# Pedro L. Contreras E.University of the Andes (Venezuela) | ULA · Department of Physics

Pedro L. Contreras E.

PhD

Venezuelan looking for a temporal lecturer position in Physics, Ph.D. in Theoretical Solid-State Physics.

## About

100

Publications

174,841

Reads

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318

Citations

Citations since 2016

Introduction

Unemployed and still survivor Venezuelan physicist, with eyes on a remote bilingual lecturership position.
I teach physics with evidence-based reasoning & action research practices.

Additional affiliations

January 2010 - present

Position

- Lecturer

Description

- 1. Contributed to the academic curriculum by teaching two undergraduate and one graduate course per semester averaging 20 students per course during 20+ semesters. 2. Served as thesis advisor, dissertation committee member, and science paper's per-reviewer encouraging younger fellows to develop problem-solving skills. 3. Delivered talks in conferences, and workshops in subject areas to liaise and network with colleagues. Proposed and developed research proposals and wrote research papers.

September 2006 - February 2009

Education

September 2001 - February 2006

September 2000 - August 2001

September 1988 - June 1994

## Publications

Publications (100)

Multiple vertical fracture sets, possibly combined with horizontal fine layering, produce an equivalent medium of monoclinic symmetry with a horizontal symmetry plane. Although monoclinic models may be rather common for fractured formations, they have hardly been used in seismic methods of fracture detection due to the large number of independent e...

We give examples of metallic Fermi surfaces with geometric structures for which the impedance under anomalous-skin-effect conditions does not become independent of the mean free path as the latter increases, and estimate the impedance of these metals.
We also elucidate how the overall Fermi surface topology affects the transition to the anomalous-...

This paper gives details of a predicted splitting of the superconducting transition temperature in Sr2RuO4 as a function of applied uniaxial stress. We also give formulas for the discontinuities in certain thermodynamic properties such as the specific heat, the thermal expansion coefficients, and the elastic compliance coefficients at various super...

We have performed for the strontium ruthenate compound, a disordered tight-binding numerical study in the unitary and intermedia scattering regimes analyzing the imaginary part of the self-consistent elastic scattering cross-section at zero temperature as a function of the superconducting gap parameter using the anisotropic limit of the γ sheet. We...

We perform a numerical study of the unitary regime as a function of disorder concentration in the imaginary part of the elastic scattering cross-section for the compound Sr2RuO4 in the flat band non-disperse limit. By using a self-consistent tight binding (TB) method, we find a couple of families of Wigner probabilistic functions that help to expla...

The analysis of travel times with moveout velocities represents one of the most widely used seismic signal processing techniques for the exploration and monitoring of oil and gas reservoirs. In travel time analysis for anisotropic elastic media with fractures, the knowledge of the conversion point at interfaces with incident longitudinal and reflec...

The analysis of travel times with move-out velocities represents one of the most widely used seismic signal processing techniques for the exploration and monitoring of Oil and Gas reservoirs. In travel time analysis for anisotropic elastic media with fractures, the knowledge of the conversion point at interfaces with incident longitudinal, and refl...

We have performed a numerical study of the self-consistent elastic scattering cross-section(SCCS) at zero temperature in the unitary strong scattering limit as a function of nonmagnetic disorder. The study of this article concentrated on a 2D first neighbor tight-binding(TB) model of the strontium doped lanthanum cuprate with an input of five TB pa...

We have performed a tight-binding (TB) numerical study of the unitary regime as a function of the energy gap parameter at zero temperature (Δγ0 ) in the imaginary part of the self-consistent elastic scattering cross-section (SCCS at T = 0 K) for the superconducting
triplet compound strontium ruthenate in the anisotropic limit of the FS γ-sheet. We...

We perform a numerical study of the self-consistent elastic scattering cross-section (SCCS) in the unitary limit (c = 0) as a function of nonmagnetic disorder concentration Γ + for a 2D first neighbor (1 st) tight-binding (TB) model of the strontium-substituted lanthanum cuprate (La2−xSrxCuO4) in two limits of physical interest. The first is a flat...

