A First Course in String Theory

What sector(s) can be combined with a left-moving NS- to form a consistent closed string sector?

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— This answer is my guess. —

**What is the meaning of “left-moving NS”?**

p.322 “Conventionally, the first input in is the left-moving sector and the second input is the right-moving sector.”

**What is the meaning of “+” in “NS+”?**

p.321 “… we truncate the NS sector to the set of states with . The resulting states comprise the so-called NS+ sector.”

“The NS+ sector contains the massless states and throw away the tachyonic states.”

**What is the meaning of “consistent” closed string sector?**

p.322 “… guarantees that the left and right sectors give identical contributions to the mass-squared:”

If NS+ is the left sector, the corresponding candidate right sectors are NS+, R+, R-.

in NS-sector, Equation (14.37):

in R-sector, Equation (14.53):

Equation (14.78):

NS+ equations of (14.38):

,

,

NS- equations of (14.38):

,

,

Mass levels of R+ and R- (Equations 14.54):

There are no mass levels in NS+, R+, or R- that can match those in NS-. So NS- can be paired only with NS-:

(NS-, NS-)

— This answer is my guess. —

— Me@2015-07-05 11:09:32 PM

2015.07.05 Sunday (c) All rights reserved by ACHK