Torelli Group: Understanding the Non-Trivial Diffeomorphisms of String Theory

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SUMMARY

The discussion centers on the Torelli group in string theory, specifically as presented in the lectures by Luest and Theisen. The Torelli group corresponds to non-trivial diffeomorphisms that maintain the homology basis while allowing for twists around trivial cycles. The conversation highlights the complexity of the moduli space of genus g Riemann surfaces, noting that for genus g > 3, the calculations become significantly more intricate. The state of the art in computing superstring amplitudes is identified as g=3, with a suggestion to explore g=4 for potential qualitative differences.

PREREQUISITES
  • Understanding of string theory fundamentals
  • Familiarity with Riemann surfaces and their properties
  • Knowledge of diffeomorphisms and their implications in topology
  • Basic grasp of moduli spaces in mathematical physics
NEXT STEPS
  • Research the properties of the Torelli group in string theory
  • Study Dehn twists and their role in topology
  • Explore the moduli space of Riemann surfaces for genus g > 3
  • Investigate superstring amplitudes and their computation techniques
USEFUL FOR

This discussion is beneficial for theoretical physicists, mathematicians specializing in topology, and researchers focused on string theory and Riemann surfaces.

Darth Sidious
Hello,

While reading the lectures of Luest and Theisen on string
theory I encountered the Torelli group. They are very vague
about it (the discussion is at pages 118-119) but they say
that it correspond to twists arround trivial cycles so the
homology basis is unchanged but these transformations
are non-trivial diffeomorphisms nevertheless.

I searched the Web for some drawing describing these
twists but I couldn't find them. Would some kind soul
explain them to me? I *think* that they should be like the
Dehn twists but I'm not sure about that.

There's some other interesting piece of information in
Luest & Theisen about the moduli space of genus g Riemann
surfaces. It seems that this moduli space gets quite
complicated for genus g > 3. I think g=3 is the state
of the art in computing superstring amplitudes (I have no
idea about bosonic string amplitudes). I therefore think it's
necessary to go at least to g=4 to see if there's something
qualitatively different there.
 
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