By comparing the experimental results obtained in the study of the electron transport and magnetic properties of samples of lightly doped strontium substituted lanthanum cuprates and the results of the theoretical analysis in the reduced elastic scattering space (RPS), we constructed the classical self-consistent strong-binding energy density profi...

We use the idea of the Wigner probability distribution (WPD) in a reduced scattering phase space (RPS) for the elastic scattering cross-section, with the help of a Tight-Binding (TB) numerical procedure allowing us to consider the anisotropic quantum effects, to phenomenologically predict several phases in these two novel unconventional superconduc...

We use the idea of the Wigner probability distribution (WPD) in a reduced scattering phase space (RPS) for the elastic scattering cross-section, with the help of a Tight-Binding (TB) numerical procedure allowing us to consider the anisotropic quantum effects, to phenomenologically predict several phases in these two novel unconventional superconduc...

We compare the quasiparticle lifetime behavior in the unitary limit of two unconventional superconductors dressed by nonmagnetic impurity scattering to differentiate an anomalous functional behavior in its shape when the disorder concentration is changed in a triplet paired model with respect to the well behave singlet model. For singlet paired sup...

Inspired by the physics of the Miyake-Narikiyo model (MN) for superconductivity in the γ sheet of Sr2RuO4, we set out to investigate numerically the behavior caused by a non-magnetic disorder in the imaginary part of the elastic scattering matrix for an anisotropic tight-binding model. We perform simulations by going from the Unitary to the Born sc...

Resumen/Abstract accepted September 2008. Conference to be held in Pereira Colombia, South America.

In this paper, we present the calculation of the density of states (DOS) and the residual density of states (RDOS) for two unconventional superconductors strontium-doped lanthanum cuprate La_{2-x}Sr_xCuO_4, which is a high-temperature superconductor (HTSC) with singlet pairing, and strontium ruthenate Sr_2RuO_4, with a triplet pairing in the Fermi...

We compare the quasiparticle lifetime behavior in the unitary limit of two unconventional superconductors dressed by nonmagnetic impurity scattering to differentiate an anomalous functional behavior in its shape when the disorder concentration is changed in a triplet paired model with respect to the well behave singlet model. For singlet paired sup...

We perform a numerical study of the unitary regime as a function of disorder concentration in the imaginary part of the elastic scattering cross-section for the compound Sr2RuO4 in the flat band non-disperse limit. By using a self-consistent tight-binding (TB) method, we find a couple of families of Wigner probabilistic functions that help to expla...

We perform a numerical study of the unitary regime as a function of disorder concentration in the imaginary part of the elastic scattering cross-section for the compound $Sr_2RuO_4$ in the flat band non-disperse limit. By using a self-consistent tight-binding (TB) method, we find a couple of families of Wigner probabilistic functions that help to e...

In this work, the behavior of magnetohydrodynamic waves in optically thin plasmas considering dissipative processes, thermal and magnetic diffusion, a given ionization, and the heating and cooling functions are investigated for several particular cases. A numerical eigenvalues analysis of the dimensionless secular equations according to various cas...

We compare the quasiparticle lifetime behavior in the unitary limit of two unconventional superconductors dressed by non-magnetic impurity scattering to differentiate an anomalous functional behavior in its shape when the disorder concentration is changed in a triplet paired model with respect to the well behave singlet model. For singlet paired su...

Inspired by the physics of the Miyake - Narikiyo model (MN) for superconductivity in the γ sheet of Sr2RuO4, we set out to investigate numerically the behavior caused by a non-magnetic disorder in the imaginary part of the elastic scattering matrix for an anisotropic tight-binding model. We perform simulations by going from the Unitary to the Born...

In this short review, some bulk threshold phenomena of the unconventional superconductivity in the strontium ruthenate compound (Sr2RuO4) are mentioned. Particularly, in Sr2RuO4, the Ehrenfest relations , the velocity propagation of the elastic field modes, and the ultrasound attenuation find a common point to study elastic anisotropic lattice fiel...

