Phase Moduli Space of Supertubes
Dongsu Bak, Yoshifumi Hyakutake, Nobuyoshi Ohta
TL;DR
The paper analyzes the phase-space landscape of 1/4-BPS supertubes with fixed D0 and F1 charges and angular momentum. Using the D2-DBI action, it derives the BPS conditions and conserved charges, identifying when deformations preserve supersymmetry and charges. It shows that circular cross-sections with uniform flux have no nontrivial flat directions, while general-shaped tubes admit continuous flat deformations when $J< Q_0 Q_1$, establishing a phase moduli space and isoperimetric bounds on cross-section length. These results illuminate how cross-sectional area changes contribute to the energy and suggest links between microstate counting, phase-space volume, and horizon properties of extremal or near-extremal black supertubes.
Abstract
We study possible deformations of BPS supertubes keeping their conserved charges fixed. We show that there is no flat direction to closed supertubes of circular cross section with uniform electric and magnetic fields, and also to open planar supertubes. We also find that there are continuously infinite flat deformations to supertubes of general shape under certain conditions.