8,712 research outputs found
Impurity Effects in Two-Electron Coupled Quantum Dots: Entanglement Modulation
We present a detailed analysis of the electronic and optical properties of
two-electron quantum dots with a two-dimensional Gaussian confinement
potential. We study the effects of Coulomb impurities and the possibility of
manipulate the entanglement of the electrons by controlling the confinement
potential parameters. The degree of entanglement becomes highly modulated by
both the location and charge screening of the impurity atom, resulting two
regimes: one of low entanglement and other of high entanglement, with both of
them mainly determined by the magnitude of the charge. It is shown that the
magnitude of the oscillator strength of the system could provide an indication
of the presence and characteristics of impurities that could largely influence
the degree of entanglement of the system.Comment: Regular Article (Journal of Physics B, in press), 9 pages, 10 figure
Rank one discrete valuations of power series fields
In this paper we study the rank one discrete valuations of the field
whose center in k\lcor\X\rcor is the maximal ideal. In
sections 2 to 6 we give a construction of a system of parametric equations
describing such valuations. This amounts to finding a parameter and a field of
coefficients. We devote section 2 to finding an element of value 1, that is, a
parameter. The field of coefficients is the residue field of the valuation, and
it is given in section 5.
The constructions given in these sections are not effective in the general
case, because we need either to use the Zorn's lemma or to know explicitly a
section of the natural homomorphism R_v\to\d between the ring and
the residue field of the valuation .
However, as a consequence of this construction, in section 7, we prove that
k((\X)) can be embedded into a field L((\Y)), where is an algebraic
extension of and the {\em ``extended valuation'' is as close as possible to
the usual order function}
On the classical-quantum correspondence for the scattering dwell time
Using results from the theory of dynamical systems, we derive a general
expression for the classical average scattering dwell time, tau_av. Remarkably,
tau_av depends only on a ratio of phase space volumes. We further show that,
for a wide class of systems, the average classical dwell time is not in
correspondence with the energy average of the quantum Wigner time delay.Comment: 5 pages, 1 figur
Top quark physics in hadron collisions
The top quark is the heaviest elementary particle observed to date. Its large
mass makes the top quark an ideal laboratory to test predictions of
perturbation theory concerning heavy quark production at hadron colliders. The
top quark is also a powerful probe for new phenomena beyond the Standard Model
of particle physics. In addition, the top quark mass is a crucial parameter for
scrutinizing the Standard Model in electroweak precision tests and for
predicting the mass of the yet unobserved Higgs boson. Ten years after the
discovery of the top quark at the Fermilab Tevatron top quark physics has
entered an era where detailed measurements of top quark properties are
undertaken. In this review article an introduction to the phenomenology of top
quark production in hadron collisions is given, the lessons learned in Tevatron
Run I are summarized, and first Run II results are discussed. A brief outlook
to the possibilities of top quark research a the Large Hadron Collider,
currently under construction at CERN, is included.Comment: 84 pages, 32 figures, accepted for publication by Reports on Progress
in Physic
Electromagnetic multipole moments of elementary spin-1/2, 1, and 3/2 particles
We study multipole decompositions of the electromagnetic currents of
spin-1/2, 1, and 3/2 particles described in terms of Lagrangians designed to
reproduce representation specific wave equations which are second order in the
momenta and which emerge within the recently elaborated Poincar\'e covariant
projector method. We calculate the electric multipoles of the above spins for
the spinor, the four-vector, and the four-vector--spinor representations,
attend to the most general non-Lagrangian spin-3/2 currents which are allowed
by Lorentz invariance to be of third order in the momenta and construct the
linear current equivalent of identical multipole moments of one of them. We
conclude that such non-Lagrangian currents are not necessarily more general
than the two-term currents emerging within the covariant projector method. We
compare our results with those of the conventional Proca-, and Rarita-Schwinger
frameworks. Finally, we test the representation dependence of the multipoles by
placing spin-1 and spin-3/2 in the respective (1,0)(0,1), and
(3/2,0)(0,3/2) single-spin representations. We observe representation
independence of the charge monopoles and the magnetic dipoles, in contrast to
the higher multipoles, which turn out to be representation dependent. In
particular, we find the bi-vector to be characterized by an
electric quadrupole moment of opposite sign to the one found in ,
and consequently, to the boson. Our finding points toward the possibility
that the meson could transform as part of an antisymmetric tensor with
an meson-like state as its representation companion.Comment: 27 pages, 2 figure
Active galactic nuclei synapses: X-ray versus optical classifications using artificial neural networks
(Abridged) Many classes of active galactic nuclei (AGN) have been defined
entirely throughout optical wavelengths while the X-ray spectra have been very
useful to investigate their inner regions. However, optical and X-ray results
show many discrepancies that have not been fully understood yet. The aim of
this paper is to study the "synapses" between the X-ray and optical
classifications.
