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ABSTRACT: A new model is proposed, in the context of Axelrod's model for the study of cultural dissemination, to include an external vector field (VF) which describes the effects of mass media on social systems. The VF acts over the whole system and it is characterized by two parameters: a nonnull overlap with each agent in the society and a confidence value of its information. Beyond a threshold value of the confidence, there is induced monocultural globalization of the system lined up with the VF. Below this value, the multicultural states are unstable and certain homogenization of the system is obtained in opposite line up according to that we have called negative publicity effect. Three regimes of behavior for the spread process of the VF information as a function of time are reported.
International Journal of Modern Physics C 01/2009; 18(20-8):1233-1245. · 0.57 Impact Factor
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ABSTRACT: A new model is proposed, in the context of Axelrod's model for the study of cultural dissemination, to include and external vector field (VF) which describes the effects of mass media on social systems. The VF acts over the whole system and it is characterized by two parameters: a non-null overlap with each agent in the society and a confidence value of its information. Beyond a threshold value of the confidence there is induced monocultural globalization of the system lined up with the VF. Below this value, the multicultural states are unstable and certain homogenization of the system is obtained in opposite line up according to that we have called {\it negative publicity} effect. Three regimes of behavior for the spread process of the VF information as a function of time are reported.
11/2008;
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Microelectronics Journal. 01/2008; 39:450-454.
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ABSTRACT: Using Heisenberg's uncertainty principle it is shown that the gravitational stability condition for a crystalline vacuum cosmic space implies to obtain an equation formally equivalent to the relation first used by Gamow to predict the present temperature of the microwave background from the matter density. The compatibility condition between the quantum and the relativistic approaches has been obtained without infinities arising from the quantum analysis or singularities arising from the relativistic theory. The action which leads to our theory is the least action possible in a quantum scheme. The energy fluctuation involved in the gravitational stabilization of vacuum space is 10 to the power of (-40) times the energy of the crystalline structure of vacuum space inside the present Universe volume.
04/2006;
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ABSTRACT: The value of the cosmological constant arising from a crystalline model for vacuum cosmic space with lattice parameter of the order of the neutron radius [1] has been calculated. The model allows to solve, in an easy way, the problem of the cosmological constant giving the right order of magnitude, which corresponds very well with the mean value of matter density in the universe. The obtained value is about 10 to the power of (-48) square Km. Diffraction experiments with non-thermal neutron beam in cosmic space are proposed to search for the possibility of crystalline structure of vacuum space and to measure the lattice parameter.
04/2006;
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Revista Mexicana de Física. 01/2005;
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ABSTRACT: When electrons or holes in 1D (quantum wires) and 2D (quantum layers) systems are confined in the lowest subband by transverse harmonic potentials, it is possible to find useful analytical expression for some important physical properties, such as the 1D and 2D effective interparticle Coulomb potentials, their Fourier transforms and their STLS dielectric functions with the corresponding collective plasma modes. Finite thickness effects of the confinement potentials can be easily identified and expanded in all formulae for carriers in the lowest subband. Finite thickness effects are much more pronounced in 1D than in 2D. We also calculate broadening effects with the Mermin correction of STLS. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (b) 02/2004; 241(4):864 - 875. · 1.32 Impact Factor
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ABSTRACT: We investigate the effect of an electric field applied tranversely to the axis of cylindrical symmetry of a cylindrical quantum wire on the ground-state energy of the electrons in the wire using an infinite confining potential well model. For low electric fields, we find a quadratic shift of the energy levels with the electric field; while for strong fields, the Stark shift of the ground-state energy increases almost linearly with the electric field. This increase is greater for wide wires, but for narrow wires, the Stark shift of the ground-state energy does not change much with the electric field. Also, at higher electric fields, the Stark shift of the ground-state energy increases with increasing wire radius. This will lead to the decrease of the effective bandgap of a semiconducting quantum wire with electric field. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (b) 10/2003; 240(3):561 - 564. · 1.32 Impact Factor
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ABSTRACT: We analyze a Wannier-Mott exciton in which the electron is constrained to move in a quantum ring and the hole moves in another concentric quantum rings. We expand the electron-hole interaction potential in terms of multipoles by assuming that both the electron and hole experience transverse harmonic confinements in the /rho and /z directions, both being in their respective transverse groundstates. For the resulting /phi-dependent Schrödinger equation we calculate the lowest exciton eigenenergies and eigenfunctions.
Physica E Low-dimensional Systems and Nanostructures 01/2002; 13:43-53. · 1.53 Impact Factor
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ABSTRACT: We employ Laplace and Fourier transforms in momentum space to find the bound states of the 1D Schrödinger equations with two different potentials; and . By performing inverse transforms we show that for the potential the solutions in real space reduce to those of the 1D hydrogen atom with eigenenergies proportional to with n integer. Analogously, we find that for the potential the eigenenergies are proportional to and the eigenfunctions can be expressed in terms of fractional derivatives. Taking into account that both potentials are singular (the potential is analytical and the potential is not), we analyse the nature of their bound states.
Journal of Physics A General Physics 12/1998; 32(10):2017.
