On theta dependence of glueballs from AdS/CFT

Gregory Gabadadze,Alberto Iglesias

doi:10.1016/j.physletb.2005.01.042

Abstract

We study the theta dependence of the glueball spectrum in a strongly coupled cousin of large N gluodynamics defined via the AdS/CFT correspondence. By explicitly diagonalizing the 10d gravity equations in the presence of the RR 3-form and 1-form fluxes we found a mixing pattern for the lowest-spin lightest glueballs. The mixing between the scalar and pseudoscalar states is not suppressed, suggesting that the CP-odd effects persist in the large N theory. As a consequence, the lightest mass eigenstate ceases to be a parity eigenstate. We found the former as a linear combination of a scalar and pseudoscalar glueballs. On the other hand, the mass eigenvalues in a theory with and without the theta term remain equal in the large N limit.

Highlights

Introduction and summaryQCD in the limit of a large number of colors, N → ∞, is expected to contain a great deal of information on confinement [1]
Large N gluodynamics with the theta term reveals a rich ground state structure with multiple vacua separated by domain walls [2, 3, 4, 5]
Certain remnants of the large N vacuum structure are expected to be present in real QCD too. Examples of this include the heavy nonperturbative states that make the domain walls [6], and new properties of axion and hadronic domain walls in a theory where the strong CP problem is solved by the axion mechanism

Summary

Introduction and summary

QCD in the limit of a large number of colors, N → ∞, is expected to contain a great deal of information on confinement [1]. The only effect of the theta term in the leading large N limit is that the lowest mass spin-zero state becomes a mixed state of 0++ and 0−+ glueballs. In order to study the theta dependence of glueballs from the Gauge/Gravity correspondence we consider the dual supergravity description of pure U(N) gauge field theory introduced in [16]. In this setup one starts with weakly coupled type IIA superstring theory in the presence of N D4-branes. This absence of backreaction on the geometry is due to the fact that in the large N limit the contribution from F(2) to (2) and (3) is subleading because the other terms contain extra powers of gs−1 ∼ N

Supergravity modes

Couplings to boundary theory