2,919 research outputs found

    Vector Currents of Massive Neutrinos of an Electroweak Nature

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    The mass of an electroweakly interacting neutrino consists of the electric and weak parts responsible for the existence of its charge, charge radius, and magnetic moment. Such connections explain the formation of paraneutrinos, for example, at the polarized neutrino electroweak scattering by spinless nuclei. We derive the structural equations that relate the self-components of mass to charge, charge radius, and magnetic moment of each neutrino as a consequence of unification of fermions of a definite flavor. They indicate the availability of neutrino universality and require following its logic in a constancy law dependence of the size implied from the multiplication of a weak mass of neutrino by its electric mass. According to this principle, all Dirac neutrinos of a vector nature, regardless of the difference in their masses, have the same charge, an identical charge radius, as well as an equal magnetic moment. Thereby, the possibility appears of establishing the laboratory limits of weak masses of the investigated types of neutrinos. Finding estimates show clearly that the earlier measured properties of these particles may testify in favor of the unified mass structure of their interaction with any of the corresponding types of gauge fields.Comment: 14 pages, LaTex, Published version in CJ

    The Minkowski metric in non-inertial observer radar coordinates

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    We give a closed expression for the Minkowski (1+1)-dimensional metric in the radar coordinates of an arbitrary non-inertial observer O in terms of O's proper acceleration. Knowledge of the metric allows the non-inertial observer to perform experiments in spacetime without making reference to inertial frames. To clarify the relation between inertial and non-inertial observers the coordinate transformation between radar and inertial coordinates, also is given. We show that every conformally flat coordinate system can be regarded as the radar coordinate system of a suitable observer for a suitable parametrization of the observer worldline. Therefore, the coordinate transformation between arbitrarily moving observers is a conformal transformation and conformally invariant (1+1)-dimensional theories lead to the same physics for all observers, independently of their relative motion.Comment: Revtex4, 6 pages, 1 figur

    On the approach to equilibrium of an Hamiltonian chain of anharmonic oscillators

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    In this note we study the approach to equilibrium of a chain of anharmonic oscillators. We find indications that a sufficiently large system always relaxes to the usual equilibrium distribution. There is no sign of an ergodicity threshold. The time however to arrive to equilibrium diverges when g0g \to 0, gg being the anharmonicity.Comment: 8 pages, 5 figure

    Relativistic Cyclotron Radiation Detection of Tritium Decay Electrons as a New Technique for Measuring the Neutrino Mass

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    The shape of the beta decay energy distribution is sensitive to the mass of the electron neutrino. Attempts to measure the endpoint shape of tritium decay have so far seen no distortion from the zero-mass form, thus placing an upper limit of m_nu_beta < 2.3 eV. Here we show that a new type of electron energy spectroscopy could improve future measurements of this spectrum and therefore of the neutrino mass. We propose to detect the coherent cyclotron radiation emitted by an energetic electron in a magnetic field. For mildly relativistic electrons, like those in tritium decay, the relativistic shift of the cyclotron frequency allows us to extract the electron energy from the emitted radiation. We present calculations for the energy resolution, noise limits, high-rate measurement capability, and systematic errors expected in such an experiment.Comment: 4 pages, 2 figure

    Finite size corrections to the radiation reaction force in classical electrodynamics

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    We introduce an effective field theory approach that describes the motion of finite size objects under the influence of electromagnetic fields. We prove that leading order effects due to the finite radius RR of a spherically symmetric charge is order R2R^2 rather than order RR in any physical model, as widely claimed in the literature. This scaling arises as a consequence of Poincar\'e and gauge symmetries, which can be shown to exclude linear corrections. We use the formalism to calculate the leading order finite size correction to the Abraham-Lorentz-Dirac force.Comment: 4 pages, 2 figure

    Quadrupole-scissors modes and nonlinear mode coupling in trapped two-component Bose-Einstein condensates

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    We theoretically investigate quadrupolar collective excitations in two-component Bose-Einstein condensates and their nonlinear dynamics associated with harmonic generation and mode coupling. Under the Thomas-Fermi approximation and the quadratic polynomial ansatz for density fluctuations, the linear analysis of the superfluid hydrodynamic equations predicts excitation frequencies of three normal modes constituted from monopole and quadrupole oscillations, and those of three scissors modes. We obtain analytically the resonance conditions for the second harmonic generation in terms of the trap aspect ratio and the strength of intercomponent interaction. The numerical simulation of the coupled Gross-Pitaevskii equations vindicates the validity of the analytical results and reveals the dynamics of the second harmonic generation and nonlinear mode coupling that lead to nonlinear oscillations of the condensate with damping and recurrence reminiscent of the Fermi-Pasta-Ulam problem.Comment: 10 pages, 5 figures, revtex

    Hi Spin Temperatures and Heating Requirements in Outer Regions of Disk Galaxies

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    ABSRACT:We show how to use 21-cm emission and absorption studies to estimate the heat inputs to the neutral gas in low pressure environments, such as in outer disks of spiral galaxies, in galactic halos or in intergalactic space. For a range of model parameters we calculate the gas kinetic and spin temperatures (TKT_K and TST_S) and the relation between TST_S and the heat input to the gas. We outline the conditions for a ``two phase medium'' to exist. We find that although TST_S can be much smaller than TKT_K, TST_S is always 3 \gg 3 K for column densities greater that 5×10185 \times 10^{18} cm2^{-2}. This excludes the possibility that relevant HI masses at the periphery of galaxies are invisible at 21-cm in emission. The outermost interstellar gas in a disk galaxy is more directly affected by external processes and in this paper we estimate the intensity of the extragalactic background at energies close to 0.1 keV by comparing our theoretical results with HI emission/absorption studies. We take into account the possibility that some energy produced in the inner regions affects the energy balance in outer regions. We find that in the absence of any other local heat source QSO dominated background models are still compatible with the spin temperature limits derived for the two best documented HI emission/absorption studies in outer regions.Comment: 24 pages, 8 figures ARCETRI-PR-93-2

    Thermodynamic constraints on fluctuation phenomena

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    The relationships between reversible Carnot cycles, the absence of perpetual motion machines and the existence of a non-decreasing, globally unique entropy function forms the starting point of many textbook presentations of the foundations of thermodynamics. However, the thermal fluctuation phenomena associated with statistical mechanics has been argued to restrict the domain of validity of this basis of the second law of thermodynamics. Here we demonstrate that fluctuation phenomena can be incorporated into the traditional presentation, extending, rather than restricting, the domain of validity of the phenomenologically motivated second law. Consistency conditions lead to constraints upon the possible spectrum of thermal fluctuations. In a special case this uniquely selects the Gibbs canonical distribution and more generally incorporates the Tsallis distributions. No particular model of microscopic dynamics need be assumed.Comment: 12 pages, 24 figure