Probe D7 Research Articles

Holographic quantum liquids in 1+1 dimensions

In this paper we initiate the study of holographic quantum liquids in 1+1 dimensions. Since the Landau Fermi liquid theory breaks down in 1+1 dimensions, it is of interest to see what holographic methods have to say about similar models. For theories with a gapless branch, the Luttinger conjecture states that there is an effective description of the physics in terms of a Luttinger liquid which is specified by two parameters. The theory we consider is the defect CFT arising due to a probe D3 brane in the AdS Schwarzschild planar black hole background. We turn on a fundamental string density on the worldvolume. Unlike higher dimensional defects, a persistent dissipationless zero sound mode is found. The thermodynamic aspects of these models are considered carefully and certain subtleties with boundary terms are explained which are unique to 1+1 dimensions. Spectral functions of bosonic and fermionic fluctuations are also considered and quasinormal modes are analysed. A prescription is given to compute spectral functions when there is mixing due to the worldvolume gauge field. We comment on the Luttinger conjecture in the light of our findings.

Holographic dual of QCD from black D5 branes

We study the dynamics of probe D7 flavor probe branes in the background of near extremal D5 branes. This model is a holographic dual to a gauge theory with spontaneous breaking of a U(Nf)L × U(Nf)R chiral symmetry. The spectrum of two such D7 embeddings, contains a single massive 4D meson coming from the world volume U(1) gauge field, the pion, and a single massive 4D scalar meson coming from fluctuations of the embedding of the brane. In addition, there are continuum five dimensional states due to the finite height of the effective potential in the radial direction. We investigate baryons in this model, and find that the size is stabilized due to the Chern-Simons term in the D7 world volume action. The model admits a Hagedorn temperature of 1/2πR where R is the radius parameter in the D5 branes metric. We investigate the pattern of chiral symmetry breaking in the deconfined phase as a function of the asymptotic separation of the branes L. We find that for πR/3 < L 1.068R that chiral symmetry is restored, and that chiral symmetry is broken for L outside this window. We further argue that the solutions with L < π/3 are only classically stable, and in fact no D7 embedding exists with these boundary conditions.

D3/D7 HOLOGRAPHIC GAUGE THEORY AND CHEMICAL POTENTIAL

N = 2 supersymmetric Yang-Mills theory with flavor hypermultiplets at finite temperature is studied for finite quark number density (nb) by a dual supergravity background with nontrivial dilaton and axion. The quarks and their number density nb are introduced by embeddings a probe D7 brane. We find a critical value of the chemical potential at the limit of nb = 0, and it coincides with the effective quark mass for nb = 0. At this point, a transition of the D7 embedding configurations occurs between their two typical ones. The phase diagrams of this transition are shown in the plane of chemical potential versus temperature for Yang-Mills theory at finite temperature. In this phase transition, the order parameter is considered as nb. This result seems to be reasonable since this theory is in the quark deconfiment phase.

D3/D7 holographic gauge theory and chemical potential

N=2 supersymmetric Yang-Mills theory with flavor hypermultiplets at finite temperature and in the dS{sub 4} space is studied for finite quark number density (n{sub b}) by a dual supergravity background with nontrivial dilaton and axion. The quarks and their number density n{sub b} are introduced by embedding a probe D7 brane. We find a critical value of the chemical potential at the limit of n{sub b}=0, and it coincides with the effective quark mass given in each theory for n{sub b}=0. At this point, a transition of the D7 embedding configurations occurs between their two typical ones. The phase diagrams of this transition are shown in the plane of chemical potential versus temperature and cosmological constant for Yang-Mills theory at finite temperature and in dS{sub 4}, respectively. In this phase transition, the order parameter is considered as n{sub b}. This result seems to be reasonable since both theories are in the quark deconfinement phase.

Cycling in the throat

We analyse the dynamics of a probe D3-(anti-)brane propagating in a warped string compactification, making use of the Dirac-Born-Infeld action approximation. We also examine the time dependent expansion of such moving branes from the ``mirage cosmology'' perspective, where cosmology is induced by the brane motion in the background spacetime. A range of physically interesting backgrounds are considered: AdS5, Klebanov-Tseytlin and Klebanov-Strassler. Our focus is on exploring what new phenomenology is obtained from giving the brane angular momentum in the extra dimensions. We find that in general, angular momentum creates a centrifugal barrier, causing bouncing cosmologies. More unexpected, and more interesting, is the existence of bound orbits, corresponding to cyclic universes.

Gauge theory in de Sitter space-time from a holographic model

Yang-Mills (YM) theory with flavor quarks in the ${\mathrm{dS}}_{4}$ is studied through the dual supergravity in the ${\mathrm{AdS}}_{5}\ifmmode\times\else\texttimes\fi{}{S}^{5}$ background with nontrivial dilaton and axion. The flavor quarks are introduced by embedding a probe D7 brane. We find that the dynamical properties of YM theory in the ${\mathrm{dS}}_{4}$ are similar to the case of the finite temperature theory given by the 5d AdS-Schwarzschild background. In the case of ${\mathrm{dS}}_{4}$, however, contrary to the finite temperature case, the gauge-field condensate plays an important role on the dynamical properties of quarks. We also give the quark-antiquark potential and meson spectra to find possible quark-bound states. We arrive at the conclusion that, while the quarks are not confined in the ${\mathrm{dS}}_{4}$, we could find stable meson states at very small cosmological constant as expected in the present universe. However, there would be no hadrons at early universe as in the inflation era.

Bulk fields inAdS5from probe D7 branes

We relate bulk fields in Randall-Sundrum AdS_5 phenomenological models to the world-volume fields of probe D7 branes in the Klebanov-Witten background of type IIB string theory. The string constructions are described by AdS_5 X T^{1,1} in their near-horizon geometry, with T^{1,1} a 5d compact internal manifold that yields N=1 supersymmetry in the dual 4d gauge theory. The effective 5d Lagrangian description derived from the explicit string construction leads to additional features that are not usually encountered in phenomenological model building.

Holographic renormalization of probe D-branes in AdS/CFT

We perform holographic renormalization for probe branes in AdS_5 x S^5. We show that for four known probe D-branes wrapping an AdS_m x S^n, the counterterms needed to render the action finite are identical to those for the free, massive scalar in AdS_m plus counterterms for the renormalization of the volume of AdS_m. The four cases we consider are the probe D7, two different probe D5's and a probe D3. In the D7 case there are scheme-dependent finite counterterms that can be fixed by supersymmetry.

Chiral dynamics from AdS space

We study the low energy dynamics of pions in a gravity dual of chiral symmetry breaking. The string theory construction consists of a probe D7 brane in the Constable Myers non-supersymmetric background, which has been shown to describe chiral symmetry breaking in the pattern of QCD. We expand the D7 brane's Dirac Born Infeld action for fluctuations that correspond to the Goldstone mode and show that they take the form of a non-linear chiral lagrangian. We numerically compute the quark condensate, pion decay constant and higher order Gasser Leutwyler coefficients. We find their form is consistent with naive dimensional analysis estimates. We also explore the gauging of the quark's chiral symmetries and the vector meson spectrum.