Inspired by the studies on the influence of transition metal impurities in high Tc superconductors and what is already known about nonmagnetic suppression of Tc in unconventional superconductors, we set out to investigate the behavior of the nonmagnetic disordered elastic scattering for a realistic 2D anisotropic high Tc superconductor with line no...

Inspired by the studies on the influence of transition metal impurities in high Tc superconductors and what is already known about nonmagnetic suppression of Tc in unconventional superconductors, we set out to investigate the behavior of the nonmagnetic disordered elastic scattering for a realistic 2D anisotropic high Tc superconductor with line no...

For pedagogical purposes, we have analyzed the relation of the total densities of states (TDOS/PDOS/OPDOS) and molecular orbital diagrams (MOD) for single and isolated molecules of Water and Nitrogen. We used the calculation level HF/6-311G, spreading the energy eigenvalues around the TDOS spikes and using the Mulliken visual analysis in Multiwfn t...

We have analyzed with pedagogical purposes the relation of the total densities of states (TDOS/PDOS/OPDOS) and molecular orbital diagrams (MOD) for single and isolated molecules of Water and Nitrogen. We use a calculation level HF/6-311G, spreading the energy eigenvalues around the TDOS spikes and using the Mulliken visual analysis in Multiwfn to s...

In this work, the behaviour of magneto-hydrodynamic waves in optically thin plasmas considering dissipative processes, thermal and magnetic diffusion, a given ionization, and the heating and cooling functions are investigated for several particular cases. A numerical eigenvalues analysis of the dimensionless secular equations according to various c...

Esta charla es un recuento del trabajo en anisotropía sísmica hecho mayormente en Intevep S.A. PDVSA en colaboración con el CWP de la Escuela de Minas de Colorado, durante los años 1995 - 2000 y 2007 - 2010.
Todos compartimos la idea de que el subsuelo terrestre necesita de la anisotropía sísmica para una mejor definición de los eventos relacionad...

The analysis of travel times with normal move-out (NMO) velocities represents one of the most widely used seismic signal processing techniques. In the travel time analysis for anisotropic homogeneous elastic media, the knowledge of the conversion point (PS) in the analysis of seismic data acquired in multicomponent surveys is crucial for the correc...

En este trabajo se visualiza la aproximación elipsoidal para las velocidades de fase de los modos longitudinal-P, y transversales-S1 y-S2 en medios que poseen simetría monoclínica.

Using an HF/6-311G level of calculation, we have analyzed the meaning of the density of states (DOS) for a single molecule of water (H2O).

In this review, some problems of the unconventional superconductivity in Sr2RuO4 are touched. In the strontium ruthenate compound (Sr2RuO4), the Ehrenfest relations, the elastic velocity propagation, and ultrasound attenuation find a common point to study elastic lattice effects. This can turn into a new role of the spin and polarization of the tra...

GNU Pytronic is some software that Ronald is developing for technicians, engineers and electronics enthusiasts. It´s basically a tool for calculating discrete electronic components.
It is developed in Python through a framework called Tkinter, it is multiplatform.
It has a version for windows and another for GNU Linux. The license is GPL-V3

The very long-standing problem of sound waves propagation in fluids is reexamined. In particular, from the analysis of the wave damping in reacting gases following the work by Einstein (1929), it is found that the damping due to the chemical reactions occurs nonetheless the second (bulk) viscosity introduced by Landau and Lifshitz (1987) is zero. T...

Implementing computational boundary conditions such as perfectly matched layers (PML) does have advantages for forwarding modeling of the Earth's crust. The mathematical modeling of many physical problems encountered in industrial applications often leads to a set of linear partial differential equations, PDEs. It considerably improves the visualiz...

In this short note following a previous set of works [3, 4, 16, 17] we repeat the
calculations for the jumps for the thermal expansion ασxy
, the specific heat Cσxy
,
and the elastic compliance Sσxy
xyxy in the basal plane of Sr2RuO4 . We use here the
4
th rank tensor notation because of the Voigt notation; where the stress and strain
are treated d...

