The quasiclassical theory of the Dirac equation with a scalar-vector interaction and its applications in the theory of heavy-light mesons

We construct a relativistic potential quark model of $D$, $D_s$, $B$, and $B_s$ mesons in which the light quark motion is described by the Dirac equation with a scalar-vector interaction and the heavy quark is considered a local source of the gluon field. The effective interquark interaction is described by a combination of the perturbative one-gluon exchange potential $V_{\mathrm{Coul}}(r)=-\xi/r$ and the long-range Lorentz-scalar and Lorentz-vector linear potentials $S_{\mathrm{l.r.}}(r)=(1-\lambda)(\sigma r+V_0)$ and $V_{\mathrm{l.r.}}(r)=\lambda(\sigma r+V_0)$, where $0\leqslant\lambda<1/2$. Within the quasiclassical approximation, we obtain simple asymptotic formulas for the energy and mass spectra and for the mean radii of $D$, $D_s$, $B$, and $B_s$ mesons, which ensure a high accuracy of calculations even for states with the radial quantum number $n_r\sim 1$. We show that the fine structure of P-wave states in heavy-light mesons is primarily sensitive to the choice of two parameters: the strong-coupling constant $\alpha_s$ and the coefficient $\lambda$ of mixing of the long-range scalar and vector potentials $S_{\mathrm{l.r.}}(r)$ and $V_{\mathrm{l.r.}}(r)$. The quasiclassical formulas for asymptotic coefficients of wave function at zero and infinity are obtained.Comment: 22 pages, 6 figure

Active rejection-enhancement of spectrally adaptive liquid crystal geometric phase vortex coronagraphs

Geometric phase optical elements made of space-variant anisotropic media customarily find their optimal operating conditions when the half-wave retardance condition is fulfilled, which allows imparting polarization-dependent changes to an incident wavefront. In practice, intrinsic limitations of man-made manufacturing process or the finite spectrum of the light source lead to a deviation from the ideal behavior. This implies the implementation of strategies to compensate for the associated efficiency losses. Here we report on how the intrinsic tunable features of self-engineered liquid crystal topological defects can be used to enhance the rejection capabilities of spectrally adaptive vector vortex coronagraphs. We also discuss the extent of which current models enable to design efficient devices

Multiple colliding electromagnetic pulses: a way to lower the threshold of e+e−e^+e^- pair production from vacuum

The scheme of simultaneous multiple pulse focusing on one spot naturally arises from the structural features of projected new laser systems, such as ELI and HiPER. It is shown that the multiple pulse configuration is beneficial for observing $e^+e^-$ pair production from vacuum under the action of sufficiently strong electromagnetic fields. The field of the focused pulses is described using a realistic three-dimensional model based on an exact solution of the Maxwell equations. The $e^+e^-$ pair production threshold in terms of electromagnetic field energy can be substantially lowered if, instead of one or even two colliding pulses, multiple pulses focused on one spot are used. The multiple pulse interaction geometry gives rise to subwavelength field features in the focal region. These features result in the production of extremely short $e^+e^-$ bunches.Comment: 10 pages, 4 figure

Algebraic approach to the spectral problem for the Schroedinger equation with power potentials

The method reducing the solution of the Schroedinger equation for several types of power potentials to the solution of the eigenvalue problem for the infinite system of algebraic equations is developed. The finite truncation of this system provides high accuracy results for low-lying levels. The proposed approach is appropriate both for analytic calculations and for numerical computations. This method allows also to determine the spectrum of the Schroedinger-like relativistic equations. The heavy quarkonium (charmonium and bottomonium) mass spectra for the Cornell potential and the sum of the Coulomb and oscillator potentials are calculated. The results are in good agreement with experimental data.Comment: 17 pages, including 6 PostScript figures (epsf style

The qqˉq \bar{q} relativistic interaction in the Wilson loop approach

We study the $q \bar{q}$ relativistic interaction starting from the Feynman-Schwinger representation of the gauge-invariant quark-antiquark Green function. We focus on the one-body limit and discuss the obtained non-perturbative interaction kernel of the Dirac equation.Comment: 5 pages, Latex (espcrc2.sty) To be published in the proceedings of High-Energy Physics International Euroconference on Quantum Chromodynamics:QCD97; 25th Anniversary of QCD, Montpellier, France, 3-9 July 199

Erratum: Does the Unruh effect exist? [JETP Lett. 65, No. 12, 902 908 (25 June 1997)]

On page 905, the second sentence after Eq. (18) should read: "If here the surface t=0 is taken as the surface of integration and the fact that the modes R μ=0 for z 0 is taken into account, then after making the change of variables (8) it might seem that (R μ,φ)M=(Φμ, φ)R.

