Coherent oscillations and incoherent tunnelling in one - dimensional asymmetric double - well potential

For a model 1d asymmetric double-well potential we calculated so-called survival probability (i.e. the probability for a particle initially localised in one well to remain there). We use a semiclassical (WKB) solution of Schroedinger equation. It is shown that behaviour essentially depends on transition probability, and on dimensionless parameter which is a ratio of characteristic frequencies for low energy non-linear in-well oscillations and inter wells tunnelling. For the potential describing a finite motion (double-well) one has always a regular behaviour. For the small value of the parameter there is well defined resonance pairs of levels and the survival probability has coherent oscillations related to resonance splitting. However for the large value of the parameter no oscillations at all for the survival probability, and there is almost an exponential decay with the characteristic time determined by Fermi golden rule. In this case one may not restrict oneself to only resonance pair levels. The number of perturbed by tunnelling levels grows proportionally to the value of this parameter (by other words instead of isolated pairs there appear the resonance regions containing the sets of strongly coupled levels). In the region of intermediate values of the parameter one has a crossover between both limiting cases, namely the exponential decay with subsequent long period recurrent behaviour.Comment: 19 pages, 7 figures, Revtex, revised version. Accepted to Phys. Rev.

Structure of TiAlN Reactive Sputtered Coatings

The Raman spectra, X-ray diffraction and hardness of the TiAlN films co-deposited on the steel substrates by reactive sputtering from Ti and Al targets in a mixture of N2 + Ar gas with two magnetrons at room temperature have been studied. From Raman spectra it is found that the position of high-frequency bands in vibrational spectra was located at 700-730 cm 1 or in the region of 830 850 cm 1 depending on the deposition parameters whereas it is not exceed 630 cm 1 from TiAlN of NaCl structure. It is found the two-phase structure of coatings: a small quantity of NaCl-type structure of TiAlN (TiN) and the disordered structure of the chains of polyhedra [TiNx] with x = 5 and x = 4. The chains of polyhedra [TiNx] with x = 4 are mainly formed at large discharge power of Al(Ti) target or at small content of N2 gas. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2492

Isovector unpolarized quark distribution in the nucleon in the large-N_c limit

We calculate the isovector (flavor-nonsinglet) unpolarized quark- and antiquark distributions in the nucleon at a low normalization point in the large-N_c limit. The nucleon is described as a soliton of the effective chiral theory. The isovector distribution appears in the next-to-leading order of the 1/N_c-expansion. Numerical results for the quark- and antiquark distributions compare well with the parametrizations of the data at a low normalization point. This large-N_c approach gives a flavor asymmetry of the antiquark distribution (violation of the Gottfried sum rule) in good agreement with the measurements.Comment: 31 pages, LaTeX, 1 table, 4 figures included using eps

Localisation of Fermions to brane: Codimension d≥2d \geq 2

We investigate $4+d$ dimensional fermionic models in which the system in codimension-$d$ supports a topologically stable solution, and in which the fermion may be localised to the brane, with power law in 'instanton' backgrounds and exponentially in 'soliton' backgrounds. When the fermions are isoscalars, the mechanism fails, while for isospinor fermions it is successful. As backgrounds we consider instantons of Yang--Mills and sigma models in even codimensions, solitons of sigma models in odd codimensions, as well as solitons of Higgs and Goldstone models in all codimensions.Comment: 20 pages latex; expande

Strings from Tachyons

We propose a new interpretation of the c=1 matrix model as the world-line theory of N unstable D-particles, in which the hermitian matrix is provided by the non- abelian open string tachyon. For D-particles in 1+1-d string theory, we find a direct quantitative match between the closed string emission due to a rolling tachyon and that due to a rolling eigenvalue in the matrix model. We explain the origin of the double-scaling limit, and interpret it as an extreme representative of a large equivalence class of dual theories. Finally, we define a concrete decoupling limit of unstable D-particles in IIB string theory that reduces to the c=1 matrix model, suggesting that 1+1-d string theory represents the near-horizon limit of an ultra-dense gas of IIB D-particles.Comment: 30 pages, 4 figures; v2: added references, improved discussion of Liouville boundary states, v3: small correction

