CRISTIAN CAMILO MONTOYA SANCHEZ - Academia.edu (original) (raw)

Papers by CRISTIAN CAMILO MONTOYA SANCHEZ

Revista De La Union Matematica Argentina, 1985

Información del artículo The distance in compact Riemannian manifolds.

Proc Amer Math Soc, 1983

In this note it is proven that a regular Riemannian s-manifold of noncompact type (see below) can... more In this note it is proven that a regular Riemannian s-manifold of noncompact type (see below) cannot be immersed isometrically and equivariantly in R". Our notation, terminology and basic facts will be those of [3]. Let (M, {Sx}) be a connected periodic regular i-manifold which is metrizable, i.e. there is a Riemannian metric g on M which is invariant with respect to the symmetries {Sx : x E M}. (Periodicity means that (M, {Sx}) has finite order [3,p. 4].) We have the group of isometries I(M, g) which is transitive on M [3, p. 2]. Contained in I(M, g) we have the group of transvections G = Tr(M, {Sx}) [3, p. 57] which is generated by the "elementary transvections", i.e. by the isometries Sx ° S~\ x, y EM. About the group G one knows: (1) G is a connected Lie group [3, II32,125]. (2) G is transitive on M [3, II33]. It is known [3, IV24] that under the above conditions (M, {Sx}) admits two complementary foliations <3X, Sj such that: (a) <¥x is invariant and its leaves are regular i-manifolds with solvable group of transvections. (b) ÍF2 is weakly invariant and its leaves are regular s-manifolds with semisimple group of transvections (compare [2, p. 208]). Definition. We shall say that (M, {Sx}) is of noncompact type if the foliation % has noncompact leaves. The objective of this note is to prove the following. Theorem. Let (M,{SX}) be a connected periodic, regular s-manifold which is metrizable and of noncompact type. Then (M,{SX)) admits no isometric equivariant immersion into a finite-dimensional real representation of G-Tr(M, {Sx}). Proof. Let us assume the existence of such an isometric immersion (m, /): (G, M)-> (I(R"), R"), where <p is a Lie group monomorphism and/is an isometric

Revista De La Union Matematica Argentina, 1992

Journal of Lie theory

In the present article we continue the study of the variety X [M ] associated to pointwise planar... more In the present article we continue the study of the variety X [M ] associated to pointwise planar normal sections of a natural imbedding for a flag manifold M . When M = G/T is the manifold of complete flags of a compact simple Lie group G, we obtain two results about subspaces of the tangent space T [T ] (M), invariant by the torus action, which give rise to real projective spaces in X [M ]. The first result determines their maximal dimension. While the other one characterizes those of maximal dimension as tangent spaces to the inner symmetric space G/K (the one of largest dimension for the group G) at a fixed point of the natural action of the torus T. The last section contains a nice application of these results.

We study an algebraic structure naturally associated to a standard imbedding of an R-space. This ... more We study an algebraic structure naturally associated to a standard imbedding of an R-space. This structure determines completely the geometry of an R-space and reduces to a Jordan Triple System if the R-space is symmetric.

Archivos Argentinos de Pediatria, 2014

Estudio transversal cuyo objetivo fue determinar la calidad de vida relacionada con la salud (CVR... more Estudio transversal cuyo objetivo fue determinar la calidad de vida relacionada con la salud (CVRS) en 92 niños y adolescentes, entre los 8 y los 18 años de edad, que vivían en un hogar temporal de un municipio colombiano. Se aplicaron pruebas para la diferencia de promedios, de correlación y se construyó un modelo logístico con el fin de identificar los factores que se asociaron al desenlace, la CVRS. No se encontraron diferencias entre los promedios del puntaje de la CVRS según sexo (p = 0.094) y además estos en las dimensiones actividad física y salud, sentimientos, autopercepción, autonomía, vida familiar, relación con los pares y entorno escolar fueron mayores que el promedio de la CVRS; ser mujer y haber sufrido algún tipo de limitación, influyen en tener puntajes de la CVRS menores de 70 puntos.

IEEE Photonics Journal, 2012

In this paper, we propose the orthogonal frequency-division multiplexinginterleaved division mult... more In this paper, we propose the orthogonal frequency-division multiplexinginterleaved division multiplexing access (OFDM-IDMA) technique for passive optical networks (PONs). We evaluate the performance of such systems and compare it with the already proposed OFDM-Access (OFDMA) technique by means of the bit error rate versus received power for two different coding schemes and different number of iterations. Results show that OFDM-IDMA technique with an unequal power allocation distribution among the different optical network units (ONUs) offers similar performance to OFDMA when used with a simple convolutional code at an aggregated rate of 4 and 8 Gbits/s. Dynamic bandwidth allocation can be easily implemented with this technique.

Handbook of Fuel Cells, 2010

Surface Science, 2003

In this work we present first principles calculations of water adsorption over charged Ag(1 1 1) ... more In this work we present first principles calculations of water adsorption over charged Ag(1 1 1) surfaces. The orientation of the adsorbed water molecule with respect to the surface changes from oxygen pointing away from the surface at negative charges to oxygen pointing towards the surface at positive charges. At zero charge the water molecule is oriented approximately parallel to the surface plane. Complete orientation of the molecule in the direction of the field is achieved for a critical charge density of 15 lC cm À2 for both positive and negative charges.

