A manifestly gauge-invariant theory of gravitational fluctuations of brane-world scenarios is discussed. Without resorting to any specific gauge choice, a general method is presented in order to disentangle the fluctuations of the brane energy-momentum from the fluctuations of the metric. As an application of the formalism, the localization of metric fluctuations on scalar branes breaking spontaneously five-dimensional Poincar\'e invariance is addressed. Only assuming that the four-dimensional Planck mass is finite and that the geometry is regular, it is demonstrated that the vector and scalar fluctuations of the metric are not localized on the brane.
Categories: hep-th gr-qc hep-ph