Two-band superconductors: Extended Ginzburg-Landau formalism by a systematic expansion in small deviation from the critical temperature

We derive the extended Ginzburg-Landau (GL) formalism for a clean s-wave two-band superconductor by employing a systematic expansion of the free-energy functional and the corresponding matrix gap equation in powers of the small deviation from the critical temperature tau = 1-T/T_c. The two lowest orders of this expansion produce the equation for T_c and the GL theory. It is shown that in agreement with previous studies, the two-band GL theory maps onto the single-band GL model and thus fails to describe the difference in the spatial profiles of the two band condensates. We prove that except for some very special cases, this difference appears already in the leading correction to the GL theory, which constitutes the extended GL formalism. We derive linear differential equations that determine the leading corrections to the band order parameters and magnetic field, discuss the validity of these equations, and consider examples of an important interplay between the band condensates. Finally, we present numerical results for the thermodynamic critical magnetic field and temperature-dependent band gaps (at zero field), which are in a very good agreement with those obtained from the full BCS approach in a wide temperature range. To this end, we emphasize the advantages of our extended GL theory in comparison with the often used two-component GL-like model based on an unreconstructed two-band generalization of the Gor'kov derivation

Physical degrees of freedom in stabilized brane world models

We consider brane world models with interbrane separation stabilized by the Goldberger-Wise scalar field. For arbitrary background, or vacuum configurations of the gravitational and scalar fields in such models, we construct the second variation Lagrangian, study its gauge invariance, find the corresponding equations of motion and decouple them in a suitable gauge. We also derive an effective four-dimensional Lagrangian for such models, which describes the massless graviton, a tower of massive gravitons and a tower of massive scalars. It is shown that for a special choice of the background solution the masses of the graviton excitations may be of the order of a few TeV, the radion mass of the order of 100 GeV, the inverse size of the extra dimension being tens of GeV. In this case the coupling of the radion to matter on the negative tension brane is approximately the same as in the unstabilized model with the same values of the fundamental five-dimensional energy scale and the interbrane distance.Comment: 17 pages, LaTeX, corrected typos, amended the normalization constants of the scalar modes and their coupling constants to matte

Disorders of the hemostasis system while doing coronary shunting on a working heart

Objective. To investigate the connection between application of solutions for infusion and parameters of the hemostasis system while the elective operations performance of coronary shunting on the working heart. Materials and methods. The results of examination and surgical treatment were analyzed in 80 patients, in whom coronary shunting on the working heart was conducted. The patients were divided into three groups: the Investigation Group I (IG I) – 20 patients, in whom colloidal solution of hydroxyethyl starch (HES) 130/0.4 was applied intraoperatively, the Investigation Group II (IG II) - 20 patients, in whom colloidal 4% solution of gelatin was used intraoperatively, and a Control Group, consisted of 40 patients, in whom only crystalloidal solutions were included in the infusion therapy program. The coagulation hemostasis indices, the blood loss volume and the need for hemotransfusion were compared. Results. In the IG I patients the volume of perioperative blood loss was more than in the IG II patients – (615 ± 191) and (438 ± 62) ml, accordingly (p=0.0003), and the coagulation hemostasis indices were trustworthily lower at the operation ending, demanding the erythrocytic mass transfusion doing in 3 (15%) patients. The IG II patients, comparing with the Control Group, suffered more volume of the blood loss - (560 ± 164) and (438 ± 62) ml, accordingly (p=0,02), and the changes in the coagulation indices, similar to changes in patients of the IG I, comparing with the Control Group patients. Any patient from the IG II needed hemotransfusion perioperatively. Conclusion. Application of colloidal solutions while doing elective operations of CSH on the  working heart leads to disorder of coagulation hemostasis, the intraoperative blood loss and the need for hemotransfusion enhancement

Non-Gaussian signatures of Tachyacoustic Cosmology

I investigate non-Gaussian signatures in the context of tachyacoustic cosmology, that is, a noninflationary model with superluminal speed of sound. I calculate the full non-Gaussian amplitude $\mathcal{A}$, its size $f_{\rm NL}$, and corresponding shapes for a red-tilted spectrum of primordial scalar perturbations. Specifically, for cuscuton-like models I show that $f_{\rm NL}\sim {\cal O}(1)$, and the shape of its non-Gaussian amplitude peaks for both equilateral and local configurations, the latter being dominant. These results, albeit similar, are quantitatively distinct from the corresponding ones obtained by Magueijo {\it{et. al}} in the context of superluminal bimetric models.Comment: Some comments and references added. Matches the version published in JCA

Gravity and non-gravity mediated couplings in multiple-field inflation

Mechanisms for the generation of primordial non-Gaussian metric fluctuations in the context of multiple-field inflation are reviewed. As long as kinetic terms remain canonical, it appears that nonlinear couplings inducing non-gaussianities can be split into two types. The extension of the one-field results to multiple degrees of freedom leads to gravity mediated couplings that are ubiquitous but generally modest. Multiple-field inflation offers however the possibility of generating non-gravity mediated coupling in isocurvature directions that can eventually induce large non-Gaussianities in the metric fluctuations. The robustness of the predictions of such models is eventually examined in view of a case study derived from a high-energy physics construction.Comment: 14 pages, 3 figures, invited review for CQG issue on non-linear cosmolog

Effects of broadening and electron overheating in tunnel structures based on metallic clusters

We study the influence of energy levels broadening and electron subsystem overheating in island electrode (cluster) on current-voltage characteristics of three-electrode structure. A calculation scheme for broadening effect in one-dimensional case is suggested. Estimation of broadening is performed for electron levels in disc-like and spherical gold clusters. Within the two-temperature model of metallic cluster and by using a size dependence of the Debye frequency the effective electron temperature as a function of bias voltage is found approximately. We suggest that the effects of broadening and electron overheating are responsible for the strong smoothing of current-voltage curves, which is observed experimentally at low temperatures in structures based on clusters consisting of accountable number of atoms.Comment: 8 pages, 5 figure