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

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

Limit quantum efficiency for violation of Clauser-Horne Inequality for qutrits

In this paper we present the results of numerical calculations about the minimal value of detection efficiency for violating the Clauser - Horne inequality for qutrits. Our results show how the use of non-maximally entangled states largely improves this limit respect to maximally entangled ones. A stronger resistance to noise is also found.Comment: Phys. Rev. A in pres

Testing Ultrafast Two-Photon Spectral Amplitudes via Optical Fibres

We test two-dimensional TPSA of biphoton light emitted via ultrafast spontaneous parametric down-conversion (SPDC) using the effect of group-velocity dispersion in optical fibres. Further, we apply this technique to demonstrate the engineering of biphoton spectral properties by acting on the pump pulse shape

Non universality of structure functions and measurement of the strange sea density

We show that there is no real conflict between the two determinations of the strange sea density from the opposite--sign dimuon production and from the difference of the $F_2$ structure functions measured in neutrino and muon deep inelastic scattering. Once non universal sea parton densities are introduced, which take into account the effects of different mass thresholds and different longitudinal contributions, the discrepancy is shown to disappear and both sets of data are simultaneously well reproduced. No need for a large strange sea content of the nucleon emerges.Comment: latex, DFTT-93-3

The time as an emergent property of quantum mechanics, a synthetic description of a first experimental approach

The "problem of time" in present physics substantially consists in the fact that a straightforward quantization of the general relativistic evolution equation and constraints generates for the Universe wave function the Wheeler-De Witt equation, which describes a static Universe. Page and Wootters considered the fact that there exist states of a system composed by entangled subsystems that are stationary, but one can interpret the component subsystems as evolving: this leads them to suppose that the global state of the universe can be envisaged as one of this static entangled state, whereas the state of the subsystems can evolve. Here we synthetically present an experiment, based on PDC polarization entangled photons, that allows showing with a practical example a situation where this idea works, i.e. a subsystem of an entangled state works as a "clock" of another subsystem

The Strange Quark Distribution

We discuss the latest CCFR determination of the strange sea density of the proton. We comment on the differences with a previous, leading--order, result and point out the relevance of quark mass effects and current non--conservation effects. By taking them into account it is possible to solve the residual discrepancy with another determination of the strange quark distribution. Two important sources of uncertainties are also analyzed.Comment: 19page