Finite Density Effect in the Gross-Neveu Model in a Weakly Curved R1×S2R^1\times S^2 Spacetime

The three-dimensional Gross-Neveu model in $R^{1} \times S^{2}$ spacetime is considered at finite particles number density. We evaluate an effective potential of the composite scalar field $\sigma(x)$, which is expressed in terms of a scalar curvature $R$ and nonzero chemical potential $\mu$. We then derive the critical values of $(R,\mu)$ at which the system undergoes the first order phase transition from the phase with broken chiral invariance to the symmetric phase.Comment: RevTeX, minor changes, new references are adde

Dynamical symmetry breaking in the Nambu-Jona-Lasino model with external gravitational and constant electric fields

An investigation of the Nambu-Jona-Lasino model with external constant electric and weak gravitational fields is carried out in three- and four- dimensional spacetimes. The effective potential of the composite bifermionic fields is calculated keeping terms linear in the curvature, while the electric field effect is treated exactly by means of the proper- time formalism. A rich dynamical symmetry breaking pattern, accompanied by phase transitions which are ruled, independently, by both the curvature and the electric field strength is found. Numerical simulations of the transitions are presented.Comment: 20 pages, LaTeX, 6 .ps-figures, Final version published in "Classical and Quantum Gravity

Dynamical symmetry breaking in the external gravitational and constant magnetic fields

We investigate the effects of the external gravitational and constant magnetic fields to the dynamical symmetrybreaking. As simple models of the dynamical symmetry breaking we consider the Nambu-Jona-Lasinio (NJL) model and the supersymmetric Nambu-Jona-Lasinio (SUSY NJL) model non-minimally interacting with the external gravitational field and minimally interacting with constant magnetic field. The explicit expressions for the scalar and spinor Green functions are found up to the linear terms on the spacetime curvature and exactly for a constant magnetic field. We obtain the effective potential of the above models from the Green functions in the magnetic field in curved spacetime. Calculating the effective potential numerically with the varying curvature and/or magnetic fields we show the effects of the external gravitational and magnetic fields to the phase structure of the theories. In particular, increase of the curvature in the spontaneously broken chiral symmetry phase due to the fixed magnetic field makes this phase to be less broken. On the same time strong magnetic field quickly induces chiral symmetry breaking even at the presence of fixed gravitational field within nonbroken phase.Comment: 23 pages, Latex, epic.sty and eepic.sty are use

Overview of the BlockNormal Event Trigger Generator

In the search for unmodeled gravitational wave bursts, there are a variety of methods that have been proposed to generate candidate events from time series data. Block Normal is a method of identifying candidate events by searching for places in the data stream where the characteristic statistics of the data change. These change-points divide the data into blocks in which the characteristics of the block are stationary. Blocks in which these characteristics are inconsistent with the long term characteristic statistics are marked as Event-Triggers which can then be investigated by a more computationally demanding multi-detector analysis.Comment: GWDAW-8 proceedings, 6 pages, 2 figure

Mesons and diquarks in neutral color superconducting quark matter with β\beta-equilibrium

The spectrum of meson and diquark excitations in cold color-superconducting (2SC) quark matter is investigated under local color and electric neutrality constraints with $\beta$-equilibrium. A 2-flavored Nambu--Jona-Lasinio type model including a baryon $\mu_B$, color $\mu_8$, and electric $\mu_Q$ chemical potentials is used. Two relations between coupling constants $H$ and $G$ in the diquark- and quark-antiquark channels, correspondingly, are treated, $H=3G/4$ and $H=G$. At $H=3G/4$ the gapless- and at $H=G$ the gapped neutral color superconductivity is realized. It is shown that color and electrical neutrality together with $\beta$-equilibrium lead to a strong mass splitting within the pion isotriplet in the 2SC phase (both gapped and gapless), in contrast with non--neutral matter. It is also shown that the properties of the physical $SU(2)_c$-singlet diquark excitation in the 2SC ground state varies for different parameterization schemes. Thus, for $H=3G/4$ one finds a heavy resonance with mass $\sim$ 1100 MeV in the non--neutral (gapped) case, whereas, if neutrality is imposed, a stable diquark with mass $\sim\mu_Q\sim$ 200 MeV appears in the gapless 2SC phase. For $H=G$, there is again a resonance (with the mass $\sim$ 300 MeV) in the neutral gapped 2SC phase. Hence, the existence of the stable massive SU(2)$_c$-singlet diquark excitation is a new peculiarity of the gapless 2SC.Comment: 18 pages, 9 figures; version accepted for publication in PR

