Rindler-like Horizon in Spherically Symmetric Spacetime

In this paper, the Rindler-like horizon in a spherically symmetric spacetime is proposed. It is showed that just like the Rindler horizon in Minkowski spacetimes, there is also a Rindler-like horizon to a family of special observers in general spherically symmetric spacetimes. The entropy of this type of horizon is calculated with the thin film brick-wall model. The significance of entropy is discussed. Our results imply some connection between Bekeinstein-Hawking entropy and entanglement entropy.     

Entropy of Spin Fields in Schwarzschild Spacetime

By using the Teukolsky master equation, we consider the gravitational,electromagnetic, and neutrino fields in Schwarzschild spacetime. The free energyand entropy of the spin fields are obtained in terms of the brick-wall model. Itis shown that the entropy of all the spin fields due to the presence of the eventhorizon is proportional to the surface area of the event horizon, and the entropyof the neutrino field is the absolute minimum.     

Nonlinear Sigma Models in (1+2) Dimensions and an Infinite Number of Conserved Currents

In this Letter, we treat nonlinear sigma models such as the C P¹-model, Q P¹-model, etc. in 1+2 dimensions. For submodels of such models, we definitely construct an infinite number of nontrivial conserved currents. Our result is a generalization of Alvarez, Ferreira and Guillen.     

Finding Dirac Spin Effect in NUT Spacetime

In the present study, we are interested in finding the spin precession of a Dirac particle in expanding and rotating NUT spaeetime. A tetrad with two functions to be determined is applied to the field equation of the teleparallel theory of gravity via a coordinate transformation. The vector, the axial-vector and the tensor parts of the torsion tensor are obtained. We found that the vector parts are in the radial and Ф-directions. The axial-vector torsion is along r-direction while its other components along θ and oh-directions vanish everywhere. The vector connected with Dirac spin has been evaluated as well.     

Energy Bounds for Static Spherically Symmetric Spacetime in f(R,G) Gravity

The main purpose of this paper is to investigate energy bounds in the context of f(R, G) gravity. To meet this aim, we choose static spherically symmetric spacetime in f(R, G) gravity to develop the field equations. We select three different models of f(R, G) gravity, which are thoroughly discussed in the literature. Firstly, the inequalities are formulated using energy bounds and then viability of the considered models are checked respectively. Graphical analysis show that specific f(R, G) gravity models are satisfied under suitable values of model parameters. It is shown that in a certain case energy bounds are satisfied expect SEC, which supports the late time acceleration expansion of unverse.     

Energy Bounds for Static Spherically Symmetric Spacetime in f(R,G) Gravity

The main purpose of this paper is to investigate energy bounds in the context of f(R,G) gravity. To meet this aim, we choose static spherically symmetric spacetime in f(R,G) gravity to develop the field equations. We select three different models of f(R,G) gravity, which are thoroughly discussed in the literature. Firstly, the inequalities are formulated using energy bounds and then viability of the considered models are checked respectively. Graphical analysis show that specific f(R,G) gravity models are satisfied under suitable values of model parameters. It is shown that in a certain case energy bounds are satisfied expect SEC, which supports the late time acceleration expansion of unverse.     

Sp(2) renormalization

The renormalization of general gauge theories on flat and curved space–time backgrounds is considered within the Sp(2)-covariant quantization method. We assume the existence of a gauge-invariant and diffeomorphism invariant regularization. Using the Sp(2)-covariant formalism one can show that the theory possesses gauge-invariant and diffeomorphism invariant renormalizability to all orders in the loop expansion and the extended BRST-symmetry after renormalization is preserved. The advantage of the Sp(2) method compared to the standard Batalin–Vilkovisky approach is that, in reducible theories, the structure of ghosts and ghosts for ghosts and auxiliary fields is described in terms of irreducible representations of the Sp(2) group. This makes the presentation of solutions to the master equations in more simple and systematic way because they are Sp(2)-scalars.     

Propagation of Scalar Fields in a Plane Symmetric Spacetime

The present article deals with solutions for a minimally coupled scalar field propagating in a static plane symmetric spacetime. The considered metric describes the curvature outside a massive infinity plate and exhibits an intrinsic naked singularity (a singular plane) that makes the accessible universe finite in extension. This solution can be interpreted as describing the spacetime of static domain walls. In this context, a first solution is given in terms of zero order Bessel functions of the first and second kind and presents a stationary pattern which is interpreted as a result of the reflection of the scalar waves at the singular plane. This is an evidence, at least for the massless scalar field, of an old interpretation given by Amundsen and Grøn regarding the behaviour of test particles near the singularity. A second solution is obtained in the limit of a weak gravitational field which is valid only far from the singularity. In this limit, it was possible to find out an analytic solution for the scalar field in terms of the Kummer and Tricomi confluent hypergeometric functions.     

Letter: Spin Polarised Magnetized Cylinders in Torsioned Spacetime

A Spin-polarised cylindrically symmetric exact class of solutions endowed with magnetic fields in Einstein-Cartan-Maxwell gravity is obtained. Application of matching conditions to this interior solution having an exterior as Einstein's vacuum solution shows that for this class of metrics the Riemann-Cartan (RC) rotation vanishes which makes the solution static. Therefore we end up with a magnetized static spin polarised cylinder where the pressure along the symmetry axis is negative.     

