2,482 research outputs found
The Rarita-Schwinger spin-3/2 equation in a nonuniform, central potential
The equations of motion for a massive spin-3/2 Rarita-Schwinger field in a
finite-range, central, Lorentz scalar potential are developed. It is shown that
the resulting density may not be everywhere positive definite.Comment: 9 pages, RevTe
Low temperature tunneling current enhancement in silicide/Si Schottky contacts with nanoscale barrier width
The low temperature electrical behavior of adjacent silicide/Si Schottky
contacts with or without dopant segregation is investigated. The electrical
characteristics are very well modeled by thermionic-field emission for
non-segregated contacts separated by micrometer-sized gaps. Still, an excess of
current occurs at low temperature for short contact separations or
dopant-segregated contacts when the voltage applied to the device is
sufficiently high. From two-dimensional self-consistent non-equilibrium Green's
function simulations, the dependence of the Schottky barrier profile on the
applied voltage, unaccounted for in usual thermionic-field emission models, is
found to be the source of this deviation
Induced Nucleon Polarization and Meson-Exchange Currents in (e,e'p) Reactions
Nucleon recoil polarization observables in reactions are
investigated using a semi-relativistic distorted-wave model which includes one-
and two-body currents with relativistic corrections. Results for the induced
polarization asymmetry are shown for closed-shell nuclei and a comparison with
available experimental data for C is provided. A careful analysis of
meson exchange currents shows that they may affect significantly the induced
polarization for high missing momentum.Comment: 7 pages, 9 figures. Revised version with small changes, new curve in
Fig. 3. To be published in PR
Is This a Joke? Detecting Humor in Spanish Tweets
While humor has been historically studied from a psychological, cognitive and
linguistic standpoint, its study from a computational perspective is an area
yet to be explored in Computational Linguistics. There exist some previous
works, but a characterization of humor that allows its automatic recognition
and generation is far from being specified. In this work we build a
crowdsourced corpus of labeled tweets, annotated according to its humor value,
letting the annotators subjectively decide which are humorous. A humor
classifier for Spanish tweets is assembled based on supervised learning,
reaching a precision of 84% and a recall of 69%.Comment: Preprint version, without referra
Inclusive versus Exclusive EM Processes in Relativistic Nuclear Systems
Connections are explored between exclusive and inclusive electron scattering
within the framework of the relativistic plane-wave impulse approximation,
beginning with an analysis of the model-independent kinematical constraints to
be found in the missing energy--missing momentum plane. From the interplay
between these constraints and the spectral function basic features of the
exclusive and inclusive nuclear responses are seen to arise. In particular, the
responses of the relativistic Fermi gas and of a specific hybrid model with
confined nucleons in the initial state are compared in this work. As expected,
the exclusive responses are significantly different in the two models, whereas
the inclusive ones are rather similar. By extending previous work on the
relativistic Fermi gas, a reduced response is introduced for the hybrid model
such that it fulfills the Coulomb and the higher-power energy-weighted sum
rules. While incorporating specific classes of off-shellness for the struck
nucleons, it is found that the reducing factor required is largely
model-independent and, as such, yields a reduced response that is useful for
extracting the Coulomb sum rule from experimental data. Finally, guided by the
difference between the energy-weighted sum rules of the two models, a version
of the relativistic Fermi gas is devised which has the 0, 1 and 2 moments of the charge response which agree rather well
with those of the hybrid model: this version thus incorporates {\em a priori}
the binding and confinement effects of the stuck nucleons while retaining the
simplicity of the original Fermi gas.Comment: LaTex file with 15 .ps figure
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A comparison of laboratory, clinical and self-report measures of prospective memory in healthy adults and individuals with brain injury
Individuals with traumatic brain injury (TBI) have demonstrated deficits in prospective memory (PM) functioning when compared to healthy adults. These deficits have been measured using laboratory measures, clinical measures and self-report questionnaires. However, PM has been shown to involve multiple cognitive processes and have a variety of stages. Thus, it is not known if these measures all assess the same aspects of PM. Thus, this study was designed to measure the convergent validity of the three types of PM measures in both healthy adults and individuals with TBI. We aimed to investigate the convergent validity of the three types of tasks in two ways. First, we sought to investigate if the PM deficits experienced by people with TBI are consistent across tasks. And, second, we sought to examine the relationship between the three types of tasks. Results demonstrated that while all three types of measures were sensitive to PM deficits in TBI, there were differences in the aspects/processes of PM being measured. Data from the laboratory measure suggested a specific difficulty with detecting the correct cue. Data from the clinical measure suggested that TBI has a greater effect on time-based cues than event-based cues and that the primary deficit is a prospective intention retrieval deficit rather than the retrospective memory component. In addition, those with TBI did not differ from healthy adults when the time delay was short enough, suggesting that PM is not universally impaired. Data from the self-report questionnaire suggested that those with TBI are more sensitive to difficulties with basic activities of daily living rather than instrumental activities on daily living. These results are discussed in terms of rehabilitation techniques that could focus first on cue detection and use basic activities of daily living as outcome measures
Red-giant stars in eccentric binaries
The unparalleled photometric data obtained by NASA’s Kepler Space Telescope has led to improved understanding of red-giant stars and binary stars. We discuss the characterization of known eccentric system, containing a solar-like oscillating red-giant primary component. We also report several new binary systems that are candidates for hosting an oscillating companion. A powerful approach to study binary stars is to combine asteroseimic techniques with light curve fitting. Seismology allows us to deduce the properties of red giants. In addition, by modeling the ellipsoidal modulations we can constrain the parameters of the binary system. An valuable independent source are ground-bases, high-resolution spectrographs
Measuring longitudinal amplitudes for electroproduction of pseudoscalar mesons using recoil polarization in parallel kinematics
We propose a new method for measuring longitudinal amplitudes for
electroproduction of pseudoscalar mesons that exploits a symmetry relation for
polarization observables in parallel kinematics. This polarization technique
does not require variation of electron scattering kinematics and avoids the
major sources of systematic errors in Rosenbluth separation.Comment: intended for Phys. Rev. C as a Brief Repor
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