So where are the Strings?


Historical
Particle accelerators in the 1960's were producing new hadrons
      Various models were developed to describe the new particles

Gabrielle Veneziano then a fellow at CERN found that particles of the strong force could be described using the gamma function of Euler's.

No one understood why this worked

This method was then overshodowed with QCD in the 1970's
       
        Why?    One reason was that the theory required the existence of a kind of particle that we didn't want -- namely a particle with no mass and two units of spin.                                              Its existence was very generic and very frustrating.
                      The second problem was that the theory required that space-time have ten dimensions (nine space and one time), whereas the correct answer is clearly                                   our (three space and one time).

In 1970 a physical picture of Veneziano's Method was discovered by Yoichiro Nambu of the University of Chicago
        Yoichiro treated the particles not as zero dimensional points, but as one dimentional vibrating strings (over time becomes known as string theory)

1970 John Schwarz finds a way to desribe fermions using string theory

1974 Schwarz and Joel Scherk discover the link between string theory and gravity - the unwanted paricle of spin 2 and no mass is the graviton!

1976 Scherk shows that fermions and bosons emerge from string theory equally (for every fermion there is a bosonic partiner and vice-versa)
                     Supersymmetry is born!

1980's   SUSY is incorperated into strings to produce powerful descriptions of the universe ->  now Superstrings    (Scherk dies :-(

              The quark model still eclipses string theory, but a few mathematically incline physisists continue the saga

 1980  Schwarz and Green,  who started working together in the 70's,  produce Type I theory which dealt with open ended strings

1981  Schwarz and Green introduce Type II theory -deals with closed strings
 
                      Both of these theories require that the strings vibrate in additional dimentions (10)

1982 Ed Witten shows that Kaluza-Klien compactification will work to compactify the additional dimensions

1984 Schwarz and Green uncover SO(32) symmetry which, when applied to Type I,  removes all anomalies

        David Gross and colleagues produce Heterotic strings using a different mathematical approach

        E8 X E8 symmetry is produced - half of the components of this symmetry describe everything in our universe
                     The other half is a duplicate, which leads to the idea of 2 universes acting on eachother only through gravity  (Dark Matter?)

 


String 90's