Confining Gauge Theories Research Articles

Holographic confining gauge theory and response to the electric field

We study the response of confining gauge theory to the external electric field by using holographic Yang-Mills theories in the large $N_c$ limit. Although the theories are in the confinement phase, we find a transition from the insulator to the conductor phase when the electric field exceeds its critical value. Then, the baryon number current is generated in the conductor phase. At the same time, in this phase, the meson melting is observed through the quasi-normal modes of meson spectrum. Possible ideas are given for the string state corresponding to the melted mesons, and they lead to the idea that the source of this current may be identified with the quarks and anti-quarks supplied by the melted mesons. We also discuss about other possible carriers. Furthermore, from the analysis of the massless quark, chiral symmetry restoration is observed at the insulator-conductor transition point by studying a confining theory in which the chiral symmetry is broken.

Accelerated strings and Unruh effect in holographic confining gauge theory

Accelerated strings and Unruh effect in holographic confining gauge theory

Holographic technicolor models and their S-parameter

We study the Peskin-Takeuchi S-parameter of holographic technicolor models. We present the recipe for computing the parameter in a generalized holographic setup. We then apply it to several holographic models that include: (a) the Sakai-Sugimoto model and (b) its non-compactified cousin, (c) a non-critical analog of (a) based on near extremal AdS6 background, (d) the KMMW model which is similar to model (a) but with D6 and anti-D6 flavor branes replacing the D8 and anti-D8 branes, (e) a model based on D5 branes compactified on two S1s with D7 and anti-D7 probe branes and (f) the conifold model with the same probe branes as in (e). The models are gravity duals of gauge theories with SU(NTC) gauge theory and with a breakdown of a flavor symmetry U(NTF) × U(NTF) → UV(NTF). The models (a), (c),(d) and (e) are duals of a confining gauge theories whereas (b) and (f) associate with non confining models. The S-parameter was found to be S=sNTC where s is given by 0.017λTC, 0.016λTC, 0.095, 0.50 and 0.043 for the (a), (b), (c), (d), (f) models respectively and for model (e) s is divergent. These results are valid in the large NTC and large λTC limit. We further derive the dependence of the S-parameter on the ``string endpoint mass of the techniquarks for the various models. We compute the masses of the low lying vector technimesons.

5D dilaton–gravity and gluon plasma thermodynamics

I will describe black–hole solutions in five–dimensional gravity with a self–interacting scalar field. The geometry is asymptotically logarithmically anti–de Sitter in the UV. A phase transition occurs if an only if the IR behavior of the dilaton potential is associated to a confining gauge theory. The transition is holographically dual to the confining/deconfining phase transition of a 4d theory closely matching pure Yang–Mills, both at zero and finite temperature. The trace anomaly equation is reproduced in the gravity picture, as a check of the duality.

The AdS/QCD correspondence: still undelivered

We consider the particle spectrum and event shapes in large N gauge theories in different regimes of the short-distance 't Hooft coupling, lambda. The mesons in the small lambda limit should have a Regge spectrum in order to agree with perturbation theory, while generically the large lambda theories with gravity duals produce spectra reminiscent of KK modes. We argue that these KK-like states are qualitatively different from QCD modes: they are deeply bound states which are sensitive to short distance interactions rather than the flux tube-like states expected in asymptotically free, confining gauge theories. In addition, we also find that the characteristic event shapes for the large lambda theories with gravity duals are close to spherical, very different from QCD-like (small lambda, small N) and Nambu-Goto-like (small lambda, large N) theories which have jets. This observation is in agreement with the conjecture of Strassler on event shapes in large 't Hooft coupling theories, which was recently proved by Hofman and Maldacena for the conformal case. This conclusion does not change even when considering soft-wall backgrounds in the gravity dual. The picture that emerges is the following: theories with small and large lambda are qualitatively different, while theories with small and large N are qualitatively similar. Thus it seems that it is the relative smallness of the 't Hooft coupling in QCD that prevents a reliable AdS/QCD correspondence from emerging, and that reproducing characteristic QCD-like behavior will require genuine stringy dynamics to be incorporated into any putative dual theory.

Baryonium in confining gauge theories

We show a new class of embedding solutions of D5 brane, which wraps on $S^5$ in the AdS${}_5\times S^5$ space-time and contains fundamental strings as U(1) flux to form a baryon vertex. The new solution given here is different from the baryon vertex since it consists of two same side (north or south) poles of $S^5$ as cusps, which are put on different points in our three dimensional space. This implies that the same magnitude of electric displacement exists at each cusp, but their orientations are opposite due to the flux number conservation. This configuration is therefore regarded as a D5-$\bar{D5}$ bound state, and we propose this as the vertex of a baryonium state, which is made of a baryon and an anti-baryon. By attaching quarks and anti-quarks to the two cusps of this vertex, it is possible to construct a realistic baryonium.

