882 research outputs found
Conserved Noether Currents, Utiyama's Theory of Invariant Variation, and Velocity Dependence in Local Gauge Invariance
The paper discusses the mathematical consequences of the application of
derived variables in gauge fields. Physics is aware of several phenomena, which
depend first of all on velocities (like e.g., the force caused by charges
moving in a magnetic field, or the Lorentz transformation). Applying the
property of the second Noether theorem, that allowed generalised variables,
this paper extends the article by Al-Kuwari and Taha (1991) with a new
conclusion. They concluded that there are no extra conserved currents
associated with local gauge invariance. We show, that in a more general case,
there are further conserved Noether currents. In its method the paper
reconstructs the clue introduced by Utiyama (1956, 1959) and followed by
Al-Kuwari and Taha (1991) in the presence of a gauge field that depends on the
co-ordinates of the velocity space. In this course we apply certain (but not
full) analogies with Mills (1989). We show, that handling the space-time
coordinates as implicit variables in the gauge field, reproduces the same
results that have been derived in the configuration space (i.e., we do not lose
information), while the proposed new treatment gives additional information
extending those. The result is an extra conserved Noether current.Comment: 14 page
CRL at Ntcir2
We have developed systems of two types for NTCIR2. One is an enhenced version
of the system we developed for NTCIR1 and IREX. It submitted retrieval results
for JJ and CC tasks. A variety of parameters were tried with the system. It
used such characteristics of newspapers as locational information in the CC
tasks. The system got good results for both of the tasks. The other system is a
portable system which avoids free parameters as much as possible. The system
submitted retrieval results for JJ, JE, EE, EJ, and CC tasks. The system
automatically determined the number of top documents and the weight of the
original query used in automatic-feedback retrieval. It also determined
relevant terms quite robustly. For EJ and JE tasks, it used document expansion
to augment the initial queries. It achieved good results, except on the CC
tasks.Comment: 11 pages. Computation and Language. This paper describes our results
of information retrieval in the NTCIR2 contes
Confinement, Vacuum Structure: from QCD to Quantum Gravity
A minimal Lorentz gauge gravity model with R^2-type Lagrangian is proposed.
In the absence of torsion the model admits a topological phase with unfixed
metric. The model possesses a minimal set of dynamical degrees of freedom for
the torsion. Remarkably, the torsion has the same number of dynamical of-shell
degrees of freedom as the metric tensor. We trace an analogy between the
structure of the quantum chromodynamics and the structure of possible theory of
quantum gravity.Comment: 7 pages; reduced version of talk given at IV International Symposium
on Symmetries in Subatomic Physics (SSP 2009), plenary session in Honor of
Yongmin Cho's 65th Birthday, Taipei, Taiwan, 2-5 June 2009; to appear in
"Symmetries in Subatomic Physics", ed. P. Hwang
Dynamic Sentence Sampling for Efficient Training of Neural Machine Translation
Traditional Neural machine translation (NMT) involves a fixed training
procedure where each sentence is sampled once during each epoch. In reality,
some sentences are well-learned during the initial few epochs; however, using
this approach, the well-learned sentences would continue to be trained along
with those sentences that were not well learned for 10-30 epochs, which results
in a wastage of time. Here, we propose an efficient method to dynamically
sample the sentences in order to accelerate the NMT training. In this approach,
a weight is assigned to each sentence based on the measured difference between
the training costs of two iterations. Further, in each epoch, a certain
percentage of sentences are dynamically sampled according to their weights.
Empirical results based on the NIST Chinese-to-English and the WMT
English-to-German tasks depict that the proposed method can significantly
accelerate the NMT training and improve the NMT performance.Comment: Revised version of ACL-201
Angular Momentum and Energy-Momentum Densities as Gauge Currents
If we replace the general spacetime group of diffeomorphisms by
transformations taking place in the tangent space, general relativity can be
interpreted as a gauge theory, and in particular as a gauge theory for the
Lorentz group. In this context, it is shown that the angular momentum and the
energy-momentum tensors of a general matter field can be obtained from the
invariance of the corresponding action integral under transformations taking
place, not in spacetime, but in the tangent space, in which case they can be
considered as gauge currents.Comment: RevTeX4, 7 pages, no figures. Presentation changes; version to appear
in Phys. Rev.
A geometrical derivation of the Dirac equation
We give a geometrical derivation of the Dirac equation by considering a
spin-1/2 particle travelling with the speed of light in a cubic spacetime
lattice. The mass of the particle acts to flip the multi-component wavefunction
at the lattice sites. Starting with a difference equation for the case of one
spatial and one time dimensions, we generalize the approach to higher
dimensions. Interactions with external electromagnetic and gravitational fields
are also considered. One logical interpretation is that only at the lattice
sites is the spin-1/2 particle aware of its mass and the presence of external
fields.Comment: 9 pages, LaTeX, version accepted for publication in Phys. Lett.
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