554 research outputs found
An assessment of Evans' unified field theory II
Evans developed a classical unified field theory of gravitation and
electromagnetism on the background of a spacetime obeying a Riemann-Cartan
geometry. In an accompanying paper I, we analyzed this theory and summarized it
in nine equations. We now propose a variational principle for Evans' theory and
show that it yields two field equations. The second field equation is algebraic
in the torsion and we can resolve it with respect to the torsion. It turns out
that for all physical cases the torsion vanishes and the first field equation,
together with Evans' unified field theory, collapses to an ordinary Einstein
equation.Comment: 11 pages of late
Female song in the hooded warbler
One female Hooded Warbler (Wilsonia citrina) was discovered singing in July 1993, and another in May 1996 among a color-banded breeding population under investigation. The first female\u27s song structurally resembled the typical male Hooded Warbler mixed-mode song in duration, frequency range, and number of syllables, although it had an atypical raspy quality. Males responded similarly to playbacks of the female song and a male song from the same population. We suggest that age and high breeding density may be explanatory factors for this rare behavior
The Nakayama automorphism of the almost Calabi-Yau algebras associated to SU(3) modular invariants
We determine the Nakayama automorphism of the almost Calabi-Yau algebra A
associated to the braided subfactors or nimrep graphs associated to each SU(3)
modular invariant. We use this to determine a resolution of A as an A-A
bimodule, which will yield a projective resolution of A.Comment: 46 pages which constitutes the published version, plus an Appendix
detailing some long calculations. arXiv admin note: text overlap with
arXiv:1110.454
An assessment of Evans' unified field theory I
Evans developed a classical unified field theory of gravitation and
electromagnetism on the background of a spacetime obeying a Riemann-Cartan
geometry. This geometry can be characterized by an orthonormal coframe theta
and a (metric compatible) Lorentz connection Gamma. These two potentials yield
the field strengths torsion T and curvature R. Evans tried to infuse
electromagnetic properties into this geometrical framework by putting the
coframe theta to be proportional to four extended electromagnetic potentials A;
these are assumed to encompass the conventional Maxwellian potential in a
suitable limit. The viable Einstein-Cartan(-Sciama-Kibble) theory of gravity
was adopted by Evans to describe the gravitational sector of his theory.
Including also the results of an accompanying paper by Obukhov and the author,
we show that Evans' ansatz for electromagnetism is untenable beyond repair both
from a geometrical as well as from a physical point of view. As a consequence,
his unified theory is obsolete.Comment: 39 pages of latex, modified because of referee report, mistakes and
typos removed, partly reformulated, taken care of M.W.Evans' rebutta
On the Exact Evaluation of Certain Instances of the Potts Partition Function by Quantum Computers
We present an efficient quantum algorithm for the exact evaluation of either
the fully ferromagnetic or anti-ferromagnetic q-state Potts partition function
Z for a family of graphs related to irreducible cyclic codes. This problem is
related to the evaluation of the Jones and Tutte polynomials. We consider the
connection between the weight enumerator polynomial from coding theory and Z
and exploit the fact that there exists a quantum algorithm for efficiently
estimating Gauss sums in order to obtain the weight enumerator for a certain
class of linear codes. In this way we demonstrate that for a certain class of
sparse graphs, which we call Irreducible Cyclic Cocycle Code (ICCC_\epsilon)
graphs, quantum computers provide a polynomial speed up in the difference
between the number of edges and vertices of the graph, and an exponential speed
up in q, over the best classical algorithms known to date
Transient behavior in Single-File Systems
We have used Monte-Carlo methods and analytical techniques to investigate the
influence of the characteristics, such as pipe length, diffusion, adsorption,
desorption and reaction rates on the transient properties of Single-File
Systems. The transient or the relaxation regime is the period in which the
system is evolving to equilibrium. We have studied the system when all the
sites are reactive and when only some of them are reactive. Comparisons between
Mean-Field predictions, Cluster Approximation predictions, and Monte Carlo
simulations for the relaxation time of the system are shown. We outline the
cases where Mean-Field analysis gives good results compared to Dynamic
