810 research outputs found
Laminar Spirals in the Outer Stationary Cylinder Couette-Taylor System
We present numerical simulations to demonstrate the existence of laminar spiral flows between both finite and infinite length concentric cylinders and finite truncated cones where only the inner wall rotates. The velocities and pressure are calculated by a spectral element/Fourier method. Different gap ratios are investigated. Convergence of the numerical results is shown with reference to flows between infinite cylinders. The presence of top and bottom endplates results in vortex dislocations that are observed at the frontiers between the Ekman vortices present at each end and the spiral vortices
Superconductivity under pressure in the Dirac semimetal PdTe2
The Dirac semimetal PdTe was recently reported to be a type-I
superconductor (1.64 K, mT) with unusual
superconductivity of the surface sheath. We here report a high-pressure study,
GPa, of the superconducting phase diagram extracted from
ac-susceptibility and transport measurements on single crystalline samples.
shows a pronounced non-monotonous variation with a maximum 1.91 K around 0.91 GPa, followed by a gradual decrease to 1.27 K at 2.5 GPa.
The critical field of bulk superconductivity in the limit ,
, follows a similar trend and consequently the -curves
under pressure collapse on a single curve: .
Surface superconductivity is robust under pressure as demonstrated by the large
superconducting screening signal that persists for applied dc-fields . Surprisingly, for GPa the superconducting transition
temperature at the surface is larger than of the bulk. Therefore
surface superconductivity may possibly have a non-trivial nature and is
connected to the topological surface states detected by ARPES. We compare the
measured pressure variation of with recent results from band structure
calculations and discuss the importance of a Van Hove singularity.Comment: manuscript 9 pages with 8 figures + supplemental material 3 pages
with 6 figure
p-wave superconductivity in iron-based superconductors
The possibility of p-wave pairing in superconductors has been proposed more than five decades ago, but has not yet been convincingly demonstrated. One difficulty is that some p-wave states are thermodynamically indistinguishable from s-wave, while others are very similar to d-wave states. Here we studied the self-field critical current of NdFeAs(O,F) thin films in order to extract absolute values of the London penetration depth, the superconducting energy gap, and the relative jump in specific heat at the superconducting transition temperature, and find that all the deduced physical parameters strongly indicate that NdFeAs(O,F) is a bulk p-wave superconductor. Further investigation revealed that single atomic layer FeSe also shows p-wave pairing. In an attempt to generalize these findings, we re-examined the whole inventory of superfluid density measurements in iron-based superconductors and show quite generally that single-band weak-coupling p-wave superconductivity is exhibited in iron-based superconductors. © 2019, The Author(s).Japan Science and Technology Corporation, JST: JPMJCR18J4Government Council on Grants, Russian FederationJapan Society for the Promotion of Science, JSPS: 16H04646АААА-А18-118020190104-3The authors thank Prof. Jeffery L. Tallon (Victoria University of Wellington, New Zealand) and Prof. Christian Bernhard (University of Fribourg, Switzerland) for helpful discussions, and also for reading and commenting on the manuscript. EFT is grateful for financial support provided by the state assignment of Minobrnauki of Russia (theme “Pressure” No. АААА-А18-118020190104-3) and by Act 211 of the Government of the Russian Federation, contract No. 02.A03.21.0006. KI and HI acknowledge support by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (B) Grant Number 16H04646, as well as JST CREST Grant Number JPMJCR18J4. The Article Processing Charge for this publication was provided by Ural Federal University, Russia
Simulation study of the inhomogeneous Olami-Feder-Christensen model of earthquakes
Statistical properties of the inhomogeneous version of the
Olami-Feder-Christensen (OFC) model of earthquakes is investigated by numerical
simulations. The spatial inhomogeneity is assumed to be dynamical. Critical
features found in the original homogeneous OFC model, e.g., the
Gutenberg-Richter law and the Omori law are often weakened or suppressed in the
presence of inhomogeneity, whereas the characteristic features found in the
original homogeneous OFC model, e.g., the near-periodic recurrence of large
events and the asperity-like phenomena persist.Comment: Shortened from the first version. To appear in European Physical
Journal
Method to enlarge the hologram viewing window using a mirror module
A liquid crystal panel for a video projector is often used for holographic television. However, its pixel size and pixel number are not enough for practical holographic 3-D display. Therefore, a multipanel configuration is generally used to increase the viewing window and displayed image size, and many spatial light modulators should be used in them. We propose a novel method to increase the viewing window of a holographic display system. The proposed method, which is implemented by using a mirror module and 4-f lens set, is to reconfigure the beam shape reflected by a spatial light modulator. The equipment is applied to a holographic display system, which has only a single spatial light modulator; a hologram could be displayed in a wider viewing window by the equipment than that of the conventional method. By the proposed method, the resolution of the reconfigured spatial light modulator has double resolution in the horizontal direction. Inversely, the vertical resolution is decreased. Even if the vertical resolution is decreased, a viewer could get 3-D effect because humans get more 3-D information in the horizontal direction. We have experimented using a liquid crystal on silicon (LcOS), whose resolution is 4096×2160pixels. The reconfigured resolution by the mirror module is 8192×1080pixels. From the experiments, the horizontal viewing window is almost two times wider than that without the mirror module. As a result, the hologram can be observed binocularly. © 2009 Society of Photo-Optical Instrumentation Engineers
Interactions of a boson in the component theory
The amplitudes for boson-boson and fermion-boson interactions are calculated
in the second order of perturbation theory in the Lobachevsky space. An
essential ingredient of the used model is the Weinberg's component
formalism for describing a particle of spin , recently developed
substantially. The boson-boson amplitude is then compared with the two-fermion
amplitude obtained long ago by Skachkov on the ground of the hamiltonian
formulation of quantum field theory on the mass hyperboloid, , proposed by Kadyshevsky. The parametrization of the amplitudes by
means of the momentum transfer in the Lobachevsky space leads to same spin
structures in the expressions of matrices for the fermion and the boson
cases. However, certain differences are found. Possible physical applications
are discussed.Comment: REVTeX 3.0 file. 12pp. Substantially revised version of IFUNAM
preprints FT-93-24, FT-93-3
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