Two-orbital Systems with Crystal Field Splitting and Interorbital Hopping

The nondegenerate two-orbital Hubbard model is studied within the dynamic mean-field theory to reveal the influence of two important factors, i.e. crystal field splitting and interorbital hopping, on orbital selective Mott transition (OSMT) and realistic compound Ca$_{2-x}$Sr$_{x}$RuO$_{4}$. A distinctive feature of the optical conductivity of the two nondegenerate bands is found in OSMT phase, where the metallic character of the wide band is indicated by a nonzero Drude peak, while the insulating narrow band has its Drude peak drop to zero in the mean time. We also find that the OSMT regime expands profoundly with the increase of interorbital hopping integrals. On the contrary, it is shown that large and negative level splitting of the two orbitals diminishes the OSMT regime completely. Applying the present findings to compound Ca$_{2-x}$Sr$_{x}$RuO$_{4}$, we demonstrate that in the doping region from $x=0.2$ to 2.0, the negative level splitting is unfavorable to the OSMT phase.Comment: 7 pages with 5 figure

Instability of Reissner-Nordstr\"{o}m black hole in Einstein-Maxwell-scalar theory

The scalarization of Reissner-Nordstr\"{o}m black holes was recently proposed in the Einstein-Maxwell-scalar theory. Here, we show that the appearance of the scalarized Reissner-Nordstr\"{o}m black hole is closely related to the Gregory-Laflamme instability of the Reissner-Nordstr\"{o}m black hole without scalar hair.Comment: 22 pages, 10 figures, version to appear in EPJ

Instability of small AdS black holes in sixth-order gravity

We investigate the stability analysis of AdS black holes in the higher dimensional sixth-order gravity. This gravity is composed of Ricci cubic gravity and Lee-Wick term. It indicates that the Ricci tensor perturbations exhibit unstable modes for small AdS black holes in Ricci cubic gravity by solving the Lichnerowicz-type linearized equation. We show that the correlated stability conjecture holds for the AdS black hole by computing all thermodynamic quantities in Ricci cubic gravity. Furthermore, we find a newly non-AdS black hole in Ricci cubic gravity by making use of a static eigenfunction of the Lichnerowicz operator.Comment: 27 pages, 4 figures. arXiv admin note: text overlap with arXiv:1801.0462

Stability of scalarized charged black holes in the Einstein-Maxwell-Scalar theory

We analyze the stability of scalarized charged black holes in the Einstein-Maxwell-Scalar (EMS) theory with quadratic coupling. These black holes are labelled by the number of $n=0,1,2,\cdots$, where $n=0$ is called the fundamental black hole and $n=1,2,\cdots$ denote the $n$-excited black holes. We show that the $n=0$ black hole is stable against full perturbations, whereas the $n=1,2$ excited black holes are unstable against the $s(l=0)$-mode scalar perturbation. This is consistent with the EMS theory with exponential coupling, but it contrasts to the $n=0$ scalarized black hole in the Einstein-Gauss-Bonnet-Scalar theory with quadratic coupling. This implies that the endpoint of unstable Reissner-Nordstr\"{o}m black holes with $\alpha>8.019$ is the $n=0$ black hole with the same $q$. Furthermore, we study the scalarized charged black holes in the EMS theory with scalar mass $m^2_\phi=\alpha/\beta$.Comment: 23 pages, 11 figures. arXiv admin note: text overlap with arXiv:1812.0360

Effects of interorbital hopping on orbital fluctuations and metal-insulator transitions: Extended linearized dynamical mean-field theory

We study the effects of interorbital hopping on orbital fluctuations and Mott-Hubbard metal-insulator transition (MIT) in the two-orbital Hubbard model within the extended linearized dynamical mean-field theory. By mapping the model onto an effective model with different bandwidths through the canonical transformation, we find that at half-filling, the increases of the interorbital Coulomb interaction $U^{\prime}$ and the Hund's coupling $J$ drive the MIT, and the critical $J_{c}$ for MIT increases with the lift of the inter-orbital hopping integral $t_{ab}$. Meanwhile at quarter filling and in the strong correlation regime, the system without $t_{ab}$ exhibits MIT with the decreasing of $J$, and favors the orbital liquid ground state. However, the system transits from metal to insulator with the increasing of t$_{ab}$, accompanied with the rising of the orbital order parameter. These results show the important role of the interorbital hopping in the orbital fluctuation and orbital ordering.Comment: 7 pages, 6 figure

On the impact of connected automated vehicles in freeway work zones: A cooperative cellular automata model based approach

PurposeFreeway work zones have been traffic bottlenecks that lead to a series of problems, including long travel time, high-speed variation, driver’s dissatisfaction and traffic congestion. This research aims to develop a collaborative component of connected and automated vehicles (CAVs) to alleviate negative effects caused by work zones. Design/methodology/approach\ua0The proposed cooperative component is incorporated in a cellular automata model to examine how and to what scale CAVs can help in improving traffic operations. Findings\ua0Simulation results show that, with the proposed component and penetration of CAVs, the average performances (travel time, safety and emission) can all be improved and the stochasticity of performances will be minimized too. Originality/valueTo the best of the authors’ knowledge, this is the first research that develops a cooperative mechanism of CAVs to improve work zone performance