290 research outputs found
Degeneracy and Para-supersymmetry of Dirac Hamiltonian in (2+1)- Spacetime
The quantum mechanics of a spin 1/2 particle on a locally spatial constant
curvature part of a (2+1)- spacetime in the presence of a constant magnetic
field of a magnetic monopole has been investigated. It has been shown that
these 2-dimensional Hamiltonians have the degeneracy group of SL(2,c), and
para-supersymmetry of arbitrary order or shape invariance. Using this symmetry
we have obtained its spectrum algebraically. The Dirac's quantization condition
has been obtained from the representation theory. Also, it is shown that the
presence of angular deficit suppresses both the degeneracy and shape
invariance.Comment: 31 pages, Latex, no figures, to be published in J. Math. Phy
Formulation of Electrodynamics with an External Source in the Presence of a Minimal Measurable Length
In a series of papers, Quesne and Tkachuk (J. Phys. A: Math. Gen.
\textbf{39}, 10909 (2006); Czech. J. Phys. \textbf{56}, 1269 (2006)) presented
a -dimensional -two-parameter Lorentz-covariant deformed
algebra which leads to a nonzero minimal measurable length. In this paper, the
Lagrangian formulation of electrodynamics in a 3+1-dimensional space-time
described by Quesne-Tkachuk algebra is studied in the special case
up to first order over the deformation parameter . It is
demonstrated that at the classical level there is a similarity between
electrodynamics in the presence of a minimal measurable length (generalized
electrodynamics) and Lee-Wick electrodynamics. We obtain the free space
solutions of the inhomogeneous Maxwell's equations in the presence of a minimal
length. These solutions describe two vector particles (a massless vector
particle and a massive vector particle). We estimate two different upper bounds
on the isotropic minimal length. The first upper bound is near to the
electroweak length scale , while the
second one is near to the length scale for the strong interactions
. The relationship between the
Gaete-Spallucci nonlocal electrodynamics (J. Phys. A: Math. Theor. \textbf{45},
065401 (2012)) and electrodynamics with a minimal length is investigated.Comment: 13 pages, no figur
Exact solutions of Dirac equation on (1+1)-dimensional spacetime coupled to a static scalar field
We use a generalized scheme of supersymmetric quantum mechanics to obtain the
energy spectrum and wave function for Dirac equation in (1+1)-dimensional
spacetime coupled to a static scalar field.Comment: 7 pages, Late
Nociceptive-Evoked Potentials Are Sensitive to Behaviorally Relevant Stimulus Displacements in Egocentric Coordinates.
Feature selection has been extensively studied in the context of goal-directed behavior, where it is heavily driven by top-down factors. A more primitive version of this function is the detection of bottom-up changes in stimulus features in the environment. Indeed, the nervous system is tuned to detect fast-rising, intense stimuli that are likely to reflect threats, such as nociceptive somatosensory stimuli. These stimuli elicit large brain potentials maximal at the scalp vertex. When elicited by nociceptive laser stimuli, these responses are labeled laser-evoked potentials (LEPs). Although it has been shown that changes in stimulus modality and increases in stimulus intensity evoke large LEPs, it has yet to be determined whether stimulus displacements affect the amplitude of the main LEP waves (N1, N2, and P2). Here, in three experiments, we identified a set of rules that the human nervous system obeys to identify changes in the spatial location of a nociceptive stimulus. We showed that the N2 wave is sensitive to: (1) large displacements between consecutive stimuli in egocentric, but not somatotopic coordinates; and (2) displacements that entail a behaviorally relevant change in the stimulus location. These findings indicate that nociceptive-evoked vertex potentials are sensitive to behaviorally relevant changes in the location of a nociceptive stimulus with respect to the body, and that the hand is a particularly behaviorally important site
Formulation of the Spinor Field in the Presence of a Minimal Length Based on the Quesne-Tkachuk Algebra
In 2006 Quesne and Tkachuk (J. Phys. A: Math. Gen. {\bf 39}, 10909, 2006)
introduced a (D+1)-dimensional -two-parameter Lorentz-covariant
deformed algebra which leads to a nonzero minimal length. In this work, the
Lagrangian formulation of the spinor field in a (3+1)-dimensional space-time
described by Quesne-Tkachuk Lorentz-covariant deformed algebra is studied in
the case where up to first order over deformation parameter
. It is shown that the modified Dirac equation which contains higher
order derivative of the wave function describes two massive particles with
different masses. We show that physically acceptable mass states can only exist
for . Applying the condition
to an electron, the upper bound for the isotropic
minimal length becomes about . This value is near to the
reduced Compton wavelength of the electron and is not incompatible with the results obtained for
the minimal length in previous investigations.Comment: 11 pages, no figur
Formulation of an Electrostatic Field with a Charge Density in the Presence of a Minimal Length Based on the Kempf Algebra
In a series of papers, Kempf and co-workers (J. Phys. A: Math. Gen. {\bf 30},
2093, (1997); Phys. Rev. D {\bf52}, 1108, (1995); Phys. Rev. D {\bf55}, 7909,
(1997)) introduced a D-dimensional -two-parameter deformed
Heisenberg algebra which leads to a nonzero minimal observable length. In this
work, the Lagrangian formulation of an electrostatic field in three spatial
dimensions described by Kempf algebra is studied in the case where
up to first order over deformation parameter . It is
shown that there is a similarity between electrostatics in the presence of a
minimal length (modified electrostatics) and higher derivative Podolsky's
electrostatics. The important property of this modified electrostatics is that
the classical self-energy of a point charge becomes a finite value. Two
different upper bounds on the isotropic minimal length of this modified
electrostatics are estimated. The first upper bound will be found by treating
the modified electrostatics as a classical electromagnetic system, while the
second one will be estimated by considering the modified electrostatics as a
quantum field theoretic model. It should be noted that the quantum upper bound
on the isotropic minimal length in this paper is near to the electroweak length
scale .Comment: 11 pages, no figur
Optimizing an Adaptive Neuro-Fuzzy Inference System for Spatial Prediction of Landslide Susceptibility Using Four State-of-the-art Metaheuristic Techniques.
Four state-of-the-art metaheuristic algorithms including the genetic algorithm (GA), particle swarm optimization (PSO), differential evolutionary (DE), and ant colony optimization (ACO) are applied to an adaptive neuro-fuzzy inference system (ANFIS) for spatial prediction of landslide susceptibility in Qazvin Province (Iran). To this end, the landslide inventory map, composed of 199 identified landslides, is divided into training and testing landslides with a 70:30 ratio. To create the spatial database, thirteen landslide conditioning factors are considered within the geographic information system (GIS). Notably, the spatial interaction between the landslides and mentioned conditioning factors is analyzed by means of frequency ratio (FR) theory. After the optimization process, it was shown that the DE-based model reaches the best response more quickly than other ensembles. The landslide susceptibility maps were developed, and the accuracy of the models was evaluated by a ranking system, based on the calculated area under the receiving operating characteristic curve (AUROC), mean absolute error, and mean square error (MSE) accuracy indices. According to the results, the GA-ANFIS with a total ranking score (TRS) = 24 presented the most accurate prediction, followed by PSO-ANFIS (TRS = 17), DE-ANFIS (TRS = 13), and ACO-ANFIS (TRS = 6). Due to the excellent results of this research, the developed landslide susceptibility maps can be applied for future planning and decision making of the related area
- …