6,111 research outputs found
Deuteron properties from muonic atom spectroscopy
Leading order () finite size corrections in muonic deuterium are
evaluated within a few body formalism for the system in muonic
deuterium and found to be sensitive to the input of the deuteron wave function.
We show that this sensitivity, taken along with the precise deuteron charge
radius determined from muonic atom spectroscopy can be used to determine the
elusive deuteron D-state probability, , for a given model of the
nucleon-nucleon (NN) potential. The radius calculated with a of 4.3\% in
the chiral NN models and about 5.7\% in the high precision NN potentials is
favoured most by the data.Comment: 14 pages, 2 figure
On Quasibound N* Nuclei
The possibility for the existence of unstable bound states of the S11 nucleon
resonance N(1535) and nuclei is investigated. These quasibound states are
speculated to be closely related to the existence of the quasibound states of
the eta mesons and nuclei. Within a simple model for the N N interaction
involving a pion and eta meson exchange, N-nucleus potentials for N*-He
and N*-Mg are evaluated and found to be of a Woods-Saxon like form which
supports two to three bound states. In case of N*-He, one state bound by
only a few keV and another by 4 MeV is found. The results are however quite
sensitive to the N N and N N vertex parameters. A rough
estimate of the width of these states, based on the mean free path of the
exchanged mesons in the nuclei leads to very broad states with 80
and 110 MeV for N*-He and N*-Mg respectively.Comment: Presented at the Jagiellonian Symposium on Fundamental and Applied
Subatomic Physics, Cracow, Poland, June 2015; to be published in Acta Physica
Polonica B (2016
Short Range Interactions in the Hydrogen Atom
In calculating the energy corrections to the hydrogen levels we can identify
two different types of modifications of the Coulomb potential , with one
of them being the standard quantum electrodynamics corrections, ,
satisfying over the whole range of
the radial variable . The other possible addition to is a potential
arising due to the finite size of the atomic nucleus and as a matter of fact,
can be larger than in a very short range. We focus here on the latter
and show that the electric potential of the proton displays some undesirable
features. Among others, the energy content of the electric field associated
with this potential is very close to the threshold of pair production.
We contrast this large electric field of the Maxwell theory with one emerging
from the non-linear Euler-Heisenberg theory and show how in this theory the
short range electric field becomes smaller and is well below the pair
production threshold
Lorentz Contracted Proton
The proton charge and magnetization density distributions can be related to
the well known Sachs electromagnetic form factors
through Fourier transforms, only in the Breit frame. The Breit frame however
moves with relativistic velocities in the Lab and a Lorentz boost must be
applied to the form factors before extracting the static properties of the
proton from the corresponding densities. Apart from this, the Fourier transform
relating the densities and form factors is inherently a non-relativistic
expression. We show that the relativistic corrections to it can be obtained by
extending the standard Breit equation to higher orders in its
expansion. We find that the inclusion of the above corrections reduces the size
of the proton determined from electron proton scattering data. Indeed the
central value of the latest proton radius of fm as determined
from e-p scattering changes to fm after applying corrections.Comment: 15 page
New biparametric families of apostol-frobenius-euler polynomials of level m
We introduce two biparametric families of Apostol-Frobenius-Euler polynomials of level-mm. We give some algebraic properties, as well as some other identities which connect these polynomial class with the generalized λλ-Stirling type numbers of the second kind, the generalized Apostol--Bernoulli polynomials, the generalized Apostol--Genocchi polynomials, the generalized Apostol--Euler polynomials and Jacobi polynomials. Finally, we will show the differential properties of this new family of polynomials
Nonlinear dynamical model for the assessment of the seismic behaviour of ferrocement houses
En este trabajo se evalúa el comportamiento cíclico de un prototipo de vivienda de ferrocemento, ensamblado mediante muros prefabricados de pared delgada, con la finalidad de identificar sus parámetros estructurales y proponer un modelo dinámico no lineal para simular el comportamiento de viviendas bajo movimientos sísmicos. Para ello se construyó un prototipo a escala real 1:1 y se probó bajo carga cíclica. De los resultados experimentales se obtuvieron: el comportamiento histerético, la rigidez elástica, la resistencia a cortante, la resistencia máxima, la ductilidad, la capacidad de disipación de energía, el amortiguamiento y el coeficiente de capacidad de disipación de energía; todos ellos, parámetros necesarios para la evaluación dinámica de la vivienda de ferrocemento bajo movimientos sísmicos. Al final se implementó el modelo dinámico no lineal de Bouc-Wen-Baber-Noori (BWBN). Este modelo permitió realizar la evaluación sísmica de la vivienda