Colima, Mexico

University of Colima

www.ucol.mx
Colima, Mexico

The University of Colima is a Mexican public university with several campuses across the state of Colima, bordering the Pacific Ocean. It was created on September 16, 1940 by the President Lázaro Cárdenas as People's University of Colima , and intended to serve the educational needs of the Michoacán, Jalisco, and Colima.The University's library system holds over 93,127 volumes. Wikipedia.


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Amore P.,University of Colima
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2017

We have found that the minimum energy configuration of N=395 charges confined in a disk and interacting via the Coulomb potential, reported by Cerkaski et al. [Phys. Rev. E 91, 032312 (2015)PLEEE81539-375510.1103/PhysRevE.91.032312], is not a global minimum of the total electrostatic energy. We have identified a large number of configurations with lower energy, where defects are present close to the center of the disk; thus, the formation of a hexagonal core and valence circular rings for the centered configurations, predicted by the model of the above-mentioned reference, is not supported by numerical evidence, and the configurations obtained with this model cannot be used as a guide for the numerical calculations, as claimed by the authors. © 2017 American Physical Society.


Gonzalez-Perez O.,University of Colima | Alvarez-Buylla A.,University of California at San Francisco
Brain Research Reviews | Year: 2011

Demyelinating diseases are characterized by an extensive loss of oligodendrocytes and myelin sheaths from axolemma. These neurological disorders are a common cause of disability in young adults, but so far, there is no effective treatment against them. It has been suggested that neural stem cells (NSCs) may play an important role in brain repair therapies. NSCs in the adult subventricular zone (SVZ), also known as Type-B cells, are multipotential cells that can self-renew and give rise to neurons and glia. Recent findings have shown that cells derived from SVZ Type-B cells actively respond to epidermal-growth-factor (EGF) stimulation becoming highly migratory and proliferative. Interestingly, a subpopulation of these EGF-activated cells expresses markers of oligodendrocyte precursor cells (OPCs). When EGF administration is removed, SVZ-derived OPCs differentiate into myelinating and pre-myelinating oligodendrocytes in the white matter tracts of corpus callosum, fimbria fornix and striatum. In the presence of a demyelinating lesion, OPCs derived from EGF-stimulated SVZ progenitors contribute to myelin repair. Given their high migratory potential and their ability to differentiate into myelin-forming cells, SVZ NSCs represent an important endogenous source of OPCs for preserving the oligodendrocyte population in the white matter and for the repair of demyelinating injuries. © 2010 Elsevier B.V.


Amore P.,University of Colima
Annals of Physics | Year: 2011

We analyze the problem of calculating the solutions and the spectrum of a string with arbitrary density and fixed ends. We build a perturbative scheme which uses a basis of WKB-type functions and obtain explicit expressions for the eigenvalues and eigenfunctions of the string. Using this approach we show that it is possible to derive the asymptotic (high energy) behavior of the string, obtaining explicit expressions for the first three coefficients (the first two can also be obtained with the WKB method). Finally, using an iterative approach we also obtain analytical expressions for the low energy behavior of the eigenvalues and eigenfunctions of a string with rapidly oscillating density, recovering (in a simpler way) results in the literature. © 2011 Elsevier Inc.


Hofmann C.P.,University of Colima
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Within the effective Lagrangian framework, we explicitly evaluate the partition function of two-dimensional ideal ferromagnets up to three loops at low temperatures and in the presence of a weak external magnetic field. The low-temperature series for the free energy density, energy density, heat capacity, entropy density, and magnetization are given and their range of validity is critically examined in view of the Mermin-Wagner theorem. The calculation involves the renormalization and numerical evaluation of a particular three-loop graph, which is discussed in detail. Interestingly, in the low-temperature series for the two-dimensional ideal ferromagnet, the spin-wave interaction manifests itself in the form of logarithmic terms. In the free energy density the leading such term is of order T4lnT: remarkably, in the case of the three-dimensional ideal ferromagnet no logarithmic terms arise in the low-temperature series. While the present study demonstrates that it is straightforward to consider effects up to three-loop order in the effective field theory framework, this precision seems to be far beyond the reach of microscopic methods such as spin-wave theory. © 2012 American Physical Society.


Hofmann C.P.,University of Colima
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

The manifestation of the spin-wave interaction in the low-temperature series of the partition function has been investigated extensively over more than seven decades in the case of the three-dimensional ferromagnet. Surprisingly, the same problem regarding ferromagnets in two spatial dimensions, to the best of our knowledge, has not been addressed in a systematic way so far. In the present paper the low-temperature properties of two-dimensional ideal ferromagnets are analyzed within the model-independent method of effective Lagrangians. The low-temperature expansion of the partition function is evaluated up to two-loop order and the general structure of this series is discussed, including the effect of a weak external magnetic field. Our results apply to two-dimensional ideal ferromagnets which exhibit a spontaneously broken spin rotation symmetry O(3)→O(2) and are defined on a square, honeycomb, triangular, or kagome lattice. Remarkably, the spin-wave interaction only sets in at three-loop order. In particular, there is no interaction term of order T3 in the low-temperature series for the free energy density. This is the analog of the statement that, in the case of three-dimensional ferromagnets, there is no interaction term of order T4 in the free energy density. We also provide a careful discussion of the implications of the Mermin-Wagner theorem in the present context and thereby put our low-temperature expansions on safe grounds. © 2012 American Physical Society.


