  String theory avoids the ultraviolet infinities that arise in trying to
quantize gravity. It is also more predictive than conventional quantum field
theory, one aspect of this being the way that it contributed to the emergence
of the concept of ``supersymmetry'' of particle interactions. There are hints
from the successes of supersymmetric unified theories of particle interactions
that supersymmetry is relevant to elementary particles at energies close to
current accelerator energies; if this is so, it will be confirmed
experimentally and supersymmetry is then also likely to be important in
cosmology, in connection with dark matter, baryogenesis, and/or inflation.
Magnetic monopoles play an important role in the structure of string theory,
and thus should certainly exist, if string theory is correct, though they may
have been diluted by inflation to an unobservable level. The monopole mass in
many attractive models is near the Planck mass, but, if unification of
elementary particle forces with gravity occurs near TeV energies through large
or warped extra dimensions, as in some recent models, then monopoles should be
below 100 TeV and in an astrophysical context would be ultrarelativistic. In
such models, supersymmetry would definitely be expected at TeV energies.
