Tectonics and volcanisms of Mars

Televised images of Mars transmitted from interplanetary stations are used to develop a theory of the structure and development of the planet. Crater chronology, the structure of planetary bodies in the Earth group, and a comparison of the Earth planetary bodies are among the factors included

Weak gravity conjecture constraints on inflation

We consider the gravitational correction to the coupling of the scalar fields. Weak gravity conjecture says that the gravitational correction to the running of scalar coupling should be less than the contribution from scalar fields. For instance, a new scale $\Lambda=\lambda_4^{1/2}M_p$ sets a UV cutoff on the validity of the effective $\lambda_4 \phi^4$ theory. Furthermore, this conjecture implies a possible constraint on the inflation model, e.g. the chaotic inflation model might be in the swampland.Comment: 11 pages, 3 figs; monor corrections; some clarifying remarks added and the final version for publication in JHE

Large Charge Four-Dimensional Extremal N=2 Black Holes with R^2-Terms

We consider N=2 supergravity in four dimensions with small R^2 curvature corrections. We construct large charge extremal supersymmetric and non-supersymmetric black hole solutions in all space, and analyze their thermodynamic properties.Comment: 18 pages. v2,3: minor fixe

Large Charge Four-Dimensional Non-Extremal N=2 Black Holes with R^2-Terms

We consider N=2 supergravity in four dimensions with small R^2 curvature corrections. We construct large charge non-extremal black hole solutions in all space, with either a supersymmetric or a non-supersymmetric extremal limit, and analyze their thermodynamic properties. This generalizes some of the extremal solutions presented in [arXiv:0902.0831]. The indexed entropy of the non-extremal extension of the supersymmetric black hole, has the form of the extremal entropy, with the charges replaced by a function of the charges, the moduli at infinity and the non-extremality parameter. This is the same behavior as in the case without R^2-terms.Comment: 13 pages. v2: stripped down to letter format, based on the background given in [arXiv:0902.0831]. v3: up to date with CQG versio

Gravitational Correction and Weak Gravity Conjecture

We consider the gravitational correction to the running of gauge coupling. Weak gravity conjecture implies that the gauge theories break down when the gravitational correction becomes greater than the contribution from gauge theories. This observation can be generalized to non-Abelian gauge theories in diverse dimensions and the cases with large extra dimensions.Comment: 8 pages; minor correction and refs adde

Shear viscosity, instability and the upper bound of the Gauss-Bonnet coupling constant

We compute the dimensionality dependence of $\eta/s$ for charged black branes with Gauss-Bonnet correction. We find that both causality and stability constrain the value of Gauss-Bonnet coupling constant to be bounded by 1/4 in the infinite dimensionality limit. We further show that higher dimensionality stabilize the gravitational perturbation. The stabilization of the perturbation in higher dimensional space-time is a straightforward consequence of the Gauss-Bonnet coupling constant bound.Comment: 16 pages,3 figures+3 tables,typos corrected, published versio

Electromagnon excitations in modulated multiferroics

The phenomenological theory of ferroelectricity in spiral magnets presented in [M. Mostovoy, Phys. Rev. Lett. 96, 067601 (2006)] is generalized to describe consistently states with both uniform and modulated-in-space ferroelectric polarizations. A key point in this description is the symmetric part of the magnetoelectric coupling since, although being irrelevant for the uniform component, it plays an essential role for the non-uniform part of the polarization. We illustrate this importance in generic examples of modulated magnetic systems: longitudinal and transverse spin-density wave states and planar cycloidal phase. We show that even in the cases with no uniform ferroelectricity induced, polarization correlation functions follow to the soft magnetic behavior of the system due to the magnetoelectric effect. Our results can be easily generalized for more complicated types of magnetic ordering, and the applications may concern various natural and artificial systems in condensed matter physics (e.g., magnon properties could be extracted from dynamic dielectric response measurements).Comment: 5 page

Higher Derivative Corrections to R-charged Black Holes: Boundary Counterterms and the Mass-Charge Relation

We carry out the holographic renormalization of Einstein-Maxwell theory with curvature-squared corrections. In particular, we demonstrate how to construct the generalized Gibbons-Hawking surface term needed to ensure a perturbatively well-defined variational principle. This treatment ensures the absence of ghost degrees of freedom at the linearized perturbative order in the higher-derivative corrections. We use the holographically renormalized action to study the thermodynamics of R-charged black holes with higher derivatives and to investigate their mass to charge ratio in the extremal limit. In five dimensions, there seems to be a connection between the sign of the higher derivative couplings required to satisfy the weak gravity conjecture and that violating the shear viscosity to entropy bound. This is in turn related to possible constraints on the central charges of the dual CFT, in particular to the sign of c-a.Comment: 30 pages. v2: references added, some equations simplifie

The effect of higher derivative correction on η/s\eta /s and conductivities in STU model

In this paper we study the ratio of shear viscosity to entropy, electrical and thermal conductivities for the R-charged black hole in STU model. We generalize previous works to the case of a black hole with three different charges. Actually we use diffusion constant to obtain ratio of shear viscosity to entropy. By applying the thermodynamical stability we recover previous results. Also we investigate the effect of higher derivative corrections.Comment: revised versio

Stop the Top Background of the Stop Search

The main background for the supersymmetric stop direct production search comes from Standard Model ttbar events. For the single-lepton search channel, we introduce a few kinematic variables to further suppress this background by focusing on its dileptonic and semileptonic topologies. All are defined to have end points in the background, but not signal distributions. They can substantially improve the stop signal significance and mass reach when combined with traditional kinematic variables such as the total missing transverse energy. Among them, our variable M^W_T2 has the best overall performance because it uses all available kinematic information, including the on-shell mass of both W's. We see 20%-30% improvement on the discovery significance and estimate that the 8 TeV LHC run with 20 fb-1 of data would be able to reach an exclusion limit of 650-700 GeV for direct stop production, as long as the stop decays dominantly to the top quark and a light stable neutralino. Most of the mass range required for the supersymmetric solution of the naturalness problem in the standard scenario can be covered.Comment: 16 pages, 5 figure