1,721,087 research outputs found
Permanently rotating devices: extracting rotation from quantum vacuum fluctuations?
No full text5 pages, 8 figuresWe 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
On magnetic-field-induced dissipationless electric current in nanowires
No full text10 pages, 13 figuresWe propose a general design of a metallic double-nanowire structure which may support an equilibrium dissipationless electric current in the presence of magnetic field. The design consists of a compact wire element of a specific shape, which is periodically extended in one spatial dimension. Topologically, each wire element is equivalent to a ring, which supports a dissipationless current in the presence of magnetic flux similarly to the persistent electric current in a normal metal nanoring. Geometrically, each wire element breaks spatial inversion symmetry so that the equilibrium electric current through the device becomes nonzero. Fabrication of such wires is within the reach of current technology
Fractal thermodynamics and ninionic statistics of coherent rotational states: realization via imaginary angular rotation in imaginary time formalism
No full textInternational audienceWe suggest the existence of systems in which the statistics of a particle changes with the quantum level it occupies. The occupation numbers in thermal equilibrium depend on a continuous statistical parameter that interpolates between bosonic or fermionic and ghost-like statistical distributions. We call such particle states ``ninions'': they are different from anyons and can exist in 3+1 dimensions. We suggest that ninions can be associated with coherent angular momentum states. In the Euclidean imaginary-time formalism, the ninionic statistics can be implemented via the rotwisted boundary conditions, which are associated with the rigid global rotation of the system with an imaginary angular frequency. The imaginary rotation is characterized by a PT-symmetric non-Hermitian Hamiltonian and possesses a well-defined thermodynamic limit. The physics of ninions in thermal equilibrium is accessible for numerical simulations on Euclidean lattices. We provide a no-go theorem on the absence of analytical continuation between real and imaginary rotations in the thermodynamic limit. The ground state of ninions shares similarity with the -vacuum in QCD. The ninions can produce negative pressure and energy, similar to the Casimir effect and the cosmological dark energy. In the thermodynamic limit, the dependence of thermal energy of free ninions on the statistical parameter is a fractal
Inhomogeneous confining-deconfining phases in rotating plasmas
No full textInternational audienceWe discuss the effects of rotation on confining properties of gauge theories focusing on compact electrodynamics in two spatial dimensions as an analytically tractable model. We show that at finite temperature, the rotation leads to a deconfining transition starting from a certain distance from the rotation axis. A uniformly rotating confining system possesses, in addition to the usual confinement and deconfinement phases, a mixed inhomogeneous phase which hosts spatially separated confinement and deconfinement regions. The phase diagram thus has two different deconfining temperatures. The first deconfining temperature can be made arbitrarily low by sufficiently rapid rotation while the second deconfining temperature is largely unaffected by the rotation. Implications of our results for the phase diagram of QCD are presented. We point out that uniformly rotating quark-gluon plasma should therefore experience an inverse hadronization effect when the hadronization starts from the core of the rotating plasma rather than from its boundary
Free magnetized knots of parity-violating deconfined matter in heavy-ion collisions
No full text7 pages, 5 figures, RevTeX 4.1We 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
On magnetic-field-induced dissipationless electric current in nanowires
No full text10 pages, 13 figuresWe propose a general design of a metallic double-nanowire structure which may support an equilibrium dissipationless electric current in the presence of magnetic field. The design consists of a compact wire element of a specific shape, which is periodically extended in one spatial dimension. Topologically, each wire element is equivalent to a ring, which supports a dissipationless current in the presence of magnetic flux similarly to the persistent electric current in a normal metal nanoring. Geometrically, each wire element breaks spatial inversion symmetry so that the equilibrium electric current through the device becomes nonzero. Fabrication of such wires is within the reach of current technology
Acceleration as refrigeration: Acceleration-induced spontaneous symmetry breaking in thermal medium
No full textInternational audienceWe argue that a uniform acceleration of matter produces an effect similar to cooling, thus leading, in particular, to the enhancement effect of spontaneous symmetry breaking. This conclusion is supported by the observation by Unruh and Weiss that thermal correlation functions computed at a temperature equal to the Unruh temperature are identical to the corresponding correlation functions in a Minkowski (zero-temperature) vacuum. We consider an example of the Nambu-Jona-Lasinio model in a co-accelerating reference frame and show that the uniform acceleration of hot gas of interacting fermions enhances the mass gap generation and increases the critical temperature of the chiral transition. We derive a simple dependence of the critical temperature of a second-order phase transition on acceleration that, as we argue, should be applicable to a broad range of field theories
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
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
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