For the first time, the new EFLUXER task allowed us to analyse broad band
X-ray spectra of emission line nuclei (ELN) without any prior spectral fitting
using artificial neural networks (ANNs). Our sample comprises 162 XMM-Newton/pn
spectra of 90 local ELN in the Palomar sample. It includes starbursts (SB),
transition objects (T2), LINERs (L1.8 and L2), and Seyferts (S1, S1.8, and S2).
The ANNs are 90% efficient at classifying the trained classes S1, S1.8, and
SB. The S1 and S1.8 classes show a wide range of S1- and S1.8-like components.
We suggest that this is related to a large degree of obscuration at X-rays. The
S1, S1.8, S2, L1.8, L2/T2/SB-AGN (SB with indications of AGN), and SB classes
have similar average X-ray spectra within each class, but these average spectra
can be distinguished from class to class. The S2 (L1.8) class is linked to the
S1.8 (S1) class with larger SB-like component than the S1.8 (S1) class. The L2,
T2, and SB-AGN classes conform a class in the X-rays similar to the S2 class
albeit with larger fractions of SB-like component. This SB-like component is
the contribution of the star-formation in the host galaxy, which is large when
the AGN is weak. An AGN-like component seems to be present in the vast majority
of the ELN, attending to the non-negligible fraction of S1-like or S1.8-like
component. This trained ANN could be used to infer optical properties from
X-ray spectra in surveys like eRosita.Comment: 15 pages, 7 figures, accepted for publication in A&A. Appendix B only
in the full version of the paper here:
https://dl.dropboxusercontent.com/u/3484086/AGNSynapsis_OGM_online.pd
Social Perception of the Residents of Olón, Montañita, and Valdivia as a Conditioning Factor in the Satisfaction of Tourists
This research aims to understand the social perception of the communities of Olón, Montañita, and Valdivia in the sociocultural, socio-territorial, and socio-cognitive dimensions, as a determining factor in the satisfaction of national and foreign tourists in terms of destination, service, and infrastructure. The design is nonexperimental, with a correlational scope and a mixed approach. Data collection techniques used were a semi-structured interview with 24 residents and a survey of 396 residents and 396 tourists. STATIS Dual and MPLS (multiway partial least squares) were the software used for the treatment of quantitative information. It was determined that the social perception in the three communes was relatively similar, the sociocultural dimension being the best scored for being linked to the tourist development of Olón and Montañita. Whereas a significant difference was observed between the communes in terms of tourist satisfaction, placing Montañita as the leader in all dimensions of the variable, followed by Olón and Valdivia. With an adjustment of 69%, the MPLS model was directly related to the variables, implying that any change in the perception of the residents affects the satisfaction of tourists.
Keywords: tourist satisfaction, social perception, spondylus route.
Resumen
El objetivo de esta investigación es conocer la percepción social de las comunidades de Olón, Montañita y Valdivia en las dimensiones socio cultural, socio territorial y socio cognitivo, como condicionante en la satisfacción de los turistas nacionales y extranjeros en cuanto al destino, servicio e infraestructura. El diseño es no experimental, de alcance correlacional y enfoque mixto; como técnicas de recolección de datos se utilizaron: entrevista semi estructurada a 24 residentes y, encuesta a 396 residentes y 396 turistas. Para el tratamiento de la información cuantitativa se utilizaron software STATIS Dual y MPLS (Multiway partial least squares). Se determinó que la percepción social en las tres comunas es relativamente similar, siendo la dimensión socio cultural la mejor puntuada por encontrarse ligada al desarrollo turístico de Olón y Montañita; mientras que, existe diferencia significativa entre las comunas en cuanto a satisfacción de los turistas, colocando a Montañita como líder en todas las dimensiones de la variable, seguida de Olón y Valdivia. Con un ajuste de 69%, el modelo MPLS relacionó directamente las variables, implicando que cualquier cambio en la percepción de los residentes incide sobre la satisfacción de los turistas.
Palabras Clave: satisfacción del turista, percepción social, ruta spondylus
Dielectric antenna effects in integrating line piezoelectric sensors for optoacoustic imaging
This work studies the adverse effects, as regards noise, of immersing in
water an integrating line piezoelectric detector devoted to optoacoustic
imaging. We found that the sensor, in conjunction with the acoustic coupling
medium (water), behaves as a resonant dielectric antenna. This phenomenon
limits the performance of the system because it efficiently captures unwanted
electromagnetic signals. The requirement of good acoustic coupling between the
water and the sensor precluded the use of a standard metallic shielding
enclosure. Therefore, we resorted to a silver-paint based electrical shield
deposited on the detector. This easy-to-implement and low-cost solution
significantly increases the signal to noise ratio and does not degrade the
acoustic performance. The noise reduction allows the use of a better
transimpedance amplifier with higher gain and bandwidth; thus achieving a very
sensitive, low-noise detection system.Comment: 7 pages, 7 figures, 1 table, submitted to Meas. Sci. Technol. on
March 24, 202
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