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gallerdude 3 months ago

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atYevP 3 months ago

Yev from Backblaze here -> That’s right! For better or worse they usually tell it like they see it, and that helps us inform decisions!

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2018.05.14 Monday ACHK

Problem 14.4b1.3

Closed string degeneracies | A First Course in String Theory


(b) State the values of \alpha' M^2 and give the separate degeneracies of bosons and fermions for the first five mass levels of the type IIA closed superstrings. Would the answer have the different for type IIB?


— This answer is my guess. —

Since for NS, the first 5 levels’ degeneracies are 8, 36, 128, 402, 1152, the degeneracies of (NS, NS) are 8^2, 36^2, 128^2, 402^2, 1152^2.

This is incorrect, for there are no (NS, NS) states. Instead, you should consider (NS+, NS+).


Since for NS+, the first 5 levels’ degeneracies are 8, 128, 1152, 7680, 42112, the degeneracies of (NS+, NS+) are 8^2, 128^2, 1152^2, 7680^2, 42112^2.

p.317 Consider the relationship of the degeneracy of R+ and that of R-:


How about the first 5 levels of R+?

The degeneracies are the same as those of R-.

p.317 Equation (14.54) “The appearance of an equal number of bosonic and fermionic states at every mass level is a signal of supersymmetry. This is, however, supersymmetry on the world-sheet.”

Equation (14.71):

f_{R-}(x) = 8 + 128 x + 1152 x^{2} + 7680 x^{3} + 42112 x^{4} + ...

p.321 “Indeed, the integer mass-squared levels in the NS generating function (14.67) have degeneracies that match those of (14.71) for the R- sector.”

— This answer is my guess. —

— Me@2018-05-14 02:51:55 PM



2018.05.14 Monday (c) All rights reserved by ACHK