Monte-Carlo results. For some specific cases we can analytically derive the
relaxation time. Occupancy profiles for different distribution of the sites
both for Mean-Field and simulations are compared. Different results for slow
and fast reaction systems and different distribution of reactive sites are
discussed.Comment: 18 pages, 19 figure
Determinant representation for some transition probabilities in the TASEP with second class particles
We study the transition probabilities for the totally asymmetric simple
exclusion process (TASEP) on the infinite integer lattice with a finite, but
arbitrary number of first and second class particles. Using the Bethe ansatz we
present an explicit expression of these quantities in terms of the Bethe wave
function. In a next step it is proved rigorously that this expression can be
written in a compact determinantal form for the case where the order of the
first and second class particles does not change in time. An independent
geometrical approach provides insight into these results and enables us to
generalize the determinantal solution to the multi-class TASEP.Comment: Minor revision; journal reference adde
Spectral Element Method for Vector Radiative Transfer Equation
A spectral element method (SEM) is developed to solve polarized radiative
transfer in multidimensional participating medium. The angular discretization
is based on the discrete-ordinates approach, and the spatial discretization is
conducted by spectral element approach. Chebyshev polynomial is used to build
basis function on each element. Four various test problems are taken as
examples to verify the performance of the SEM. The effectiveness of the SEM is
demonstrated. The h and the p convergence characteristics of the SEM are
studied. The convergence rate of p-refinement follows the exponential decay
trend and is superior to that of h-refinement. The accuracy and efficiency of
the higher order approximation in the SEM is well demonstrated for the solution
of the VRTE. The predicted angular distribution of brightness temperature and
Stokes vector by the SEM agree very well with the benchmark solutions in
references. Numerical results show that the SEM is accurate, flexible and
effective to solve multidimensional polarized radiative transfer problems.Comment: The paper have bee published in JQSR
Dynamics of liquid He-4 in confined geometries from Time-Dependent Density Functional calculations
We present numerical results obtained from Time-Dependent Density Functional
calculations of the dynamics of liquid He-4 in different environments
characterized by geometrical confinement. The time-dependent density profile
and velocity field of He-4 are obtained by means of direct numerical
integration of the non-linear Schrodinger equation associated with a
phenomenological energy functional which describes accurately both the static
and dynamic properties of bulk liquid He-4. Our implementation allows for a
general solution in 3-D (i.e. no symmetries are assumed in order to simplify
the calculations). We apply our method to study the real-time dynamics of pure
and alkali-doped clusters, of a monolayer film on a weakly attractive surface
and a nano-droplet spreading on a solid surface.Comment: q 1 tex file + 9 Ps figure
The impact of working memory load on task execution and online plan adjustment during multitasking in a virtual environment
Three experiments investigated the impact of working memory load on online plan adjustment during a test of multitasking in young, nonexpert, adult participants. Multitasking was assessed using the Edinburgh Virtual Errands Test (EVET). Participants were asked to memorize either good or poor plans for performing multiple errands and were assessed both on task completion and on the extent to which they modified their plans during EVET performance. EVET was performed twice, with and without a secondary task loading a component of working memory. In Experiment 1, articulatory suppression was used to load the phonological loop. In Experiment 2, oral random generation was used to load executive functions. In Experiment 3, spatial working memory was loaded with an auditory spatial localization task. EVET performance for both good- and poor-planning groups was disrupted by random generation and sound localization, but not by articulatory suppression. Additionally, people given a poor plan were able to overcome this initial disadvantage by modifying their plans online. It was concluded that, in addition to executive functions, multiple errands performance draws heavily on spatial, but not verbal, working memory resources but can be successfully completed on the basis of modifying plans online, despite a secondary task load
- …