String mass shifts Original Research Article

We study closed string one-loop amplitudes in string theory, in particular the average mass shift for states at given mass and Neveu–Schwarz charges. Our analysis is based only on well-defined string amplitudes and the exploitation of symmetries and unitarity properties of the torus amplitudes. We obtain the result image in D space–time dimensions for the average closed string mas-shift (image for states with non-zero Neveu–Schwarz charges Q). An interesting picture of one-loop corrections for the string in non-supersymmetric configurations comes out: the dominant interactions responsible for these corrections are of long-range type (namely, gravitational) and it appears that perturbations theory is generally reliable on the spectrum of massive string states.