1,721,108 research outputs found
Superconducting properties of vacuum in strong magnetic field
Full text linkInternational audienceWe discuss superconducting phases of vacuum induced by strong magnetic field in the electroweak model and in Quantum Chromodynamics (QCD) at zero temperature. In these phases, the vacuum behaves as an anisotropic inhomogeneous superconductor which supports superconductivity along the axis of the magnetic field while in the transversal directions, the superconductivity does not exist. The magnetic-field-induced anisotropic superconductivity appears as a result of condensation of electrically charged spin-one particles, which are elementary W bosons in the case of the electroweak model and composite quark-antiquark pairs with quantum numbers of ρ -mesons in the case of QCD. Due to the anisotropic nature of superconductivity, the Meissner effect is absent. Intrinsic inhomogeneities of the superconducting ground state are characterized by ensembles of certain topological vortices in an analogy with a mixed Abrikosov state of a type-II superconductivit
QCD string breaking in strong magnetic field
No full text10 pages, 2 figuresInternational audienceAt sufficiently large separation between a quark and an antiquark the QCD string breaks into parts due to creation of light quark-antiquark pairs. We show that a background magnetic field affects the breaking of the QCD string oriented in the transverse directions with respect to the axis of the magnetic field. Using semiclassical approach we argue that above certain the background magnetic field the breaking of the transverse string should become energetically unfavorable
Vacuum superconductivity, conventional superconductivity and Schwinger pair production
No full text15 pages, 6 figures, 6 tables; plenary talk at Quantum Field Theory Under the Influence of External Conditions 2011 (QFEXT11), Benasque, Spain, September 18-24, 2011International audienceIn a background of a very strong magnetic field a quantum vacuum may turn into a new phase characterized by anisotropic electromagnetic superconductivity. The phase transition should take place at a critical magnetic field of the hadronic strength (B_c \approx 10^{16} Tesla or eB_c \approx 0.6 GeV^2). The transition occurs due to an interplay between electromagnetic and strong interactions: virtual quark-antiquark pairs popup from the vacuum and create -- due to the presence of the intense magnetic field -- electrically charged and electrically neutral spin-one condensates with quantum numbers of \rho mesons. The ground state of the new phase is a complicated honeycomblike superposition of superconductor and superfluid vortex lattices surrounded by overlapping charged and neutral condensates. In this talk we discuss similarities and differences between the superconducting state of vacuum and conventional superconductivity, and between the magnetic-field-induced vacuum superconductivity and electric-field-induced Schwinger pair production
Rotating Casimir systems: magnetic-field-enhanced perpetual motion, possible realization in doped nanotubes, and laws of thermodynamics
Full text link18 pages, 10 figures, 1 tableInternational audienceRecently, we have demonstrated that for a certain class of Casimir-type systems ("devices") the energy of zero-point vacuum fluctuations reaches its global minimum when the device rotates about a certain axis rather than remains static. This rotational vacuum effect may lead to the emergence of permanently rotating objects provided the negative rotational energy of zero-point fluctuations cancels the positive rotational energy of the device itself. In this paper, we show that for massless electrically charged particles the rotational vacuum effect should be drastically (astronomically) enhanced in the presence of a magnetic field. As an illustration, we show that in a background of experimentally available magnetic fields the zero-point energy of massless excitations in rotating torus-shaped doped carbon nanotubes may indeed overwhelm the classical energy of rotation for certain angular frequencies so that the permanently rotating state is energetically favored. The suggested "zero-point-driven" devices--which have no internally moving parts--correspond to a perpetuum mobile of a new, fourth kind: They do not produce any work despite the fact that their equilibrium (ground) state corresponds to a permanent rotation even in the presence of an external environment. We show that our proposal is consistent with the laws of thermodynamics
Comment on "Charged vector mesons in a strong magnetic field"
Full text link4 pages, 4 figuresInternational audienceIn 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
Vafa-Witten theorem, vector meson condensates and magnetic-field-induced electromagnetic superconductivity of vacuum
Full text link2 pagesInternational audienceWe 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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Negative moment of inertia of large- gluons on a ring
No full textInternational audienceWe study SU() Yang-Mills theory in dimensions at finite temperature on a spatial ring that rotates uniformly in a plane. We show that the effect of rotation results only in a simple kinematic enhancement of the gauge coupling , which becomes rescaled by a Lorentz factor corresponding to the tangential rotational velocity of the ring. Using well-established analytic results in Yang-Mills theory in the 't Hooft limit of an infinite number of colors, we demonstrate that the moment of inertia of the large- gluon plasma on the ring is negative. This counterintuitive conclusion is, however, in agreement with recent first-principle numerical simulations of hot dimensional SU(3) Yang-Mills theory that also reported a negative moment of inertia for gluon plasma in an experimentally relevant window of temperatures above the deconfinement transition. Furthermore, we argue that our picture provides a qualitative explanation for three other intriguing features observed in lattice simulations of vortical QCD: the emergence of a spatially inhomogeneous mixed phase, the inconsistency of its spatial structure with a standard picture dictated by the Tolman-Ehrenfest law, and the enhancement of the critical deconfining temperature by rotation
QCD Vacuum as Dual Superconductor: Quark Confinement and Topology
No full textInternational audienceQuantum chromodynamics exhibits two important nonperturbative phenomena: color confinement and chiral symmetry breaking. These dynamical vacuum effects determine the crucial features of the hadronic phase, such as mass gap generation and the absence of colored asymptotic physical states. Unfortunately, despite their fundamental importance for our understanding of nature, neither of these phenomena can be derived analytically, starting from QCD Lagrangian. There are, however, phenomenological models that allow us to understand the nonperturbative features of the QCD vacuum and put them together into a coherent picture. In this chapter, we discuss one of the most successful phenomenological approaches to QCD based on a representation of the gluonic vacuum as a dual superconductor. First, we review Abelian gauge models pos- sessing monopole condensation, which supports the formation of confining string and leads to mass gap generation. Then, we discuss how one can incorporate a similar mechanism in QCD, including the identification of monopole-like gluon configurations in the context of the topology of the color gauge group. Also, we describe the numerical results of first-principle simulations demonstrating that the QCD vacuum exhibits monopole condensation, which supports its dual superconducting properties and leads to the formation of the confining chromoelectric string. Furthermore, the numerical simulations show, somewhat unexpectedly, that the monopole condensate produces the chiral condensate and thus generates the dynamical breaking of the chiral symmetry. Thus, the dual superconductor mechanism describes the essential features of the QCD vacuum related to its confining and chiral features
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