22,671 research outputs found
Precision heat forming of tetrafluoroethylene tubing
An invention that provides a method of altering the size of tetrafluoroethylene tubing which is only available in limited combination of wall thicknesses and diameter are discussed. The method includes the steps of sliding the tetrafluoroethylene tubing onto an aluminum mandrel and clamping the ends of the tubing to the mandrel by means of clamps. The tetrafluorethylene tubing and mandrel are then placed in a supporting coil which with the mandrel and tetrafluorethylene tubing are then positioned in a insulated steel pipe which is normally covered with a fiber glass insulator to smooth out temperature distribution therein. The entire structure is then placed in an event which heats the tetrafluorethylene tubing which is then shrunk by the heat to the outer dimension of the aluminum mandrel. After cooling the aluminum mandrel is removed from the newly sized tetrafluorethylene tubing by a conventional chemical milling process
Physical interpretation of NUT solution
We show that the well-known NUT solution can be correctly interpreted as
describing the exterior field of two counter-rotating semi-infinite sources
possessing negative masses and infinite angular momenta which are attached to
the poles of a static finite rod of positive mass.Comment: 7 pages, 1 figure, submitted to Classical and Quantum Gravit
Polyakov loop in chiral quark models at finite temperature
We describe how the inclusion of the gluonic Polyakov loop incorporates large
gauge invariance and drastically modifies finite temperature calculations in
chiral quark models after color neutral states are singled out. This generates
an effective theory of quarks and Polyakov loops as basic degrees of freedom.
We find a strong suppression of finite temperature effects in hadronic
observables triggered by approximate triality conservation (Polyakov cooling),
so that while the center symmetry breaking is exponentially small with the
constituent quark mass, chiral symmetry restoration is exponentially small with
the pion mass. To illustrate the point we compute some low energy observables
at finite temperature and show that the finite temperature corrections to the
low energy coefficients are suppressed due to color average of the
Polyakov loop. Our analysis also shows how the phenomenology of chiral quark
models at finite temperature can be made compatible with the expectations of
chiral perturbation theory. The implications for the simultaneous center
symmetry breaking-chiral symmetry restoration phase transition are also
discussed.Comment: 24 pages, 8 ps figures. Figure and appendix added. To appear in
Physical Review
Nonintegrability of the two-body problem in constant curvature spaces
We consider the reduced two-body problem with the Newton and the oscillator
potentials on the sphere and the hyperbolic plane .
For both types of interaction we prove the nonexistence of an additional
meromorphic integral for the complexified dynamic systems.Comment: 20 pages, typos correcte
Harmonic states for the free particle
Different families of states, which are solutions of the time-dependent free
Schr\"odinger equation, are imported from the harmonic oscillator using the
Quantum Arnold Transformation introduced in a previous paper. Among them,
infinite series of states are given that are normalizable, expand the whole
space of solutions, are spatially multi-localized and are eigenstates of a
suitably defined number operator. Associated with these states new sets of
coherent and squeezed states for the free particle are defined representing
traveling, squeezed, multi-localized wave packets. These states are also
constructed in higher dimensions, leading to the quantum mechanical version of
the Hermite-Gauss and Laguerre-Gauss states of paraxial wave optics. Some
applications of these new families of states and procedures to experimentally
realize and manipulate them are outlined.Comment: 21 pages, 3 figures. Title changed, content added, references adde
Large quantum nonlinear dynamic susceptibility of single-molecule magnets
The nonlinear dynamical response of Mn single-molecule magnets is
experimentally found to be very large, quite insensitive to the spin-lattice
coupling constant, and displaying peaks reversed with respect to classical
superparamagnets. It is shown that these features are caused by the strong
field dependence of the relaxation rate due to the detuning of energy levels
between which tunneling takes place. The nonlinear susceptibility technique,
previously overlooked, is thus proposed as a privileged probe to ascertain the
occurrence of quantum effects in mesoscopic magnetic systems.Comment: 4 pages, 4 figure
How can exact and approximate solutions of Einstein's field equations be compared?
The problem of comparison of the stationary axisymmetric vacuum solutions
obtained within the framework of exact and approximate approaches for the
description of the same general relativistic systems is considered. We suggest
two ways of carrying out such comparison: (i) through the calculation of the
Ernst complex potential associated with the approximate solution whose form on
the symmetry axis is subsequently used for the identification of the exact
solution possessing the same multipole structure, and (ii) the generation of
approximate solutions from exact ones by expanding the latter in series of
powers of a small parameter. The central result of our paper is the derivation
of the correct approximate analogues of the double-Kerr solution possessing the
physically meaningful equilibrium configurations. We also show that the
interpretation of an approximate solution originally attributed to it on the
basis of some general physical suppositions may not coincide with its true
nature established with the aid of a more accurate technique.Comment: 32 pages, 5 figure
Global Partial Density of States: Statistics and Localization Length in Quasi-one Dimensional disordered systems
We study the distributions functions for global partial density of states
(GPDOS) in quasi-one-dimensional (Q1D) disordered wires as a function of
disorder parameter from metal to insulator. We consider two different models
for disordered Q1D wire: a set of two dimensional potentials with an
arbitrary signs and strengths placed randomly, and a tight-binding Hamiltonian
with several modes and on-site disorder. The Green functions (GF) for two
models were calculated analytically and it was shown that the poles of GF can
be presented as determinant of the rank , where is the number of
scatters. We show that the variances of partial GPDOS in the metal to insulator
crossover regime are crossing. The critical value of disorder where we
have crossover can be used for calculation a localization length in Q1D
systems.Comment: RevTex4 8 .eps figure
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