Posted:

**Aug 03, 2010 7:02 pm**Just a rough idea would be good - I'm still struggling to get an idea how LQG works at the moment so no time to read about strings, but any little insights would be useful and probably of interest to lots of people.

I know there are many variants of string/brane/M theory, but I was just trying to understand how vibration modes of a string could possibly give rise to the multiplicity of particles we see. I had a look at this and it contains the statement

This is what I don't get - particles have all sorts of properties - mass, charge, hypercharge, isospin.... Where do these come from in the sting picture ? Normally particles are described in terms of gauge theories, with the fermions described in terms of representations of the gauge group and the force carrying bosons as connections in bundles built from the gauge group. But, where does the gauge group fit in in string theory ? Spacetime has lots of dimensions, some of which are compactified - is the gauge group somewhere in this compactification or what ?

I know there are many variants of string/brane/M theory, but I was just trying to understand how vibration modes of a string could possibly give rise to the multiplicity of particles we see. I had a look at this and it contains the statement

The frequency of the string determines what type of particle it is.

This is what I don't get - particles have all sorts of properties - mass, charge, hypercharge, isospin.... Where do these come from in the sting picture ? Normally particles are described in terms of gauge theories, with the fermions described in terms of representations of the gauge group and the force carrying bosons as connections in bundles built from the gauge group. But, where does the gauge group fit in in string theory ? Spacetime has lots of dimensions, some of which are compactified - is the gauge group somewhere in this compactification or what ?