Thermal Hadron Spectrum ine+e−Annihilation From Gauge-String Duality

We compute the inclusive spectrum of produced particles in e;{+}e;{-} annihilation in confining gauge theories that have a gravity dual and show that the momentum distribution exhibits thermal behavior.

Deconfinement and Thermodynamics in Improved Holographic QCD

The glueball spectrum and thermodynamics of 5D dilaton gravity duals to confining gauge theories is explored. We show that they exhibit a first order Hawking-Page type phase transition. For the transition temperature, we find T c = 280 MeV. The temperature dependence of various thermodynamic quantities such as the pressure, entropy and speed of sound is calculated. The results are in agreement with the corresponding lattice data.

Deconfinement and Gluon Plasma Dynamics in Improved Holographic QCD

The thermodynamics of 5D dilaton gravity duals to confining gauge theories is analyzed. We show that they exhibit a first order Hawking-Page type phase transition. In the explicit background of improved holographic QCD of [U. Gursoy and E. Kiritsis, J. High Energy Phys. 02 (2008) 03210.1088/1126-6708/2008/02/032] [U. Gursoy, E. Kiritsis, and F. Nitti, J. High Energy Phys. 02 (2008) 01910.1088/1126-6708/2008/02/019], we find T_{c}=235 MeV. The temperature dependence of various thermodynamic quantities such as the pressure, entropy, and speed of sound is calculated. The results are in agreement with the corresponding lattice data.

ELECTROWEAK SYMMETRY BREAKING AND COLD DARK MATTER FROM HIDDEN SECTOR TECHNICOLORS

We consider models with a vectorlike confining gauge theory in the hidden sector, and demonstrate that the origin of the electroweak symmetry breaking (EWSB) is due to the dimensional transmutation in the hidden sector gauge theory, and the lightest mesons in the hidden sector could be a good cold dark matter (CDM) candidate. There would be more than one neutral Higgs-like scalar bosons, and they could decay mainly into the CDM pair, if that decay channel is kinemtically allowed.

Topological entanglement entropy and holography

We study the entanglement entropy in confining theories with gravity duals using the holographic prescription of Ryu and Takayanagi. The entanglement entropy between a region and its complement is proportional to the minimal area of a bulk hypersurface ending on their border. We consider a disk in 2+1 dimensions and a ball in 3+1 dimensions and find in both cases two types of bulk hypersurfaces with different topology, similar to the case of the slab geometry considered by Klebanov, Kutasov and Murugan. Depending on the value of the radius, one or the other type of hypersurfaces dominates the calculation of entanglement entropy. In 2+1 dimensions a useful measure of topological order of the ground state is the topological entanglement entropy, which is defined to be the constant term in the entanglement entropy of a disk in the limit of large radius. We compute this quantity and find that it vanishes for confining gauge theory, in accord with our expectations. In 3+1 dimensions the analogous quantity is shown to be generically nonzero and cutoff-dependent.

Numerical study of entanglement entropy in [formula omitted] lattice gauge theory

The entropy of entanglement between a three-dimensional slab of thickness l and its complement is studied numerically for four-dimensional S U ( 2 ) lattice gauge theory. We find a signature of a nonanalytic behavior of the entanglement entropy, which was predicted recently for large N c confining gauge theories in the framework of AdS/CFT correspondence. The derivative of the entanglement entropy over l is likely to have a discontinuity at some l = l c . It is argued that such behavior persists even at finite temperatures, probably turning into a sort of crossover for temperatures larger than the temperature of the deconfinement phase transition. We also confirm that the entanglement entropy contains quadratically divergent l-independent term, and that the nondivergent terms behave as l −2 at small distances.

The Hagedorn temperature and open QCD-string tachyons in pure [formula omitted] super-Yang–Mills

We consider large-N confining gauge theories with a Hagedorn density of states. In such theories the potential between a pair of colour-singlet sources may diverge at a critical distance rc=1/TH. We consider, in particular, pure N=1 super-Yang–Mills theory and argue that when a domain wall and an anti-domain wall are brought to a distance near rc the interaction potential is better described by an “open QCD-string channel”. We interpret the divergence of the potential in terms of a tachyonic mode and relate its mass to the Hagedorn temperature. Finally we relate our result to a theorem of Kutasov and Seiberg and argue that the presence of an open string tachyonic mode in the annulus amplitude implies an exponential density of states in the UV of the closed string channel.

