One of the strongest constraints on the existence of large, compact, "gravi
ty-only" dimensions comes from SN1987a. If the rate of energy loss into the
se putative extra dimensions is too high, then the neutrino pulse from the
supernova will differ from that actually seen. The dominant mechanism for t
he production of Kaluza-Klein gravitons and dilatons in the supernova is vi
a gravistrahlung and dilastrahlung from the nucleon-nucleon system. In this
payer we compute the rates For these processes in a model-independent way
using low-energy theorems which relate the emissivities to the measured nuc
leon-nucleon cross section. This is possible because for soft gravitons and
dilatons the leading contribution to the energy-loss rate is from graphs i
n which the gravitational radiation is produced from external nucleon legs.
Previous calculations neglected these mechanisms. We re-evaluate the bound
s on toroidally-compactified "gravity-only" dimensions, and find that consi
stency with the observed SN1987a neutrino signal requires that if there are
two such dimensions then their radius must be less than 1 micron. (C) 2001
Elsevier Science B.V. All rights reserved.