The Hawking-Page phase transitions in the extended phase space in the Gauss-Bonnet gravity

In this paper, the Hawking-Page phase transitions between the black holes and thermal anti-de Sitter (AdS) space are studied with the Gauss-Bonnet term in the extended phase space, in which the varying cosmological constant plays the role of an effective thermodynamic pressure. The Gauss-Bonnet term exhibits its effects via introducing the corrections to the black hole entropy and Gibbs free energy. The global phase structures, especially the phase transition temperature $T_{\rm HP}$ and the Gibbs free energy $G$, are systematically investigated, first for the Schwarzschild-AdS black holes and then for the charged and rotating AdS black holes in the grand canonical ensembles, with both analytical and numerical methods. It is found that there are terminal points in the coexistence lines, and $T_{\rm HP}$ decreases at large electric potentials and angular velocities and also decreases with the Gauss-Bonnet coupling constant $\alpha$.Comment: 13 pages, 13 figure

The Joule--Thomson and Joule--Thomson-like effects of the black holes in a cavity

When a black hole is enclosed in a cavity in asymptotically flat space, an effective volume can be introduced, and an effective pressure can be further defined as its conjugate variable. By this means, an extended phase space is constructed in a cavity, which resembles that in the anti-de Sitter (AdS) space in many aspects. However, there are still some notable dissimilarities simultaneously. In this work, the Joule--Thomson (JT) effect of the black holes, widely discussed in the AdS space as an isenthalpic (constant-mass) process, is shown to only have cooling region in a cavity. On the contrary, in a constant-thermal-energy process (the JT-like effect), there is only heating region in a cavity. Altogether, different from the AdS case, there is no inversion temperature or inversion curve in a cavity. Our work reveals the subtle discrepancy between the two different extended phase spaces that is sensitive to the specific boundary conditions.Comment: 20 pages, 2 figure

Superfluid Condensate Fraction and Pairing Wave Function of the Unitary Fermi Gas

The unitary Fermi gas is a many-body system of two-component fermions with zero-range interactions tuned to infinite scattering length. Despite much activity and interest in unitary Fermi gases and its universal properties, there have been great difficulties in performing accurate calculations of the superfluid condensate fraction and pairing wave function. In this work we present auxiliary-field lattice Monte Carlo simulations using a novel lattice interaction which accelerates the approach to the continuum limit, thereby allowing for robust calculations of these difficult observables. As a benchmark test we compute the ground state energy of 33 spin-up and 33 spin-down particles. As a fraction of the free Fermi gas energy $E_{FG}$, we find $E_0/E_{FG}= 0.369(2), 0.372(2)$, using two different definitions of the finite-system energy ratio, in agreement with the latest theoretical and experimental results. We then determine the condensate fraction by measuring off-diagonal long-range order in the two-body density matrix. We find that the fraction of condensed pairs is $\alpha = 0.43(2)$. We also extract the pairing wave function and find the pair correlation length to be $\zeta_pk_F = 1.8(3) \hbar$, where $k_F$ is the Fermi momentum. Provided that the simulations can be performed without severe sign oscillations, the methods we present here can be applied to superfluid neutron matter as well as more exotic P-wave and D-wave superfluids.Comment: 12 pages and 11 figures, final version to appear Physical Review

Time fractals and discrete scale invariance with trapped ions

We show that a one-dimensional chain of trapped ions can be engineered to produce a quantum mechanical system with discrete scale invariance and fractal-like time dependence. By discrete scale invariance we mean a system that replicates itself under a rescaling of distance for some scale factor, and a time fractal is a signal that is invariant under the rescaling of time. These features are reminiscent of the Efimov effect, which has been predicted and observed in bound states of three-body systems. We demonstrate that discrete scale invariance in the trapped ion system can be controlled with two independently tunable parameters. We also discuss the extension to n-body states where the discrete scaling symmetry has an exotic heterogeneous structure. The results we present can be realized using currently available technologies developed for trapped ion quantum systems.Comment: 4 + 5 pages (main + supplemental materials), 2 + 3 figures (main + supplemental materials), version to appear in Physical Review A Rapid Communication

SIMULATION STUDY ON PERMANENT MAGNET WIND POWER GENERATION SYSTEM BASED ON PSIM

ABSTRACT: Through systematically analyzing the mathematical theory knowledge of the small and medium-sized direct-drive permanent magnet wind power system, this paper has designed a rated power of 3kW wind power system under the environment of PSIM9.0 software. The wind power system model has been built, the back-to-back double-PWM control circuit has been designed and the simulation analysis has been completed. In the circumstance of wind speed changes, the simulation results show that the output power of the generator side is stable and the DC voltage of the inverter side is constant, which suggests the correct control strategy, the favorable system stability, and the achieved design goal. The work already done in this article provides a good platform and infrastructure for systematically analyzing the small and medium-sized wind power system. Keywords: PSIM; wind power system; PMSG; full power converter; simulation analysis. I.INTRODUCTION With the increasing depletion of fossil energy, and the continuing deterioration of global environment, the wind power generation, as one kind of new energy power generations, has been paid further attention by the governments and researchers with its unique advantages. Recently, along with the small and medium-sized independent power generation achieving strong support by the relevant national policies, small and medium-sized wind turbines have been vigorously promoted and applied Study in this paper is based on PSIM9.0 simulation software. PSIM9.0 is a dedicated simulation software for power electronics and motor control study, it has the main features of user interface simple, learning and understanding easy, operation convenient, simulation fast, simulation waveforms clear and intuitive, etc Utilizing MATLAB/Simulink and PSCAD/EMTDC respectively, literature [3] and [4] have completed the WECS related research work. These two softwares are so powerful that they can realize the complex simulation analysis, however, they launch slowly, have longer simulation time and more complex component modules and control loops while compared with PSIM. Although the simulation software in literatur