1,693 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
Comment on Path Integral Derivation of Schr\"odinger Equation in Spaces with Curvature and Torsion
We present a derivation of the Schr\"odinger equation for a path integral of
a point particle in a space with curvature and torsion which is considerably
shorter and more elegant than what is commonly found in the literature.Comment: LaTeX file in sr
Addendum to paper: Strong-Coupling Behavior of -Theories and Critical Exponents [Phys. Rev. D 57, 2264 (1998)]
The graphical extrapolation procedure to infinite order of variational
perturbation theory in a recent calculation of critical exponents of
three-dimensional -theories at infinite couplings is improved by
another way of plotting the results.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_re257a/preprint.htm
Modelling two-dimensional Crystals with Defects under Stress: Superelongation of Carbon Nanotubes at high Temperatures
We calculate analytically the phase diagram of a two-dimensional square
crystal and its wrapped version with defects under external homogeneous stress
as a function of temperature using a simple elastic lattice model that allows
for defect formation. The temperature dependence turns out to be very weak. The
results are relevant for recent stress experiments on carbon nanotubes. Under
increasing stress, we find a crossover regime which we identify with a cracking
transition that is almost independent of temperature. Furthermore, we find an
almost stress-independent melting point. In addition, we derive an enhanced
ductility with relative strains before cracking between 200-400%, in agreement
with carbon nanotube experiments. The specific values depend on the Poisson
ratio and the angle between the external force and the crystal axes. We give
arguments that the results for carbon nanotubes are not much different to the
wrapped square crystal.Comment: 12 pages, 6 eps figures, section VI added discussing the
modifications of our model when applied to tube
Nonholonomic Mapping Principle for Classical Mechanics in Spaces with Curvature and Torsion. New Covariant Conservation Law for Energy-Momentum Tensor
The lecture explains the geometric basis for the recently-discovered
nonholonomic mapping principle which specifies certain laws of nature in
spacetimes with curvature and torsion from those in flat spacetime, thus
replacing and extending Einstein's equivalence principle. An important
consequence is a new action principle for determining the equation of motion of
a free spinless point particle in such spacetimes. Surprisingly, this equation
contains a torsion force, although the action involves only the metric. This
force changes geodesic into autoparallel trajectories, which are a direct
manifestation of inertia. The geometric origin of the torsion force is a
closure failure of parallelograms. The torsion force changes the covariant
conservation law of the energy-momentum tensor whose new form is derived.Comment: Corrected typos. Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Paper also at
http://www.physik.fu-berlin.de/~kleinert/kleiner_re261/preprint.htm
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