2,919 research outputs found

### Vector Currents of Massive Neutrinos of an Electroweak Nature

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

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

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
$g \to 0$, $g$ 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

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

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 $R$ of a spherically
symmetric charge is order $R^2$ rather than order $R$ 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

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

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 ($T_K$ and $T_S$) and the relation between $T_S$ and the heat
input to the gas. We outline the conditions for a ``two phase medium'' to
exist. We find that although $T_S$ can be much smaller than $T_K$, $T_S$ is
always $\gg 3$ K for column densities greater that $5 \times 10^{18}$
cm$^{-2}$. 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

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

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