Surface Science, 1999

We have performed embedded atom calculations for a number of systems of electrochemical interest ... more We have performed embedded atom calculations for a number of systems of electrochemical interest involving a metallic singlecrystal substrate and a metallic adsorbate. Different thermodynamic contributions to the so-called underpotential shift are calculated and analyzed comparatively, drawing some general trends. The metal pairs considered involve silver, gold, platinum, palladium and copper. We consider the possibility of underpotential deposition through the excess of binding energy, arriving at two novel conclusions. First, for some systems consisting of metal M 1 and M 2 , underpotential deposition should be energetically possible in both cases, that is M 1 on M 2 and M 2 on M 1. Second, anions may play a decisive role in changing the energetics of some systems. In particular cases like copper on Au(111) they may be responsible to a large extent for the existence of an underpotential deposition. Entropic contributions were neglected in the present analysis.

Química Nova, 2006

ELECTROGENERATED CHEMILUMINESCENCE OF LUMINOL USING LOW-COST ELECTRODES. The purpose of the study... more ELECTROGENERATED CHEMILUMINESCENCE OF LUMINOL USING LOW-COST ELECTRODES. The purpose of the study was to observe eletrogenerated chemiluminescence (ECL) of luminol using different materials as electrodes such as wires, nails, coins, razor blades, etc. Based on the experimental observations and the mechanisms proposed in the literature, students should be capable of analyzing their results in order to understand the phenomena studied. Students could then elaborate a mechanism of action consistent with the experimental results which could rationalize the formation of intermediates in the reaction and the dependence of ECL on solution pH in addition to other points of interest.

Proceedings of the American Mathematical Society, 1983

Proceedings of the American Mathematical Society, 1976

Differentiable actions of cyclic groups of odd order on compact, connected, orientable manifolds ... more Differentiable actions of cyclic groups of odd order on compact, connected, orientable manifolds with only two fixed points are studied in order to obtain conditions under which the representations of the group on the tangent spaces at the fixed points are equivalent.

Physical Review D, 2005

We have measured the azimuthal angular correlation of bb production, using 86:5 pb ÿ1 of data col... more We have measured the azimuthal angular correlation of bb production, using 86:5 pb ÿ1 of data collected by Collider Detector at Fermilab (CDF) in pp collisions at s p 1:8 TeV during 1994-1995. In high-energy pp collisions, such as at the Tevatron, bb production can be schematically categorized into three mechanisms. The leading-order (LO) process is ''flavor creation,'' where both b and b quarks substantially participate in the hard scattering and result in a distinct back-to-back signal in final state. The ''flavor excitation'' and the ''gluon splitting'' processes, which appear at next-leadingorder (NLO), are known to make a comparable contribution to total bb cross section, while providing very different opening angle distributions from the LO process. An azimuthal opening angle between bottom and antibottom, , has been used for the correlation measurement to probe the interaction creating bb pairs. The distribution has been obtained from two different methods. One method measures the between bottom hadrons using events with two reconstructed secondary vertex tags. The other method uses bb ! J= X'X 0 events, where the charged lepton (') is an electron (e) or a muon (), to measure between bottom quarks. The bb purity is determined as a function of by fitting the decay length of the J= and the impact parameter of the '. Both methods quantify the contribution from higher-order production mechanisms by the fraction of the bb pairs produced in the same azimuthal hemisphere, f toward. The measured f toward values are consistent with both parton shower Monte Carlo and NLO QCD predictions.

Physical Chemistry Chemical Physics, 2013

Accelerated molecular dynamics and quantum conductance calculations are employed to shed light on... more Accelerated molecular dynamics and quantum conductance calculations are employed to shed light onto the electrochemical properties of the Au|1,8-octanedithiol|Au junction. Widely different contact geometries with varying degrees of roughness are examined. Strikingly, the two extreme situations considered in this work, tip-tip and tip-perfect surface junctions, give almost indistinguishable conductances. This result contrasts the usual notion that different S-Au bonding geometries combined with molecular torsions provide the explanation for the experimentally observed sets (low, medium, high) of conductance peaks. In this work, we provide an alternative explanation for the occurrence of these sets in terms of the specific anchoring sites of the molecule to the tip, which in turn determines the interaction of a portion of the carbon chain with the tip.

Journal of Physics: Condensed Matter, 2007

Page 1. Dynamical simulation of inelastic quantum transport This article has been downloaded from... more Page 1. Dynamical simulation of inelastic quantum transport This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2007 J. Phys.: Condens. Matter 19 196201 (http://iopscience.iop.org/0953-8984/19/19/196201) ...

Journal of Physics: Condensed Matter, 2013

Optical properties of TiO(2) nanoclusters (with more than 30 TiO(2) units) were calculated within... more Optical properties of TiO(2) nanoclusters (with more than 30 TiO(2) units) were calculated within a fully atomistic quantum dynamic framework. We use a time dependent tight-binding model to describe the electronic structure of TiO(2) nanoclusters in order to compute their optical properties. We present calculated absorption spectra for a series of nanospheres of different radii and crystal structures. Our results show that bare TiO(2) nanoclusters have the same adsorption edge for direct electronic transition independently of the crystal structure and the nanocluster size. We report values of the adsorption edge of around 3.0 eV for all structures analyzed. In the present work we demonstrate that, for small clusters, both the direct transition absorption edge and the blue shifting phenomena are masked by thermal disorder.