We consider one model of black hole radiation in which the equation of motion of a matter field is modified to cut off high frequency modes. The spectrum in the model has already been analytically derived in the low frequency range, which has resulted in the Planckian distribution of the Hawking temperature. On the other hand, it has been numerically shown that its spectrum deviates from the thermal one in the high frequency range. In this paper, we analytically derive the form of the deviation in the high frequency range. Our result can qualitatively explain the nature of the numerically calculated spectrum. The origin of the deviation is clarified by a simple discussion.

• Received 11 May 1999

DOI:https://doi.org/10.1103/PhysRevD.61.084023