There is a claim that a static-charged black hole (Reissner-Nordström black hole) can be overcharged by absorbing a charged test particle. If it is true, it might give a counter example to the weak cosmic censorship conjecture, which states that spacetime singularities are never observed by a distant observer. However, so far the proposed process has only been analyzed within a test particle approximation. Here, we claim that the backreaction effects of a charged particle cannot be neglected when judging whether the suggested process is really a counter example to the cosmic censorship conjecture. Furthermore, we argue that all the backreaction effects can be properly taken into account when we consider the trajectory of a particle on the border between the plunge and bounce orbits. In such marginal cases, we find that the Reissner-Nordström black hole can never be overcharged via the absorption of a charged particle. Since all the plunge orbits are expected to have a higher energy than the marginal orbit, we conclude that there is no supporting evidence that indicates the violation of the cosmic censorship in the proposed overcharging process.

We investigate the radial behavior of galactic rotation curves by a Fourth Order Gravity adding also the dark matter component. The Fourth Order Gravity is a theory of gravity described by Lagrangian generalizing the one of Hilbert-Einstein containing a generic function of the Ricci scalar, the Ricci and Riemann tensor. A systematic analysis of rotation curves, in the Newtonian Limit of theory, induced by all galactic substructures of ordinary matter is shown. This analysis is presented for Fourth Order Gravity with and without dark matter. The outcomes are compared with respect to the classical outcomes of General Relativity. The gravitational potential of pointlike mass is the usual potential corrected by two Yukawa terms. The rotation curve is higher or also lower than curve of General Relativity if in the Lagrangian the Ricci scalar square is dominant or not with respect to the contribution of the Ricci tensor square. The theoretical spatial behaviors of rotation curve are compared with the experimental data for the Milky Way and the galaxy NGC 3198. Although the Fourth Order Gravity gives more rotational contributions, in the limit of large distances the Keplerian behavior is ever present, and it is missing only if we add the dark matter component. However by modifying the theory of gravity, consequently, also the spatial description of dark matter could undergo a modification and the free parameters of model can assume different values. After an analytical discussion of theoretical behaviors and the comparing with experimental evidence we can claim that any Fourth Order Gravity is not successful to explain the galactic rotation curves. In the last part of paper we analyze the gravitational potential induced by Lagrangian containing only powers of Ricci scalar. In this case we find an inconsistency in the boundary conditions in the passage from matter to the vacuum.

We explore the sensitivity of weak gravitational lensing to second-order corrections to the spacetime metric within a cosmological adaptation of the parametrized post-Newtonian framework. Whereas one might expect nonlinearities of the gravitational field to introduce non-Gaussianity into the statistics of the lensing convergence field, we show that such corrections are actually always small within a broad class of scalar-tensor theories of gravity. We show this by first computing the weak lensing convergence within our parametrized framework to second order in the gravitational potential, and then computing the relevant post-Newtonian parameters for scalar-tensor gravity theories. In doing so we show that this potential systematic factor is generically negligible, thus clearing the way for weak lensing to provide a direct tracer of mass on cosmological scales for a wide class of gravity theories despite uncertainties in the precise nature of the departures from general relativity.

We study the possibility for detecting gamma-ray emission from galaxy clusters. We consider (1) leptophilic models of dark matter (DM) annihilation that include a Sommerfeld enhancement (SFE), (2) different representative benchmark models of supersymmetric DM, and (3) cosmic-ray (CR) induced pion decay. Among all clusters/groups of a flux-limited x-ray sample, we predict Virgo, Fornax, and M49 to be the brightest DM sources and find a particularly low CR-induced background for Fornax. For a minimum substructure mass given by the DM free-streaming scale, cluster halos maximize the substructure boost for which we find a factor of $\gtrsim 1000$. Since regions around the virial radius dominate the annihilation flux of substructures, the resulting surface brightness profiles are almost flat. This makes it very challenging to detect this flux with imaging atmospheric Cherenkov telescopes since their sensitivity drops approximately linearly with radius and they typically have 5–10 linear resolution elements across a cluster. Assuming cold dark matter with a substructure mass distribution down to an Earth mass and using extended Fermi upper limits, we rule out the leptophilic models in their present form in 28 clusters, and limit the boost from SFE in M49 and Fornax to be $\lesssim 5$. This corresponds to a limit on SFE in the Milky Way of $\lesssim 3$, which is too small to account for the increasing positron fraction with energy as seen by PAMELA and challenges the DM interpretation. Alternatively, if SFE is realized in nature, this would imply a limiting substructure mass of $M_{\lim }>{10}^4{M}_{\odot }$—a problem for structure formation in most particle physics models. Using individual cluster observations, it will be challenging for Fermi to constrain our selection of DM benchmark models without SFE. The Fermi upper limits are, however, closing in on our predictions for the CR flux using an analytic model based on cosmological hydrodynamical cluster simulations. We limit the CR-to-thermal pressure in nearby bright galaxy clusters of the Fermi sample to $\lesssim 10\%$ and in Norma and Coma to $\lesssim 3\%$. Thus, we will soon start to constrain the underlying CR physics such as shock acceleration efficiencies or CR transport properties.