The Effective Action For Brane Localized Gauge Fields

The low energy effective action including gauge field degrees of freedom on a non-BPS p=2 brane embedded in a N=1, D=4 target superspace is obtained through the method of nonlinear realizations of the associated super-Poincare symmetries. The invariant interactions of the gauge fields and the brane excitation modes corresponding to the Nambu-Goldstone degrees of freedom resulting from the broken space translational symmetry and the target space supersymmetries are determined. Brane localized matter field interactions with the gauge fields are obtained through the construction of the combined gauge and super-Poincare covariant derivatives for the matter fields.Comment: 12 pages, no figure

SU(4) Chiral Quark Model with Configuration Mixing

Chiral quark model with configuration mixing and broken SU(3)\times U(1) symmetry has been extended to include the contribution from c\bar c fluctuations by considering broken SU(4) instead of SU(3). The implications of such a model have been studied for quark flavor and spin distribution functions corresponding to E866 and the NMC data. The predicted parameters regarding the charm spin distribution functions, for example, \Delta c, \frac{\Delta c}{{\Delta \Sigma}}, \frac{\Delta c}{c} as well as the charm quark distribution functions, for example, \bar c, \frac{2\bar c}{(\bar u+\bar d)}, \frac{2 \bar c}{(u+d)} and \frac{(c+ \bar c)}{\sum (q+\bar q)} are in agreement with other similar calculations. Specifically, we find \Delta c=-0.009, \frac{\Delta c}{{\Delta \Sigma}}=-0.02, \bar c=0.03 and \frac{(c+ \bar c)}{\sum (q+\bar q)}=0.02 for the \chiQM parameters a=0.1, \alpha=0.4, \beta=0.7, \zeta_{E866}=-1-2 \beta, \zeta_{NMC}=-2-2 \beta and \gamma=0.3, the latter appears due to the extension of SU(3) to SU(4).Comment: 10 RevTeX pages. Accepted for publication in Phys. Rev.

AdS/CFT Equivalence Transformation

We show that any conformal field theory in d-dimensional Minkowski space, in a phase with spontaneously broken conformal symmetry and with the dilaton among its fields, can be rewritten in terms of the static gauge (d-1)-brane on AdS_(d+1) by means of an invertible change of variables. This nonlinear holographic transformation maps the Minkowski space coordinates onto the brane worldvolume ones and the dilaton onto the transverse AdS brane coordinate. One of the consequences of the existence of this map is that any (d-1)-brane worldvolume action on AdS_(d+1)\times X^m (with X^m standing for the sphere S^m or more complicated curved manifold) admits an equivalent description in Minkowski space as a nonlinear and higher-derivative extension of some conventional conformal field theory action, with the conformal group being realized in a standard way. The holographic transformation explicitly relates the standard realization of the conformal group to its field-dependent nonlinear realization as the isometry group of the brane AdS_(d+1) background. Some possible implications of this transformation, in particular, for the study of the quantum effective action of N=4 super Yang-Mills theory in the context of AdS/CFT correspondence, are briefly discussed.Comment: LaTeX, 19 pages, minor correction in Abstrac

Portable bioluminescent platform for in vivo monitoring of biological processes in non-transgenic animals.

Bioluminescent imaging (BLI) is one of the most powerful and widely used preclinical imaging modalities. However, the current technology relies on the use of transgenic luciferase-expressing cells and animals and therefore can only be applied to a limited number of existing animal models of human disease. Here, we report the development of a "portable bioluminescent" (PBL) technology that overcomes most of the major limitations of traditional BLI. We demonstrate that the PBL method is capable of noninvasive measuring the activity of both extracellular (e.g., dipeptidyl peptidase 4) and intracellular (e.g., cytochrome P450) enzymes in vivo in non-luciferase-expressing mice. Moreover, we successfully utilize PBL technology in dogs and human cadaver, paving the way for the translation of functional BLI to the noninvasive quantification of biological processes in large animals. The PBL methodology can be easily adapted for the noninvasive monitoring of a plethora of diseases across multiple species