Gravitational consequences of confined fields in braneworlds

In the braneworld scenario, matter fields are usually assumed to be confined to branes in a higher dimensional spacetime, with a stress energy tensor that is sharply peaked on the brane. A field theoretic way to achieve this is by coupling a bulk field to a topological defect which makes up the brane. We point out that in contrast to fermion fields, the stress energy tensor of a confined scalar field contains a term that is of the form of the second derivative of a sharply peaked function. This produces large metric perturbations on the brane. However, the resulting gravitational effect is equivalent to a local self-interaction term, and may be negated by artificially inserting an opposite self-interaction for the underlying theory. We comment on the possible generalization to other bosonic fields as well as the potential observability.