NS-branes in 5d brane world models

Abstract

We study codimension-1 brane solutions of the 5d brane world models compactified on $S_1/{\mathbb{Z}}_2$. In string theoretical setup they suggest that the background branes located at orbifold fixed points should be NS-branes (in the five dimensional sense), rather than D-branes. Indeed, the existence of the background NS-branes is indispensable to obtain flat geometry $M_4\times S_1/{\mathbb{Z}}_2$ where $M_4$ represents the 4d Minkowski spacetime, and without these branes the 5d metric becomes singular everywhere. This result is very reminiscent of the $(p+3)$d effective string theory \cite{1} where the NS-NS type $p$-brane is indispensable to obtain a flat geometry $R_2$ or $R_2/{\mathbb{Z}}_n$ on the transverse dimensions. Without this NS-NS type $p$-brane the 2d transverse space becomes a pin-shaped singular space. The correspondence between these two theories leads us to a conjecture that the whole flat backgrounds of the string theory inherently invovle the NS-branes implicitly in their ansatz, and hence the true background $p$-branes immanent in our spacetime may be NS-branes, instead of D-branes. We argue that this result can have a significant consequence in the context of the cosmological constant problem.

Section 6 has been revised

References in corpus (4)

• Cosmological constant, brane tension and large hierarchy in a generalized Randall-Sundrum braneworld scenario
• A comment on $p$-branes of ($p+3$)$\mathrm{d}$ string theory
• A self-tuning mechanism in (3+p)d gravity-scalar theory
• D-brane orbiting NS5-branes

Cited by in corpus (5)

• Null fluid collapse in brane world models
• Remark on Calabi-Yau vacua of the string theory and the cosmological constant problem
• Proposed experimental test of Randall-Sundrum Models
• Inflation driven by single geometric tachyon with D-brane orbiting around NS5-branes
• Anisotropic evolution of 4-brane in a 6D generalized Randall-Sundrum model