Two component model for a description of nucleon structure functions in low-x region

Two component model for a description of the electromagnetic nucleon structure functions in low-x region, based on generalized vector dominance and color dipole approaches is briefly described. The model operates with the mesons of rho-family having the mass spectrum which is equidistant on square mass and takes into account the nondiagonal transitions in meson-nucleon scattering. The special cut-off factors are introduced in the model, to exclude the gamma-qq-V transitions in the case of the narrow qq-pairs. For the color dipole part of the model the well known FKS-parameterization is used.Comment: Presented at 15th International Symposium on Very High Energy Cosmic Ray Interactions (ISVHECRI 2008), Paris, France, 1-6 Sep. 2008. 4 pages, 2 figure

Measuring the prompt atmospheric neutrino flux with down-going muons in neutrino telescopes

In the TeV energy region and above, the uncertainty in the level of prompt atmospheric neutrinos would limit the search for diffuse astrophysical neutrinos. We suggest that neutrino telescopes may provide an empirical determination of the flux of prompt atmospheric electron and muon neutrinos by measuring the flux of prompt down-going muons. Our suggestion is based on the consideration that prompt neutrino and prompt muon fluxes at sea level are almost identical.Comment: 4 pages, 3 figure

Adiabatic Output Coupling of a Bose Gas at Finite Temperatures

We develop a general theory of adiabatic output coupling from trapped atomic Bose-Einstein Condensates at finite temperatures. For weak coupling, the output rate from the condensate, and the excited levels in the trap, settles in a time proportional to the inverse of the spectral width of the coupling to the output modes. We discuss the properties of the output atoms in the quasi-steady-state where the population in the trap is not appreciably depleted. We show how the composition of the output beam, containing condensate and thermal component, may be controlled by changing the frequency of the output coupler. This composition determines the first and second order coherence of the output beam. We discuss the changes in the composition of the bose gas left in the trap and show how nonresonant output coupling can stimulate either the evaporation of thermal excitations in the trap or the growth of non-thermal excitations, when pairs of correlated atoms leave the condensate.Comment: 22 pages, 6 Figs. To appear in Physical Review A All the typos from the previous submission have been fixe

Shot Noise in Nanoscale Conductors From First Principles

We describe a field-theoretic approach to calculate quantum shot noise in nanoscale conductors from first principles. Our starting point is the second-quantization field operator to calculate shot noise in terms of single quasi-particle wavefunctions obtained self-consistently within density functional theory. The approach is valid in both linear and nonlinear response and is particularly suitable in studying shot noise in atomic-scale conductors. As an example we study shot noise in Si atomic wires between metal electrodes. We find that shot noise is strongly nonlinear as a function of bias and it is enhanced for one- and two-Si wires due to the large contribution from the metal electrodes. For longer wires it shows an oscillatory behavior for even and odd number of atoms with opposite trend with respect to the conductance, indicating that current fluctuations persist with increasing wire length.Comment: 4 pages, 4 figure

Palynostratigraphy and palynofacies of the early Eocene Gurha lignite mine, Rajasthan, India

A 105 m early Eocene section exposed in the Gurha mine in the Nagaur-Ganganagar Basin, Rajasthan, India, archiving remains of equatorial vegetation at a time of extreme global warmth and close to the onset of the India-Eurasia collision, is investigated using palynostratigraphic and palynofacies analyses. Four palynozones e.g., Palmidites plicatus Singh, Botryococcus braunii Kützing, Triangulorites bellus Kar and Ovoidites ligneolus are identified stratigraphically on the basis of abundance of these pollen taxa over others. The occurrence of taxonomically highly diverse angiosperm pollen in all the four palynozones attests to an extremely rich near-coastal tropical flora subject to frequent wildfires under a strongly seasonal precipitation regime. Palynotaxa characteristic of these palynozones are widely distributed in other early Paleogene sediments of India. Sedimentary organic matter (structured terrestrial, biodegraded, amorphous, grey amorphous, resins, charcoal/black-brown debris and algal remains) recovered from mire and lacustrine sediments are of terrestrial origin, recording fluctuations in burial anoxia and salinity. Episodes of elevated salinity are due either to seepage of marine waters and/or a periodic excess of evaporation over precipitation at times when the depositional system was closed

Entangled Hanbury Brown Twiss effects with edge states

Electronic Hanbury Brown Twiss correlations are discussed for geometries in which transport is along adiabatically guided edge channels. We briefly discuss partition noise experiments and discuss the effect of inelastic scattering and dephasing on current correlations. We then consider a two-source Hanbury Brown Twiss experiment which demonstrates strikingly that even in geometries without an Aharonov-Bohm effect in the conductance matrix (second-order interference), correlation functions can (due to fourth-order interference) be sensitive to a flux. Interestingly we find that this fourth-order interference effect is closely related to orbital entanglement. The entanglement can be detected via violation of a Bell Inequality in this geometry even so particles emanate from uncorrelated sources.Comment: International Symposium "Quantum Hall Effect: Past, Present and Future

