Closed strings from decaying D-branes

TL;DR

This paper analyzes the emission of closed strings during the decay of unstable D-branes, revealing divergence issues for low-dimensional branes and proposing a cutoff for the D0 brane case to obtain finite energy states.

Contribution

It provides a detailed calculation of closed string radiation from decaying D-branes and relates the resulting states to D-instantons, highlighting divergence behaviors based on brane dimensionality.

Findings

Infinite radiated energy for p ≤ 2 branes at leading order.

Finite radiated energy for p > 2 branes.

A cutoff can produce finite energy states for D0 branes.

Abstract

We compute the emission of closed string radiation from homogeneous rolling tachyons. For an unstable decaying D$p$-brane the radiated energy is infinite to leading order for $p\leq 2$ and finite for $p>2$. The closed string state produced by a decaying brane is closely related to the state produced by D-instantons at a critical Euclidean distance from $t=0$. In the case of a D0 brane one can cutoff this divergence so that we get a finite energy final state which would be the state that the brane decays into.