sage
发表文章数: 1125
武功等级: 天山六阳掌
(第六重)
内力值: 535/535
Physics benchmarks of String theory: Anomaly
2) after QCD
after QCD, string theory lost its candidacy as theory of strong
interactions (It might still be actually theory of strong interaction ). On
the other hand, it has massless spin-2 states. therefore, it could be
a theory for gravity.
A very small group of people still worked on it, noticeably John
Schwarz.
3) reduction to low energy theory
In order to apply string theory to the results of our low energy
experiments, we will have to focus on its low energy degrees of
freedom. We can do that by following the standard procedure of
effective Lagrangian. Actually, if we just work out the zero mass
modes of the theory, the leading terms in the Lagrangian are largely
determined by the symmetries.
However, for a while, string theory does not seem to make sense for
such a reduction.
From string theory point of view, the theory appear to be
fine. However, if one look at the low energy degrees of freedom,
there seems to be anomalies for the symmetries of the string theory.
At least for that time, the anomaly problem seems to be the most
serious physics obstacle that string theory has. It is not clear
whether string theory is just fundamentally imcompatible with field
theory.
John Schwarz and Michael Green realized that there is some subtle
terms missed by the simple reduction and inclusion of those terms cure
the anomaly problem. At least psychologically, this is one of the most
important break throughs in string theory. String theory passed the
first test of possibly being a useful theory for physics.
| 发表时间：2005-09-22, 09:07:59 |
 作者资料
|
walk_f