Measurement of the optical properties of lunar rocks in the transition zone, resulting from observations made by Lunokhod 2

Photometric measurements were carried out directly on the lunar surface with the aid of a calibration device, a plate with fields of different brightness, placed in the field of view of the panoramic telephotometers. The brightness of the fields of the calibration plate were measured in preliminary studies, relative to the brightness of a magnesia screen. This permitted determination of the reflectance features of the surficial lunar material relative to the standard most widely used in brightness studies of natural substances. The total brightness of sections a few centimeters across was recorded in direct proximity to the apparatus. The total area investigated in one panorama was about one square meter. Several areas in the mare and highland regions were studied. The albedos of various surface objects were obtained. A comparison of the brightness measurements with data from the RIFMA-M instrument discloses a correlation of the albedo change with change in chemical composition of the surface rock. Direct photometric studies of the lunar surface in the "mare-highland" transition zone assist in tracing the transition from one type of rock to another, and in obtaining information on the processes of material exchange between these two types of lunar landscape

Faddeev calculation of a K−ppK^- p p quasi-bound state

We report on the first genuinely three-body ${\bar K}NN - \pi \Sigma N$ coupled-channel Faddeev calculation in search for quasi-bound states in the $K^- p p$ system. The main absorptivity in the $K^- p$ subsystem is accounted for by fitting to $K^- p$ data near threshold. Our calculation yields one such quasi-bound state, with $I=1/2$, $J^{\pi}=0^-$, bound in the range $B \sim 55-70$ MeV, with a width of $\Gamma \sim 95-110$ MeV. These results differ substantially from previous estimates, and are at odds with the $K^- p p \to \Lambda p$ signal observed by the FINUDA collaboration.Comment: Minor editorial revision; version accepted for publication in Phys. Rev. Let

Stability of Sarma phases in density imbalanced electron-hole bilayer systems

We study excitonic condensation in an electron-hole bilayer system with unequal layer densities at zero temperature. Using mean-field theory we solve the BCS gap equations numerically and investigate the effects of intra-layer interactions. We analyze the stability of the Sarma phase with \bk,-\bk pairing by calculating the superfluid mass density and also by checking the compressibility matrix. We find that with bare Coulomb interactions the superfluid density is always positive in the Sarma phase, due to a peculiar momentum structure of the gap function originating from the singular behavior of the Coulomb potential at zero momentum and the presence of a sharp Fermi surface. Introducing a simple model for screening, we find that the superfluid density becomes negative in some regions of the phase diagram, corresponding to an instability towards a Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) type superfluid phase. Thus, intra-layer interaction and screening together can lead to a rich phase diagram in the BCS-BEC crossover regime in electron-hole bilayer systems

Drag of superfluid current in bilayer Bose systems

An effect of nondissipative drag of a superfluid flow in a system of two Bose gases confined in two parallel quasi two-dimensional traps is studied. Using an approach based on introduction of density and phase operators we compute the drag current at zero and finite temperatures for arbitrary ratio of densities of the particles in the adjacent layers. We demonstrate that in a system of two ring-shape traps the "drag force" influences on the drag trap in the same way as an external magnetic flux influences on a superconducting ring. It allows to use the drag effect to control persistent current states in superfluids and opens a possibility for implementing a Bose analog of the superconducting Josephson flux qubit.Comment: 12 pages, 2 figures, new section is added, refs are adde

Superfluidity of electron-hole pairs in randomly inhomogeneous bilayer systems

In bilayer systems electron-hole (e-h) pairs with spatially separated components (i.e., with electrons in one layer and holes in the other) can be condensed to a superfluid state when the temperature is lowered. This article deals with the influence of randomly distributed inhomogeneities on the superfluid properties of such bilayer systems in a strong perpendicular magnetic field. Ionized impurities and roughenings of the conducting layers are shown to decrease the superfluid current density of the e-h pairs. When the interlayer distance is smaller than or close to the magnetic length, the fluctuations of the interlayer distance considerably reduce the superfluid transition temperature.Comment: 13 pages, 3 figure

Lattice solitons in quasicondensates

We analyze finite temperature effects in the generation of bright solitons in condensates in optical lattices. We show that even in the presence of strong phase fluctuations solitonic structures with well defined phase profile can be created. We propose a novel family of variational functions which describe well the properties of these solitons and account for the non-linear effects in the band structure. We discuss also the mobility and collisions of these localized wave packets.Comment: 4 pages, 2 figure

Test of the τ-model of Bose–Einstein correlations and reconstruction of the source function in hadronic Z-boson decay at LEP

Bose–Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed in terms of various parametrizations. A good description is achieved using a Lévy stable distribution in conjunction with a model where a particle’s momentum is correlated with its space–time point of production, the τ-model. Using this description and the measured rapidity and transverse momentum distributions, the space–time evolution of particle emission in two-jet events is reconstructed. However, the elongation of the particle emission region previously observed is not accommodated in the τ-model, and this is investigated using an ad hoc modification

Effects of perturbative exchanges in a QCD-string model

The QCD-string model for baryons derived by Simonov and used for the calculation of baryon magnetic moments in a previous paper is extended to include also perturbative gluon and meson exchanges. The mass spectrum of the baryon multiplet is studied. For the meson interaction either the pseudoscalar or pseudovector coupling is used. Predictions are compared with the experimental data. Besides these exchanges the influence of excited quark orbitals on the baryon ground state are considered by performing a multichannel calculation. The nucleon-Delta splitting increases due to the mixing of higher quark states while the baryon magnetic momenta decrease. The multichannel calculation with perturbative exchanges is shown to yield reasonable magnetic moments while the mass spectrum is close to experiment.Comment: 37 pages Revtex with 2 figures, to be published in Phys. Atom. Nucl. dedicated to the 70th Birthday of Yu. A. Simono