Holographic DC Conductivity for a Power-law Maxwell Field

We consider a neutral and static black brane background with a probe power-law Maxwell field. Via the membrane paradigm, an expression for the holographic DC conductivity of the dual conserved current is obtained. We also discuss the dependence of the DC conductivity on the temperature, charge density and spatial components of the external field strength in the boundary theory. Our results show that there might be more than one phase in the boundary theory. Phase transitions could occur where the DC conductivity or its derivatives are not continuous. Specifically, we find that one phase possesses a charge-conjugation symmetric contribution, negative magneto-resistance and Mott-like behavior.Comment: 19 pages, 11 figures. arXiv admin note: text overlap with arXiv:1711.0329

Loop Corrections in Double Field Theory: Non-trivial Dilaton Potentials

It is believed that the invariance of the generalised diffeomorphisms prevents any non-trivial dilaton potential from double field theory. It is therefore difficult to include loop corrections in the formalism. We show that by redefining a non-local dilaton field, under strong constraint which is necessary to preserve the gauge invariance of double field theory, the theory does permit non-constant dilaton potentials and loop corrections. If the fields have dependence on only one single coordinate, the non-local dilaton is identical to the ordinary one with an additive constant.Comment: V3, 11 pages, references added, typos corrected, version to appear in JHE

Holographic DC Conductivity for Backreacted Nonlinear Electrodynamics with Momentum Dissipation

We consider a holographic model with the charge current dual to a general nonlinear electrodynamics (NLED) field. Taking into account the backreaction of the NLED field on the geometry and introducing axionic scalars to generate momentum dissipation, we obtain expressions for DC conductivities with a finite magnetic field. The properties of the in-plane resistance are examined in several NLED models. For Maxwell-Chern-Simons electrodynamics, negative magneto-resistance and Mott-like behavior could appear in some parameter space region. Depending on the sign of the parameters, we expect the NLED models to mimic some type of weak or strong interactions between electrons. In the latter case, negative magneto-resistance and Mott-like behavior can be realized at low temperatures. Moreover, the Mott insulator to metal transition induced by a magnetic field is also observed at low temperatures.Comment: 28 pages, 31 figures. Added reference

Quantum gravity effects on compact star cores

Using the Tolman-Oppenheimer-Volkoff equation and the equation of state of zero temperature ultra-relativistic Fermi gas based on generalized uncertainty principle (GUP), the quantum gravitational effects on the cores of compact stars are discussed. Our results show that ${2m(r)}/ {r}$ varies with $r$. Quantum gravity plays an important role in the region $r\sim 10^3 r_0$, where $r_0\sim \beta_0 l_p$, $l_p$ is the Planck length and $\beta_0$ is a dimensionless parameter accounting for quantum gravity effects. Furthermore, near the center of compact stars, we find that the metric components are $g_{tt}\sim r^4$ and $g_{rr}=[1-{r}^2/(6r_0^2)]^{-1}$. All these effects are different from those obtained from classical gravity. These results can be applied to neutron stars or denser ones like quark stars. The observed masses of neutron stars ($\leq 2M_\odot$) indicate that $\beta_0$ can not exceed $10^{37}$, not as good as the upper bound $\beta_0<10^{34}$ from simple electroweak consideration. This means that incorporating either quantum gravity effects or nuclear interactions, one obtains almost the same mass limits of neutron stars.Comment: 12 pages, 1 figure, added brief review on compact stars configurations, abstract expanded, references added, typo corrected, published versio