Zc(3900)Z_c(3900): Confronting theory and lattice simulations

We consider a recent $T$-matrix analysis by Albaladejo {\it et al.}, [Phys.\ Lett.\ B {\bf 755}, 337 (2016)] which accounts for the $J/\psi\pi$ and $D^\ast\bar{D}$ coupled--channels dynamics, and that successfully describes the experimental information concerning the recently discovered $Z_c(3900)^\pm$. Within such scheme, the data can be similarly well described in two different scenarios, where the $Z_c(3900)$ is either a resonance or a virtual state. To shed light into the nature of this state, we apply this formalism in a finite box with the aim of comparing with recent Lattice QCD (LQCD) simulations. We see that the energy levels obtained for both scenarios agree well with those obtained in the single-volume LQCD simulation reported in Prelovsek {\it et al.} [Phys.\ Rev.\ D {\bf 91}, 014504 (2015)], making thus difficult to disentangle between both possibilities. We also study the volume dependence of the energy levels obtained with our formalism, and suggest that LQCD simulations performed at several volumes could help in discerning the actual nature of the intriguing $Z_c(3900)$ state

Gravitational coupling of neutrinos in a medium

In a medium that contains electrons but not the other charged leptons, such as normal matter, the gravitational interactions of neutrinos are not the same for all the neutrino flavors. We calculate the leading order matter-induced corrections to the neutrino gravitational interactions in such a medium and consider some of their physical implications.Comment: 21 pages, Latex, uses axodraw.sty (typos corrected; two references added. To appear in Phys. Rev. D

Gravitational couplings of charged leptons in a medium

We calculate the leading order matter-induced corrections to the gravitational interactions of charged leptons and their antiparticles in a medium that contains electrons but not the other charged leptons, such as normal matter. The gravitational coupling, which is universal at the tree level, is found to be flavor-dependent, and also different for the corresponding antiparticles, when the corrections of $O(\alpha)$ are taken into account. General expressions are obtained for the matter-induced corrections to the gravitational mass in a generic matter background, and explicit formulas for those corrections are given in terms of the macroscopic parameters of the medium for particular conditions of the background gases.Comment: Latex, axodraw, 39 pages. Added a few stylistic corrections and clarifying statements in the treatment of the photon tadpole diagra

Ultrafast relaxation rates and reversal time in disordered ferrimagnets

In response to ultrafast laser pulses, single-phase metals have been classified as “fast” (with magnetization quenching on the time scale of the order of 100 fs and recovery in the time scale of several picoseconds and below) and “slow” (with longer characteristic time scales). Disordered ferrimagnetic alloys consisting of a combination of “fast” transition (TM) and “slow” rare-earth (RE) metals have been shown to exhibit an ultrafast all-optical switching mediated by the heat mechanism. The behavior of the characteristic time scales of coupled alloys is more complicated and is influenced by many parameters such as the intersublattice exchange, doping (RE) concentration, and the temperature. Here, the longitudinal relaxation times of each sublattice are analyzed within the Landau-Lifshitz-Bloch framework. We show that for moderate intersublattice coupling strength both materials slow down as a function of slow (RE) material concentration. For larger coupling, the fast (TM) material may become faster, while the slow (RE) one is still slower. These conclusions may have important implications in the switching time of disordered ferrimagnets such as GdFeCo with partial clustering. Using atomistic modeling, we show that in the moderately coupled case, the reversal would start in the Gd-rich region, while the situation may be reversed if the coupling strength is larger

Gravitational decay of the Z-boson

We study the decay process of the Z boson to a photon and a graviton. The most general form of the on-shell amplitude, subject to the constraints due to the conservation of the electromagnetic and the energy-momentum tensor, is determined. The amplitude is expressed in terms of three form factors, two of which are CP-odd while one is CP-even. The latter, which is the only non-zero form factor at the one-loop level, is computed in the standard model and the decay rate is determined.Comment: 30 pages, Latex, uses Axodraw. (Some typographical errors corrected, and some references added in the new version.

Multiscale modeling of ultrafast element-specific magnetization dynamics of ferromagnetic alloys

A hierarchical multiscale approach to model the magnetization dynamics of ferromagnetic ran- dom alloys is presented. First-principles calculations of the Heisenberg exchange integrals are linked to atomistic spin models based upon the stochastic Landau-Lifshitz-Gilbert (LLG) equation to calculate temperature-dependent parameters (e.g., effective exchange interactions, damping param- eters). These parameters are subsequently used in the Landau-Lifshitz-Bloch (LLB) model for multi-sublattice magnets to calculate numerically and analytically the ultrafast demagnetization times. The developed multiscale method is applied here to FeNi (permalloy) as well as to copper- doped FeNi alloys. We find that after an ultrafast heat pulse the Ni sublattice demagnetizes faster than the Fe sublattice for the here-studied FeNi-based alloys

The Implementation of the Least Restrictive Environment Provision of the Individuals with Disabilities Education Act (IDEA) for Secondary Students with Learning Disabilities on Guam

This study examined the implementation of the least restrictive environment (LRE) provision of the Individuals with Disabilities Education Act (IDEA) for secondary students with learning disabilities on Guam. The research questions for the study addressed the following areas: (a) perceptions of the definition of LRE, (b) factors influencing the implementation of LRE, and (c) determination of LRE in relation to the national trends and literature. This research utilized the qualitative method of collecting and analyzing data that included interviews and review of written documents. Parents and school personnel from the secondary schools, involved in the implementation of the least restrictive environment, were interviewed to obtain their perception of the definition of LRE and the factors influencing its implementation. The responses of the interviews were triangulated with information from randomly selected Individual Education Programs (IEPs) and placement rates for secondary students with learning disabilities from the 1995–96 to the 1999–2000 school years. A summary of the responses by school personnel to the question related to the definition of LRE resulted in the following: (a) least restrictive environment refers to the needs of the child, (b) least restrictive environment refers to ensuring access to education for the child, (c) least restrictive environment addresses both access to the general education classroom as well as the individual needs of the child, and (d) least restrictive environment refers to the rights of the child to an education. School personnel also identified seven factors as having an influence in its implementation: (a) IDEA requirement of 1997 related to access and progress in the general curriculum, (b) federal policy, (c) DOE structure and educational delivery system, (d) advocacy, (e) due process and litigations, (f) preparation of individuals involved with the implementation of LRE, and (g) values and beliefs. With the parents, the majority of them indicated they were not familiar with the term least restrictive environment. For the parents, the following were identified as having an influence on the implementation of LRE: (a) the distribution of funds, (b) advocacy, (c) due process and litigations, (d) preparation of individuals responsible for the implementation of LRE, and (e) values and beliefs. School personnel and parents identified the administrator and the consulting resource teacher (CRT) as the individuals most influential in ensuring the implementation of LRE. A review of the IEPs for the past five years revealed that students with learning disabilities have been placed in more restrictive settings as compared with the national average. IEP committees often did not consider the continuum of placement or, when they are considered, the continuum begins with the resource room. IEPs lacked evidence to support the placement into more restrictive settings due to unsatisfactory results in the general education classroom even with the provision of supplementary aids and services to meet the individual needs of the child. In conclusion, it is evident that school personnel and parents responsible for the implementation of the least restrictive environment (LRE) requirement of the Individuals with Disabilities Education Act (IDEA) do not have a clear understanding of the LRE requirement. In addition, the review of the IEPs and placement rates revealed that Guam secondary schools indicated a preference towards the placement of secondary students with learning disabilities in more restrictive settings. This implies the need for training for school personnel