Recombination of Intersecting D-branes by Local Tachyon Condensation

TL;DR

The paper addresses how recombination of intersecting D-branes can be described in a low-energy setting and its relation to tachyon condensation and Sen's conjecture. It models the system with a 1+1D SU(2) super Yang-Mills background representing intersecting D-strings, identifies a localized off-diagonal tachyon with mass $m_0^2=-q$ (where $q=(1/(π α')) tan(θ/2)$) and shows its condensation produces the recombined brane profile $Y(x)=± π α' sqrt(q^2 x^2 + C^2 e^{- q x^2})$, geometrizing open-string tachyon condensation. In the large angle regime, a brane-antibrane tachyon action reproduces the same localization and spectrum, providing a bridge to string field theory descriptions and supporting Sen's conjecture. The dynamical aspect is explored by computing the throat-formation decay width between non-parallel branes, showing the decay probability decreases as the angle approaches π, with potential implications for tachyon-driven cosmological scenarios.

Abstract

We provide a simple low energy description of recombination of intersecting D-branes using super Yang-Mills theory. The recombination is realized by condensation of an off-diagonal tachyonic fluctuation localized at the intersecting point. The recombination process is equivalent to brane-antibrane annihilation, thus our result confirms Sen's conjecture on tachyon condensation, although we work in the super Yang-Mills theory whose energy scale is much lower than alpha'. We also discuss the decay width of non-parallelly separated D-branes.

Figures (5)

• Figure 1: Two D-strings are intersecting with each other at an angle $\theta$. The wavy line depicts a fundamental string connecting the D-strings. The worldvolumes are parametrized by the horizontal direction $x$ while its displacement from the $x$ axis is given by the transverse Higgs field $Y(x)$.
• Figure 2: Intersecting D-strings are recombined. Here we draw the configuration (2.18) with parameters $q=\tan (\theta / 2)=0.1$ and $C=\sqrt{q}/4$ (with $\pi \alpha' = 1$).
• Figure 3: For large $C$, physically unacceptable recombination is provided by (2.18). Here we have chosen the same value of $q$ as in the previous figure but with $C=2\sqrt{q} > \sqrt{q}$. This exceeds the validity of the approximation and thus prohibited. Before the configuration reaches this form, the nonlinear effect of fluctuations becomes important.
• Figure 4: D-string recombination with $\theta \sim \pi$. By rotating these figures by $\pi/2$, one can see the brane-antibrane annihilation occurring around the origin.
• Figure 5: Intersecting branes are separated.