Pseudo spin-orbit coupling of Dirac particles in graphene spintronics

We study the pseudo spin-orbital (SO) effects experienced by massive Dirac particles in graphene, which can potentially be of a larger magnitude compared to the conventional Rashba SO effects experienced by particles in a 2DEG semiconductor heterostructure. In order to generate a uniform vertical pseudo SO field, we propose an artificial atomic structure, consisting of a graphene ring and a charged nanodot at the center which produces a large radial electric field. In this structure, a large pseudo SO coupling strength can be achieved by accelerating the Dirac particles around the ring, due to the small energy gap in graphene and the large radial electric field emanating from the charged nanodot. We discuss the theoretical possibility of harnessing the pseudo SO effects in mesoscopic applications, e.g. pseudo spin relaxation and switching.Comment: 12 pages, 1 figur

Measuring spin in coalescing binaries of neutron stars showing double precursors

Gamma-ray bursts resulting from binary neutron-star mergers are sometimes preceded by precursor flares. These harbingers may be ignited by quasi-normal modes, excited by orbital resonances, shattering the stellar crust of one of the inspiralling stars up to $\gtrsim10$ seconds before coalescence. In the rare case that a system displays two precursors, successive overtones of either interface- or $g$-modes may be responsible for the overstrainings. Since the free-mode frequencies of these overtones have an almost constant ratio, and the inertial-frame frequencies for rotating stars are shifted relative to static ones, the spin frequency of the flaring component can be constrained as a function of the equation of state, the binary mass ratio, the mode quantum numbers, and the spin-orbit misalignment angle. As a demonstration of the method, we find that the precursors of GRB090510 hint at a spin frequency range of $2 \lesssim \nu_{\star}/\text{Hz} \lesssim 20$ for the shattering star if we allow for an arbitrary misalignment angle, assuming $\ell=2$ $g$-modes account for the events.Comment: 11 pages, 6 figures, 2 tables, with an appendix containing 1 figur

Method and apparatus for non-contact charge measurement

A method and apparatus for the accurate non-contact detection and measurement of static electric charge on an object using a reciprocating sensing probe that moves relative to the object. A monitor measures the signal generated as a result of this cyclical movement so as to detect the electrostatic charge on the object

General-relativistic treatment of tidal gg-mode resonances in coalescing binaries of neutron stars. II. As triggers for precursor flares of short gamma-ray bursts

In some short gamma-ray bursts, precursor flares occurring $\sim$ seconds prior to the main episode have been observed. These flares may then be associated with the last few cycles of the inspiral when the orbital frequency is a few hundred Hz. During these final cycles, tidal forces can resonantly excite quasi-normal modes in the inspiralling stars, leading to a rapid increase in their amplitude. It has been shown that these modes can exert sufficiently strong strains onto the neutron star crust to instigate yieldings. Due to the typical frequencies of $g$-modes being $\sim 100\text{ Hz}$, their resonances with the orbital frequency match the precursor timings and warrant further investigation. Adopting realistic equations of state and solving the general-relativistic pulsation equations, we study $g$-mode resonances in coalescing quasi-circular binaries, where we consider various stellar rotation rates, degrees of stratification, and magnetic field structures. We show that for some combination of stellar parameters, the resonantly excited $g_1$- and $g_2$-modes may lead to crustal failure and trigger precursor flares.Comment: 14 pages, 8 figures, 2 tables, submitted to MNRA

A Tracker Solution for a Holographic Dark Energy Model

We investigate a kind of holographic dark energy model with the future event horizon the IR cutoff and the equation of state -1. In this model, the constraint on the equation of state automatically specifies an interaction between matter and dark energy. With this interaction included, an accelerating expansion is obtained as well as the transition from deceleration to acceleration. It is found that there exists a stable tracker solution for the numerical parameter $d>1$, and $d$ smaller than one will not lead to a physical solution. This model provides another possible phenomenological framework to alleviate the cosmological coincidence problem in the context of holographic dark energy. Some properties of the evolution which are relevant to cosmological parameters are also discussed.Comment: 10 pages, 3 figures; accepted for publication in Int.J.Mod.Phys.

Asymptotics of a discrete-time particle system near a reflecting boundary

We examine a discrete-time Markovian particle system on the quarter-plane introduced by M. Defosseux. The vertical boundary acts as a reflecting wall. The particle system lies in the Anisotropic Kardar-Parisi-Zhang with a wall universality class. After projecting to a single horizontal level, we take the longtime asymptotics and obtain the discrete Jacobi and symmetric Pearcey kernels. This is achieved by showing that the particle system is identical to a Markov chain arising from representations of the infinite-dimensional orthogonal group. The fixed-time marginals of this Markov chain are known to be determinantal point processes, allowing us to take the limit of the correlation kernel. We also give a simple example which shows that in the multi-level case, the particle system and the Markov chain evolve differently.Comment: 16 pages, Version 2 improves the expositio

Index of Refraction Matched Nanoparticles and Methods of Use

Embodiments of the present disclosure provide for nanoparticles, methods of making nanoparticles, materials including nanoparticles, the use of materials including nanoparticles, and the like