String Theory For Dummies

From String Theory For Dummies by Andrew Zimmerman Jones

 [with Daniel Robbins

]

String theory, often called the “theory of everything,” is a relatively young science that includes such unusual concepts as superstrings, branes, and extra dimensions. Scientists are hopeful that string theory will unlock one of the biggest mysteries of the universe, namely how gravity and quantum physics fit together.

Superpartners in String Theory

String theory’s concept of supersymmetry is a fancy way of saying that each particle has a related particle called a superpartner. Keeping track of the names of these superpartners can be tricky, so here are the rules in a nutshell.

• The superpartner of a fermion begins with an “s,” so the superpartner of an “electron” is the “selectron” and the superpartner of the “quark” is the “squark.”

• The superpartner of a boson ends in “–ino,” so the superpartner of a “photon” is the “photino” and of the “graviton” is the “gravitino.”

Use the following table to see some examples of the superpartner names.

Some Superpartner Names

Standard Particle	Superpartner
Higgs boson	Higgsino
Neutrino	Sneutrino
Lepton	Slepton
Z boson	Zino
W boson	Wino
Gluon	Gluino
Muon	Smuon
Top quark	Stop squark

Keeping Track of String Theory’s Many Names

String theory has gone through many name changes over the years. This list provides an at-a-glance look at some of the major names for different types of string theory. Some versions have more specific variations, which are shown as subentries. (These different variants are related in complex ways and sometimes overlap, so this breakdown into subentries is based on the order in which the theories developed.) Now if you hear these names, you’ll know they’re talking about string theory!

• Bosonic string theory

• Superstring theory (or Supersymmetric string theory)

  • Type I, Type IIA, Type IIB, Heterotic string theories (Type HE, Type HO)

• M-theory

  • Matrix theory

• Brane world scenarios

  • Randall-Sundrum models (or RS1 and RS2)

• F-theory

Key Events in String Theory History

Although string theory is a young science, it has had many notable achievements. What follows are some landmark events in the history of string theory:

1968: Gabriele Veneziano originally proposes the dual resonance model.

1970: String theory is created when physicists interpret Veneziano’s model as describing a universe of vibrating strings.

1971: Supersymmetry is incorporated, creating superstring theory.

1974: String theories are shown to require extra dimensions. An object similar to the graviton is found in superstring theories.

1984: The first superstring revolution begins when it’s shown that anomalies are absent in superstring theory.

1985: Heterotic string theory is developed. Calabi-Yau manifolds are shown to compactify the extra dimensions.

1995: Edward Witten proposes M-theory as unification of superstring theories, starting the second superstring revolution. Joe Polchinski shows branes are necessarily included in string theory.

1996: String theory is used to analyze black hole

Read more: http://ca.dummies.com/how-to/content/string-theory-for-dummies-cheat-sheet.html#ixzz0j8POdgaA

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