Counting surface states in the loop quantum gravity

We adopt the point of view that (Riemannian) classical and (loop-based) quantum descriptions of geometry are macro- and micro-descriptions in the usual statistical mechanical sense. This gives rise to the notion of geometrical entropy, which is defined as the logarithm of the number of different quantum states which correspond to one and the same classical geometry configuration (macro-state). We apply this idea to gravitational degrees of freedom induced on an arbitrarily chosen in space 2-dimensional surface. Considering an `ensemble' of particularly simple quantum states, we show that the geometrical entropy $S(A)$ corresponding to a macro-state specified by a total area $A$ of the surface is proportional to the area $S(A)=\alpha A$, with $\alpha$ being approximately equal to $1/16\pi l_p^2$. The result holds both for case of open and closed surfaces. We discuss briefly physical motivations for our choice of the ensemble of quantum states.Comment: This paper is a substantially modified version of the paper `The Bekenstein bound and non-perturbative quantum gravity'. Although the main result (i.e. the result of calculation of the number of quantum states that correspond to one and the same area of 2-d surface) remains unchanged, it is presented now from a different point of view. The new version contains a discussion both of the case of open and closed surfaces, and a discussion of a possibility to generalize the result obtained considering arbitrary surface quantum states. LaTeX, 21 pages, 6 figures adde

Single fluxon in double stacked Josephson junctions: Analytic solution

We derive an approximate analytic solution for a single fluxon in a double stacked Josephson junctions (SJJ's) for arbitrary junction parameters and coupling strengths. It is shown that the fluxon in a double SJJ's can be characterized by two components, with different Swihart velocities and Josephson penetration depths. Using the perturbation theory we find the second order correction to the solution and analyze its accuracy. Comparison with direct numerical simulations shows a quantitative agreement between exact and approximate analytic solutions. It is shown that due to the presence of two components, the fluxon in SJJ's may have an unusual shape with an inverted magnetic field in the second junction when the velocity of the fluxon is approaching the lower Swihart velocity.Comment: 4 pages, 3 figure

In-plane fluxon in layered superconductors with arbitrary number of layers

I derive an approximate analytic solution for the in-plane vortex (fluxon) in layered superconductors and stacked Josephson junctions (SJJ's) with arbitrary number of layers. The validity of the solution is verified by numerical simulation. It is shown that in SJJ's with large number of thin layers, phase/current and magnetic field of the fluxon are decoupled from each other. The variation of phase/current is confined within the Josephson penetration depth, $\lambda_J$, along the layers, while magnetic field decays at the effective London penetration depth, $\lambda_c \gg \lambda_J$. For comparison with real high-$T_c$ superconducting samples, large scale numerical simulations with up to 600 SJJ's and with in-plane length up to 4000 $\lambda_J$%, are presented. It is shown, that the most striking feature of the fluxon is a Josephson core, manifesting itself as a sharp peak in magnetic induction at the fluxon center.Comment: 4 pages, 4 figures. Was presented in part at the First Euroconference on Vortex Matter in Superconductors (Crete, September 1999

Discrimination between the superconducting gap and the pseudo-gap in Bi2212 from intrinsic tunneling spectroscopy in magnetic field

Intrinsic tunneling spectroscopy in high magnetic field ($H$) is used for a direct test of superconducting features in a quasiparticle density of states of high-$T_c$ superconductors. We were able to distinguish with a great clarity two co-existing gaps: (i) the superconducting gap, which closes as $H \to H_{c2}(T)$ and $T\to T_c(H)$, and (ii) the $c$-axis pseudo-gap, which does not change neither with $H$, nor $T$. Strikingly different magnetic field dependencies, together with previously observed different temperature dependencies of the two gaps ~\cite{Krasnov}, speak against the superconducting origin of the pseudo-gap.Comment: 4 pages, 4 eps figure

The effect of accelerated cooling on the structure of pipe steels for thermomechanical controlled processing

Scanning electron microscopy with orientation analysis by the electron backscatter diffraction (EBSD) method is used to study microstructures and textures formed in low-carbon low-alloy pipe steel after thermomechanical controlled processing (TMCP) and subsequent quenching with cooling rates of 50 to 700 °/s. It has been established that, in the range of industrial rates of cooling between 50 and 350 °/s from austenitic regions, the γ→α transformation starts at temperatures of 700-670 °C and proceeds by the shear mechanism. As a result, a bainite structure of different dispersity with martensitic inclusions is predominantly formed. © 2018 Author(s)

Time Budget in Two Desert Gerbils: is the Diet Important?

We studied time budgets and dietary intake in two desert gerbillids, Psammomys obesus, a diurnal herbivore, and Meriones crassus, a nocturnal granivore feeding three different types of diet (millet seeds together with leaves of Atriplex halimus for M. crassus, fresh leaves of A. halimus or fresh stems of Anabasis syriaca for P. obesus). M. crassus spent the lowest proportion of its time budget for feeding compared to P. obesus. Number of feeding sessions in M. crassus was approximately the same but each separate feeding session was almost three times shorter than those in P. obesus. No difference in temporal pattern of feeding was found between P. obesus fed different plants, in spite of sharp differences in chemical composition of food. P. obesus fed A. halimus was active significantly less time than M. crassus, whereas P. obesus fed A. syriaca stayed active the same time as M. crassus. Dry matter intake of P. obesus fed A. halimus was much higher than that of M. crassus and dry matter intake of P. obesus fed A. syriaca was lower than even that in M. crassus