Longitudinal and Transverse Nuclear Shadowing

Nuclear shadowing arises from multiple scattering of the hadronic fluctuations of the virtual photon in a nucleus. We predict different longitudinal and transverse shadowing and an A-dependence of R which can be up to a 50% effect. The possibility of detecting nuclear effects on R at HERA is discussed.Comment: latex, 6 page

Extracting the Strange Density from xF3xF_3

We present a QCD analysis of the strange and charm contributions to the neutrino deep inelastic structure function $xF_3$. We show that next-to-leading order effects, which are relatively important for $F_2$, play a lesser role in the case of $xF_3$. The neutrino--antineutrino difference $xF_3^{\nu} - xF_3^{\bar \nu}$ provides a new determination of the strange density, which exhibits some advantages with respect to other traditional methods.Comment: 12 page

Evaluation of fuzzy inference systems using fuzzy least squares

Efforts to develop evaluation methods for fuzzy inference systems which are not based on crisp, quantitative data or processes (i.e., where the phenomenon the system is built to describe or control is inherently fuzzy) are just beginning. This paper suggests that the method of fuzzy least squares can be used to perform such evaluations. Regressing the desired outputs onto the inferred outputs can provide both global and local measures of success. The global measures have some value in an absolute sense, but they are particularly useful when competing solutions (e.g., different numbers of rules, different fuzzy input partitions) are being compared. The local measure described here can be used to identify specific areas of poor fit where special measures (e.g., the use of emphatic or suppressive rules) can be applied. Several examples are discussed which illustrate the applicability of the method as an evaluation tool

On the low x behaviour of nuclear shadowing

We calculate the x dependence of nuclear shadowing at moderate values of Q^2 by using HERA diffractive data and, for consistency, F2 parameterization of ZEUS. We show that no decrease of shadowing occurs down to very low x (x = 10^-4).Comment: 9 pages, submitted on june for publicatio

Unitarization of Structure Functions at Large 1/x{\bf 1/x}

We discuss the effects of the $s$-channel unitarization on the $x$ and $Q^{2}$ dependence of structure functions. The unitarization is implemented at the level of photoabsorption cross sections by resorting to the light--cone wave functions of virtual photons and to the diagonalization property of the scattering matrix in a basis of Fock states of the photon with fixed transverse size. Triple pomeron effects are also explicitly taken into account. We find large unitarity corrections to the structure functions at $x < 10^{-2}$. The results are in very good agreement with the existing NMC and the preliminary HERA data.Comment: 12 page

Leptoproduction of charm revisited

We calculate the energy--momentum distribution of the charmed quarks produced in neutrino reactions on protons, quantifying the importance of mass and current non--conservation effects. We study the strange and charm distributions probed in neutrino interactions in the presently accessible kinematical region. Some ambiguities inherent to the extraction of the parton densities from dimuon data are pointed out.Comment: 9 pages, DFTT 72/9

Atomic Josephson vortex

We show that Josephson vortices in a quasi-1D atomic Bose Josephson junction can be controllably manipulated by imposing a difference of chemical potentials on the atomic BEC waveguides forming the junction. This effect, which has its origin in the Berry phase structure of a vortex, turns out to be very robust in the whole range of the parameters where such vortices can exist. We also propose that a Josephson vortex can be created by the phase imprinting technique and can be identified by a specific tangential feature in the interference picture produced by expanding clouds released from the waveguides.Comment: 7 pages, 3 figures, revtex4, submitted to Phys. Rev. A, title and abstract changed, old sections revised, new sections added, references adde

Observation of a New Fluxon Resonant Mechanism in Annular Josephson Tunnel Structures

A novel dynamical state has been observed in the dynamics of a perdurbed sine-Gordon system. This resonant state, has been experimentally observed as a singularity in the dc current voltage characteristic of an annular Josephson tunnel junction, excited in the presence of a magnetic field. With this respect, it can be assimilated to self-resonances known as Fiske steps. Differently from these, however, we demonstrate, on the basis of numerical simulations, that its detailed dynamics involves rotating fluxon pairs, a mechanism associated, so far, to self-resonances known as zero-field steps.Comment: 4 pages, 2 figures, submitted to Physical Review Letter