111,534 research outputs found
On domain walls in a Ginzburg-Landau non-linear S^2-sigma model
The domain wall solutions of a Ginzburg-Landau non-linear -sigma hybrid
model are unveiled. There are three types of basic topological walls and two
types of degenerate families of composite - one topological, the other
non-topological- walls. The domain wall solutions are identified as the finite
action trajectories (in infinite time) of a related mechanical system that is
Hamilton-Jacobi separable in sphero-conical coordinates. The physical and
mathematical features of these domain walls are thoroughly discussed.Comment: 26 pages, 18 figure
Deformed defects for scalar fields with polynomial interactions
In this paper we use the deformation procedure introduced in former work on
deformed defects to investigate several new models for real scalar field. We
introduce an interesting deformation function, from which we obtain two
distinct families of models, labeled by the parameters that identify the
deformation function. We investigate these models, which identify a broad class
of polynomial interactions. We find exact solutions describing global defects,
and we study the corresponding stability very carefully.Comment: 8 pages, 5 eps figures, to appear in PR
Asymmetric kink scattering in a two-component scalar field theory model
Producción CientÃficaIn this paper the kink scattering in a two-component scalar field theory model in (1+1)-Minkowskian
space-time is addressed. The potential term U(fi_1; fi_2) is given by a polynomial of fourth degree in the
first field component and of sixth degree in the second one. The novel characteristic of this model is
that the kink variety describes two different types of extended particles. These particles are characterized
by its topological charge but also by a new feature determined by a discrete charge L = 0,1,-1.
For this reason, the kink scattering involves a very rich variety of processes, which comprises kink
annihilation, reflection, charge exchange, transmutation, etc. It has been found that not only the final
velocity of the scattered kinks, but also the final nature of the emerging lumps after the collision are
very sensitive on the initial velocities. Asymmetric scattering processes arise when Type I and Type
II particles are obliged to collide. In this case, ten different final scenarios are possible. Symmetric
scattering events are also discussed.In this paper the kink scattering in a two-component scalar field theory model in (1+1)-Minkowskian space-time is addressed. The potential term U(Ï•1, Ï•2) is given by a polynomial of fourth degree in the first field component and of sixth degree in the second one. The novel characteristic of this model is that the kink variety describes two different types of extended particles. These particles are characterized by its topological charge but also by a new feature determined by a discrete charge . For this reason, the kink scattering involves a very rich variety of processes, which comprises kink annihilation, reflection, charge exchange, transmutation, etc. It has been found that not only the final velocity of the scattered kinks, but also the final nature of the emerging lumps after the collision are very sensitive on the initial velocities. Asymmetric scattering processes arise when Type I and Type II particles are obliged to collide. In this case, ten different final scenarios are possible. Symmetric scattering events are also discussed.Ministerio de EconomÃa, Ciencia y Competitividad (grant MTM2014-57129-C2-1-P)Junta de Castilla y Leon (grant VA057U16
First-grade Latino English language learners' performance on story problems in spanish versus english
To explore whether teaching English Language Learners (ELLs) with an emphasis on English story problem is appropriate, we compared the performance of a group of Latino first graders when working in Spanish and in English on two equivalent sets of story problems. The students’ performance was slightly higher in English than in Spanish, but lower than monolingual students from other studies. ELLs’ success in English indicated that the children’s knowledge of conversational English was sufficient to comprehend story problems, leading us to conclude that teaching through story problems is a viable approach with ELLs
Quantum fluctuations around low-dimensional topological defects
In these Lectures a method is described to analyze the effect of quantum
fluctuations on topological defect backgrounds up to the one-loop level. The
method is based on the spectral heat kernel/zeta function regularization
procedure, and it is first applied to various types of kinks arising in several
deformed linear and non-linear sigma models with different numbers of scalar
fields. In the second part, the same conceptual framework is constructed for
the topological solitons of the planar semilocal Abelian Higgs model, built
from a doublet of complex scalar fields and one U(1) gauge field.Comment: 63 pages, 14 figures, expanded version of two lectures given by
J.M.G. in 5th International School on Field Theory and Gravitation, Cuiaba,
Brazi
The Kink variety in systems of two coupled scalar fields in two space-time dimensions
In this paper we describe the moduli space of kinks in a class of systems of
two coupled real scalar fields in (1+1) Minkowskian space-time. The main
feature of the class is the spontaneous breaking of a discrete symmetry of
(real) Ginzburg-Landau type that guarantees the existence of kink topological
defects.Comment: 12 pages, 5 figures. To appear in Phys. Rev.
The Flow Constraint Influence on the Properties of Nuclear Matter Critical Endpoint
We propose a novel family of equations of state for symmetric nuclear matter
based on the induced surface tension concept for the hard-core repulsion. It is
shown that having only four adjustable parameters the suggested equations of
state can, simultaneously, reproduce not only the main properties of the
nuclear matter ground state, but the proton flow constraint up its maximal
particle number densities. Varying the model parameters we carefully examine
the range of values of incompressibility constant of normal nuclear matter and
its critical temperature which are consistent with the proton flow constraint.
This analysis allows us to show that the physically most justified value of
nuclear matter critical temperature is 15.5-18 MeV, the incompressibility
constant is 270-315 MeV and the hard-core radius of nucleons is less than 0.4
fm.Comment: 8 pages, 3 figure
N=2 Supersymmetric Kinks and real algebraic curves
The kinks of the (1+1)-dimensional Wess-Zumino model with polynomic
superpotential are investigated and shown to be related to real algebraic
curves.Comment: 8 pages, LaTeX, epsfig, 4 figures include
A time-dependent Schr\"odinger equation for molecular core-hole dynamics
X-ray spectroscopy is an important tool for the investigation of matter. X
rays primarily interact with inner-shell electrons creating core (inner-shell)
holes that will decay on the time scale of attoseconds to few femtoseconds
through electron relaxations involving the emission of a photon or an electron.
The advent of femtosecond x-ray pulses expands x-ray spectroscopy to the time
domain and will eventually allow the control of core-hole population on
timescales comparable to core-vacancy lifetimes. For both cases, a theoretical
approach that accounts for the x-ray interaction while the electron relaxations
occur is required. Here we describe a time-dependent framework, based on
solving the time-dependent Schr\"odinger equation, that is suitable for
describing the induced electron and nuclear dynamics
Face engagement during infancy predicts later face recognition ability in younger siblings of children with autism
Face recognition difficulties are frequently documented in children with autism spectrum disorders (ASD). It has been hypothesized that these difficulties result from a reduced interest in faces early in life, leading to decreased cortical specialization and atypical development of the neural circuitry for face processing. However, a recent study by our lab demonstrated that infants at increased familial risk for ASD, irrespective of their diagnostic status at 3 years, exhibit a clear orienting response to faces. The present study was conducted as a follow-up on the same cohort to investigate how measures of early engagement with faces relate to face-processing abilities later in life. We also investigated whether face recognition difficulties are specifically related to an ASD diagnosis, or whether they are present at a higher rate in all those at familial risk. At 3 years we found a reduced ability to recognize unfamiliar faces in the high-risk group that was not specific to those children who received an ASD diagnosis, consistent with face recognition difficulties being an endophenotype of the disorder. Furthermore, we found that longer looking at faces at 7 months was associated with poorer performance on the face recognition task at 3 years in the high- risk group. These findings suggest that longer looking at faces in infants at risk for ASD might reflect early face-processing difficulties and predicts difficulties with recognizing faces later in life
- …