Mesons and diquarks in the color neutral 2SC phase of dense cold quark matter

The spectrum of meson and diquark excitations of dense color neutral cold quark matter is investigated in the framework of a 2-flavored Nambu--Jona-Lasinio type model, including a quark $\mu$- and color $\mu_8$ chemical potential. It was found out that in the color superconducting (2SC) phase, i.e. at $\mu>\mu_c=342$ MeV, $\mu_8$ aquires rather small values $\sim$ 10 MeV in order to ensure the color neutrality. In this phase the $\pi$- and $\sigma$ meson masses are evaluated around $\sim$ 330 MeV. The spectrum of scalar diquarks in the color neutral 2SC phase consists of a heavy ($\rm SU_c(2)$-singlet) resonance with mass $\sim$ 1100 MeV, four light diquarks with mass $3|\mu_8|$, and one Nambu --Goldstone boson which is in accordance with the Goldstone theorem. Moreover, in the 2SC phase there are five light stable particles as well as a heavy resonance in the spectrum of pseudo-scalar diquarks. In the color symmetric phase, i.e. for $\mu <\mu_c$, a mass splitting of scalar diquarks and antidiquarks is shown to arise if $\mu\ne 0$, contrary to the case of $\mu = 0$, where the masses of scalar antidiquarks and diquarks are degenerate at the value $\sim$~700 MeV. If the coupling strength in the pseudo-scalar diquark channel is the same as in the scalar diquark one (as for QCD-inspired NJL models), then in the color symmetric phase pseudo-scalar diquarks are not allowed to exist as stable particles.Comment: 18 pages, 4 figures; version accepted for the publication in PR

Universal Holographic Chiral Dynamics in an External Magnetic Field

In this work we further extend the investigation of holographic gauge theories in external magnetic fields, continuing earlier work. We study the phenomenon of magnetic catalysis of mass generation in 1+3 and 1+2 dimensions, using D3/D7- and D3/D5-brane systems, respectively. We obtain the low energy effective actions of the corresponding pseudo Goldstone bosons and study their dispersion relations. The D3/D7 system exhibits the usual Gell-Mann--Oakes--Renner (GMOR) relation and a relativistic dispersion relation, while the D3/D5 system exhibits a quadratic non-relativistic dispersion relation and a modified linear GMOR relation. The low energy effective action of the D3/D5 system is related to that describing magnon excitations in a ferromagnet. We also study properties of general Dp/Dq systems in an external magnetic field and verify the universality of the magnetic catalysis of dynamical symmetry breaking.Comment: 41 pages, 11 figures, references adde

Hot Defect Superconformal Field Theory in an External Magnetic Field

In this paper we investigate the influence of an external magnetic field on a flavoured holographic gauge theory dual to the D3/D5 intersection at finite temperature. Our study shows that the external magnetic field has a freezing effect on the confinement/ deconfinement phase transition. We construct the corresponding phase diagram. We investigate some thermodynamic quantities of the theory. A study of the entropy reveals enhanced relative jump of the entropy at the "chiral" phase transition. A study of the magnetization shows that both the confined and deconfined phases exhibit diamagnetic response. The diamagnetic response in the deconfined phase has a stronger temperature dependence reflecting the temperature dependence of the conductivity. We study the meson spectrum of the theory and analyze the stability of the different phases looking at both normal and quasi-normal semi-classical excitations. For the symmetry breaking phase we analyze the corresponding pseudo-Goldstone modes and prove that they satisfy non-relativistic dispersion relation.Comment: 42 pages, 14 figure

Quark and pion condensation in a chromomagnetic background field

The general features of quark and pion condensation in dense quark matter with flavor asymmetry have been considered at finite temperature in the presence of a chromomagnetic background field modelling the gluon condensate. In particular, pion condensation in the case of a constant abelian chromomagnetic field and zero temperature has been studied both analytically and numerically. Under the influence of the chromomagnetic background field the effective potential of the system is found to have a global minimum for a finite pion condensate even for small values of the effective quark coupling constant. In the strong field limit, an effective dimensional reduction has been found to take place.Comment: 17 pages, 6 figure

Chromomagnetic Catalysis of Color Superconductivity in a (2+1)-dimensional NJL Model

The influence of a constant uniform external chromomagnetic field $H$ on the formation of color superconductivity has been investigated. The consideration was performed in the framework of a (2+1)-dimensional Nambu--Jona-Lasinio model with two different four-fermionic structures responsible for $$and diquark$$ condensates. In particular, it was shown that there exists a critical value $H_c$ of the external chromomagnetic field such that at $H>H_c$ a nonvanishing diquark condensate is dynamically created (the so-called chromomagnetic catalysis effect of color superconductivity). Moreover, external chromomagnetic fields may in some cases enhance the diquark condensate of color superconductivity.Comment: 32 pages, 2 figures, revte