4 N ov 1 99 4 Preprint PNPI - 2010 , November 1994 . 2 d gravity stress tensor and the problem of the calculation of the multi - loop amplitudes in the string theory
نویسنده
چکیده
2d gravity stress tensor and the problem of the calculation of the multi-loop amplitudes in the string theory Abstract It is shown that the vacuum value of the 2d gravity stress tensor in the free field theory is singular in the fundamental region on the complex plane where the genus-n > 1 Riemann surface are mapped. Because of the above singularity, one can not construct modular invariant multi-loop amplitudes. The discussed singularity is due to the singularity in the vacuum value of the 2d gravity field that turns out to be on the genus-n > 1 Riemann surfaces.
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