Decay of scalar variance in isotropic turbulence in a bounded domain

The decay of scalar variance in isotropic turbulence in a bounded domain is investigated. Extending the study of Touil, Bertoglio and Shao (2002; Journal of Turbulence, 03, 49) to the case of a passive scalar, the effect of the finite size of the domain on the lengthscales of turbulent eddies and scalar structures is studied by truncating the infrared range of the wavenumber spectra. Analytical arguments based on a simple model for the spectral distributions show that the decay exponent for the variance of scalar fluctuations is proportional to the ratio of the Kolmogorov constant to the Corrsin-Obukhov constant. This result is verified by closure calculations in which the Corrsin-Obukhov constant is artificially varied. Large-eddy simulations provide support to the results and give an estimation of the value of the decay exponent and of the scalar to velocity time scale ratio

Octet Baryon Magnetic Moments in the Chiral Quark Model with Configuration Mixing

The Coleman-Glashow sum-rule for magnetic moments is always fulfilled in the chiral quark model, independently of SU(3) symmetry breaking. This is due to the structure of the wave functions, coming from the non-relativistic quark model. Experimentally, the Coleman-Glashow sum-rule is violated by about ten standard deviations. To overcome this problem, two models of wave functions with configuration mixing are studied. One of these models violates the Coleman-Glashow sum-rule to the right degree and also reproduces the octet baryon magnetic moments rather accurately.Comment: 22 pages, RevTe

Ferromagnetism below 10 K in Mn doped BiTe

Ferromagnetism is observed below 10 K in [Bi0.75Te0.125Mn0.125]Te. This material has the BiTe structure, which is made from the stacking of two Te-Bi-Te-Bi-Te blocks and one Bi-Bi block per unit cell. Crystal structure analysis shows that Mn is localized in the Bi2 blocks, and is accompanied by an equal amount of TeBi anti-site occupancy in the Bi2Te3 blocks. These TeBi anti-site defects greatly enhance the Mn solubility. This is demonstrated by comparison of the [Bi1-xMnx]Te and [Bi1-2xTexMnx]Te series; in the former, the solubility is limited to x = 0.067, while the latter has xmax = 0.125. The magnetism in [Bi1-xMnx]Te changes little with x, while that for [Bi1-2xTexMnx]Te shows a clear variation, leading to ferromagnetism for x > 0.067. Magnetic hysteresis and the anomalous Hall Effect are observed for the ferromagnetic samples.Comment: Accepted for publication in Phys. Rev.

Theoretical investigation of magnetic order in ReOFeAs, Re = Ce, Pr

Density functional theory (DFT) calculations are carried out on ReOFeAs, Re = Ce, Pr, the parent compounds of the high-T$_c$ superconductors ReO$_{1-x}$F$_{x}$FeAs, in order to determine the magnetic order of the ground state. It is found that the magnetic moments on the Fe sites adopt a collinear antiferromagnetic order, similar to the case of LaOFeAs. Within the generalized gradient approximation along with Coulomb onsite repulsion (GGA+U), we show that the Re magnetic moments also adopt an antiferromagnetic order for which, within the ReO layer, same spin Re sites lie along a zigzag line perpendicular to the Fe spin stripes. While within GGA the Re 4f band crosses the Fermi level, upon inclusion of onsite Coulomb interaction the 4f band splits and moves away from the Fermi level, making ReOFeAs a Mott insulator.Comment: 5 pages, 4 figure

Octet Magnetic Moments with Null Instantons and Semibosonized Nambu-Jona-Lasinio Model

It is shown that the difference between the magnetic moment results in the quark model with null instantons and semibosonized Nambu-Jona-Lasinio model lies in the description of the magnetic moment of the $\Lambda$-hyperon.Comment: RevTex, 6 pages, submitted to Progr.Theor.Phy

Decuplet baryon magnetic moments in a QCD-based quark model beyond quenched approximation

We study the decuplet baryon magnetic moments in a QCD-based quark model beyond quenched approximation. Our approach for unquenching the theory is based on the heavy baryon perturbation theory in which the axial couplings for baryon - meson and the meson-meson-photon couplings from the chiral perturbation theory are used together with the QM moment couplings. It also involves the introduction of a form factor characterizing the structure of baryons considered as composite particles. Using the parameters obtained from fitting the octet baryon magnetic moments, we predict the decuplet baryon magnetic moments. The $\Omega^-$ magnetic moment is found to be in good agreement with experiment: $\mu_{\Omega^-}$ is predicted to be $-1.97 \mu_N$ compared to the experimental result of ($-$2.02 $\pm$ 0.05) $\mu_N$.Comment: 19 pages, 2 figure

The Physical Projector and Topological Quantum Field Theories: U(1) Chern-Simons Theory in 2+1 Dimensions

The recently proposed physical projector approach to the quantisation of gauge invariant systems is applied to the U(1) Chern-Simons theory in 2+1 dimensions as one of the simplest examples of a topological quantum field theory. The physical projector is explicitely demonstrated to be capable of effecting the required projection from the initially infinite number of degrees of freedom to the finite set of gauge invariant physical states whose properties are determined by the topology of the underlying manifold.Comment: 24 pages, no figures, plain LaTeX file; one more reference added. Final version to appear in Jour. Phys.

The Lie Algebraic Significance of Symmetric Informationally Complete Measurements

Examples of symmetric informationally complete positive operator valued measures (SIC-POVMs) have been constructed in every dimension less than or equal to 67. However, it remains an open question whether they exist in all finite dimensions. A SIC-POVM is usually thought of as a highly symmetric structure in quantum state space. However, its elements can equally well be regarded as a basis for the Lie algebra gl(d,C). In this paper we examine the resulting structure constants, which are calculated from the traces of the triple products of the SIC-POVM elements and which, it turns out, characterize the SIC-POVM up to unitary equivalence. We show that the structure constants have numerous remarkable properties. In particular we show that the existence of a SIC-POVM in dimension d is equivalent to the existence of a certain structure in the adjoint representation of gl(d,C). We hope that transforming the problem in this way, from a question about quantum state space to a question about Lie algebras, may help to make the existence problem tractable.Comment: 56 page

Daily fluctuations of negative affect are only weakly associated with tremor symptoms in functional and organic tremor patients

BACKGROUND: There is a long-standing research history on the presumed psychological origin of functional movement disorders. Most studies do not address the heterogeneity in functional movement disorders and do not distinguish between risk factors, causes and consequences. We studied the associations between negative affect and objective as well as subjective symptom levels in patients with functional and organic tremor. METHODS: Thirty-three patients with a functional (14) or organic tremor (19) completed a web-based diary on subjective symptom burden and negative affect, five times a day for 30 days (total number of observations = 4759). During the same period, the participants wore an accelerometer to objectively record tremor. Vector autoregressive modelling was used to determine the time-lagged and contemporaneous associations between negative affect and objective/subjective tremor symptoms, both on an individual and a group level. RESULTS: In contrast to previous literature, patients with a functional or organic tremor showed a weak contemporaneous association between negative affect and objective/subjective tremor symptoms (on average r = 0.038 and 0.174 respectively). Time-lagged associations between negative affect and objective/subjective tremor symptoms were mixed in effect and direction and only present in a subset of patients, with no differences between patients with functional or organic tremor. CONCLUSIONS: Negative affect is only weakly associated with objective/subjective tremor symptoms, both on the contemporaneous and time-lagged associations, and these associations were mainly similar between patients with functional or organic tremor. These results argue against a strong influence of daily stress on tremor symptoms in patients with a functional or organic tremor