- #51
mitchell porter
Gold Member
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Here is a paper claiming http://arxiv.org/abs/1106.4804" . What they mean are compactifications which have the "minimal supersymmetric standard model" as a low-energy limit. The MSSM in turn has the standard model as a low-energy limit. However, this is the MSSM and SM without particular parameter values. That is, the SM has those two dozen parameters like particle masses, coupling constants, and mixing matrices; and the MSSM, when SUSY-breaking potential is considered, has over 100. The theory, at a certain level of abstaction, is defined by equations in which all those parameters are just unspecified constants. So then you could say that the version of the SM which applies to the real world is the one with all the measured values for those parameters.martinbn said:
Roughly speaking, a stringy standard model is one which reduces to the 'abstract' SM or MSSM at low energies. There isn't any model which is known to give the right values for all the various parameters, though in some cases there are arguments that the parameters in the model will have the right order of magnitude or the right hierarchy of ratios. The situation is like this because such parameters are typically very hard to calculate (i.e. in many cases we just don't know how to do so). String phenomenology proceeds through the discovery of new classes of string model which might match reality (e.g. the industry, beginning a few years ago, in "F-theory GUTs"), and with incremental improvement to the calculability and qualitative phenomenological viability of known classes of models. The paper that I linked above is state of the art in heterotic phenomenology, the oldest type of superstring phenomenology (dating back to 1985).
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