The testing of general relativity at cosmological scales has become a possible and timely endeavor that is not only motivated by the pressing question of cosmic acceleration but also by the proposals of some extensions to general relativity that would manifest themselves at large scales of distance. We analyze here correlations between modified gravity growth parameters and some core cosmological parameters using the latest cosmological data sets including the refined Cosmic Evolution Survey 3D weak lensing. We provide the parametrized modified growth equations and their evolution. We implement known functional and binning approaches, and propose a new hybrid approach to evolve the modified gravity parameters in redshift (time) and scale. The hybrid parametrization combines a binned redshift dependence and a smooth evolution in scale avoiding a jump in the matter power spectrum. The formalism developed to test the consistency of current and future data with general relativity is implemented in a package that we make publicly available and call ISiTGR (Integrated Software in Testing General Relativity), an integrated set of modified modules for the publicly available packages CosmoMC and CAMB, including a modified version of the integrated Sachs-Wolfe-galaxy cross correlation module of Ho et al. and a new weak-lensing likelihood module for the refined Hubble Space Telescope Cosmic Evolution Survey weak gravitational lensing tomography data. We obtain parameter constraints and correlation coefficients finding that modified gravity parameters are significantly correlated with ${\sigma }_8$ and mildly correlated with ${\Omega }_m$, for all evolution methods. The degeneracies between ${\sigma }_8$ and modified gravity parameters are found to be substantial for the functional form and also for some specific bins in the hybrid and binned methods indicating that these degeneracies will need to be taken into consideration when using future high precision data.

We discuss how the experimental neutrino oscillation data can be realized in the framework of the baryon triality ($B_3$) constrained supersymmetric standard model. We show how to obtain phenomenologically viable solutions, which are compatible with the recent Wilkinson Microwave Anisotropy Probe observations. We present results for the hierarchical, inverted and degenerate cases which illustrate the possible size and structure of the lepton number violating couplings. We work with a new, as-yet unpublished version of SOFTSUSY where we implemented full one-loop neutrino masses. Finally, we shortly discuss some phenomenological implications at the LHC.

We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a data set corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the $t\overline{t}$ forward-backward asymmetry to be $(9.2\pm 3.7)\%$ at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be $(19.6\pm 6.5)\%$. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be $(15.2\pm 4.0)\%$. The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.

We study dynamical partially-localized brane solutions in higher dimensions. We give new descriptions of the relevant solutions of dynamical branes which are localized along both the overall and relative transverse directions. The starting point is a system of $p_r$-branes ending on a $p_s$-brane with a time-dependent warp factor. This system can be related to $\mathrm{D}{p}_r-{\mathrm{Dp}}_s$ brane system in string theory, where one brane is localized at the delocalized other brane. We then show that these give Friedmann-Lemaitre-Robertson-Walker cosmological solutions. Our approach leads to a new and manifest description of the brane configurations near the delocalized branes, and new solutions in the wave or KK-monopole background in terms of certain partial differential equations in $D$ dimensions including ten and eleven dimensions.

The low-energy physics of systems with spontaneous symmetry breaking is governed by the associated Nambu-Goldstone (NG) bosons. While NG bosons in Lorentz-invariant systems are well understood, the precise characterization of their number and dispersion relations in a general quantum many-body system is still an open problem. An inequality relating the number of NG bosons and their dispersion relations to the number of broken symmetry generators was found by Nielsen and Chadha. In this paper, we give a presumably first example of a system in which the Nielsen-Chadha inequality is actually not saturated. We suggest that the number of NG bosons is exactly equal to the number of broken generators minus the number of pairs of broken generators whose commutator has a nonzero vacuum expectation value. This naturally leads us to a proposal for a different classification of NG bosons.

