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Adventures in String Theory. Science One, April 7 th , 2011. What are the basic building blocks of nature?. Old Answer. Air Earth Fire Water. Modern Answer. Modern physics: understand in detail how nature works at distances 100,000,000,000,000 times smaller than we can see!. - PowerPoint PPT Presentation
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Adventures in String Theory
Science One, April 7th, 2011
What are the basic building
blocks of nature?
Old Answer
Air Earth FireWater
Modern Answer
Modern physics: understand in detail how nature works at distances 100,000,000,000,000 times smaller than we can see!
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
The Basic Building Blocks?
Air Earth
Fire Water
Proton Neutron
Electron Photon
Questions
Why this set of particles and interactions?
Are these particles really elementary?
Are there more particles or forces?
What about gravity?
General Relativity
•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
How did the universe begin?
Old Answer
Modern Answer: the Big Bang
General relativity
universe has expanded and cooled for 13.6 billion years from extremely hot, dense state
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!
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
String interactions
time
Particle interactions arise from splitting and joining of strings
String interactions
Particle interactions arise from splitting and joining of strings
String interactions
Particle interactions arise from splitting and joining of strings
String interactions
Particle interactions arise from splitting and joining of strings
String interactions
Particle interactions arise from splitting and joining of strings
String interactions
Basic law of string physics:
Strings move to minimize the area of their worldsheet
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!
Extra DimensionsSurprise: even the number of dimensions is fixed!
We see: 4
String theory predicts: 10
BUT: recall that space can be curved
Garden-variety extra dimensions
Our universe:
Hose universe:
The shape of the extra dimensions1 extra dimension:
2 extra dimensions:
6 extra dimensions:
Many possibilities for the shape / size / topology of extra dimensions
...
...
Physics from geometry
The Landscape of String TheoryExtra dimensions dynamical:Only special shapes are stable
Different possibilities for 4D physics
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?
The End of the Universe?
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