Topological phase transitions between chiral and helical spin textures in a lattice with spin-orbit coupling and a magnetic field

We consider the combined effects of large spin-orbit couplings and a perpendicular magnetic field in a 2D honeycomb fermionic lattice. This system provides an elegant setup to generate versatile spin textures propagating along the edge of a sample. The spin-orbit coupling is shown to induce topological phase transitions between a helical quantum spin Hall phase and a chiral spin-imbalanced quantum Hall state. Besides, we find that the spin orientation of a single topological edge state can be tuned by a Rashba spin-orbit coupling, opening an interesting route towards quantum spin manipulation. We discuss the possible realization of our results using cold atoms trapped in optical lattices, where large synthetic magnetic fields and spin-orbit couplings can be engineered and finely tuned. In particular, this system would lead to the observation of a time-reversal-symmetry-broken quantum spin Hall phase.Comment: 8 pages, 3 figures, Accepted in Europhys. Lett. (Dec 2011

Metabolomic changes in lactating multiparous naturally MAP-infected Holstein-Friesian dairy cows suggest changes in mitochondrial energy pathways

Mycobacterium avium subspecies paratuberculosis (MAP) is the causative organism of Johne's Disease, a chronic intestinal infection of ruminants. Infected cows begin shedding MAP within the asymptomatic, subclinical stage of infection before clinical signs, such as weight loss, diarrhoea and reduced milk yields develop within the clinical stages of disease. Herein, we examine the milk metabolomic profiles of naturally MAP-infected Holstein-Friesian cows. The study used biobanked milk samples which were collected 73.4 ± 3.79 (early lactation) and 143 ± 3.79 (mean ± SE) (mid-lactation) days post-calving from 5 MAP-infected and 5 control multiparous cows. The milk metabolome was assessed using flow infusion electrospray high-resolution mass spectrometry (FIE-HRMS) for sensitive, non-targeted metabolite fingerprinting. Metabolite fingerprinting assessments using partial least squares discriminate analyses (PLS-DA) indicated that lactation stage was a larger source of variation than MAP status. Examining each lactation stage separately for changes associated to MAP-infection status identified 45 metabolites, 33 in early lactation and 12 in mid-lactation, but only 6 metabolites were targeted in both stages of lactation. Pathway enrichment analysis suggested that MAP affected the malate-aspartate shuffle during early lactation. Pearson's correlation analysis indicated relationships between milk lactose concentrations in mid-lactation and 6 metabolites that were tentatively linked to MAP-infection status. The targeted metabolites were suggestive of wider changes in the bioenergetic metabolism that appear to be an acceleration of the effects of progressing lactation in healthy cows. Additionally, milk lactose concentrations suggest that MAP reduces the availability of lactose derivatives

Analysis of chemical constituents in medicinal plants of selected districts of Pakhtoonkhwa, Pakistan

Alkaloids, flavonoids and saponins were determined in the Teraxacam officinale, Cichorium intybus and Figonia tritica. Quantative determinations of crude alkaloids, flavonoids and saponins (g kg-1) and their percentages (%) were determined in C. intybus, T. officinale and F. critica collected from Kohat, Mardan, Nowshera and Peshawar regions. Thin layer chromatography (TLC) study of the alkaloids, flavonoids and saponins were carried out with different solvent systems and color of the spot and Rf value of each constituent was determined. Among the samples of C. intybus, relatively higher contents of alkaloids (14 g kg-1) were found in the sample collected from Mardan region, followed by the sample gathered from Nowshera which is equal to 13.8g kg-1. Higher contents of flavonoids were found in C. intybus collected from Kohat region which was 23.48 g kg-1. The other remaining samples of C. intybus ranged in the decreasing order of 19.7, 17.2 and 10.0 g kg-1 for the ones collected from Nowshera, Mardan and Peshawar, respectively. The overall saponin contents remained almost low as compared to the alkaloid and flavonoid contents.Key words: Alkaloids, flavonoids, saponins, TLC study, medicinal plants