Thermal Entanglement of an XY Two-Qutrit Spin Chain with Dzialoshinski-Moriya Interaction

The effect of Dzialoshinski-Moriya （DM） interaction on thermal entanglement of an XY two-qutrit spin chain is investigated. We find that DM interaction and the anisotropy parameter can enhance quantum thermal entanglement to a maximal value individually. However, when both of them take large values, the entanglement is not enhanced, but is destroyed. Our analysis will shed some light on the understanding of the effect of the DM interaction on thermal entanglement of an XY two-qutrit spin chain.     

ESR studies in γ‐irradiated and PS‐radiation‐grafted poly(vinylidene fluoride)

The fluoropolymer poly(vinylidene fluoride) was irradiated with γ rays to induce a polystyrene (PS) radiation grafting via an indirect method. Electron spin resonance and Fourier transform infrared studies were performed to identify the species that initiated the PS grafting. Specific experiments were performed to prove separately the importance of each kind of radical. A localization of the radicals in this irradiated polymer is proposed, and a kinetic model of the grafting is given. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1437–1448, 2001     

Ground-state long-range order in quasi-one-dimensional Heisenberg quantum antiferromagnets: high-order coupled-cluster calculations

We investigate the ground-state magnetic long-range order of quasi-one-dimensional quantum Heisenberg antiferromagnets for spin quantum numbers s = 1/2 and s = 1. We use the coupled cluster method to calculate the sublattice magnetization and its dependence on the inter-chain coupling J_⊥. We find that for the unfrustrated spin-1/2 system, an infinitesimal inter-chain coupling is sufficient to stabilize magnetic long-range order, in agreement with results obtained by other methods. For s = 1, we find that a finite inter-chain coupling is necessary to stabilize magnetic long-range order. Furthermore, we consider a quasi one-dimensional spin-1/2 system, where a frustrating next-nearest neighbor in-chain coupling is included. We find that for stronger frustration as well, a finite inter-chain coupling is necessary to have magnetic long-range order in the ground state, and that the strength of the inter-chain coupling necessary to establish magnetic long-range order is related to the size of the spin gap of the isolated chain.     

Why Does the Geometric Product Simplify the Equations of Physics?

In the last decades it was observed that Clifford algebras and geometric product provide a model for different physical phenomena. We propose an explanation of this observation based on the theory of bounded symmetric domains and the algebraic structure associated with them. The invariance of physical laws is a result of symmetry of the physical world that is often expressed by the symmetry of the state space for the system implying that this state space is a symmetric domain. For example, the ball of all possible velocities is a bounded symmetric domain. The symmetry on this ball follow from the symmetry of the space-time transformations between two inertial systems, which fixes the so-called symmetric velocity between them. The Lorenz transformations acts on the ball Sof symmetric velocities by conformal transformations. The ball Sis a spin ball (type IV in Cartan's classification). The Lie algebra of this ball is defined a triple product that is closely related to geometric product. The relativistic dynamic equations in mechanics and for the Lorenz force is described by this Lie algebra and the triple product.     

Spin concentration in a possible ESR dosimeter: An electron spin echo study on X-irradiated ammonium tartrate

Several single crystals and powder samples of ammonium tartrate, recently proposed as a possible ESR dosimeter, have been X-irradiated with different doses. The total radical concentration has been determined by quantitative cw ESR, by comparison with a standard. The samples have been studied by electron spin echo spectroscopy. The two-pulse echo decay has been obtained and simulated by a single exponential function for different values of the microwave power of the pulses and for different pulse lengths. The dependence of the phase memory time TM on the microwave power has been exploited to get information on the contribution of the instantaneous diffusion to spin dephasing. At room temperature in the range of radical concentrations of 10(18)-10(19) spins/cm3 the instantaneous diffusion is the dominant spin dephasing mechanism. The linear dependence of the instantaneous diffusion on the total concentration of the radicals is in agreement with the theory. From the latter result we conclude that the average radical-radical distance corresponds to a random distribution of the radicals in the matrix. A simple method of measuring the radical concentration by the ESE decays in powder samples of irradiated ammonium tartrate is described.     

对过程e~＋e~－→J／ψ→γ＋X（J~（PC），X→BB（重子，反重子）的角分布和共振态X的自旋－宇称分析

用螺旋度角分布方法对过程ｅ＋ｅ－～Ｊ／ψ→γ＋Ｘ（ＪＰＣ）→ＢＢ（重子，反重子）进行了分析，得到了Ｘ具有不同自旋─—宇称时角分布及投影角分布的形式，从而可以通过对实验数据的分析来确定共振态Ｘ的自旋性质．     

ESR spectrometer with a loop-gap resonator for cw and time resolved studies in a superconducting magnet

The design and performance of an electron spin resonance spectrometer operating at 3 and 9 GHz microwave frequencies combined with a 9-T superconducting magnet are described. The probehead contains a compact two-loop, one gap resonator, and is inside the variable temperature insert of the magnet enabling measurements in the 0-9T magnetic field and 1.5-400 K temperature range. The spectrometer allows studies on systems where resonance occurs at fields far above the g approximately 2 paramagnetic condition such as in antiferromagnets. The low quality factor of the resonator allows time resolved experiments such as, e.g., longitudinally detected ESR. We demonstrate the performance of the spectrometer on the NaNiO2 antiferromagnet, the MgB2 superconductor, and the RbC60 conducting alkaline fulleride polymer.     

Hestenes' Tetrad and Spin Connections

Defining a spin connection is necessary for formulating Dirac's bispinor equation in a curved space-time. Hestenes has shown that a bispinor field is equivalent to an orthonormal tetrad of vector fields together with a complex scalar field. In this paper, we show that using Hestenes' tetrad for the spin connection in a Riemannian space-time leads to a Yang-Mills formulation of the Dirac Lagrangian in which the bispinor field Ψ is mapped to a set of SL(2,R)× U(1) gauge potentials F_α^K and a complex scalar field ρ. This result was previously proved for a Minkowski space-time using Fierz identities. As an application we derive several different non-Riemannian spin connections found in the literature directly from an arbitrary linear connection acting on the tensor fields (F_α^K, ρ). We also derive spin connections for which Dirac's bispinor equation is form invariant. Previous work has not considered form invariance of the Dirac equation as a criterion for defining a general spin connection.     

Perturbation approach to elastic constitutive relations of polycrystals

Herein we obtain a formula for the effective elastic stiffness tensor C^eff of an orthorhombic aggregate of cubic crystallites by the perturbation method. The effective elastic stiffness tensor of the polycrystal gives the relationship between volume average stress and volume average strain. Under Voigt's model, Reuss’ model and Man's theory, the elastic constitutive relation accounts for the effect of the orientation distribution function (ODF) up to terms linear in the texture coefficients. However, the formula derived in this paper delineates the effect of crystallographic texture on elastic response and shows quadratic texture dependence. The formula is very simple. We also consider the influence of grain shape to elastic constitutive relations of polycrystals. Some examples are given to compare computational results of the formula with those given by Voigt's model, Reuss's model, the finite element method, and the self-consistent method. In Section 3, we also present an expression of the perturbation displacement field, in which Green's function for an orthorhombic aggregate of cubic crystallites is included.