Brane Fluctuation and New Counting Rules for Kaluza-Klein Towers

Abstract

In models with extra dimensions, branes have been usually treated as solid bodies though they are prohibited by the relativity. In the previous letter, we proposed a method of taking account of brane fluctuation by introducing Nambu-Goldstone bosons, and prove that when a tension of the brane is small, the interaction between boundary fields and Kaluza-Klein modes is suppressed exponentially. In this letter, we further investigate this suppression in more generic configuration, and obtain three counting rules, ``AND'', ``OR'' and ``STACK'' rules, depending on the softness of branes and the character of fields on the branes four dimensions. The choice determines the number of Kaluza-Klein towers contributing to renormalization group equations, leading to a remarkable change in the running behavior of coupling constants.