Vol. 48 No. 1 (2002): Revista Mexicana de Física.

Published: 2002-01-01

Articles

  • Trace anomaly for 4D higher derivative scalar-dilaton theory

    F. Aceves de la Cruz, V.I. Tkach
    1-0
    Abstract:
    Trace anomaly for conformally invariant higher derivative 4D scalar-dilaton theory is obtained by means of calculating divergent part of one-loop effective action for such system. Its applications are briefly mentioned.
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  • Un nuevo método general para transformar canónicamente una hamiltoniana en otra de forma dada

    Alberto Gómez Trapote.
    4-0
    Abstract:
    The more general method to perform a cononical transformation of a Hamiltonian into another one of a given form is based on the repeated use of the Hamilton-Jacobi equation. This is usually a tedious technique which leads to some particular solutions of the problem. We present a new general method which does not rely on the Hamilton-Jacobi equation and moreover it gives all the possible solutions.
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  • About ambiguities appearing on the study of classical and quantum harmonic oscillator

    G. López
    10-0
    Abstract:
    A family of nonequivalents Lagrangians and Hamiltonians are given for the one-dimensional harmonic oscillator. These Lagrangians are deduced using the constant of motion approach. The study is focused on one of these Lagrangians and Hamiltonians to analyze their implications on the quantization of the one-dimensional harmonic oscillator. The main feature is the incomnpatibilities of the units in the usual quantization approaches. Using the velocity quantization approach it is possible to get rid of this incompatibility units problem.
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  • Supersymmetry and the constants of motion of the two-dimensional isotropic harmonic oscillator

    G.F. Torres del Castillo, T. Tepper García
    16-0
    Abstract:
    It is shown that the constants of motion of the two-dimensional isotropic harmonic oscillator not related to the rotational invariance of the Hamiltonian can be derived using the ideas of supersymmetric quantum mechanics.
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  • Cosmological constant and brane new world

    Shin'ichi Nojiri., Octavio Obregon., Sergei D. Odintsov
    19-0
    Abstract:
    The estimation of the cosmological constant in inflationary brane new world models is done. It is shown that basically it is quite large, of the same order as in anomaly-driven inflation. However, for some fine-tuning of bulk gravitational constant and AdS scale parameter $l^2$ it maybe reduced to sufficiently small value. Bulk higher derivative AdS gravity with quantum brane matter may also serve as the model where small positive cosmological constant occurs.
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  • Matthews' theorem in effective Yang-Mills theories

    L.T. López-Lozano, J.J. Toscano
    23-0
    Abstract:
    We study the quantization of effective Yang-Mills theories within the path integral formalism. In particular, the equivalence of the Hamiltonian and Lagrangian path integral quantization (Matthews' theorem) is probed for an effective Yang-Mills Lagrangian without matter fields, which includes all the invariant terms up to dimension six. This theorem is probed from point of views of both the gauge and BRST symmetries. The importance of the BRST symmetry in probing this theorem is stressed. We found that the functional integration on the generalized momenta are of Gaussian type and that they do not contribute to physical quantities as a consequence of the symmetries of the effective Lagrangian, which leads to a Lorentz and BRST invariant Lagrangian path integral.
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  • Hierarchical radiative quark mass matrices with an $\pmb{{\rm U}(1)_{\rm X}^{}}$ horizontal symmetry model

    E. García, A. Hernández-Galeana, D. Jaramillo, W.A. Ponce, A. Zepeda
    32-0
    Abstract:
    In a model with a gauge group ${\rm G}_{\rm SM}^{}\otimes{\rm U} (1)_{\rm X}^{}$, where ${\rm G}_{\rm SM}^{}\equiv{\rm SU}(3)_{\rm C}^{} \otimes{\rm SU}(2)_{\rm L}^{}\otimes {\rm U}(1)_{\rm Y}^{}$ is the standard model gauge group and ${\rm U}(1)_{\rm X}^{}$ is a horizontal local gauge symmetry, we propose a radiative generation of the spectrum of quark masses and mixing angles. The assignment of horizontal charges is such that at tree level only the third family is massive. Using these tree level masses and introducing exotic scalars, the light families of quarks acquire hierarchical masses through radiative corrections. The rank three quark mass matrices obtained are written in terms of a minimal set of free parameters of the model, whose values are estimated performing a numerical fit. The resulting quark masses and CKM mixing angles turn out to be in good agreement with the experimental values.
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  • The spectra of a Hamiltonian with a linear radial potential derived by a variational calculation based on a set of harmonic oscillator states

