Critical behavior of a bounded Kardar-Parisi-Zhang equation

A host of spatially extended systems, both in physics and in other disciplines, are well described at a coarse-grained scale by a Langevin equation with multiplicative-noise. Such systems may exhibit non-equilibrium phase transitions, which can be classified into universality classes. Here we study in detail one of such classes that can be mapped into a Kardar-Parisi-Zhang (KPZ) interface equation with a positive (negative) non-linearity in the presence of a bounding lower (upper) wall. The wall limits the possible values taken by the height variable, introducing a lower (upper) cut-off, and induce a phase transition between a pinned (active) and a depinned (absorbing) phase. This transition is studied here using mean field and field theoretical arguments, as well as from a numerical point of view. Its main properties and critical features, as well as some challenging theoretical difficulties, are reported. The differences with other multiplicative noise and bounded-KPZ universality classes are stressed, and the effects caused by the introduction of ``attractive'' walls, relevant in some physical contexts, are also analyzed.Comment: Invited paper to a special issue of the Brazilian J. of Physics. 5 eps Figures. 9 pagres. Revtex

Revivals, classical periodicity, and zitterbewegung of electron currents in monolayer graphene

Revivals of electric current in graphene in the presence of an external magnetic field are described. It is shown that when the electrons are prepared in the form of wave packets assuming a Gaussian population of only positive (or negative) energy Landau levels, the presence of the magnetic field induce revivals of the electron currents, besides the classical cyclotron motion. When the population comprises both positive and negative energy Landau levels, revivals of the electric current manifest simultaneously with zitterbewegung and the classical cyclotron motion. We relate the temporal scales of these three effects and discuss to what extent these results hold for real graphene samples

Hispanic Acculturation and Perceived Discrimination\u27s Impact on Emerging Adult\u27s Internalizing and Externalizing Symptoms Over Time: A Longitudinal Investigation.

Perceived discrimination and acculturation are key minority status and cultural variables that impact Hispanic mental health. Despite discrimination being a chronic stressor and acculturation being a developmental process, the impact of these experiences have been primarily investigated cross-sectionally. This paper uses longitudinal analyses to explore how perceived discrimination and acculturation impact growth internalizing and externalizing symptoms over time, adding nuance to previous literature. Using the Pathways to Desistance Mexican American sample (N =332), this paper utilized latent growth curve analyses to evaluate acculturative theories on mental health and the immediate and longitudinal impact of discrimination on a broad spectrum of mental health outcomes. Results indicate that higher initial status in Mexican orientation predicted less growth in internalizing symptoms, and growth in Mexican orientation predicted less growth in alcohol use, substance use, and criminal offending over time. Interestingly, growth in American cultural orientation did not predict growth in internalizing or externalizing symptoms. Baseline perceived police discrimination cross-sectionally was associated with greater internalizing, substance use, and criminal offending, but did not predict growth in mental health challenges. Moderation analyses also indicated that higher initial status in Mexican orientation and American orientation was related to less growth in internalizing symptoms but unrelated to externalizing symptoms. Neither Mexican nor American orientation moderated the impact of discrimination on internalizing or externalizing symptoms. Altogether these results provide no support for the position of Americanization being key to better mental health outcomes, and supports the acculturative theories that point to integrated cultural identities and strong Hispanic cultural identity being protective against mental health