Particle–antiparticle asymmetry from magnetogenesis through the Landau mechanism

Motivated by string theory an extension of the Landau problem to quantum field theory is considered. We show that the commutator between momenta of the fields violates Lorentz and CPT invariance leading to an alternative method of understanding the question of particle–antiparticle asymmetry. The presence of magnetic field at very early moments of the universe would then suggest that the particle–antiparticle asymmetry can be understood as a consequence of magnetogenesis.     

Motion of vortex lines and mutual friction in superfluid4He nearT λ

The motion of a single vortex line in superfluid⁴He nearT is studied within modelF. The linear response of the vortex-line velocityv _L to a homogeneous counterflowv _s –v _n is calculated up to lowest order of renormalized perturbation theory. The critical temperature dependence is taken into account via the renormalizationgroup theory. Non-asymptotic critical effects are found to be important. The results are generalized to describe collective vortex motion and mutual friction in rotating superfluid⁴He. The phenomenological mutual-friction coefficientsB andB of Hall and Vinen are determined without adjustment of parameters. ForB quantitative agreement with experiments nearT is found whereas forB the agreement is only semiquantiative.     

Vortex–shock and vortex–vortex interactions in the compressible starting jet from two beveled nozzle configurations

Journal of Visualization - An experiment was conducted to investigate the flow structures in the compressible starting jet from two beveled nozzles (45 $$^{\circ }$$ and 30 $$^{\circ }$$ nozzle...     

Tension–compression asymmetry and size effects in nanocrystalline Ni nanowires

We investigate size effects in nanocrystalline nickel nanowires using molecular dynamics and an EAM potential. Both compressive and tensile deformation tests were performed for nanowires with radii ranging from 5 to 18?nm and a grain size of 10?nm. The wires contained up to four million atoms and were tested using a strain rate of 3.33?×?10⁸?s^?1. The results are compared with similar tests for a periodic system, which models a bulk macroscopic sample size of the same nanocrystalline material. The importance of dislocation-mediated plasticity decreases as the wire diameter is decreased and is more relevant under compression than under tension. A significant tension–compression asymmetry was observed, which is strongly dependent on the wire size. For the bulk nanocrystalline samples and larger wire radii, the flow stresses are higher under compression than under tension. This effect decreases as the wire radius decreases and is reversed for the smallest wires tested. Our results can be explained by the interplay of nano-scale effects in the grain sizes and in the wire radii.     

CP violation and the matter–antimatter asymmetry of the Universe

In our everyday environment one observes only matter. Thatʼs quite a fortunate situation! Any sizeable presence of antimatter on Earth, from the enormous energy it would release through annihilation with matter, would prevent us talking about it! For the physicist this fact, at first sight obvious, is nevertheless a kind of surprise: antimatter, which is observed in cosmic rays, in radioactive decays of nuclei, which has been copiously produced and extensively studied in accelerators and which is nowadays currently used in hospitals, turns out to have pretty much the same properties as matter. Moreover, the fact that matter dominates appears to be a general property of our Universe: no evidence of large quantities of antimatter has been observed at any distance from us. Why would matter have taken the advantage on antimatter? In this short review we explain how, through a limited number of basic elements, one can find answers to this question. Matter and antimatter have, in fact, not exactly the same properties: from laboratory experiments CP conservation is known not to be a fundamental law of nature.     

Solid friction from stick–slip down to pinning and aging

We review the present state of understanding of solid friction at low velocities and for systems with negligibly small wear effects. We first analyze in detail the behavior of friction at interfaces between macroscopic hard rough solids, whose main dynamical features are well described by the Rice–Ruina rate and state-dependent constitutive law. We show that it results from two combined effects: (i) the threshold rheology of nanometer-thick junctions jammed under confinement into a soft glassy structure and (ii) the geometric aging, i.e. slow growth of the real area of contact via asperity creep interrupted by sliding. Closer analysis leads to identifying a second aging-rejuvenation process, at work within the junctions themselves. We compare the effects of structural aging at such multicontact, very highly confined, interfaces with those met under different confinement levels, namely boundary lubricated contacts and extended adhesive interfaces involving soft materials (hydrogels, elastomers). This leads us to propose a classification of frictional junctions in terms of the relative importance of jamming and adsorption-induced metastability.