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ABSTRACT: We obtain an approximated expression for steady state distance headway that takes into account all the physical processes involved in real braking. This simple approximated formula gives a good description of the empirical data. The peculiarity of this approximation is that at small vehicle speed the gap increases with an increase in speed sharper than a linear function, whereas in most models this function gap vs. speed is a linear function or weaker than the linear function. A new concept of the production rate of entropy due to traffic flow has been presented. With the use of such a concept the percentage of increase in the fuel consumption rate due to velocity fluctuations on the traffic flow is easily determined. The same percentage of increase in the fuel consumption rate could be obtained as a function of the fluctuations on the CO2 production rate due to the traffic flow. The practical applications of such analysis are obvious. It is possible that the use of the simple model developed here could be very useful in the conceptual scheme of the three-phase traffic theory.
Physica A: Statistical Mechanics and its Applications. 361(2):630-642.
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ABSTRACT: We carry out a detailed variational calculation of the binding energies of hydrogenic impurities in a cubic quantum box as a function of both the impurity position and an applied electric field. It is found that the binding energy of the impurities is highly dependent on the impurity position, and the electric field splits the energy of impurities on points of the box which are equivalent in the absence of the electric field. When the impurity is located at the upper half of the cube and the field pushes the particle downwards, then the binding energy decreases, whereas the Stark shift exhibits a minimum.
Phys. Rev. B. 71(7).
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Revista Mexicana de Física, ISSN 0035-001X, Vol. 51, Nº. 4, 2005, pags. 387-390.
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ABSTRACT: A non-equilibrium statistical theory for aging dissipative systems formed by atoms is developed and applied to electromigration damage in conductors. A modification of Black’s mean failure time is presented. We describe the experimental relationship between the initial rate of increase in the functional damage and the electric conductor lifetime. Also, for situations where electromigration damage is mainly due to heat dissipation caused by conduction inside the conductor, it was possible to obtain a mean-field theory which yields expressions (that agree with the experimental data) for the increase of resistance with the current stressing time, in test probes of different materials, and for the total volume of hillocks as a function of the current stressing time.
Physica A: Statistical Mechanics and its Applications.
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ABSTRACT: In this work, we study the behavior of the electron–hole transition energy in a GaAs–Ga1−xAlxAs pillbox immersed in a system of Ga1−yAlyAs as a function of thickness of the ladder barrier potential for a fixed length of the pillbox, length of the pillbox, thickness of the ladder barriers and pillbox position in the host of Ga1−yAlyAs. The behavior of the electron–hole transition energy as a function of an applied hydrostatic pressure and an applied magnetic field is also studied. For both electron and hole we found that in the strong confinement regime (L⩽10 Å) energy of the ground state as function of the position of the pillbox relative to the ladder barrier potential presents a behavior similar to the binding energy of a hydrogenic impurity in quantum wells, quantum wires and quantum dots [L. Esaki, R. Tsu, IBM J. Res. Dev. 14 (1970) 61; G. Bastard, Phys. Rev. B 24 (1981) 4714; N. Porras-Montenegro, J. López-Gondar, L.E. Oliveira, Phys. Rev. B 43 (1991) 1824]. Electron–heavy hole transition energies increase with the applied magnetic field. Also, we have found that these transition energies, as a function of the applied hydrostatic pressure, present an excellent agreement with experimental reports by Venkateswaran et al. [phys. Rev. B 33 (1986) 8416].
Microelectronics Journal 39:450-454. · 0.92 Impact Factor
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ABSTRACT: We present calculations for the inelastic scattering of electrons by the surface of binary conductor-conductor periodic superlattices described by local and nonlocal models. The conducting layers consist of metals or highly doped semiconductors and we include their spatial dispersion through the presence of longitudinal plasmons described by a hydrodynamic model. These modes manifest themselves as a series of peaks in the electron-energy-loss spectroscopy spectrum superimposed on the main structure due to the excitation of two coupled surface-plasmon bands. These peaks depend upon the nature of the first layer and are sensitive to the first few layers.
Phys. Rev. B. 57(23).
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ABSTRACT: We analyze a Wannier-Mott exciton in which the electron and hole are constrained to move in two separated and parallel quantum wires. We expand the electron-hole interaction potential in terms of multipoles by assuming that both the electron and hole experience transverse harmonic confinements in the x and y directions, both being in their respective transverse ground states. For the resulting z-dependent Schrödinger equation, we calculate in detail eigenenergies and eigenfunctions for the exciton ground and first excited states as functions of the transverse dimension of the wires and their separation distance. Also, we calculate the higher eigenenergies and eigenfunctions approximately by using a WKB formalism.
Phys. Rev. B. 57(3).
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ABSTRACT: An study of the effects of three-body interactions in the process of coalition formation is presented. In particular, we modify a spin glass model of bimodal propensities and also a Potts model in order to include a particular three-body Hamiltonian that reproduces the main features of the required interactions. The model can be used to study conflicts, political struggles, political parties, social networks, wars and organizational structures. As an application, we analyze a simplified model of the Iraq war.
Physica A: Statistical Mechanics and its Applications.
