  It has recently been shown that the thermodynamics of a FRW universe can be
fully derived using the generalized uncertainty principle (GUP) in extra
dimensions as a primary input. There is a phenomenologically close relation
between the GUP and Modified Dispersion Relations (MDR). However, the form of
the MDR in theories with extra dimensions is as yet not known. The purpose of
this letter is to derive the MDR in extra dimensional scenarios. To achieve
this goal, we focus our attention on the thermodynamics of a FRW universe
within a proposed MDR in an extra dimensional model universe. We then compare
our results with the well-known results for the thermodynamics of a FRW
universe in an extra dimensional GUP setup. The result shows that the entropy
functionals calculated in these two approaches are the same, pointing to a
possible conclusion that these approaches are equivalent. In this way, we
derive the MDR form in a model universe with extra dimensions that would have
interesting implications on the construction of the ultimate quantum gravity
scenario.
