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The String Theory

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Ellie Xu

on 9 January 2015

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Transcript of The String Theory

The String Theory

By: Viola zhang, ellie xu, despoina sparakis, daniel zabari

While quantum mechanics is successful in predicting how objects behave in the subatomic realm and general relativity on a larger scale, the two are incompatible
When we attempt to combine the two theories, we get infinities
No single theory explains all 4 fundamental forces
History of
String Theory


Future Applications
Why it Matters
Physicists use Einstein's relativity when dealing with large objects and quantum mechanics when dealing with small objects
One problem is black holes
Black holes are both very small and have a large gravitational force
Which theory do we use?

Gabriele Veneziano
: kickstart string theory by using Eurler's equation to describe strong force
Yoichiro Nambu, Holger Nielson, Leonard Susskind
: independently came up of strings (dual resonance models)
Pierre Ramond
modified theory to include the fermions and gravitons
Johns Schawartz, Joel Scherk
: include gravity in string theory
Before String Theory:
-1919: Theodor Kaluza , extra dimensions
Oskar Klein: why we don't see the 5th dimension
-1943: birth of quantum mechanics
Werner Heisenberg: S-matrix theory

Michael Green, John Schwartz
: Superstring theory made mainstream by cancelling quantum anomalies
-1994: Perturbation, D-brane
First String Theory:
accounted for bosons, not fermions, 26 space-time dimensions and emergence of an impossible negative mass particle (tachyon)

Modern String Theory:
Strings are the fundamental building blocks of matter. There are 11 dimensions. 6 of them are small Calabi-Yau shapes attached to space-time.

: the 6 extra dimensions are explained to exist because of

manifolds: the different ways the 6 extra dimensions compact

: these "membranes" can have up to 9 dimensions; natural places for the "endpoints" of strings, non-perturbative

•T-Duality: led to Mirror Symmetry (1980s): Calabi-Yau shapes are in pairs--extra dimensions with radii r (expanding) and a/r (contracting) have the same physics
*[a=Planck length]

•S-Duality: coupling constant determines the strength between particles; relates theories with coupling constants g and 1/g; led to M-theory

•Ads/CFT Correspondence: theories of gravity in 5D and that of QFT in 4D are dualities because of the extension of gravity on a 5D AdS space; let to guage-gravity correspondence: gravitational theories in (N+1)D=non-gravitational QFT in ND
Eva Silverstein
: develops mechanisms for breaking supersymmetry and stabilizing extra dimensions; addressed quantum gravity by using UV completion of gravity
Melanie Becker
Katrin Becker
worked on Calabi-Yau manifolds
Chiara Nappi
: thermal interpretation of QFT in deSitter space; investigated properties of baryons; behavior of open strings in background electromagnetic fields; analysis of black holes

Can't be proven by experimentation (too small, dimensions we can't see)
Needs 11 dimensions to work, none were observed
Calabi-Yau Shapes
There are many possible shapes for the universes to take. String theorists can't figure out which shape they take the form of

Why isn't there background independence and how come everything is approximated?
String Theory will hopefully unify the four forces, but even if it does, there are still many questions left unanswered...
String Theory may help
1. Dark energy and dark matter
2. Nature of black holes
3. Apparent acceleration of the expansion of the universe
4. Behavior of matter during the Big Bang
Late 1960s, 1970s: String Theory Starts
First Revolution
Edward Witten
(5 string theories actually have the same physics just different coupling constants; is 11 dimensions because of
; 11D looks like 10D because the 11th dimension is so small--contingent with the string theories!) , supermembrane
Second Revolution
More Research on String Theory
Quantum Computing
-Quantum Computing will revolutionize the future of computing, and String Theory will help us reach it.
-No longer will we have to put up with the slow speeds of electrons moving through superconductors; Our computers will do calculations at the speed of light.
-Beams of light do not interfere with each other, so the computer can send and receive multiple calculations at once from different sources and sensors.
Qubits vs. Bits
-Qbits and Bits are very similar
-Bits have two possible values, (0 and 1)
-Qubits can theoretically have an infinite number of values since they can be positioned in any angle.
-An infinite number of values will allow for much faster mathematical calculations.
-Larger numbers can be stored in less space, allowing for faster...well... EVERYTHING.
Quantum Mechanics and General Relativity
Two very different theories
David Gross and Paul
Once a string has
enough energy to probe at
the Planck length, adding
more energy decreases its
Strings aren't affected
by quantum undulations
Questions About the Universe
Physicists have discovered many different particles
Vibrations of strings form different particles
There are many different types of particles because there are many ways a string can vibrate (strings can be open ended or closed)
String theory explains why the universe has 3 dimensions
Strings can wrap around
dimensions and stop them from
String and antistring collisions
destroy both, producing an
unwrapped dimension
Dimension can expand
Why the universe is fine-tuned for life
There are many universes, one would eventually be suitable for life
Works Cited
"Why String Theory | a Layman's Journey to the Frontiers of
Physics." Why String Theory | a Layman's Journey to the
Frontiers of Physics. N.p., n.d. Web. 06 Jan. 2015.
"The Official String Theory Web Site." The Official
String Theory Web Site. N.p., n.d. Web. 06 Jan.
"What Is String Theory ?" What Is String Theory ? N.p.,
n.d. Web. 06 Jan. 2015.
"Beyond String Theory Introduction." Beyond String
Theory Introduction. N.p., n.d. Web. 06 Jan. 2015.

Carol. STRING THEORY (n.d.): n. pag. Web.

"Dark Matter." : Extra Dimensions. N.p., n.d. Web. 06
Jan. 2015.

Mcgreevy, John, and 200 April 4. April 4, 2008What Is
String Theory? (n.d.): n. pag. Web.
Greene, B. The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory. New York: W.W. Norton, 1999. Print.

"Centre for Research in String Theory." Overview. N.p., n.d. Web. 06 Jan. 2015.
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