Rho meson condensation at finite isospin chemical potential in a holographic model for QCD

We analyze the effect of an isospin chemical potential μI in the Sakai-Sugimoto model, which is the string dual of a confining gauge theory related to large Nc QCD, at temperatures below the chiral symmetry restoration temperature. For small chemical potentials we show that the results agree with expectations from the low-energy chiral Lagrangian, and the charged pion condenses. When the chemical potential reaches a critical value μI = μcrit ≃ 1.7mρ, the lowest vector meson (the ``rho meson'') becomes massless, and it condenses (in addition to the pion condensate) for μI > μcrit. This spontaneously breaks the rotational symmetry, as well as a residual U(1) flavor symmetry. We numerically construct the resulting new ground state for μI > μcrit.

Geometric transitions and D-term SUSY breaking

We propose a new way of using geometric transitions to study metastable vacua in string theory and certain confining gauge theories. The gauge theories in question are N = 2 supersymmetric theories deformed to N = 1 by superpotential terms. We first geometrically engineer supersymmetry-breaking vacua by wrapping D5 branes on rigid 2-cycles in non-compact Calabi–Yau geometries, such that the central charges of the branes are misaligned. In a limit of slightly misaligned charges, this has a gauge theory description, where supersymmetry is broken by Fayet–Iliopoulos D-terms. Geometric transitions relate these configurations to dual Calabi–Yaus with fluxes, where H RR , H NS and dJ are all non-vanishing. We argue that the dual geometry can be effectively used to study the resulting non-supersymmetric, confining vacua.

Glueballs vs. gluinoballs: Fluctuation spectra in non-AdS/non-CFT

Building on earlier results on holographic bulk dynamics in confining gauge theories, we compute the spin-0 and spin-2 spectra of the Maldacena–Nuñez and Klebanov–Strassler theories, that have non-singular supergravity duals. We construct and apply a numerical recipe for computing mass spectra from certain determinants. In the Klebanov–Strassler case, the spectra of states containing the glueball and gluinoball are universal and quadratic in the supergravity approximation, i.e., their mass-squareds depend on consecutive number as m 2 ∼ n 2 for large n, with a universal proportionality constant. The hardwall approximation appears to work poorly when compared to the unique spectra we find in the full theory with a smooth cap-off in the infrared.

Chiral symmetry breaking as open string tachyon condensation

We consider a general framework to study holographically the dynamics of fundamental quarks in a confining gauge theory. Flavors are introduced by placing a set of (coincident) branes and antibranes on a background dual to a confining color theory. The spectrum contains an open string tachyon and its condensation describes the U ( N f ) L × U ( N f ) R → U ( N f ) V symmetry breaking. By studying worldvolume gauge transformations of the flavor brane action, we obtain the QCD global anomalies and an IR condition that allows to fix the quark condensate in terms of the quark mass. We find the expected N f 2 Goldstone bosons (for m q = 0 ), the Gell-Mann–Oakes–Renner relation (for m q small) and the η ′ mass. Remarkably, the linear confinement behavior for the masses of highly excited spin-1 mesons, m n 2 ∼ n is naturally reproduced.

A simple model of low-scale direct gauge mediation

We construct a calculable model of low-energy direct gauge mediation making use of the metastable supersymmetry breaking vacua recently discovered by Intriligator, Seiberg and Shih. The standard model gauge group is a subgroup of the global symmetries of the SUSY breaking sector and messengers play an essential role in dynamical SUSY breaking: they are composites of a confining gauge theory, and the holomorphic scalar messenger mass appears as a consequence of the confining dynamics. The SUSY breaking scale is around 100 TeV nevertheless the model is calculable. The minimal non-renormalizable coupling of the Higgs to the DSB sector leads in a simple way to a mu-term, while the B-term arises at two-loop order resulting in a moderately large tan beta. A novel feature of this class of models is that some particles from the dynamical SUSY breaking sector may be accessible at the LHC.

Heavy hadron spectra from spin chains and strings

We study the spectrum of hadronic states made up of very massive complex scalar fields in a confining gauge theory admitting a supergravity dual background. We show that for a sub-sector of operators dual to certain spinning strings, the mass spectrum exhibits an integrable structure equal to the Heisenberg spin chain, up to an overall factor. This result is compared with the corresponding string prediction.

The conformal anomaly of k-strings

Simple scaling properties of correlation functions of a confining gauge theory in d-dimensions lead to the conclusion that k-string dynamics is described, in the infrared limit, by a two-dimensional conformal field theory with conformal anomaly c=(d-2)T_k/T_1, where T_k is the k-string tension. This result applies to any gauge theory with stable k-strings. We check it in a 3D Z_4 gauge model at finite temperature, where a string effect directly related to c can be clearly identified.