Diffractive deeply inelastic scattering of hadronic states with small transverse size

Diffractive deeply inelastic scattering from a hadron is described in terms of diffractive quark and gluon distributions. If the transverse size of the hadronic state is sufficiently small, these distributions are calculable using perturbation theory. We present such a calculation and discuss the underlying dynamics. We comment on the relation between this dynamics and the pattern of scaling violation observed in the hard diffraction of large-size states at HERA.Comment: 8 pages including 3 figures, REVTE

Building a refinement checker for Z

In previous work we have described how refinements can be checked using a temporal logic based model-checker, and how we have built a model-checker for Z by providing a translation of Z into the SAL input language. In this paper we draw these two strands of work together and discuss how we have implemented refinement checking in our Z2SAL toolset. The net effect of this work is that the SAL toolset can be used to check refinements between Z specifications supplied as input files written in the LaTeX mark-up. Two examples are used to illustrate the approach and compare it with a manual translation and refinement check.Comment: In Proceedings Refine 2011, arXiv:1106.348

Electrodynamic Limit in a Model for Charged Solitons

We consider a model of topological solitons where charged particles have finite mass and the electric charge is quantised already at the classical level. In the electrodynamic limit, which physically corresponds to electrodynamics of solitons of zero size, the Lagrangian of this model has two degrees of freedom only and reduces to the Lagrangian of the Maxwell field in dual representation. We derive the equations of motion and discuss their relations with Maxwell's equations. It is shown that Coulomb and Lorentz forces are a consequence of topology. Further, we relate the U(1) gauge invariance of electrodynamics to the geometry of the soliton field, give a general relation for the derivation of the soliton field from the field strength tensor in electrodynamics and use this relation to express homogeneous electric fields in terms of the soliton field.Comment: 13 pages, 4 figures, Introduction and Section II (Model Lagrangian) rewritten, new chapters concerning electrodynamic limit and discussion of causality inserte

Waring's number for large subgroups of double-struck Z_p

Let p be a prime, Z_p be the finite field in p elements, k be a positive integer, and A be the multiplicative subgroup of nonzero k-th powers in Z_p. The goal of this paper is to determine, for a given positive integer s, a value t_s such that if |A| ≫ t_s then every element of Z_p is a sum of s k-th powers. We obtain t_4 = p^{\frac{22}{39} + \in}, t_5 = p^{\frac{15}{29} + \in} and for s s ≥ 6, t_s = p^{\frac{9s+45}{29s+33} + \in}. For s ≥ 24 further improvements are made, such as t_32 = p^{\frac{5}{16} + \in} and t_128 = p^{\frac{1}{4}}

Phenomenological description of the gamma* p cross section at low Q2

Low Q2 photon-proton cross sections are analysed using a simple, QCD-motivated parametrisation $\sigma_{\gamma^\star p}\propto 1/(Q^2+Q_0^2)$, which gives a good description of the data. The Q2 dependence of the gamma* p cross section is discussed in terms of the partonic transverse momenta of the hadronic state the photon fluctuates into.Comment: 14 pages, revtex, epsfig, 2 figure

Inelastic diffraction and color-singlet gluon-clusters in high-energy hadron-hadron and lepton-hadron collisions

It is proposed, that ``the colorless objects'' which manifest themselves in large-rapidity-gap events are color-singlet gluon-clusters due to self-organized criticality (SOC), and that optical-geometrical concepts and methods are useful in examing the space-time properties of such objects. A simple analytical expression for the $t$-dependence of the inelastic single diffractive cross section $d\sigma/dt$ ($t$ is the four-momentum transfer squared) is derived. Comparison with the existing data and predictions for future experiments are presented. The main differences and similarities between the SOC-approach and the ``Partons in the Pomeron (Pomeron and Reggeon)''-approach are discussed.Comment: 12 pages, 2 figure

Critical holes in undercooled wetting layers

The profile of a critical hole in an undercooled wetting layer is determined by the saddle-point equation of a standard interface Hamiltonian supported by convenient boundary conditions. It is shown that this saddle-point equation can be mapped onto an autonomous dynamical system in a three-dimensional phase space. The corresponding flux has a polynomial form and in general displays four fixed points, each with different stability properties. On the basis of this picture we derive the thermodynamic behaviour of critical holes in three different nucleation regimes of the phase diagram.Comment: 18 pages, LaTeX, 6 figures Postscript, submitted to J. Phys.

New Global Defect Structures

We investigate the presence of defects in systems described by real scalar field in (D,1) spacetime dimensions. We show that when the potential assumes specific form, there are models which support stable global defects for D arbitrary. We also show how to find first-order differential equations that solve the equations of motion, and how to solve models in D dimensions via soluble problems in D=1. We illustrate the procedure examining specific models and finding explicit solutions.Comment: RevTex4, 4 pages, 3 eps figures; to be published in Phys. Rev. Let

Comparison of data and process refinement

When is it reasonable, or possible, to refine a one place buffer into a two place buffer? In order to answer this question we characterise refinement based on substitution in restricted contexts. We see that data refinement (specifically in Z) and process refinement give differing answers to the original question, and we compare the precise circumstances which give rise to this difference by translating programs and processes into labelled transition systems, so providing a common basis upon which to make the comparison. We also look at the closely related area of subtyping of objects. Along the way we see how all these sorts of computational construct are related as far as refinement is concerned, discover and characterise some (as far as we can tell) new sorts of refinement and, finally, point up some research avenues for the future