Download String Theory

• String theory is an attempt at understanding
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how the universe works: both what it’s
made of and how it behaves.
The very basic idea is that particles aren’t
points, but instead stretched strings.
The strings can either be closed, like a ring,
or open.
o This along with the way they vibrate give them their
traits, making electrons different from muons, for
example.
• One of the reasons why string theory is so
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popular is that it explains gravity on a
quantum level, which isn’t nearly as easy
with point particles.
It’s also a path to connecting the 4
fundamental interactions: gravity,
electromagnetic, weak and strong forces
It also doesn’t seem to have any major
discrepancies with what we already know
• Since string theory is about particles in high
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energies, this is all very theoretical – we
have no way of experimenting these ideas.
It’s also very new, and research is on-going.
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The theory of extra dimensions
Kaluza and Klein made a crucial
discovery for inventing string
theory between 1921 and 1927:
electromagnetism can be derived
from gravity if there are four
space dimensions
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Gabriele Veneziano, a researcher at CERN noticed that properties of
strong nuclear force have in common with the Euler beta-function in 1968
Deeper research revealed that the interactions of elementary particles
modeled as one–dimensional strings were described thoroughly by the
Euler beta-function.
Later experiments in the 1970s revealed that many of the theory's
predictions were noticeable only with experimental data.
Point-particle theory succeeded and string theory was left behind
The reason for this was that String vibrations produce observable
properties that we see in fundamental particles, for instance, string
theory seemed to provide vibrating configurations that corresponded to
the properties of gluons
It also provided other vibrating patterns which were soon shown to
correspond with properties of the graviton which were not welcome
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Super string theories are string theories including fermionic vibrations
The first super string revolution was brought to publicity by Michael Green
and John Schwarz in 1984
o It resolved the conflict between string theory and quantum mechanics
and also proved that string theory encompasses the fundamental
forces and all the matter in existence
The super string revolution brought physicists around the world to once
again research the same theory they had earlier abandoned
It was thought that the theory was the most promising to unify physical
theories
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After years, investigations led to the invention of
super symmetry
The next few years showed that the features of
the standard model can be derived from the new
string theory but the equations of the new theory
were so difficult that the exact form could not be
defined
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approximations had to be used which were found insufficient, and
string theory was discarded
This resolved the conflict between string theory
and quantum mechanics and also proved that
string theory encompasses the fundamental forces
and all the matter in existence
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The second super string revolution started in 1995 at a conference
called Strings, where Edward Witten suggested moving to further
research areas
He was one of those who found evidence for different superstring
theories, like M-theory
The consequences of his ideas are still being analyzed by theorists
seeking the final answers from what they believe will prove to be
the “theory of everything”
-Five different string theories
-The beginning of everything is “Bosonic String Theory”
-Bosonic String Theory is the original version of string theory, developed in
the late 1960s.
-That original String Theory only described particles that were bosons, and it
did not describe Fermions at all. So quarks and electrons, for instance, were
not included in Bosonic String Theory.
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-By introducing supersymmetry to Bosonic
String Theory, we can obtain a new
theory that describes everything... The
forces and the matter which make up
the Universe.
-The basic idea of supersymmetry is
that every fundamental particle has its
own so called “superpartner”. All
superpartners have same features as
their original particle but they have halfinteger spin.
-There are three different superstring
theories which make sense, i.e. display
no mathematical inconsistencies.
-In two of them strings are closed and
from third on open strings are the
building blocks.
-Mixing the best features of the
bosonic string and the
superstring theories, we can
create two other consistent
theories of strings, Heterotic
String Theories.
• So now we have five different
theories of strings which
comprise 10 dimensions.
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The basic assumption is that we obviously have only three
dimensions of space and one of time. However, if we assume that
six of these dimensions are curled up very tightly, then we may
never be aware of their existence. But one of the most remarkable
predictions of String Theory is that space-time has ten dimensions!
Later in 1995 the most well known researcher of string theories
Edward Witten with his colleague Paul Townsend found the 11th
dimension.
M-theory
-New idea was that instead of one there are five different, healthy
theories of strings (three superstrings and two heterotic strings)
there is only one theory
-those five different theories are part of one theory, they are only
different aspect.
This was called M-theory.
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M-theory includes 11 dimensions
o four space-time dimensions + seven very very small dimensions
The first "theory of all“
o Explains forces and matter
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o The first theory which is able to explain BOTH quantum mechanics and general
gravity
It would also seem to be able to explain black holes
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http://www.onemanswonder.com/2011/11/us-versus-us-tied-togetherby-string.html
http://en.wikipedia.org/wiki/String_theory
http://www.superstringtheory.com/history/history4.html
http://www.fractalforums.com/general-discussion-b77/imaginarynumbers/
http://responsiveuniverse.wordpress.com/2011/11/30/can-astrophysicsprove-that-an-afterlife-exists/
http://www.mozardien.com/halls/2011/12/30/superstring-theory-solvedby-supercomputer/
http://library.thinkquest.org/27930/stringhistory.htm
http://www.damtp.cam.ac.uk/research/gr/public/qg_ss.html
http://superstringtheory.com/