11,823 research outputs found
Universality Principle for Orbital Angular Momentum and Spin in Gravity with Torsion
We argue that compatibility with elementary particle physics requires
gravitational theories with torsion to be unable to distinguish between orbital
angular momentum and spin. An important consequence of this principle is that
spinless particles must move along autoparallel trajectories, not along
geodesics.Comment: Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
paper also at http://www.physik.fu-berlin.de/~kleinert/kleiner_re27
Superconducting niobium thin film slow-wave structures
A superconducting comb structure as a slow-wave element in a traveling-wave maser will significantly improve maser noise temperature and gain by reducing the insertion loss. The results of the insertion loss measurements of superconducting niobium slow-wave structures subjected to maser operating conditions at X-Band frequencies are presented
Tetragonal CuO: A new end member of the 3d transition metal monoxides
Monoclinic CuO is anomalous both structurally as well as electronically in
the 3 transition metal oxide series. All the others have the cubic rock salt
structure. Here we report the synthesis and electronic property determination
of a tetragonal (elongated rock salt) form of CuO created using an epitaxial
thin film deposition approach. In situ photoelectron spectroscopy suggests an
enhanced charge transfer gap with the overall bonding more ionic. As
an end member of the 3d transition monoxides, its magnetic properties should be
that of a high antiferromagnet
Fermion Helicity Flip Induced by Torsion Field
We show that in theories of gravitation with torsion the helicity of fermion
particles is not conserved and we calculate the probability of spin flip, which
is related to the anti-symmetric part of affine connection. Some cosmological
consequences are discussed.Comment: 6 pages, to appear in Europhysics Letter
Two-dimensional molecular para-hydrogen and ortho-deuterium at zero temperature
We study molecular para-hydrogen (p-) and ortho-deuterium
(o-) in two dimensions and in the limit of zero temperature by
means of the diffusion Monte Carlo method. We report energetic and structural
properties of both systems like the total and kinetic energy per particle,
radial pair distribution function, and Lindemann's ratio in the low pressure
regime. By comparing the total energy per particle as a function of the density
in liquid and solid p-, we show that molecular para-hydrogen, and
also ortho-deuterium, remain solid at zero temperature. Interestingly, we
assess the quality of three different symmetrized trial wave functions, based
on the Nosanow-Jastrow model, in the p- solid film at the
variational level. In particular, we analyze a new type of symmetrized trial
wave function which has been used very recently to describe solid He and
found that also characterizes hydrogen satisfactorily. With this wave function,
we show that the one-body density matrix of solid p- possesses off-diagonal long range order, with a condensate fraction
that increases sizably in the negative pressure regime.Comment: 11 pages, 9 figure
Dilute Bose gases interacting via power-law potentials
Neutral atoms interact through a van der Waals potential which asymptotically
falls off as r^{-6}. In ultracold gases, this interaction can be described to a
good approximation by the atom-atom scattering length. However, corrections
arise that depend on the characteristic length of the van der Waals potential.
We parameterize these corrections by analyzing the energies of two- and
few-atom systems under external harmonic confinement, obtained by numerically
and analytically solving the Schrodinger equation. We generalize our results to
particles interacting through a longer-ranged potential which asymptotically
falls off as r^{-4}.Comment: 7 pages, 4 figure
XUV Frequency Combs via Femtosecond Enhancement Cavities
We review the current state of tabletop extreme ultraviolet (XUV) sources
based on high harmonic generation (HHG) in femtosecond enhancement cavities
(fsEC). Recent developments have enabled generation of high photon flux (1014
photons/sec) in the XUV, at high repetition rates (>50 MHz) and spanning the
spectral region from 40 nm - 120 nm. This level of performance has enabled
precision spectroscopy with XUV frequency combs and promises further
applications in XUV spectroscopic and photoemission studies. We discuss the
theory of operation and experimental details of the fsEC and XUV generation
based on HHG, including current technical challenges to increasing the photon
flux and maximum photon energy produced by this type of system. Current and
future applications for these sources are also discussed.Comment: invited review article, 38 page
Spinless Matter in Transposed-Equi-Affine Theory of Gravity
We derive and discus the equations of motion for spinless matter:
relativistic spinless scalar fields, particles and fluids in the recently
proposed by A. Saa model of gravity with covariantly constant volume with
respect to the transposed connection in Einstein-Cartan spaces.
A new interpretation of this theory as a theory with variable Plank
"constant" is suggested.
We show that the consistency of the semiclassical limit of the wave equation
and classical motion dictates a new definite universal interaction of torsion
with massive fields.Comment: 29 pages, latex, no figures. New Section on semiclassical limit of
wave equation added; old references rearranged; new references, remarks,
comments, and acknowledgments added; typos correcte
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