In this short note following a previous set of works [3, 4, 16, 17] we repeat the calculations for the jumps for the thermal expansion ασxy, the specific heat Cσxy, and the elastic compliance Sσxyxyxy in the basal plane of Sr2RuO4 . We use here the 4th rank tensor notation because of the Voigt notation; where the stress and strain are treated diffe...

This work performs a comparative numerical study of the impurity average self-frequency in an unconventional superconducting alloy with non-magnetic impurities. Two methods are used: the Levenberg-Marquardt algorithm as a nonlinear minimization problem, and a fixed-point iteration procedure. The unconventional superconducting renormalized by impuri...

In this short note, we repeat the calculations the jumps for the specific heat Cσxy, the elastic compliance Sσxyxyxy and the thermal expansion ασxy due to a shear stress σxy in the basal plane of Sr2RuO4. Henceforth we clarify some issues regarding the elastic theoretical framework suitable to explain the sound speed experiments of Lupien et al. (2...

Multi-azimuth walkaway vertical seismic profiling (VSP) is an established technique for the estimation of in situ slowness surfaces and inferring anisotropy parameters. Normally, this the technique requires the assumption of lateral homogeneity, which makes the horizontal slowness components at depths of downhole receivers equal to those measured a...

Multi-azimuth walkaway vertical seismic profiling (VSP) is an established technique for the estimation of in situ slowness surfaces and inferring anisotropy parameters. Normally, this technique requires the assumption of lateral homogeneity, which makes the horizontal slowness components at depths of downhole receivers equal to those measured at th...

In this short note, we calculate the jumps for the specific heat C$_{\sigma_{xy}}$, the elastic compliance S$_{xyxy}^{\sigma_{xy}}$ and the thermal expansion $\alpha_{\sigma_{xy}}$ due to a shear stress $\sigma_{xy}$ in the basal plane of \sr. Henceforth we clarify some issues regarding the elastic theoretical framework suitable to explain the soun...

Implementing computational boundary conditions, such as perfectly matched layers PML does have advantages for forwarding modeling of the earth's crust. The mathematical modeling of many physical problems encountered in industrial applications often leads to a system of linear partial differential equations-PDEs. It considerably improves the visuali...

Multiple vertical fracture sets, possibly combined with horizontal fine layering, produce an equivalent medium of monoclinic symmetry with a horizontal symmetry plane. Here, we show that multi component wide azimuth reflection data (combined with known vertical velocity or reflector depth) or multi-azimuth walkaway $VSP$ surveys provide enough info...

This work performs a comparative numerical study of the impurity average self-frequency \bw in an unconventional superconducting alloy with non-magnetic impurities. Two methods are used: the Levenberg-Marquardt algorithm as a non-linear minimization problem, and a fixed-point iteration procedure. The unconventional superconducting renormalized by i...

This paper gives a detailed numerical study of the superconducting electronic heat transport in the unconventional multiband superconductor Strontium Ruthenate Sr$_2$RuO$_4$. The study demostrates that a model with different nodal structures on different sheets of the Fermi surface is able to describe quantitatively experimental heat transport data...

The very long standing problem of sound waves propagation in fluids is reexamined. In particular, from the analysis of the wave damping in reacting gases following the work of Einsten \citep{Ein}, it is found that the damping due to the chemical reactions occurs nonetheless the second (bulk) viscosity introduced by Landau \& Lifshitz \citep{LL86} i...

In this work, a numerical study of the superconducting specific heat of the unconventional multiband superconductor Strontium Ruthenate is performed. Two band gaps models are employed, and the results rendered for each of them are compared. One of the models, previously proposed by one of the authors to explain the experimental temperature behavior...

In this work, after reviewing the theory of the elastic properties of strontium ruthenate, an extension suitable to explain the sound speed experiments of Lupien et. al. \protect\cite{lup2} and Clifford et. al. \protect\cite{clif1} is carried out. It is found that the discontinuity in the elastic constant C66 gives unambiguous experimental evidence...

