Holographic p-wave superconductivity from higher derivative theory

We construct a holographic SU(2) p-wave superconductor model with Weyl corrections. The high derivative (HD) terms do not seem to spoil the generation of the p-wave superconducting phase. We mainly study the properties of AC conductivity, which is absent in holographic SU(2) p-wave superconductor with Weyl corrections. The conductivities in superconducting phase exhibit obvious anisotropic behaviors. Along y direction, the conductivity $$\sigma _{yy}$$ σ yy is similar to that of holographic s-wave superconductor. The superconducting energy gap exhibits a wide extension. For the conductivity $$\sigma _{xx}$$ σ xx along x direction, the behaviors of the real part in the normal state are closely similar to that of $$\sigma _{yy}$$ σ yy . However, the anisotropy of the conductivity obviously shows up in the superconducting phase. A Drude-like peak at low frequency emerges in $$Re\sigma _{xx}$$ R e σ xx once the system enters into the superconducting phase, regardless of the behaviors in normal state.

A note on Kerr/CFT and Wald entropy discrepancy in high derivative gravities

We examine the Kerr/CFT correspondence in Einstein gravity extended with quadratic curvature invariants. We consider two explicit examples in four and five dimensions and compute the central charges of the asymptotic symmetry algebras of the near horizon geometries, using the improved version of the BBC formalism that encompasses the information of the Lagrangian. We find that the resulting Cardy entropy differs from the Wald entropy, caused by the Riemann-squared RμνρσRμνρσ term.

Analytical Study of the Holographic Superconductor from Higher Derivative Theory

In this paper, we analytically study the holographic superconductor models with the high derivative (HD) coupling terms. Using the Sturm-Liouville (S-L) eigenvalue method, we perturbatively calculate the critical temperature. The analytical results are in good agreement with the numerical results. It confirms that the perturbative method in terms of the HD coupling parameters is available. Along the same line, we analytically calculate the value of the condensation near the critical temperature. We find that the phase transition is second order with mean field behavior, which is independent of the HD coupling parameters. Then, in the low-temperature limit, we also calculate the conductivity, which is qualitatively consistent with the numerical one. We find that the superconducting energy gap is proportional to the value of the condensation. But we note that since the condensation changes with the HD coupling parameters, as the function of the HD coupling parameters, the superconducting energy gap follows the same change trend as that of the condensation.

Effect of Prime Mover Governor Parameters on Low Frequency Oscillation

The mechanism of power system low frequency oscillation was discussed in this paper. The coupling model between turbine governor system of plant and power system was established in MATLAB. The possibility of power system low frequency oscillation induced by unit-grid coupling was researched in detail. The simulation results indicate that power system low frequency oscillation will occur under disturbance, if a high derivative gain is used in PID controllers of hydraulic turbine governing system and partial derivative of turbine power output with respect to head varies with load. As for steam turbine, the PID parameters of governor system have important effect on small-signal stability of power system when the damp of power system is not very strong. The power oscillations caused by disturbance is decreased with the use of PID controller in governing system, whereas power oscillation is increased with the use of PI controller.