  There is evidence that trans-Planckian physics does not affect the Hawking
radiation in four dimensions and, consequently, deviations from the linear
dispersion relation (for massless particles) at very high energies cannot be
revealed using four-dimensional black holes. We study this issue in the context
of models with extra spatial dimensions and show that small black holes that
could be produced in accelerators might also provide a chance of testing the
high energy regime where non-linear dispersion relations are generally
expected.
