3,349 research outputs found

    Non-standard Dirac adjoint spinor: The emergence of a new dual

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    In this present communication we provide a new derivation of the Dirac dual structure by employing a different approach from the originally proposed. Following a general and rigorous mathematical process to compute the dual structure, we investigate if is possible to break the existing "rigidity" in its primordial formulation. For this task, firstly, we look towards to understand the core of the Dirac spinors construction and then, we suggest to built an alternative dual structure for the Dirac spinor, which preserve an invariant norm under any SL(2,C)SL(2,\mathcal{C}) transformation. Finally, we verify if the prominent physical contents are maintained or if it is affected by such construction.Comment: 7 pages, 0 figure

    Neural Controller for a Mobile Robot in a Nonstationary Enviornment

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    Recently it has been introduced a neural controller for a mobile robot that learns both forward and inverse odometry of a differential-drive robot through an unsupervised learning-by-doing cycle. This article introduces an obstacle avoidance module that is integrated into the neural controller. This module makes use of sensory information to determine at each instant a desired angle and distance that causes the robot to navigate around obstacles on the way to a final target. Obstacle avoidance is performed in a reactive manner by representing the objects and target in the robot's environment as Gaussian functions. However, the influence of the Gaussians is modulated dynamically on the basis of the robot's behavior in a way that avoids problems with local minima. The proposed module enables the robot to operate successfully with different obstacle configurations, such as corridors, mazes, doors and even concave obstacles.Air Force Office of Scientific Research (F49620-92-J-0499

    Effect of Abrasive Size on Wear

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    Questing for Algebraic Mass Dimension One Spinor Fields

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    This work deals with new classes of spinors of mass dimension one in Minkowski spacetime. In order to accomplish it, the Lounesto classification scheme and the inversion theorem are going to be used. The algebraic framework shall be revisited by explicating the central point performed by the Fierz aggregate. Then the spinor classification is generalized in order to encompass the new mass dimension one spinors. The spinor operator is shown to play a prominent role to engender the new mass dimension one spinors, accordingly.Comment: 7 pages, final version to appear in Eur. Phys. J.

    On the bilinear covariants associated to mass dimension one spinors

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    In this paper we approach the issue of Clifford algebra basis deformation, allowing for bilinear covariants associated to Elko spinors which satisfy the Fierz-Pauli-Kofink identities. We present a complete analysis of covariance, taking into account the involved dual structure associated to Elko. Moreover, the possible generalizations to the recently presented new dual structure are performed.Comment: 9 pages, 0 figure

    Discriminating among theories of spiral structure using Gaia DR2

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    We compare the distribution in position and velocity of nearby stars from the Gaia DR2 radial velocity sample with predictions of current theories for spirals in disc galaxies. Although the rich substructure in velocity space contains the same information, we find it more revealing to reproject the data into action-angle variables, and we describe why resonant scattering would be more readily identifiable in these variables. We compute the predicted changes to the phase space density, in multiple different projections, that would be caused by a simplified isolated spiral pattern, finding widely differing predictions from each theory. We conclude that the phase space structure present in the Gaia data shares many of the qualitative features expected in the transient spiral mode model. We argue that the popular picture of apparently swing-amplified spirals results from the superposition of a few underlying spiral modes.Comment: Revised version accepted to appear in MNRAS. Some significant improvements. A full resolution version of Fig 4 is available from http://www.physics.rutgers.edu/~sellwood/mult_res.pd

    La comunicación interpersonal como modelo teórico de las comunicaciones humanas

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    Toda teoría se funda en la experiencia. Si entre las experiencias observadas existe una que sea la más frecuente, universal e importante, la teoría debe preferentemente fundarse en ella, como prototipo. Este principio nos guiará en el estudio de la comunicación interpersonal. El hombre aun antes de ser, necesita como condición previa la comunicación personal. La concepción misma es fruto de la más perfecta y completa comunicación interpersonal, la del padre y la de la madre: transmisión de genes por la compenetración de dos seres complementarios en un amor erótico, psíquico y social. Si examinamos el comportamiento en el tiempo de la infancia, veremos que la comunicación interpersonal es la primera experiencia del hombre-feto dentro del útero materno; existe una comunicación envolvente y táctil durante nueve meses. La comunicación táctil es tierna, continua y transformadora en la etapa fetal y deja sello indeleble en la historia posterior del hombre y sólo cambian las formas táctiles con otras personas en la vida adulta.ITESO, A.C

    Type-4 spinors: transmuting from Elko to single-helicity spinors

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    In this communication we briefly report an unexpected theoretical discovery which emerge from the mapping of Elko mass-dimension-one spinors into single helicity spinors. Such procedure unveils a class of spinor which is classified as type-4 spinor field within Lounesto classification. In this paper we explore the underlying physical and mathematical contents of the type-4 spinor.Comment: 9 pages, 0 figure
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