prefabricada de ferrocemento bajo sismos ocurridos.This article evaluates the cyclic behaviour of a prototype of a precast ferrocement house, which is assembled using precast thin walls, in order to identify its structural parameters and propose a nonlinear dynamical model which is able to simulate the behaviour of those houses when subjected to seismic loading. For this purpose, a full-scale precast ferrocement house was tested under cyclic loading conditions. From the experimental results, the hysteretic behaviour, the elastic stiffness, the shear resistance, the maximum strength, the ductility, the energy dissipation, the equivalent damping and its coefficient of energy dissipation were assessed; those parameters are needed in order to evaluate the dynamic behaviour of ferrocement dwellings when subjected to earthquakes. At the end, the Bouc-Wen-Baber-Noori (BWBN) model of hysteresis was implemented. The model allowed performing the seismic evaluation of the precast ferrocement house under seismic activity.Peer Reviewe
Compact Brillouin devices through hybrid integration on Silicon
A range of unique capabilities in optical and microwave signal processing
have been demonstrated using stimulated Brillouin scattering. The desire to
harness Brillouin scattering in mass manufacturable integrated circuits has led
to a focus on silicon-based material platforms. Remarkable progress in
silicon-based Brillouin waveguides has been made, but results have been
hindered by nonlinear losses present at telecommunications wavelengths. Here,
we report a new approach to surpass this issue through the integration of a
high Brillouin gain material, As2S3, onto a silicon chip. We fabricated a
compact spiral device, within a silicon circuit, achieving an order of
magnitude improvement in Brillouin amplification. To establish the flexibility
of this approach, we fabricated a ring resonator with free spectral range
precisely matched to the Brillouin shift, enabling the first demonstration of
Brillouin lasing in a silicon integrated circuit. Combining active photonic
components with the SBS devices shown here will enable the creation of compact,
mass manufacturable optical circuits with enhanced functionality
Who uses Transport Network Companies?: Characterization of Demand and its Relationship with Public Transit in Medellín
Transport Network Companies (TNCs) have become a popular alternative for mobility due to their ability to provide on-demand flexible mobility services. By offering smartphone-based, ride-hailing services capable of satisfying specific travel needs, these modes have transformed urban mobility worldwide. However, to-date, few studies have examined the impacts in the Latin American context. This analysis is a critical first step in developing policies to promote efficient and sustainable transport systems in the Latin-American region. This research examines the factors affecting the adoption of on-demand ride services in Medellín, Colombia. It also explores whether these are substituting or competing with public transit. First, it provides a descriptive analysis in which we relate the usage of platform-based services with neighborhood characteristics, socioeconomic information of individuals and families, and trip-level details. Next, factors contributing to the election of platform-based services modeled using discrete choice models. The results show that wealthy and highly educated families with low vehicle availability are more likely to use TNCs compared to other groups in Medellín. Evidence also points at gender effects, with being female significantly increasing the probability of using a TNC service. Finally, we observe both transit complementary and substitution patterns of use, depending on the context and by whom the service is requested
Large Fermi-energy shift and suppression of trivial surface states in NbP Weyl semimetal thin films
Weyl semimetals, a class of 3D topological materials, exhibit a unique electronic structure featuring linear band crossings and disjoint surface states (Fermi-arcs). While first demonstrations of topologically driven phenomena have been realized in bulk crystals, efficient routes to control the electronic structure have remained largely unexplored. Here, a dramatic modification of the electronic structure in epitaxially grown NbP Weyl semimetal thin films is reported, using in situ surface engineering and chemical doping strategies that do not alter the NbP lattice structure and symmetry, retaining its topological nature. Through the preparation of a dangling-bond-free, P-terminated surface which manifests in a surface reconstruction, all the well-known trivial surface states of NbP are fully suppressed, resulting in a purely topological Fermi-arc dispersion. In addition, a substantial Fermi-energy shift from -0.2 to 0.3 eV across the Weyl points is achieved by surface chemical doping, unlocking access to the hitherto unexplored n-type region of the Weyl spectrum. These findings constitute a milestone toward surface-state and Fermi-level engineering of topological bands in Weyl semimetals, and, while there are still challenges in minimizing doping-driven disorder and grain boundary density in the films, they do represent a major advance to realize device heterostructures based on Weyl physics
- …