    M. Moshinsk, A. Suárez Moreno, .
    39-0
    Abstract:
    In relation with a quark interaction confinement potential a linear radial one is frequently used. As the spectrum of the resulting Hamiltonian is not available in an analytic fashion, we determine it in this paper using a variational procedure based on a set of appropriate harmonic oscillator states.
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  • Emission of electron density waves by neutrinos in a dense medium

    Subhendra Mohant., Sarira Sahu., Srubabati Goswami., .
    43-0
    Abstract:
    We study the production of electron density waves by neutrinos propagating through a plasma. We treat this process in field theoretically as a Cherenkov emission of phonons (quanta of electron density waves) by neutrinos. The energy transferred to a supernova shock wave by phonon emission from neutrinos is a factor $2\times 10^2$ times the corresponding energy deposited by plasmon (longitudinal photon) emission.
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  • Magnetic moments of decuplet baryons

    Sarira Sahu.
    48-0
    Abstract:
    Using the momentum projection technique of Peierls and Yoccoz in the non-scaling color dielectric model (CDM), the decuplet baryons magnetic moments are calculated and compared with the available experimental and theoretical results. The calculated values of the magnetic moments of $\Delta^{++}$ and $\Omega^-$ in CDM are close to the observed values.
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  • Thermalization process of a photo-generated plasma in semiconductors

    M.A. Rodríguez-Meza, J.L. Carrillo
    52-0
    Abstract:
    The kinetics of ultra-fast processes which leads to the thermalization condition of a photo-excited plasma in semiconductor systems is studied theoretically. We analyze the time evolution of a carrier population generated by a finite optical pulse, from the beginning of the pulse until the time in which the carrier population reaches a quasi-equilibrium condition. We calculate the energy fluxes caused by the main interaction mechanisms along the different stages the system passes through. Our analysis is done by using a set of non-linear rate equations which govern the time evolution of the carrier population in the energy space. We consider the main interaction mechanisms, including dynamic screening and phonon population effects.
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  • Multitarget system for growth of thin films by pulsed laser deposition

    M. Herrera, R. Castro-Rodríguez, O. Gómez, V. Rejón, P. Bartolo-Pérez, S. Barkun, A. Martel, J.L. Peña
    61-0
    Abstract:
    In this work we present the design, construction and the evaluation of a system to growth multiple layers of thin films using the pulsed laser deposition (PLD). The system is equipped with a mechanism of multiple targets and substrates. It has two revolving plates that can be manipulated from outside the chamber. The first serves to interchange four targets without breaking the vacuum or altering the internal conditions of the chamber. It also allows to put to the target in rotation around it's own axis. This rotation gives uniformity to the wearing down of the target thus enhancing the uniformity of the growing film. The second plate allows to change the substrate without opening the vacuum chamber. This second plate has three substrate holders. The system has a substrate heather that works at a maximum temperature of~$600^\circ$C. Both mechanisms are mounted in individual standard 6 inches ConFlat flanges and can be used in cameras of high or ultrahigh vacuum. The working chamber is evacuated by a standard oil diffusion pumping system. A Nd:YAG (Neodymium Yttrium Aluminum Garnet) infrared laser at wavelength of 1064 nm and about $25 $Wcm$^{2}$/pulse is used to vaporize the target. The capability of the system is evaluated by growing several basic structures of super-stratum CdTe-CdS used for solar cell on conductive glass (TCO): TCO/CdS, TCO/CdTe and TCO/CdS/CdTe and characterizing them by grazing incidence X-ray diffraction (GIXRD).
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  • Mathieu functions revisited: matrix evaluation and generating functions

    L. Chaos-Cador, E. Le, -Koo.
    67-0
    Abstract:
    An updated didactical approach to Mathieu functions is presented as an alternative to the orthodox treatment. The matrix evaluation of the angular Mathieu functions is not only pertinent, but long over due, after seventy five years of matrix quantum mechanics and with the availability of computing tools. Plane waves are identified as generating functions of the Mathieu functions, showing their explicit expansions. Some mathematical and physical applications are illustrated.
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  • A simple and effective approach to calculate the energy of complex atoms

    Héctor O. Di Rocco
    76-0
    Abstract:
    It is shown in this paper that, using only common concepts of well known modern physics and quantum mechanics textbooks (as one- and two-electron atoms, perturbation theory), we can develop a simple and powerful method to calculate the binding energies of complex electron configurations, as well as ionization energies, X-ray levels, etc.
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