Multiple vertical fracture sets, combined with horizontal fine layering produce an equivalent medium of orthorhombic or monoclinic symmetry. This is particularly important in fracture reservoir characterization. Fractured reservoirs are azimuthal anisotropic with respect to elastic-wave propagation. In this work we introduce an ellipsoidal approxim...

In this work, by employing Density Functional Theory, we compute and discuss some geometric and magnetic properties of the monomer, dimer and trimer of NiFe2 O4 . The calculations are performed at the UDFT/ B3LYP level of calculation, by employing the LANL2DZ effective pseudo potential. The results of the Mulliken spin densities and the spin polari...

AI and Data Science are a breakthrough in computer programming that combines lots of major subjects and topics. We intent to link topics such as applied math, and databases to address problems associated with learning machines and data science. Google search, health, oil R&D exploration, environment, atmospheric and solar physics, finance, astronom...

In this work, by employing Density Functional Theory, we compute and discuss some geometric and magnetic properties of the monomer, dimer and trimer of NiFe2 O4 . The calculations are performed at the UDFT/ B3LYP level of calculation, by employing the LANL2DZ effective pseudo potential. The results of the Mulliken spin densities and the spin polari...

In this work, after reviewing the theory of the elastic properties of Sr 2 RuO 4 , an extension suitable to explain the sound speed experiments of Lupien et al. [2] and Clifford et al. [3] is carried out. It is found that the discontinuity in the elastic constant C 66 gives unambiguous experimental evidence that the Sr 2 RuO 4 superconducting order...

The density of states is a very important concept within the solid state physics and conceptually represents the number of states per unit of energy. Since in the solid state the energy levels can be represented as a continuum the density of states can be plotted as a smooth curve. In an isolated molecule, the energy levels are discrete so the conc...

This is a pedagogical talk for the Science Faculty in the International Year of Light 2015.
It covers the topic of photonic crystals and the localization of light.

In this work, a numerical study of the superconducting specific heat of the unconventional multiband superconductor Strontium Ruthenate, Sr2RuO4 , is performed. Two band gaps models are employed, and the results rendered for each of them are compared. One of the models, previously proposed by one of the authors to explain the experimental temperatu...

Multiple vertical fracture sets, combined with horizontal fine layering produce an equivalent medium of orthorhombic or monoclinic symmetry. This is particular important in fracture reservoir characterization, and since natural fractures usually occur in vertical sets, fractured reservoirs are azimuthally anisotropic with respect to elastic-wave pr...

El análisis de las velocidades interválicas y los tiempos de transito representan una de las técnicas de procesamiento de señales sísmicas más usadas. El conocimiento del punto de conversión en el análisis de datos sísmicos adquiridos en el procesamiento multicomponente es crucial para la interpretación correcta de la data. En este trabajo se muest...

En este trabajo se introduce una aproximación elipsoidal para las velocidades de fase de los modos longitudinal -P, y transversales -S1 y -S2 en medios que poseen simetría monoclínica. Esta nueva aproximación es válida para ángulos polares pequeños cerca de la dirección vertical pero sin restricciones en el ángulo acimutal y para grados arbitrarios...

En este trabajo se introduce una aproximación elipsoidal para las velocidades de fase de los modos longitudinal -P, y transversales -S1 y -S2 en medios que poseen simetría monoclínica. Esta nueva aproximación es válida para ángulos polares pequeños cerca de la dirección vertical, pero sin restricciones en el ángulo acimutal y para grados arbitrario...

This paper gives a detailed numerical study of the superconducting electronic heat transport in the unconventional multiband superconductor Strontium Ruthenate Sr2RuO4. The study demonstrates that a model with different nodal structures on different sheets of the Fermi surface is able to describe quantitatively experimental heat transport data. The...

A Rashba metal is a two dimensional electron system with noncentrosymetric crystal structure. This lack of spatial symmetry gives rise to the spin‐orbit interaction term in the effective 2D Hamiltonian with an asymmetric potential which breaks both the inversion symmetry and the spin rotation symmetry. As the presence of the spin‐orbit term not lon...