Some Multi-Quark Potentials, Pseudo-Potentials and AdS/QCD

The static three-quark potential and pseudo-potential of a pure SU(3) gauge theory are studied in a five-dimensional framework known as AdS/QCD. The results support the Y-ansatz for the baryonic area law. A comparison with the quark-antiquark calculations shows the universality of the string tension as well as the spatial string tension. We also discuss extensions to SU(N) gauge theories.Comment: 18 pages, 7 figures; v2: a few sentences added and typos correcte

Two-photon correlations as a sign of sharp transition in quark-gluon plasma

The photon production arising due to time variation of the medium has been considered. The Hamilton formalism for photons in time-variable medium (plasma) has been developed with application to inclusive photon production. The results have been used for calculation of the photon production in the course of transition from quark-gluon phase to hadronic phase in relativistic heavy ion collisions. The relative strength of the effect as well as specific two- photon correlations have been evaluated. It has been demonstrated that the opposite side two-photon correlations are indicative of the sharp transition from the quark-gluon phase to hadrons.Comment: 23 pages, 2 figure

Spin nematic phases in models of correlated electron systems: a numerical study

Strongly interacting systems are known to often spontaneously develop exotic ground states under certain conditions. For instance, spin nematic phases have been discovered in various magnetic models. Such phases, which break spin symmetry but have no net local magnetization, have also been proposed by Nersesyan et al. (J. Phys.: Cond. Matt. 3, 3353 (1991)) in the context of electronic models. We introduce a N-flavor microscopic model that interpolates from the large-N limit, where mean-field is valid and such a nematic phase occurs, to the more realistic N=1 case. By using a sign-free quantum Monte-Carlo, we show the existence of a spin nematic phase (analogous to a spin flux phase) for finite N; when N decreases, quantum fluctuations increase and this phase ultimately disappears in favor of an s-wave superconducting state. We also show that this nematic phase extends up to a finite critical charge doping. Dynamical studies allow us to clarify the Fermi surface property: in the nematic phase at half-filling, it consists of 4 points and the low-energy structure has a Dirac cone-like shape. Under doping, we observe clear signatures of Fermi pockets around these points. This is one of the few examples where numerical simulations show how quantum fluctuations can destroy a large-N phase.Comment: 9 pages, 19 figures. Problem with figures has been fixe

Microwave stabilization of edge transport and zero-resistance states

Edge channels play a crucial role for electron transport in two dimensional electron gas under magnetic field. It is usually thought that ballistic transport along edges occurs only in the quantum regime with low filling factors. We show that a microwave field can stabilize edge trajectories even in the semiclassical regime leading to a vanishing longitudinal resistance. This mechanism gives a clear physical interpretation for observed zero-resistance states

Heavy-Quark Potentials and AdS/QCD

We give an example of modeling phenomenological heavy-quark potentials in a five-dimensional framework nowadays known as AdS/QCD. In particular we emphasize the absence of infrared renormalons.Comment: 10 pages, 3 figures; v3: some corrections, to appear in PR

Non-dissipative drag of superflow in a two-component Bose gas

A microscopic theory of a non-dissipative drag in a two-component superfluid Bose gas is developed. The expression for the drag current in the system with the components of different atomic masses, densities and scattering lengths is derived. It is shown that the drag current is proportional to the square root of the gas parameter. The temperature dependence of the drag current is studied and it is shown that at temperature of order or smaller than the interaction energy the temperature reduction of the drag current is rather small. A possible way of measuring the drag factor is proposed. A toroidal system with the drag component confined in two half-ring wells separated by two Josephson barriers is considered. Under certain condition such a system can be treated as a Bose-Einstein counterpart of the Josephson charge qubit in an external magnetic field. It is shown that the measurement of the difference of number of atoms in two wells under a controlled evolution of the state of the qubit allows to determine the drag factor.Comment: 13 pages, 3 figures. This preprint is extended and substantially revised variant of related preprint cond-mat/040456

Relaxation of superflow in a network: an application to the dislocation model of supersolidity of helium crystals

We have considered the dislocation network model for the supersolid state in He-4 crystals. In difference with uniform 2D and 3D systems, the temperature of superfluid transition T_c in the network is much smaller than the degeneracy temperature T_d. It is shown that a crossover into a quasi superfluid state occurs in the temperature interval between T_c and T_d. Below the crossover temperature the time of decay of the flow increases exponentially under decrease of the temperature. The crossover has a continuous character and the crossover temperature does not depend on the density of dislocations.Comment: Corrected typo