Having to move much more quickly now, Huggett briefly goes over how ST implies General Relativity, first in empty space and then adding in some matter. Question 6: What is the significance of these results?
Huggett claims that one possible answer is: String theory is actually background independent.
Assume (i) that ST is an adequate TOE, in sense that the string spectrum includes quanta for all the background fields you like; and (ii) that the terms in the action accurately capture the effective behavior of those coherent states. Then by (i) the G_mu_nu field is composed of stringy excitations, and by (ii) it satises the Einstein Field Equations (making it the gravitational field, and the excitations gravitons). In other words, in the most literal sense the general relativistic theory of spacetime is a low energy effective theory of strings.
Which ought to get philosophers excited!
No time for questions 😦
2 thoughts on “Live blogging: Huggett”
The results are that to low order in perturbation theory, conformal symmetry of string theory requires that background fields satisfy the Einstein Field Equations. For example, if you replace the Minkowski metric in the action with a general metric – so it is the only background field – then it must be Ricci flat. Vistarini’s talk went into more detail, and also addressed the issue of why quantized string theory should be conformally symmetric (as I noted above, the classical action just is). But if background fields just represent the effect of coherent states – so the quantum theory is just an expansion about a coherent state – then we have learned something very important about the collective behaviour of string quanta describing gravitons.
Thanks Carl – great job!
Dear reader – my paper will soon be available on the website.