Non-equilibrium condensation process in holographic superconductor with nonlinear electrodynamics

We study the non-equilibrium condensation process in a holographic superconductor with nonlinear corrections to the U(1) gauge field. We start with an asymptotic Anti-de-Sitter(AdS) black hole against a complex scalar perturbation at the initial time, and solve the dynamics of the gravitational systems in the bulk. When the black hole temperature T is smaller than a critical value Tc, the scalar perturbation grows exponentially till saturation, the final state of spacetime approaches to a hairy black hole. In the bulk theory, we find the clue of the influence of nonlinear corrections in the gauge field on the process of the scalar field condensation. We show that the bulk dynamics in the non-equilibrium process is completely consistent with the observations on the boundary order parameter. Furthermore we examine the time evolution of horizons in the bulk non-equilibrium transformation process from the bald AdS black hole to the AdS hairy hole. Both the evolution of apparent and event horizons show that the original AdS black hole configuration requires more time to finish the transformation to become a hairy black hole if there is nonlinear correction to the electromagnetic field. We generalize our non-equilibrium discussions to the holographic entanglement entropy and find that the holographic entanglement entropy can give us further understanding of the influence of the nonlinearity in the gauge field on the scalar condensation. In our analysis, we also compare the effect of different models on the corrections to the gauge field on the formation of holographic superconductor.Comment: 22 pages,accepted for publication in JHE

On the thermodynamics of the black hole and hairy black hole transitions in the asymptotically flat spacetime with a box

We study the asymptotically flat quasi-local black hole/hairy black hole model with nonzero mass of the scalar filed. We disclose effects of the scalar mass on transitions in a grand canonical ensemble with condensation behaviors of a parameter $\psi_{2}$, which is similar to approaches in holographic theories. We find that more negative scalar mass makes the phase transition easier to happen. We also obtain an analytical relation $\psi_{2}\varpropto(T_{c}-T)^{1/2}$ around the critical phase transition points implying a second order phase transition. Besides the parameter $\psi_{2}$, we show that metric solutions can be used to disclose properties of transitions. In this work, we observe that phase transitions in a box are strikingly similar to holographic transitions in the AdS gravity and the similarity provides insights into holographic theories.Comment: 12 pages, 6 figures. Accepted for publication in EPJC. arXiv admin note: text overlap with arXiv:1705.0869

Adolescent Internet Use, Academic Performances, and Problem Behaviors: Findings from a national sample of rural and urban China

Adolescent internet use in non-western countries and its association with behavioral problems are understudied. Informed by Bronfenbrenner’s socioecological framework and displacement hypothesis, the present study explored adolescent internet use in rural and urban China, and examined the mediation of academic performances between internet use and problem behaviors. Drawn from a nationally representative program, samples for this study included 3,379 adolescents aged between 9-17 years from 29 provinces. Results showed that rural adolescents had less access to mobile phones and internet, as well as a lower frequency of internet use than urban peers. Hybrid structural equation modeling results revealed that academic grade rankings fully mediated the association between internet use and externalizing behaviors. Academic self-rating negatively associated with both internalizing and externalizing behaviors. Stepwise regression results indicated rural adolescents who have internet access were more vulnerable to negative influences of increased internet entertainment time than urban peers. Findings contributed to the understanding of internet use and developmental outcomes of adolescents in rural and urban residency in China. Implications are discussed for practices, policies, and future research. Advisor: Yan Ruth Xi

Signature of the Van der Waals like small-large charged AdS black hole phase transition in quasinormal modes

We calculate the quasinormal modes of massless scalar perturbations around small and large four-dimensional Reissner-Nordstrom-Anti de Sitter (RN-AdS) black holes. We find a dramatic change in the slopes of quasinormal frequencies in small and large black holes near the critical point where the Van der Waals like thermodynamic phase transition happens. This further supports that the quasinormal mode can be a dynamic probe of the thermodynamic phase transition.Comment: 20 pages,11 figures.The new version is accepted for publication in JHE