Vafa-Witten theorem, vector meson condensates and magnetic-field-induced electromagnetic superconductivity of vacuum

We show that the electromagnetic superconductivity of vacuum in strong magnetic field background is consistent with the Vafa-Witten theorem because the charged vector meson condensates lock relevant internal global symmetries of QCD with the electromagnetic gauge group.Comment: 2 page

Permanently rotating devices: extracting rotation from quantum vacuum fluctuations?

We propose a set of devices of simple geometrical design which may exhibit a permanent rotation due to quantum (vacuum) fluctuations. These objects - which have no moving parts - impose certain boundary conditions on quantum fluctuations thus affecting their vacuum energy similarly to the standard Casimir effect. The boundary conditions are chosen in such a way that the vacuum energy for a static device is larger compared to the energy of the vacuum fluctuations in a state when the device rotates about a certain axis. The optimal frequency of rotation is determined by geometry and moment of inertia of the device. We illustrate our ideas in a vacuum of a massless scalar field theory using simplest Dirichlet-type boundary conditions. We also propose an experimental setup to verify the existence of the rotational vacuum effect.Comment: 5 pages, 8 figures; comments are welcom

Gluodynamics in External Field: A Test of the Dual Superconductor Picture

We study gluodynamics in an external Abelian electromagnetic field within the dual superconductor approach. We show that the SU(2) gluodynamics should possess a deconfining phase transition at zero temperature at certain value of the external field. A dual superconductor model for the SU(3) gauge theory in external field predicts a rich phase structure containing confinement, asymmetric confinement and deconfinement phases. These results can be used to check the validity of the dual superconductor description of gluodynamics in external fields. We also discuss the gauge-independence of the obtained results.Comment: Talk given at ``Confinement 2003'', RIKEN, Wako, Japan, July 21-24, 2003; 5 pages, 1 figure, uses ws-procs9x6.cl

Comment on "Charged vector mesons in a strong magnetic field"

In a recent paper Y. Hidaka and A. Yamamoto [Phys. Rev. D 87 (2013) 094502] claim -- using both analytical and numerical approaches -- that the charged rho mesons cannot condense in the vacuum subjected to a strong magnetic field. In this Comment we point out that both analytical and numerical results of this paper are consistent with the inhomogeneous rho-meson condensation. Furthermore, we show that the numerical results of the paper support the presence of the expected (in quenched lattice QCD) crossover transition driven by the rho-meson condensation. Finally, we stress that the inhomogeneous rho-meson condensation is consistent with both Vafa-Witten and Elitzur theorems.Comment: 4 pages, 4 figure

Can nothing be a superconductor and a superfluid?

A superconductor is a material that conducts electric current with no resistance. Superconductivity and magnetism are known to be antagonistic phenomena: superconductors expel weak external magnetic field (the Meissner effect) while a sufficiently strong magnetic field, in general, destroys superconductivity. In a seemingly contradictory statement, we show that a very strong magnetic field can turn an empty space into a superconductor. The external magnetic field required for this effect should be about 10^{16} Tesla (eB ~ 1 GeV^2). The physical mechanism of the exotic vacuum superconductivity is as follows: in strong magnetic field the dynamics of virtual quarks and antiquarks is effectively one-dimensional because these electrically charged particles tend to move along the lines of the magnetic field. In one spatial dimension a gluon-mediated attraction between a quark and an antiquark of different flavors inevitably leads to formation of a colorless spin-triplet bound state (a vector analogue of the Cooper pair) with quantum numbers of an electrically charged rho meson. Such quark-antiquark pairs condense to form an anisotropic inhomogeneous superconducting state similar to the Abrikosov vortex lattice in a type-II superconductor. The onset of the superconductivity of the charged rho mesons should also induce an inhomogeneous superfluidity of the neutral rho mesons. The vacuum superconductivity should survive at very high temperatures of typical Quantum Chromodynamics (QCD) scale of 10^{12} K (T ~ 100 MeV). We propose the phase diagram of QCD in the plane "magnetic field - temperature".Comment: 10 pages, 5 figures, contribution to the proceedings of the workshop "The many faces of QCD", 2-5 November 2010, Gent, Belgiu

Anomalous Transport Due to the Conformal Anomaly

We show that the scale (conformal) anomaly in field theories leads to new anomalous transport effects that emerge in an external electromagnetic field in an inhomogeneous gravitational background. In inflating geometry the QED scale anomaly locally generates an electric current that flows in opposite direction with respect to background electric field (the scale electric effect). In a static spatially inhomogeneous gravitational background the dissipationless electric current flows transversely both to the magnetic field axis and to the gradient of the inhomogeneity (the scale magnetic effect). The anomalous currents are proportional to the beta function of the theory.Comment: 6 pages, 2 figures; v2: clarifying remarks added, relation to the Schwinger effect in de Sitter space discussed, published versio

Free magnetized knots of parity-violating deconfined matter in heavy-ion collisions

We show that the local parity violation in the quark-gluon plasma supports existence of free (meta)stable knots of deconfined hot quark matter stabilized by superstrong magnetic fields. The magnetic field in the knots resembles the spheromak plasma state of the magnetic confinement approach to nuclear fusion. The size of the knot is quantized, being inversely proportional to the chiral conductivity of the quark-gluon plasma. The parity symmetry is broken inside the knot. Particles produced in the decays of the knots have unusual azimuthal distribution and specific flavor content. We argue that these knots may be created in noncentral heavy-ion collisions.Comment: 7 pages, 5 figures, RevTeX 4.

Background magnetic field stabilizes QCD string against breaking

The confinement of quarks in hadrons occurs due to formation of QCD string. At large separation between the quarks the QCD string breaks into pieces due to light quark-antiquark pair creation. We argue that there exist a critical background magnetic field e B ~ 16 m_\pi^2, above which the string breaking is impossible in the transverse directions with respect to the axis of the magnetic field. Thus, at strong enough magnetic field a new, asymmetrically confining phase may form. The effect - which can potentially be tested at LHC/ALICE experiment - leads to abundance of u-quark rich hadrons and to excess of radially excited mesons in the noncentral heavy-ion collisions compared to the central ones.Comment: 4 pages, 2 figures, uses RevTeX 4.