Gauge Fields and Scalars in Rolling Tachyon Backgrounds
We investigate the dynamics of gauge and scalar fields on
unstable D-branes with rolling tachyons. Assuming an FRW
metric on the brane, we find a solution of the tachyon
equation of motion which is valid for arbitrary tachyon
potentials and scale factors. The equations of motion for a
U(1) gauge field and a scalar field in this background are
derived. These fields see an effective metric which differs
from the original FRW metric. The field equations receive
large corrections due to the curvature of the effective
metric as well as the time variation of the gauge coupling.
The equations of state for these fields resemble those of
nonrelativistic matter rather than massless particles.
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