Hofmann C.P.,University of Colima
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

The thermodynamic properties of ferromagnetic spin chains have been analyzed with a variety of microscopic methods over the years: Bethe ansatz, spin-wave theory, Schwinger-boson mean-field theory, Green functions, and renormalization group methods. Surprisingly, in all these different studies, the manifestation of the spin-wave interaction in the low-temperature series for the thermodynamic quantities, in the presence of a finite magnetic field, has been largely neglected. In the present work, we address this problem by following a different path, based on the systematic effective Lagrangian method. We evaluate the partition function up to two-loop order and derive the low-temperature expansion of the energy density, entropy density, heat capacity, magnetization, and susceptibility in the presence of a weak external magnetic field. Remarkably, the spin-wave interaction only manifests itself beyond two-loop order. In particular, there is no term of order T2 in the low-temperature series of the free energy density. This is the analog of Dyson's statement that there is no term of order T4 in the low-temperature series of the free energy density in the case of three-dimensional ideal ferromagnets. The range of validity of our series is critically examined in view of the nonperturbatively generated energy gap. We also compare our results with the condensed matter literature and point out that there are some misleading statements. © 2013 American Physical Society.


Amore P.,University of Colima
Annals of Physics | Year: 2013

We derive explicit expressions for the sum rules of the eigenvalues of inhomogeneous strings with arbitrary density and with different boundary conditions. We show that the sum rule of order N may be obtained in terms of a diagrammatic expansion, with (N - 1) ! / 2 independent diagrams. These sum rules are used to derive upper and lower bounds to the energy of the fundamental mode of an inhomogeneous string; we also show that it is possible to improve these approximations taking into account the asymptotic behavior of the spectrum and applying the Shanks transformation to the sequence of approximations obtained to the different orders. We discuss three applications of these results. © 2013 Elsevier Inc.


Amore P.,University of Colima
Annals of Physics | Year: 2013

We derive general expressions for the sum rules of the eigenvalues of drums of arbitrary shape and arbitrary density, obeying different boundary conditions. The formulas that we present are a generalization of the analogous formulas for one dimensional inhomogeneous systems that we have obtained in a previous paper. We also discuss the extension of these formulas to higher dimensions. We show that in the special case of a density depending only on one variable the sum rules of any integer order can be expressed in terms of a single series. As an application of our result we derive exact sum rules for the homogeneous circular annulus with different boundary conditions, for a homogeneous circular sector and for a radially inhomogeneous circular annulus with Dirichlet boundary conditions. © 2013 Elsevier Inc.


Hofmann C.P.,University of Colima
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

Using the low-energy effective field theory for magnons, we systematically evaluate the partition function of the O(3) ferromagnet up to three loops. Dyson, in his pioneering microscopic analysis of the Heisenberg model, showed that the spin-wave interaction starts manifesting itself in the low-temperature expansion of the spontaneous magnetization of an ideal ferromagnet only at order T4. Although several authors tried to go beyond Dyson's result, to the best of our knowledge, a fully systematic and rigorous investigation of higher-order terms induced by the spin-wave interaction has never been achieved. As we demonstrate in the present paper, it is straightforward to evaluate the partition function of an ideal ferromagnet beyond Dyson's analysis, using effective Lagrangian techniques. In particular, we show that the next-to-leading contribution to the spontaneous magnetization resulting from the spin-wave interaction already sets in at order T9/2-in contrast to all claims that have appeared before in the literature. Remarkably, the corresponding coefficient is completely determined by the leading-order effective Lagrangian and is thus independent of the anisotropies of the cubic lattice. We also consider even higher-order corrections and thereby solve-once and for all-the question of how the spin-wave interaction in an ideal ferromagnet manifests itself in the spontaneous magnetization beyond the Dyson term. © 2011 American Physical Society.


Hofmann C.P.,University of Colima
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

Within the framework of effective Lagrangians we calculate the free energy density for an O (N) antiferromagnet in 2+1 dimensions up to three-loop order in the perturbative expansion and derive the low-temperature series for various thermodynamic quantities. In particular, we show that the magnon-magnon interaction in the O(3) antiferromagnet in d=2+1 -the O(3)-invariant quantum Heisenberg antiferromagnet on a square or a honeycomb lattice-is very weak and repulsive and manifests itself through a term proportional to five powers of the temperature in the free energy density. Remarkably, the corresponding coefficient is fully determined by the leading-order effective Lagrangian L eff 2 and does not involve any higher-order effective constants from L eff 4 related to the anisotropies of the lattice-the symmetries are thus very restrictive in d=2+1. We also compare our results that apply to O (N) antiferromagnets in 2+1 dimensions with those for O (N) antiferromagnets in 3+1 dimensions. The present work demonstrates the efficiency of the fully systematic effective Lagrangian method in the condensed-matter domain, which clearly proves to be superior to spin-wave theory. We would like to emphasize that the structure of the low-temperature series derived in the present work is model independent and universal as it only relies on symmetry considerations. © 2010 The American Physical Society.

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