8,590 research outputs found
Finite formation time effects in inclusive and semi-inclusive electro-disintegration of few-body nuclei
Finite Formation Time (FFT) effects in the exclusive reaction ^4He(e,e'p)^3H
at high values of Q^2 are introduced and discussed. It is shown that the
minimum in the momentum distributions predicted by the Plane Wave Impulse
Approximation (PWIA), which is filled by the Glauber-type Final State
Interaction (FSI), is completely recovered when FFT effects are taken into
account. The semi-inclusive process ^4 He(e,e'p)X is also investigated.Comment: 4 pages, 2 eps figure
Quaternion Octonion Reformulation of Quantum Chromodynamics
We have made an attempt to develop the quaternionic formulation of Yang -
Mill's field equations and octonion reformulation of quantum chromo dynamics
(QCD). Starting with the Lagrangian density, we have discussed the field
equations of SU(2) and SU(3) gauge fields for both cases of global and local
gauge symmetries. It has been shown that the three quaternion units explain the
structure of Yang- Mill's field while the seven octonion units provide the
consistent structure of SU(3)_{C} gauge symmetry of quantum chromo dynamics
Final state interaction in inclusive and exclusive quasi-elastic processes
We discuss a new approach to final state interactions, that keeps explicitly
into account the virtuality of the ejected nucleon in quasi-elastic
scattering at very large , and we present some recent results, at
moderately large values, for the nuclear transparency in ,
and and for the momentum distributions of .Comment: 10 pages, 5 figures, Prepared for the workshop "Cortona 2000, VIII
Convegno su Problemi di Fisica Nucleare Teorica
Approximability results for stable marriage problems with ties
We consider instances of the classical stable marriage problem in which persons may include ties in their preference lists. We show that, in such a setting, strong lower bounds hold for the approximability of each of the problems of finding an egalitarian, minimum regret and sex-equal stable matching. We also consider stable marriage instances in which persons may express unacceptable partners in addition to ties. In this setting, we prove that there are constants delta, delta' such that each of the problems of approximating a maximum and minimum cardinality stable matching within factors of delta, delta' (respectively) is NP-hard, under strong restrictions. We also give an approximation algorithm for both problems that has a performance guarantee expressible in terms of the number of lists with ties. This significantly improves on the best-known previous performance guarantee, for the case that the ties are sparse. Our results have applications to large-scale centralized matching schemes
Imaginary in all directions: an elegant formulation of special relativity and classical electrodynamics
A suitable parameterization of space-time in terms of one complex and three
quaternionic imaginary units allows Lorentz transformations to be implemented
as multiplication by complex-quaternionic numbers rather than matrices.
Maxwell's equations reduce to a single equation.Comment: 8 page
Calculations of Branching Ratios for Radiative-Capture, One-Proton, and Two-Neutron Channels in the Fusion Reaction Bi+Zn
We discuss the possibility of the non-one-neutron emission channels in the
cold fusion reaction Zn + Bi to produce the element Z=113. For
this purpose, we calculate the evaporation-residue cross sections of
one-proton, radiative-capture, and two-neutron emissions relative to the
one-neutron emission in the reaction Zn + Bi. To estimate the
upper bounds of those quantities, we vary model parameters in the calculations,
such as the level-density parameter and the height of the fission barrier. We
conclude that the highest possibility is for the 2n reaction channel, and its
upper bounds are 2.4 and at most less than 7.9% with unrealistic parameter
values, under the actual experimental conditions of [J. Phys. Soc. Jpn. {\bf
73} (2004) 2593].Comment: 6 pages, 4 figure
Mott Transition in the Two-Dimensional Flux Phase
Effects of the electron-electron interaction in the two-dimensional flux
phase are investigated. We treat the half-filled Hubbard model with a magnetic
flux per plaquette by the quantum Monte Carlo method. When the
interaction is small, an antiferromagnetic long-range does not exist and the
charge fluctuation is different from that of the Mott insulator It suggests
that the Mott transition occurs at finite strength of the interaction in the
flux phase, which is in contrast to the standard Hubbard model.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
BRST invariant Lagrangian of spontaneously broken gauge theories in noncommutative geometry
The quantization of spontaneously broken gauge theories in noncommutative
geometry(NCG) has been sought for some time, because quantization is crucial
for making the NCG approach a reliable and physically acceptable theory. Lee,
Hwang and Ne'eman recently succeeded in realizing the BRST quantization of
gauge theories in NCG in the matrix derivative approach proposed by Coquereaux
et al. The present author has proposed a characteristic formulation to
reconstruct a gauge theory in NCG on the discrete space .
Since this formulation is a generalization of the differential geometry on the
ordinary manifold to that on the discrete manifold, it is more familiar than
other approaches. In this paper, we show that within our formulation we can
obtain the BRST invariant Lagrangian in the same way as Lee, Hwang and Ne'eman
and apply it to the SU(2)U(1) gauge theory.Comment: RevTeX, page
Image restoration using the Q-Ising spin glass
We investigate static and dynamic properties of gray-scale image restoration
(GSIR) by making use of the Q-Ising spin glass model, whose ladder symmetry
allows to take in account the distance between two spins. We thus give an
explicit expression of the Hamming distance between the original and restored
images as a function of the hyper-parameters in the mean field limit. Finally,
numerical simulations for real-world pictures are carried out to prove the
efficiency of our model.Comment: 27pages, 13figures, revte
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