INSTABILITY OF A NIELSEN-OLESEN VORTEX EMBEDDED IN THE ELECTROWEAK THEORY: II. ELECTROWEAK VORTICES AND GAUGE EQUIVALENCE

Vortex configurations in the electroweak gauge theory are investigated. Two gauge-inequivalent solutions of the field equations, the Z and W vortices, have previously been found. They correspond to embeddings of the abelian Nielsen-Olesen vortex solution into a U(1) subgroup of SU(2)xU(1). It is shown here that any electroweak vortex solution can be mapped into a solution of the same energy with a vanishing upper component of the Higgs field. The correspondence is a gauge equivalence for all vortex solutions except those for which the winding numbers of the upper and lower Higgs components add to zero. This class of solutions, which includes the W vortex, instead corresponds to a singular solution in the one-component gauge. The results, combined with numerical investigations, provide an argument against the existence of other vortex solutions in the gauge-Higgs sector of the Standard Model.Comment: 6 pages, plain latex, no figures, submitted to Mod. Phys. Lett. A as "Electroweak Vortices and Gauge Equivalence"

Capillary Wave Theory of Adsorbed Liquid Films and the Structure of the Liquid-Vapor Interface

In this paper we try to work out in detail the implications of a microscopic theory for capillary waves under the assumption that the density is given along lines normal to the interface. Our study provides interface Hamiltonians for adsorbed films in a variety of systems, and shows that the corrections to the classical capillary wave spectrum are of the same order as the surface tension. This implies that it is possible, at least in principle, to measure them in x-ray surface scattering experiments. Interestingly, our study also sheds some light on the nature of the liquid-vapor interface in the absence of external fields and allows us to reconcile the Fisk-Widom scaling hypothesis with capillary wave theory.Comment: Revised version, 51 pages, 4 figure

Gravitation as a Supersymmetric Gauge Theory

We propose a gauge theory of gravitation. The gauge potential is a connection of the Super SL(2,C) group. A MacDowell-Mansouri type of action is proposed where the action is quadratic in the Super SL(2,C) curvature and depends purely on gauge connection. By breaking the symmetry of the Super SL(2,C) topological gauge theory to SL(2,C), a spinor metric is naturally defined. With an auxiliary anti-commuting spinor field, the theory is reduced to general relativity. The Hamiltonian variables are related to the ones given by Ashtekar. The auxiliary spinor field plays the role of Witten spinor in the positive energy proof for gravitation.Comment: 11 pages, accepted for publication in Physics Letters

Localized corrosion of high performance metal alloys in an acid/salt environment

Various vacuum jacketed cryogenic supply lines at the Space Shuttle launch site at Kennedy Space Center use convoluted flexible expansion joints. The atmosphere at the launch site has a very high salt content, and during a launch, fuel combustion products include hydrochloric acid. This extremely corrosive environment has caused pitting corrosion failure in the thin walled 304L stainless steel flex hoses. A search was done to find a more corrosion resistant replacement material. The study focussed on 19 metal alloys. Tests which were performed include electrochemical corrosion testing, accelerated corrosion testing in a salt fog chamber, and long term exposure at a beach corrosion testing site. Based on the results of these tests, several nickel based alloys were found to have very high resistance to this corrosive environment. Also, there was excellent agreement between the electrochemical tests and the actual beach exposure tests. This suggests that electrochemical testing may be useful for narrowing the field of potential candidate alloys before subjecting samples to long term beach exposure

Singularities of Scattering Amplitudes on Unphysical Sheets and Their Interpretation

The analytic structure of two-particle scattering amplitudes on the unphysical sheet of the Riemann surface reached by crossing the two-particle cut is discussed. The singularities of the amplitudes there are shown to be poles and their physical interpretation is studied. The way in which bound states appear on the physical sheet in the Mandelstam representation, both as isolated poles and as cuts, is traced in detail. The properties of partial wave amplitudes and of the full amplitude as a function of energy and angle and of energy and momentum transfer are discussed. Finally, a few remarks are made in connection with unstable states

Damped reaction field method and the accelerated convergence of the real space Ewald summation

In this paper we study a general theoretical framework which allows to approximate the real space Ewald sum by means of effective force shifted screened potentials, together with a self term. Using this strategy it is possible to generalize the reaction field method, as a means to approximate the real space Ewald sum. We show that this method exhibits faster convergence of the Coulomb energy than several schemes proposed recently in the literature while enjoying a much more sound and clear electrostatic significance. In terms of the damping parameter of the screened potential, we are able to identify two clearly distinct regimes of convergence. Firstly, a reaction field regime corresponding to the limit of small screening, where effective pair potentials converge faster than the Ewald sum. Secondly, an Ewald regime, where the plain real space Ewald sum converges faster. Tuning the screening parameter for optimal convergence occurs essentially at the crossover. The implication is that effective pair potentials are an alternative to the Ewald sum only in those cases where optimization of the convergence error is not possible.Comment: 30 pages, 13 figures. Update

International low back pain guidelines: A comparison of two research based models of care for the management of acute low back pain.

Evidence based guidelines for the management of acute low back pain (ALBP) have been formulated by numerous countries. There are discrepancies between guidelines regarding physiotherapy treatment. The aim of this study was to compare two research based models derived from international LBP guidelines. A single-blind randomised controlled trial was undertaken in a physiotherapy outpatients department. Subjects with ALBP were randomly allocated to an ‘assess/advise/treat’ group (n = 50) or an ‘assess/advise/wait’ group (n = 52). The primary outcome measure was the Roland and Morris Disability Questionnaire (RMDQ). Secondary outcome measures of pain (VAS, usual pain intensity) depressive symptoms (MZSRDS) somatic distress (MSPQ) anxiety (STAIS) quality of life (SF36) and general health (EuroQol) were also obtained. Outcomes were assessed at 6-weeks, 3-months and 6-months. At 6-weeks subjects in the assess/advise/treat group demonstrated less LBP related disability (p = 0.02) and depressive symptoms (p = 0.01), as well as better general health (p = 0.006, p = 0.05), vitality (p \u3c 0.001), social functioning (p = 0.004) and mental health (p = 0.002). At long-term assessment (3 and 6 months) subjects in the assess/advise/treat group were less distressed (p = 0.004), anxious (p = 0.01) and had fewer depressive symptoms (p = 0.001), as well as reporting better general health (p = 0.009, p = 0.05), emotional role (p = 0.03) and mental health (p = 0.04). Active physiotherapy produces better short-term outcomes than advice. Delaying treatment has no long-term consequences on pain or disability, but affects the development of psychosocial features

Inherent Holography In Fuzzy Spaces and An N-tropic Approach To The Cosmological Constant Problem

In this letter we show that the noncommutative spaces, and in particular fuzzy spheres, are natural candidates which explicitly exhibit the holography, by noting that the smallest physically accessible volume is much larger that the expected Planckian size. Moreover, we show that fuzzy spheres provide us with a new approach, ''an $N$-tropic'' approach, to the cosmological constant problem, though in a Euclidean space-time.Comment: 11 pages, no figures; v3: Presentation improved by adding a discussion on the Schwarzchild blackhole entropy, the version to appear in PL