Mesons from global Anti-de Sitter space

TL;DR

This paper investigates meson spectra in a gauge/gravity duality setting with probe branes in global AdS space, revealing phase transitions and matching supergravity with free field theory results at zero quark mass.

Contribution

It provides a detailed analysis of meson spectra from probe branes in global AdS, including numerical and analytical results, and confirms the physical interpretation of meson stability.

Findings

Meson spectra exhibit a phase transition as a function of quark mass.

Analytical spectra at zero quark mass match free field theory results.

Higher meson levels are equidistant and related to operator scaling dimensions.

Abstract

In the context of gauge/gravity duality, we study both probe D7-- and probe D5--branes in global Anti-de Sitter space. The dual field theory is N=4 theory on R x S^3 with added flavour. The branes undergo a geometrical phase transition in this geometry as function of the bare quark mass m_q in units of 1/R with R the S^3 radius. The meson spectra are obtained from fluctuations of the brane probes. First, we study them numerically for finite quark mass through the phase transition. Moreover, at zero quark mass we calculate the meson spectra analytically both in supergravity and in free field theory on R x S^3 and find that the results match: For the chiral primaries, the lowest level is given by the zero point energy or by the scaling dimension of the operator corresponding to the fluctuations, respectively. The higher levels are equidistant. Similar results apply to the descendents. Our results confirm the physical interpretation that the mesons cannot pair-produce any further when their zero-point energy exceeds their binding energy.