Gyrating Strings: A new instability of black strings?

TL;DR

This paper proposes a new thermodynamic instability in near-extremal spinning D1-D5-P black strings, where excess angular momentum causes the string to become a rotating helical coil, challenging existing conjectures about black string stability.

Contribution

It introduces a novel instability mechanism involving gyration and orbital angular momentum transfer, providing a counter-example to the Gubser-Mitra conjecture.

Findings

Instability occurs when angular momentum exceeds a critical value.

String transitions into a rotating helical coil configuration.

Arguments extend to D-brane bound states in string theory.

Abstract

A thermodynamic argument is presented suggesting that near-extremal spinning D1-D5-P black strings become unstable when their angular momentum exceeds $J_{crit} = {3Q_1Q_5}/2\sqrt{2}$. In contrast, the dimensionally reduced black holes are thermodynamically stable. The proposed instability involves a phase in which the spin angular momentum above $J_{crit}$ is transferred to gyration of the string in space; i.e., to orbital angular momentum of parts of the string about the mean location in space. Thus the string becomes a rotating helical coil. We note that an instability of this form would yield a counter-example to the Gubser-Mitra conjecture, which proposes a particular link between dynamic black string instabilities and the thermodynamics of black strings. There may also be other instabilities associated with radiation modes of various fields. Our arguments also apply to the D-brane bound states associated with these black strings in weakly coupled string theory.