Adventures in String Theory
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Transcript of Adventures in String Theory
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Adventures in String Theory
Science One, April 7th, 2011
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What are the basic building
blocks of nature?
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Old Answer
Air Earth FireWater
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Modern Answer
Modern physics: understand in detail how nature works at distances 100,000,000,000,000 times smaller than we can see!
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The Standard Model of Particle PhysicsAll matter made of elementary particles
-different masses and spins
Forces arise from basic interactions of these particles
Rules for interactions determined by quantum mechanics and special relativity ~20 parameters
electromagnetic strong
weak
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The Basic Building Blocks?
Air Earth
Fire Water
Proton Neutron
Electron Photon
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Questions
Why this set of particles and interactions?
Are these particles really elementary?
Are there more particles or forces?
What about gravity?
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General Relativity
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•Accurately predicts gravitational effects from solar system dynamics to the evolution of the whole universe.
•Predicts new phenomena, e.g. black holes, gravity waves, expansion of the universe
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How did the universe begin?
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Old Answer
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Modern Answer: the Big Bang
General relativity
universe has expanded and cooled for 13.6 billion years from extremely hot, dense state
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Questions
What happened in the first instant of the big bang (or before)?
What is inside a black hole?
We need a quantum mechanical theory of gravity!
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String Theory: the Basics
Basic building block: string (1 dimensional loop of energy)
Quantum mechanics
Specific vibrational modes with definite energy and angular momentum
We see: particles with different mass and spin
m = E/c2
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String interactions
time
Particle interactions arise from splitting and joining of strings
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String interactions
Particle interactions arise from splitting and joining of strings
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String interactions
Particle interactions arise from splitting and joining of strings
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String interactions
Particle interactions arise from splitting and joining of strings
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String interactions
Particle interactions arise from splitting and joining of strings
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String interactions
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Basic law of string physics:
Strings move to minimize the area of their worldsheet
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String physics: strings vibrate, join, split via basic law + quantum mechanics
We see: various types of particles with forces arising from basic interactions INCLUDING gravity
String theory automatically gives a theory of quantum gravity and particle physics with no parameters!
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Extra DimensionsSurprise: even the number of dimensions is fixed!
We see: 4
String theory predicts: 10
BUT: recall that space can be curved
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Garden-variety extra dimensions
Our universe:
Hose universe:
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The shape of the extra dimensions1 extra dimension:
2 extra dimensions:
6 extra dimensions:
Many possibilities for the shape / size / topology of extra dimensions
...
...
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Physics from geometry
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The Landscape of String TheoryExtra dimensions dynamical:Only special shapes are stable
Different possibilities for 4D physics
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Big question: does one of these stable shapes give the physics we observe?
Currently: just starting to understand the possibilities
Can we make new predictions that can be tested experimentally?
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The End of the Universe?