BTZ Black Hole as Solution of 3d Higher Spin Gauge Theory

BTZ black hole is interpreted as exact solution of 3d higher spin gauge theory. Solutions for free massless fields in BTZ black hole background are constructed with the help of the star-product algebra formalism underlying the formulation of 3d higher spin theory. It is shown that a part of higher spin symmetries remains unbroken for special values of the BTZ parameters.Comment: 31 pages, LaTeX; references correcte

Three terminal capacitance technique for magnetostriction and thermal expansion measurements

An instrument has been constructed to measure a large range of magnetostriction and thermal expansion between room temperature and 4 K in a superconductive split-coil magnet, that allows investigation in magnetic fields up to 12 T. The very small bulk samples (up to 1 mm in size) as well as big ones (up to 13 mm) of the irregular form can be measured. The possibility of magnetostriction investigation in thin films is shown. A general account is given of both electrical and the mechanical aspects of the design of capacitance cell and their associated electronic circuitry. A simple lever device is proposed to increase the sensitivity twice. The resulting obtained sensitivity can be 0.5 Angstrom. The performance of the technique is illustrated by some preliminary measurements of the magnetostriction of superconducting MgB2, thermal expansion of (La0.8Ba0.2)0.93MnO3 single crystal and magnetoelastic behavior of the Ni/Si(111) and La0.7Sr0.3CoO3/SAT0.7CAT0.1LA0.2(001) cantilevers.Comment: 6 pages, 6 figures, journal pape

Pseudoclassical description of scalar particle in non-Abelian background and path-integral representations

Path-integral representations for a scalar particle propagator in non-Abelian external backgrounds are derived. To this aim, we generalize the procedure proposed by Gitman and Schvartsman 1993 of path-integral construction to any representation of SU(N) given in terms of antisymmetric generators. And for arbitrary representations of SU(N), we present an alternative construction by means of fermionic coherent states. From the path-integral representations we derive pseudoclassical actions for a scalar particle placed in non-Abelian backgrounds. These actions are classically analyzed and then quantized to prove their consistency

Radioactive contamination of ZnWO4 crystal scintillators

The radioactive contamination of ZnWO4 crystal scintillators has been measured deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN in Italy with a total exposure 3197 kg x h. Monte Carlo simulation, time-amplitude and pulse-shape analyses of the data have been applied to estimate the radioactive contamination of the ZnWO4 samples. One of the ZnWO4 crystals has also been tested by ultra-low background gamma spectrometry. The radioactive contaminations of the ZnWO4 samples do not exceed 0.002 -- 0.8 mBq/kg (depending on the radionuclide), the total alpha activity is in the range: 0.2 - 2 mBq/kg. Particular radioactivity, beta active 65Zn and alpha active 180W, has been detected. The effect of the re-crystallization on the radiopurity of the ZnWO4 crystal has been studied. The radioactive contamination of samples of the ceramic details of the set-ups used in the crystals growth has been checked by low background gamma spectrometry. A project scheme on further improvement of the radiopurity level of the ZnWO4 crystal scintillators is briefly addressed.Comment: 15 pages, 8 figures, 6 tables, submitted for publicatio

Purely spatial diffusion of H atoms in solid normal- and para-hydrogen films

We present an experimental study of quantum diffusion of atomic hydrogen in solid H-2 films at temperatures below 1 K. The atoms are generated via electron impact dissociation by running a continuous rf discharge in helium gas above the H-2 film for long (up to 30 days) times. We are able to distinguish between the diffusion of the atoms moving towards each other followed by their recombination and the pure spatial diffusion driven by the density gradient. We found that in both cases the flux of phonons generated by the discharge above the surface of molecular film is essential to observe the slow diffusive motion. We obtained rates of pure spatial diffusion of H atoms in normal-H-2 (75% ortho, 25% para) films which were two orders of magnitude faster than those obtained from the H atom recombination, the quantity used in all previous work to characterize the mobility of H atoms in solid H-2. We investigated the influence of the film thickness and its ortho-para composition on recombination and pure spatial diffusion. For thin enough films of 0.16 mu m we observed complete diffusion of the H atoms through the entire film thickness. We observed peculiar behavior of the samples with ortho-H-2 (o-H-2) concentration below 5%. The recombination rate in these samples was an order of magnitude faster while the rate of spatial diffusion was somewhat slower than in films containing larger o-H-2 concentrations. The rate of production of H atoms in the low o-H-2 samples turned out to be an order of magnitude larger. We discuss possible explanations of these somewhat contradictory observations

Evidence for melting of HD and D-2 clusters in solid neon below 1 K

We report on an electron spin resonance study of H and D atoms stabilized in solid mixtures of neon, molecular deuterium, and hydrogen deuteride. We observed that H and D atoms can be stabilized in pure HD and D-2 clusters formed in pores of solid Ne as well as in a Ne environment. Raising temperature from 0.1 to 1.3 K results in a rapid recombination of a significant fraction of both H and D atoms in HD and D-2 clusters. The recombination rate appears to be five and seven orders of magnitude faster than in solid bulk samples of HD and D-2, respectively. We explain this recombination rate enhancement by melting of clusters of molecular hydrogen isotopes, similar to what has been observed for atomic hydrogen in H-2 clusters [Sheludiakov et al., Phys. Rev. B 97, 104108 (2018)]. Our observations do not provide evidence for a superfluid behavior of these clusters at temperatures of 0.1-1.3 K

Electron spin resonance study of atomic hydrogen stabilized in solid neon below 1 K

We report on an electron spin resonance study of atomic hydrogen stabilized in solid Ne matrices carried out at a high field of 4.6 T and temperatures below 1 K. The films of Ne, slowly deposited on the substrate at a temperature of similar to 1 K, exhibited a high degree of porosity. We found that H atoms may be trapped in two different substitutional positions in the Ne lattice as well as inside clusters of pure molecular H-2 in the pores of the Ne film. The latter type of atoms was very unstable against recombination at temperatures 0.3-0.6 K. Based on the observed nearly instant decays after rapid small increases of temperature, we evaluate the lower limit of the recombination rate constant k(r) >= 5 x 10(-20) cm(3) s(-1) at 0.6 K, five orders of magnitude larger than that previously found in the thin films of pure H-2 at the same temperature. Such behavior assumes a very high mobility of atoms and may indicate a solid-to-liquid transition for H-2 clusters of certain sizes, similar to that observed in experiments with H-2 clusters inside helium droplets [Phys. Rev. Lett. 101, 205301 (2008)]. We found that the efficiency of dissociation of H-2 in neon films is enhanced by two orders of magnitude compared to that in pure H-2 as a result of the strong action of secondary electrons