Local densities, distribution functions, and wave function correlations for spatially resolved shot noise at nanocontacts

We consider a current-carrying, phase-coherent multi-probe conductor to which a small tunneling contact is attached. We treat the conductor and the tunneling contact as a phase-coherent entity and use a Green's function formulation of the scattering approach. We show that the average current and the current fluctuations at the tunneling contact are determined by an effective local non-equilibrium distribution function. This function characterizes the distribution of charge-carriers (or quasi-particles) inside the conductor. It is an exact quantum-mechanical expression and contains the phase-coherence of the particles via local partial densities of states, called injectivities. The distribution function is analyzed for different systems in the zero-temperature limit as well as at finite temperature. Furthermore, we investigate in detail the correlations of the currents measured at two different contacts of a four-probe sample, where two of the probes are only weakly coupled contacts. In particular, we show that the correlations of the currents are at zero-temperature given by spatially non-diagonal injectivities and emissivities. These non-diagonal densities are sensitive to correlations of wave functions and the phase of the wave functions. We consider ballistic conductors and metallic diffusive conductors. We also analyze the Aharonov-Bohm oscillations in the shot noise correlations of a conductor which in the absence of the nano-contacts exhibits no flux-sensitivity in the conductance.Comment: 17 pages, 8 figure

Stokes Diagnostis of 2D MHD-simulated Solar Magnetogranulation

We study the properties of solar magnetic fields on scales less than the spatial resolution of solar telescopes. A synthetic infrared spectropolarimetric diagnostics based on a 2D MHD simulation of magnetoconvection is used for this. We analyze two time sequences of snapshots that likely represent two regions of the network fields with their immediate surrounding on the solar surface with the unsigned magnetic flux density of 300 and 140 G. In the first region we find from probability density functions of the magnetic field strength that the most probable field strength at logtau_5=0 is equal to 250 G. Weak fields (B < 500 G) occupy about 70% of the surface, while stronger fields (B 1000 G) occupy only 9.7% of the surface. The magnetic flux is -28 G and its imbalance is -0.04. In the second region, these parameters are correspondingly equal to 150 G, 93.3 %, 0.3 %, -40 G, and -0.10. We estimate the distribution of line-of-sight velocities on the surface of log tau_5=-1. The mean velocity is equal to 0.4 km/s in the first simulated region. The averaged velocity in the granules is -1.2 km/s and in the intergranules is 2.5 km/s. In the second region, the corresponding values of the mean velocities are equal to 0, -1.8, 1.5 km/s. In addition we analyze the asymmetry of synthetic Stokes-V profiles of the Fe I 1564.8 nm line. The mean values of the amplitude and area asymmetry do not exceed 1%. The spatially smoothed amplitude asymmetry is increased to 10% while the area asymmetry is only slightly varied.Comment: 24 pages, 12 figure

Continuous-distribution puddle model for conduction in trilayer graphene

An insulator-to-metal transition is observed in trilayer graphene based on the temperature dependence of the resistance under different applied gate voltages. At small gate voltages the resistance decreases with increasing temperature due to the increase in carrier concentration resulting from thermal excitation of electron-hole pairs. At large gate voltages excitation of electron-hole pairs is suppressed, and the resistance increases with increasing temperature because of the enhanced electron-phonon scattering. We find that the simple model with overlapping conduction and valence bands, each with quadratic dispersion relations, is unsatisfactory. Instead, we conclude that impurities in the substrate that create local puddles of higher electron or hole densities are responsible for the residual conductivity at low temperatures. The best fit is obtained using a continuous distribution of puddles. From the fit the average of the electron and hole effective masses can be determined.Comment: 18 pages, 5 figure

Branching and annihilating Levy flights

We consider a system of particles undergoing the branching and annihilating reactions A -> (m+1)A and A + A -> 0, with m even. The particles move via long-range Levy flights, where the probability of moving a distance r decays as r^{-d-sigma}. We analyze this system of branching and annihilating Levy flights (BALF) using field theoretic renormalization group techniques close to the upper critical dimension d_c=sigma, with sigma<2. These results are then compared with Monte-Carlo simulations in d=1. For sigma close to unity in d=1, the critical point for the transition from an absorbing to an active phase occurs at zero branching. However, for sigma bigger than about 3/2 in d=1, the critical branching rate moves smoothly away from zero with increasing sigma, and the transition lies in a different universality class, inaccessible to controlled perturbative expansions. We measure the exponents in both universality classes and examine their behavior as a function of sigma.Comment: 9 pages, 4 figure