Solid friction from stick–slip down to pinning and aging

All authors

Tristan Baumberger &; Christiane Caroli

https://doi.org/10.1080/00018730600732186

Published online:

28 November 2010

Table     

Supersymmetric Chern–Simons vortex systems and extended supersymmetric quantum mechanics algebras

We study N=2$N=2$ supersymmetric Chern–Simons Higgs models in (2+1)$(2+1)$-dimensions and the existence of extended underlying supersymmetric quantum mechanics algebras. Our findings indicate that the fermionic zero modes quantum system in conjunction with the system of zero modes corresponding to bosonic fluctuations, are related to an N=4$N=4$ extended 1-dimensional supersymmetric algebra with central charge, a result closely connected to the N=2$N=2$ spacetime supersymmetry of the total system. We also add soft supersymmetric terms to the fermionic sector in order to examine how this affects the index of the corresponding Dirac operator, with the latter characterizing the degeneracy of the solitonic solutions. In addition, we analyze the impact of the underlying supersymmetric quantum algebras to the zero mode bosonic fluctuations. This is relevant to the quantum theory of self-dual vortices and particularly for the symmetries of the metric of the space of vortices solutions and also for the non-zero mode states of bosonic fluctuations.     

Dynamics in mesoscopic superconducting rings: Multiple phase-slips and vortex–antivortex pairs

We investigate the situation where a mesoscopic 1D ring or 2D cylinder is subject to a magnetic field by simulating the time dependant Ginzburg–Landau equations with periodic boundary conditions. We investigate the different possible evolutions for the 1D phase slip phenomenon. The case of the multiple phase slips is analyzed in details and we study the competition between simultaneous and consecutive multiple phase slips analytically and numerically. In 2D we study the creation of vortex–antivortex pairs. Following the theory of the Kibble–Zurek mechanism, we quenched the sample by applying a strong current and observe vortex–antivortex pairs dynamics.     

Vortex definition and “vortex criteria”

正It is well known that the vorticityω=▽×u,where u is fluid velocity,has clear mathematic definition,but for viscous flow the definition of a vortex remains an open problem for long[1,2],which has now evolved to a big confusion     

Homological perspective on edge modes in linear Yang–Mills and Chern–Simons theory

Letters in Mathematical Physics - We provide an elegant homological construction of the extended phase space for linear Yang–Mills theory on an oriented and time-oriented Lorentzian manifold...     

Site–site potential function and second virial coefficients for linear molecules

The second virial coefficients for several linear molecules were calculated using the 2CLJ potential including the electrostatic and induction effects with modified mixing rules for unlike pairs. Least squares fits of experimental values for B(T) were used to calculate the energy parameters σ and ε in the LJ core potential for N₂, O₂, Cl₂, F₂, CO, CO₂, NO, N₂O, C₂H₆, C₂F₆ and the strongly polar molecules CH₃Cl, CH₃F, CH₃CF₃, CH₃CHF₂, and CF₃CH₂F. The analysis takes into account rotation of the dipole out of the molecular axis. The calculated results for the second virial coefficient agree well with experimental data. In addition, the effect of the induction terms on the potential for calculating the second virial coefficient is shown to be important only for the molecules with strong dipole or quadrupole moments.     

Autosoliton in Ablowitz–Ladik chain with linear damping and nonlinear amplification

The existence of discrete autosolitons in a nonlinear lattice is studied. The Ablowitz–Ladik (AL) model with linear damping, nonlinear cubic amplification and quintic damping and complex second difference representing the discrete analog of the filter is investigated. The parameters of the autosoliton are calculated using the perturbation theory for the AL model. Analytical predictions are confirmed by numerical simulations of the AL model with nonconservative perturbations.     

Raman characterization of Ti–6Al–4V oxides and thermal history after kinetic friction

Raman spectroscopy is applied to study the surfaces of a pair of tantalum and titanium alloy samples after high-speed dry friction. The surface of titanium alloy (Ti–6Al–4V) shows titanium oxides on the rubbing surfaces. Raman spectra enable to differentiate the allotropic phases of anatase or rutile. The presence of these phases is the signature of the local thermal history during the friction tests. Moreover, Raman mapping allows localizing area the flash temperatures that may have been produced by the friction between sample asperities.     

