20,507 research outputs found
A Wilson-Yukawa model with a chiral spectrum in 2D
We summarize our recent study of the fermion spectrum in a fermion-scalar 2D
model with a chiral global symmetry. This model is
obtained from a two-cutoff lattice formulation of a 2D U(1) chiral gauge
theory, in the limit of zero gauge coupling. The massless fermion spectrum
found deep in the vortex phase is undoubled and chiral.Comment: 3 pages, LaTeX, uses espcrc2.sty. To appear in proceedings of Lattice
97, Edinbugh, Scotlan
The role of excitons and trions on electron spin polarization in quantum wells
We have studied the time evolution of the electron spin polarization under
continuous photoexcitation in remotely n-doped semiconductor quantum wells. The
doped region allows us to get the necessary excess of free electrons to form
trions. We have considered electron resonant photoexcitation at free, exciton
and trion electron energy levels. Also, we have studied the relative effect of
photoexcitation energy density and doping concentration. In order to obtain the
two-dimensional density evolution of the different species, we have performed
dynamic calculations through the matrix density formalism. Our results indicate
that photoexcitation of free electron level leads to a higher spin
polarization. Also, we have found that increasing the photoexcitation energy or
diminishing the doping enhances spin polarization.Comment: 30 pages, 11 figures, 1 tabl
Interpolation of Non-abelian Lattice Gauge Fields
We propose a method for interpolating non-abelian lattice gauge fields to the
continuum, or to a finer lattice, which satisfies the properties of (i)
transverse continuity, (ii) (lattice) rotation and translation covariance,
(iii) gauge covariance, (iv) locality. These are the properties required for
use in our earlier proposal for non-perturbative formulation and simulation of
chiral gauge theories.Comment: A few typos corrected, a reference and a clarifying comment added. To
appear in Nuclear Physics B. 16 pages, LateX, 1 figure. This interpolation
scheme is intended for use in our formulation of lattice chiral gauge theory,
Nucl. Phys. B455 (1990) 287, hep-ph/950633
The information content of regional employment data for forecasting aggregate conditions
We consider whether disaggregated data enhances the efficiency of aggregate employment forecasts. We find that incorporating spatial interaction into a disaggregated forecasting model lowers the out-of-sample mean-squared-error from a univariate aggregate model by 70 percent at a two-year horizon.Econometrics ; Forecasting
Guaranteed emergence of genuine entanglement in 3-qubit evolving systems
Multipartite entanglement has been shown to be of particular relevance for a
better understanding and exploitation of the dynamics and flow of entanglement
in multiparty systems. This calls for analysis aimed at identifying the
appropriate processes that guarantee the emergence of multipartite entanglement
in a wide range of scenarios. Here we carry on such analysis considering a
system of two initially entangled qubits, one of which is let to interact with
a third qubit according to an arbitrary unitary evolution. We establish
necessary and sufficient conditions on the corresponding Kraus operators, to
discern whether the evolved state pertains to either one of the classes of
3-qubit pure states that exhibit some kind of entanglement, namely biseparable,
W-, and GHZ- genuine entangled classes. Our results provide a classification of
the Kraus operators according to their capacity of producing 3-qubit
entanglement, and pave the way for extending the analysis to larger systems and
determining the particular interactions that must be implemented in order to
create, enhance and distribute entanglement in a specific manner.Comment: Two new subsections included. Accepted for publication in The
European Physical Journal
Coherent XUV generation driven by sharp metal tips photoemission
It was already experimentally demonstrated that high-energy electrons can be
generated using metal nanotips as active media. In addition, it has been
theoretically proven that the high-energy tail of the photoemitted electrons is
intrinsically linked to the recollision phenomenon. Through this recollision
process it is also possible to convert the energy gained by the laser-emitted
electron in the continuum in a coherent XUV photon. It means the emission of
harmonic radiation appears to be feasible, although it has not been
experimentally demonstrated hitherto till now. In this paper, we employ a
quantum mechanical approach to model the electron dipole moment including both
the laser experimental conditions and the bulk matter properties and predict is
possible to generate coherent UV and XUV radiation using metal nanotips as
sources. Our quantum mechanical results are fully supported by their classical
counterparts.Comment: arXiv admin note: substantial text overlap with arXiv:1309.034
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