Gauging Newton's Law

We derive both Lagrangian and Hamiltonian mechanics as gauge theories of Newtonian mechanics. Systematic development of the distinct symmetries of dynamics and measurement suggest that gauge theory may be motivated as a reconciliation of dynamics with measurement. Applying this principle to Newton's law with the simplest measurement theory leads to Lagrangian mechanics, while use of conformal measurement theory leads to Hamilton's equations.Comment: 44 pages, no figures, LaTe

Dilatation of saphenous vein grafts by nitric oxide

Objectives:To investigate firstly whether flow-dependent vasodilation is maintained in vein grafts, and secondly whether nitric oxide donors dilate vein grafts to improve the flow through graft stenoses.Design, materials and methods:The vasodilatation of mature patent vein grafts, in response to reactive hyperaemia and glyceryl trinitrate (GTN), was assessed by the change in external diameter using duplex ultrasonography. The severity (ratio of proximal systolic velocity, V1, to peak systolic velocity at the stenosis, V2, of vein graft stenoses was determined by duplex ultrasonography before and after 24 h of local application of GTN patches.Results:In post-occlusion hyperaemia the diameter of patent distal vein grafts (n = 7) increased to a maximum of 112±1.9% of resting diameter after 2 min, p = 0.026. The diameter increased further to 117±2.5% of the resting value 5 min after oral GTN (n = 5), p = 0.007. The velocity ratio, V2/V1, through graft stenoses (n = 6) decreased by 20 ± 5% after application of GTN patches, principally as a result of reduction in V2, mean difference 0.8, p = 0.15. The changes in response to GTN were more evident for proximal than distal vein graft stenoses.Conclusion:Flow-induced vasodilatation responses, which have been attributed to the endothelial release of nitric oxide, are maintained in patent vein grafts: the grafts dilate even further in response to GTN. The application of GTN patches close to a vein graft stenosis appears to reduce the velocity ratio through vein graft stenoses. GTN patches might be used to reduce the risk of graft occlusion when there is a delay between the detection and the treatment of haemodynamically significant graft stenoses

Light Unstable Sterile Neutrino

The three massless active (doublet) neutrinos may mix with two heavy and one \underline {light} sterile (singlet) neutrinos so that the induced masses and mixings among the former are able to explain the present data on atmospheric and solar neutrino oscillations. If the LSND result is also to be explained, one active neutrino mass eigenstate must mix with the light sterile neutrino. A specific model is proposed with the spontaneous and soft explicit breaking of a new global $U(1)_S$ symmetry so that a sterile neutrino will decay into an active antineutrino and a nearly massless pseudo-Majoron.Comment: Discussion and references adde

A two-mass expanding exact space-time solution

In order to understand how locally static configurations around gravitationally bound bodies can be embedded in an expanding universe, we investigate the solutions of general relativity describing a space-time whose spatial sections have the topology of a 3-sphere with two identical masses at the poles. We show that Israel junction conditions imply that two spherically symmetric static regions around the masses cannot be glued together. If one is interested in an exterior solution, this prevents the geometry around the masses to be of the Schwarzschild type and leads to the introduction of a cosmological constant. The study of the extension of the Kottler space-time shows that there exists a non-static solution consisting of two static regions surrounding the masses that match a Kantowski-Sachs expanding region on the cosmological horizon. The comparison with a Swiss-Cheese construction is also discussed.Comment: 15 pages, 5 figures. Replaced to match the published versio

Axions and their Relatives

A review of the status of axions and axion-like particles is given. Special attention is devoted to the recent results of the PVLAS collaboration, which are in conflict with the CAST data and with the astrophysical constraints. Solutions to the puzzle and the implications for new physics are discussed. The question of axion-like particles being dark matter is also addressed.Comment: Updated version of an invited talk at the Axion Training (CERN, December 2005). To appear as a Lecture Notes in Physics (Springer-Verlag), edited by B. Beltran, M. Kuster and G. Raffel