Exotic vortex structures of the dipolar Bose–Einstein condensates trapped in harmonic-like and toroidal potential

Based on the tunable intensity and waist of Gaussian laser, harmonic-like and toroidal potentials can be achieved and the ground-state properties of the dipolar Bose–Einstein condensate (BEC) trapped in such potentials are investigated. It is found that, in the harmonic-like potential, the singly and doubly quantized vortices can exist in the scale condensate and translate respectively into vortex pairs and triangular vortex lattice with increasing dipole–dipole interaction (DDI). Especially, the sandwich-like structure can be observed in the ground-state density profiles by tuning the direction and strength of DDI for some rotating frequency. In the toroidal potential, the competition between the inter-component interaction and DDI can induce the transition between immiscible and miscible states, and results in the structures of a doubly quantized vortex surrounded by a vortex ring. It is worth emphasizing that, with the increasing of DDI, the doubly quantized vortex in the harmonic-like potential becomes two singly quantized vortices, while in the toroidal potential it is no happen due to the presence of Gaussian barrier.     

Unified picture for Dirac neutrinos,dark matter,dark energy and matter–antimatter asymmetry

We propose a unified scenario to generate the masses of Dirac neutrinos and cold dark matter at the TeV scale, understand the origin of dark energy and explain the matter–antimatter asymmetry of the universe. This model can lead to significant impact on the Higgs searches at LHC.     

Synthesis and formation mechanism of Ag–Ni alloy nanoparticles at room temperature

Ag–Ni nanoparticles were prepared with a chemical reduction method in the presence of polyvinylpyrrolidone (PVP) used as a stabilizing agent. During the synthesis of Ag–Ni nanoparticles, silver nitrate was used as the Ag⁺ source while nickel sulfate hexahydrate was used as Ni²⁺ source. Mixed solutions of Ag⁺ source and Ni²⁺ source were used as the precursors and sodium borohydride was used as the reducing agent. Five ratios of Ag⁺/Ni²⁺ (9:1, 3:1, 1:1, 1:3, and 1:9) suspensions were prepared in the corresponding precursors. Ag–Ni alloy nanoparticles were obtained with this method at room temperature. Scanning electronic microscope (SEM), energy dispersive spectrum (EDS), high resolution transmission electron microscope (HRTEM) were used to characterize the morphology, composition and crystal structure of the nanoparticles. The crystal structure was also investigated with X-ray diffraction (XRD). In all five Ag/Ni ratios, two kinds of particle structures were observed that are single crystal structure and five-fold twinned structure respectively. Free energy of nanoparticles with different crystal structures were calculated at each Ag/Ni ratio. Calculated results revealed that, with identical volume, free energy of single crystal particle is lower than multi-twinned particle and the difference becomes smaller with the increase of particle size; increase of Ni content will lead the increase of free energy for both structures. Formation of different crystal structures are decided by the structure of the original nuclei at the very early stage of the reduction process.     

High efficiency and broad bandwidth terahertz vortex beam generation based on ultra-thin transmission Pancharatnam–Berry metasurfaces

The terahertz(THz) vortex beam generators are designed and theoretically investigated based on single-layer ultra-thin transmission metasurfaces. Noncontinuous phase changes of metasurfaces are obtained by utilizing Pancharatnam–Berry phase elements, which possess different rotation angles and are arranged on two concentric rings centered on the origin.The circularly polarized incident THz beam could be turned into a cross-polarization transmission wave, and the orbital angular momentum(OAM) varies in value by lh. The l values change from ±1 to ±5, and the maximal cross-polarization conversion efficiency that could be achieved is 23%, which nearly reaches the theoretical limit of a single-layer structure.The frequency range of the designed vortex generator is from 1.2 THz to 1.9 THz, and the generated THz vortex beam could keep a high fidelity in the operating bandwidth. The propagation behavior of the emerged THz vortex beam is analyzed in detail. Our work offers a novel way of designing ultra-thin and single-layer vortex beam generators, which have low process complexity, high conversion efficiency and broad bandwidth.