Energy Distribution for a Power Model of the Plane Symmetric Spacetime in f (R) Gravity

The study of the energy localization in f(R)theories of gravity has attracted much interest in recent years.In this paper,the vacuum solutions of the modified field equations for a power model of plane symmetric metric are studied in metric f(R)gravity with the assumption of constant Ricci scalar.Next,we determine the energy-momentum complexes in f(R)theories of gravity for this spacetime for some important models.We also show that these models satisfy the stability and constant curvature conditions.     

Energy Distribution for a Power Model of the Plane Symmetric Spacetime in f(R) Gravity

The study of the energy localization in f(R) theories of gravity has attracted much interest in recent years. In this paper, the vacuum solutions of the modified field equations for a power model of plane symmetric metric are studied in metric f(R) gravity with the assumption of constant Ricci scalar. Next, we determine the energy-momentum complexes in f(R) theories of gravity for this spacetime for some important models. We also show that these models satisfy the stability and constant curvature conditions.     

Persistence of Spin Edge Currents in Disordered Quantum Spin Hall Systems

For a disordered two-dimensional model of a topological insulator (such as a Kane-Mele model with disordered potential) with small coupling of spin invariance and time-reversal symmetry breaking terms (such as a Rashba spin-orbit coupling and a Zeeman term), it is proved that the spin edge currents persist provided there is a spectral gap and the spin Chern numbers are well-defined and non-trivial. These are sufficient conditions for being in the quantum spin Hall phase. The result materializes the general philosophy that topological insulators are topologically non-trivial bulk systems with persistent edge or surface currents.     

More Nonlocal Conserved Currents in Chiral Sigma Models

The infinite many nonlocal conserved currents are given for the principal chiral model. Wess-Zuminc-Witten chiral model and the supersymmetric chiral model with respect to the new hidden symmetry transformatione. It is shown that these conserved currents are related to the classical r-matrix and thus decompose into many families. The approach used here provides a systematic method to derive the Casimir operators for the infinite dimensional Lie algebras in its nonunitary and nonhighest weight representations.     

The Role of Spin in Entanglement Generated by Expanding Spacetime

We investigate the effects of spin on entanglement arising in Dirac field in an expanding spacetime characterized by the Robertson-Walker metric. We present a general approach that allows us to treat the case where only charge conservation is required, as well as the case where also angular momentum conservation is required. We find that in both situations entanglement originated from the vacuum and quantified by subsystem entropy behaves the same and does not qualitatively deviates from the spinless case. Differences only arise when particles and/or antiparticles are present in the input state.     

Tortoise Coordinates and Hawking Radiation in a Dynamical Spherically Symmetric Spacetime

Hawking effect from dynamical spherical Vaidya black hole, Vaidya-Bonner black hole, and Vaidya-de Sitter black hole is investigated using the improved Damour-Ruffini method. After the new tortoise coordinate transformation in which the position r of event horizon is an undetermined function and the temperature parameter κ is an undetermined constant, the Klein-Gordon equation can be written as the standard form at the event horizon, and both r and κ can be determined automatically. Then extending the outgoing wave from outside to inside of the horizon analytically, the Hawking temperature can also be obtained automatically.     

Spin glass behavior in the new amorphous alloys M2SnTe4 (M=Cr,Mn, Fe)

The amorphous alloys M₂SnTe₄ (M=Cr, Mn, Fe) are prepared by a new method involving the oxidation of main group polyanions (Zintl anions) by transition metal cations in solution at or below room temperature. The M₂SnTe₄ materials undergo a transition to a spin glass state at 12 K ? T_f ? 20 K and were characterized by dc magnetization, ⁵⁷Fe and ¹¹⁹Sn Mossbauer and x-ray diffraction measurements as well as the behavior of the remanent magnetization.     

Spin 0 and Spin 1/2 Particles in a Spherically Symmetric Static Gravity and a Coulomb Field

A relativistic particle in an attractive Coulomb field as well as a static and spherically symmetric gravitational field is studied. The gravitational field is treated perturbatively and the energy levels are obtained for both spin 0 (Klein-Gordon) and spin 1/2 (Dirac) particles. The results are shown to coincide with each other as well as the result of the nonrelativistic (Schr?dinger) equation in the nonrelativistic limit.     

Spin transmutation in (2 + 1) dimensions

We study a relativistic anyon model with a spin-j matter field minimally coupled to an abelian Chem-Simons gauge field with a statistical parameter α. A spin and statistics transmutation is shown in terms of the continuum random walk method. An integer or odd-half-integer part of α can be reabsorbed by change of j. We discuss the equivalence of a large class of Chern-Simons matter models for given j and α.     

Spin frustration in Y(Sc)Mn2

The relaxation rate of muon polarization of Y_0.97Sc_0.03Mn₂ with a magnetic lattice composed of corner‐shared tetrahedrons shows a broad peak around 2.5 K indicating a random spin freezing at low temperatures. The substitution by nonmagnetic Al atoms for 10% Mn atoms raises the spin freezing temperature to 45 K. The present work shows clearly that due to the strong geometrical frustration, the ground state of the system is singlet tetrahedrons mixed with frozen paramagnetic tetrahedrons. This revised version was published online in July 2006 with corrections to the Cover Date.