Quantum Gravity
Reproduce Gravity
Compute Quantum Corrections
Describe How Gravity and Matter Interact
Explain Inflation
Explain What Happens When Someone Enters a Black Hole
Explain Whether Singularities Are Allowed
Explain the Birth and Death of Black Holes
Explain the Holographic Principle
Provide Testable Predictions
Describe Its Own Limitations
Index
EULA