Validity of Flavor Symmetry and Charge Symmetry for Parton Distributions

Recent experimental measurements of the Gottfried Sum Rule, and pp and pD Drell-Yan processes, suggest significant violation of flavor symmetry in the proton sea. This interpretation rests on the assumption of parton charge symmetry. Our model calculations suggest charge symmetry violation [CSV] for parton valence distributions of a few percent. Precision measurements of structure functions in muon and neutrino experiments allow us to set rather stringent experimental limits on CSV in certain kinematic regions. In another region, these experiments suggest substantial CSV effects. We suggest experiments which could test parton CSV.Comment: 8 pages, 4 figures, talk at Workshop on Future Directions in Quark-Nuclear Physics, Center for the Subatomic Structure of Matter, Adelaide, Australia, Mar 9-20, 1998, to appear in conference proceeding

The reaction Δ+N→N+N+ϕ\Delta+N\to N+N+\phi in ion-ion collisions

We study the threshold $\phi$-meson production in the process $\Delta+N\to N+N+\phi$, which appears as a possible important mechanism in high energy nuclei-nuclei collisions. The isotopic invariance of the strong interaction and the selection rules due to P-parity and total angular momentum result in a general and model independent parametrization of the spin structure of the matrix element in terms of three partial amplitudes. In the framework of one-pion exchange model these amplitudes can be derived in terms of the two threshold partial amplitudes for the process $\pi+N\to N+\phi$. We predict the ratio of cross sections for $\phi-$meson production in $pp$- and $\Delta N$-collisions and the polarization properties of the $\phi$-meson, in $\Delta+N\to N+N+\phi$, as a function of a single parameter, which characterizes the relative role of transversal and longitudinal $\phi$-meson polarizations in the process $\pi+N\to N+\phi$.Comment: 10 pages 3 figure

Indirect search for dark matter: prospects for GLAST

Possible indirect detection of neutralino, through its gamma-ray annihilation product, by the forthcoming GLAST satellite from our galactic halo, M31, M87 and the dwarf galaxies Draco and Sagittarius is studied. Gamma-ray fluxes are evaluated for the two representative energy thresholds, 0.1 GeV and 1.0 GeV, at which the spatial resolution of GLAST varies considerably. Apart from dwarfs which are described either by a modified Plummer profile or by a tidally-truncated King profiles, fluxes are compared for halos with central cusps and cores. It is demonstrated that substructures, irrespective of their profiles, enhance the gamma-ray emission only marginally. The expected gamma-ray intensity above 1 GeV at high galactic latitudes is consistent with the residual emission derived from EGRET data if the density profile has a central core and the neutralino mass is less than 50 GeV, whereas for a central cusp only a substantial enhancement would explain the observations. From M31, the flux can be detected above 0.1 GeV and 1.0 GeV by GLAST only if the neutralino mass is below 300 GeV and if the density profile has a central cusp, case in which a significant boost in the gamma-ray emission is produced by the central black hole. For Sagittarius, the flux above 0.1 GeV is detectable by GLAST provided the neutralino mass is below 50 GeV. From M87 and Draco the fluxes are always below the sensitivity limit of GLAST.Comment: 14 Pages, 7 Figures, 3 Tables, version to appear on Physical Review

Partial Deconfinement in Color Superconductivity

We analyze the fate of the unbroken SU(2) color gauge interactions for 2 light flavors color superconductivity at non zero temperature. Using a simple model we compute the deconfining/confining critical temperature and show that is smaller than the critical temperature for the onset of the superconductive state itself. The breaking of Lorentz invariance, induced already at zero temperature by the quark chemical potential, is shown to heavily affect the value of the critical temperature and all of the relevant features related to the deconfining transition. Modifying the Polyakov loop model to describe the SU(2) immersed in the diquark medium we argue that the deconfinement transition is second order. Having constructed part of the equation of state for the 2 color superconducting phase at low temperatures our results are relevant for the physics of compact objects featuring a two flavor color superconductive state.Comment: 9 pp, 4 eps-figs, version to appear in PR