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The no-ghost theorem for string theory in curved backgrounds with a flat timelike direction

Masako Asano·Makoto Natsuume
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Abstract

It is well-known that the standard no-ghost theorem can be extended straightforwardly to the general c=26 CFT on R^{d-1,1} \times K, where 2 \leq d \leq 26 and K is a compact unitary CFT of appropriate central charge. We prove the no-ghost theorem for d=1, i.e., when only the timelike direction is flat. This is done using the technique of Frenkel, Garland and Zuckerman.

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Masako Asano, Makoto Natsuume. 2000-07-19. The no-ghost theorem for string theory in curved backgrounds with a flat timelike direction. https://doi.org/10.1016/s0550-3213(00)00495-8

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