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We investigate brane in
ation driven by two stacks of mobile branes in a throat. The stack closest to the
bottom of the throat annihilates first with anti-branes, resulting in particle production and a change of the
equation of state parameter w. We calculate analytically some observable signatures of the collision; related
decays are common in multi-eld in
ation, providing the motivation for this case study. The discontinuity in
w enters the matching conditions relating perturbations in the remaining degree of freedom before and after
the collision, aecting the power-spectrum of curvature perturbations. We nd an oscillatory modulation of
the power spectrum for scales within the horizon at the time of the collision, and a slightly redder spectrum
on super-horizon scales. We comment on implications for staggered infation.
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