Vol. 55 No. 2 Jul-Dec (2009): Revista Mexicana de Física E

Published: 2009-01-01

Artículos

  • Exact solution for the one-dimensional third-neighbour Ising model

    J.Pablo Martínez-Garcilazo., R. Márquez-Islas, C. Ramírez-Romero
    136-140
    Abstract:
    Following the transfer matrix approach, we compute the exact solution for the one-dimensional Ising model with interactions up to third neighbours. We write the result in a compact form, and we show that it coincides with earlier numerical computations.
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  • Concentrador parabólico compuesto: una descripción opto-geométrica

    S. Tapia S., J.A. del Río P.
    141-153
    Abstract:
    In solar energy technologies the compound parabolic concentrator (CPC) is one of the most used devices due to its high concentration. Although this device can be used to illustrate optical and geometrical principles, a detailed demonstration of its properties has not been presented in the open literature. In this paper, we present a geometrical and optical demonstration of its properties. Besides, this work can be used as an example in the optics and analytical geometry courses.
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  • Triangular grid generators for the eigenvalue calculation with edge elements

    G.M. Ortigoza Capetillo
    154-160
    Abstract:
    In this work we investigate some computational aspects of the eigenvalue calculation with edge elements, those include: the importance of the grid generator and node-edge numbering. As the examples show, the sparse structure of the mass and stiffness matrices is highly influenced by the edge numbering of the different grid generators tested. Significant bandwidth reduction can be obtained by the proper combination of the edge numbering scheme with the grid generator method. Moreover, an ordering algorithm such as the Reverse Cuthill-McKee can improve the bandwidth reduction which is necessary to reduce storage requirements.
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  • Estabilidad de un péndulo con forzamiento periódico arbitrario

    P. Quintero-Cabra, J. Silva-Valencia, H. Alejo-Martínez
    161-167
    Abstract:
    The dynamics of a driven pendulum at arbitrary angles and signals is studied using the lagrangian formalism and the effective potential method. We make a general discussion of the problem and consider three particular driving signals: sinusoidal, square and triangular. Was found that the cut off frequency, which determines the transition between the stability and nonstability regions depends on the type of signal used. For square driving the lower bound is minimum, while for the triangular drive is a maximum, the usual case of sinusoidal driving was found between the previous ones.
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  • Gravitational pocket billiards with Mathematica$\texttrademark$

    C. Antón, J.L. Brun
    168-175
    Abstract:
    Playing pocket billiards with two gravitational attracting balls and a non-interacting hole requires one to know the trajectories of the balls and therefore to be an ``artisan'' in the so-called two-body problem, one of the milestones for undergraduate students of Classical Mechanics.
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  • Interacción de un láser con un ion atrapado incluyendo dependencia temporal

    J.M. Vargas-Martínez, E.A. Martí-Panameño, H. Moya-Cessa
    176-190
    Abstract:
    Nowadays it is possible to trap single ions in Paul or Penning traps, charged particles are confined in space via electromagnetic fields. A trapped ion can have a lot vibrational energy which is undesirable in some applications. In this paper, starting from the Hamiltonian of a trapped ion in a harmonic potential, we show that it is possible to get Jaynes-Cummings and anti- Jaynes- Cummings- like transitions in the intermediate intensity regime, that is, adjusting the intensity of the laser that induce the coupling between the internal and vibrational states of the ion proportionally to the vibrational frequency of the ion; these transitions are useful because make it possible to extract the vibrational energy. In our treatment we consider that the ion and the laser are in resonance what eliminate the need of using tuned lasers. Also, the problem of a trapped ion in a trap with time-dependent parameters interacting with a laser field is analyzed. By using a set of time-dependent unitary transformations is shown that this system is equivalent to the interaction between a quantized field and a two level system with time dependent parameters. The Hamiltonian is linearized in such a way that can be solved with methods that are found in some papers and that involve time-dependent parameters. The linearization is free of approximations and assumptions on the parameters of the system as are, for instance, the Lamb-Dicke parameter, the time-dependency of the frequency trap and the detuning, with what we can obtain the best solution for this kind of system. Also, we show a particular case of time-dependency of the trap.
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  • Exact calculation of the number of degrees of freedom of a rigid body composed of n particles

    J. Bernal, R. Flowers-Cano, A. Carbajal-Dominguez
    191-195
    Abstract:
    In this work we correct a calculation made by Albert Einstein that appears in his book titled The Meaning of Relativity (Princeton, 1953), and by means of which he tries to obtain the number of degrees of freedom of a system composed of n particles with fixed relative distances and which are immersed in a three-dimensional space. As a result of our analysis, we develop expressions which yield the number of degrees of freedom of an analogous system, not only in three, but in any arbitrary number D of dimensions.
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  • The Cauchy problem for a forced harmonic oscillator

    R.M. Lopez, S.K. Suslov
    196-215

  • Some thoughts on the philosophy of color

    Vicente Aboites.
    216-220
    Abstract:
    Some of the main current philosophical theories of color are briefly presented. Based on them and as an analogy, several hypothetical philosophies of heat are offered. Finally, after a discussion and criticism of the hypothetical philosophies of heat, a proposal is offered to deal with the problem of color which solves some of the troubles faced by some current philosophies of color. The limitations of this proposal are also mentioned and discussed
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  • Luz y sombra de Galileo Galilei

    J.L. Álvarez García
    221-227
    Abstract:
    Beyond the various formal images about Galileo Galilei that exist, in this paper I present an image focused on his character and personality, which may allow to explain some important facts of the great Italian scientist's life. Galileo's relationship with Kepler and the first reactions of the Italian academics, after his discoveries with the telescope are analyzed with some detail.
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