String entropy and black hole entropy

wam_mi

Hi there,

I have recently read that by varying the string coupling adiabatically (hence the mass of the black hole as well), there is a transition going from a black hole to a single highly excited string. I would like to ask a few questions, and they are:

(i) What does it actually mean when we say we vary the string coupling adiabatically? Why is this an isentropic process?

(ii) What are the differences for black hole transition in the case of (a) extremal black holes, and (b) near-extremal black holes? Does the black hole evolve to a collection of free strings or one highly excited strings?

(iii) Why are strings the only object that remain to have finite energy in a compactified spatial dimension? Why couldn't we use other objects (say a membrane) to get involved in compactification?

(iv) I tried to look for related journals and review papers online (arxiv.org) but I couldn't find the derivation of the identification between string entropy and black hole entropy. Could anyone tell me where to find this derivation?


Thanks a lot!

Demystifier

(i) Here, by definition, adiabatically means - without changing entropy. This also answers your second question.

(ii) Black hole eventually evolves to a state with higher entropy, which turns out to be one highly excited string.

(iii) Are we still talking about black holes?

(iv) Check out
http://lanl.arxiv.org/abs/gr-qc/9704072
See also the book by Susskind and Lindsey: An introduction to black holes, information, and the string theory revolution

wam_mi

Hi Demystifier,

Thank you for your reply. Yes, I am still talking about black holes. So why are strings the only object that remain to have finite energy in a compactified spatial dimension? Why couldn't we use other objects (say a membrane) to get involved in compactification?

Thanks a lot!!

P.S. May I ask you if you are the author of "String Theory Demystifier"? If so, thank you for sharing your thoughts on this challenging topic! Many thanks!!

Demystifier

I'm not the author of that (good) book.
(But I am the author of
http://xxx.lanl.gov/abs/quant-ph/0609163
if you are interested in it.)

Anyway, I think the answer to your question (iii) has something to do with the fact that we assume the low coupling limit. But perhaps somebody else can make a better answer, because I'm not very good in branes.