The D3/D7 holographic model aims at a better approximation to QCD by adding to $N=4$ SYM theory $N_f$ of $N=2$ supersymmetric hypermultiplets in the fundamental representation of $SU(N_c)$—the “flavor fields” representing the quarks. Motivated by a recent observation of the importance of the Wess-Zumino-like (WZ) term for realizing the chiral magnetic effect within this model, we revisit the phase diagram of the finite temperature, massless D3/D7 model in the presence of external electric/magnetic fields and at finite chemical potential. We point out that the A-V-V triangle anomaly represented by the WZ term in the D7 brane probe action implies the existence of new phases that have been overlooked in the previous studies. In the case of an external magnetic field and at finite chemical potential, we find a “chiral helix” phase in which the $U(1{)}_A$ angle of D7 brane embedding increases monotonically along the direction of the magnetic field—this is a geometric realization of the chiral spiral phase in QCD. We also show that in the case of parallel electric and magnetic fields ($E$, $B$) there exists a phase in which the D7 brane spontaneously begins to rotate, so that the $U(1{)}_A$ angle changes as a function of time—this may be called the “spontaneous rotation” phase; it is a geometrical realization of a phase with nonzero chiral chemical potential. Our results call for a more thorough study of the ($T$, $B$, $E$, $\mu$) phase diagram of the massless D3/D7 model taking a complete account of the WZ term. We also speculate about the possible phase diagram in the massive case.

We describe an analytic continuation of the Euclidean Grosse-Wulkenhaar and Langmann-Szabo-Zarembo models which defines a one-parameter family of duality covariant noncommutative field theories interpolating between Euclidean and Minkowski space versions of these models, and provides an alternative regularization to the usual Feynman prescription. This regularization allows for a matrix model representation of the field theories in terms of a complex generalization of the usual basis of Landau wave functions. The corresponding propagators are calculated and identified with the Feynman propagators of the field theories. The regulated quantum field theories are shown to be UV/IR-duality covariant. We study the asymptotics of the regularized propagators in position and matrix space representations, and confirm that they generically possess a comparably good decay behavior as in the Euclidean case.

We calculate analytically a back reaction of the stationary spherical accretion flow near the event horizon and near the inner Cauchy horizon of the charged black hole. It is shown that corresponding back-reaction corrections to the black hole metric depend only on the fluid accretion rate and diverge in the case of an extremely charged black hole. In result, the test fluid approximation for stationary accretion is violated for extreme black holes. This behavior of the accreting black hole is in accordance with the third law of black hole thermodynamics, forbidding the practical attainability of the extreme state.

We obtain a class of magnetically charged solutions in $2+1$ dimensional Einstein-Power-Maxwell theory. In the linear Maxwell limit, such horizonless solutions are known to exist. We show that in $3D$ geometry, black hole solutions with magnetic charge do not exist even if it is sourced by the power-Maxwell field. Physical properties of the solution with particular power $k$ of the Maxwell field is investigated. The true timelike naked curvature singularity develops when $k>1$ which constitutes one of the striking effects of the power-Maxwell field. For specific power parameter $k$, the occurrence of a timelike naked singularity is analyzed in the quantum mechanical point of view. Quantum test fields obeying the Klein-Gordon and the Dirac equations are used to probe the singularity. It is shown that the class of static pure magnetic spacetime in the power-Maxwell theory is quantum-mechanically singular when it is probed with fields obeying Klein-Gordon and Dirac equations in the generic case.

Electromagnetic and gravitational radiation do not propagate solely on the null cone in a generic curved spacetime. They develop “tails,” traveling at all speeds equal to and less than unity. If sizeable, this off-the-null-cone effect could mean objects at cosmological distances, such as supernovae, appear dimmer than they really are. Their light curves may be distorted relative to their flat spacetime counterparts. These in turn could affect how we infer the properties and evolution of the Universe or the objects it contains. Within the gravitational context, the tail effect induces a self-force that causes a compact object orbiting a massive black hole to deviate from an otherwise geodesic path. This needs to be taken into account when modeling the gravitational waves expected from such sources. Motivated by these considerations, we develop perturbation theory for solving the massless scalar, photon, and graviton retarded Green’s functions in perturbed spacetimes $g_{\mu \nu }={\overline{g}}_{\mu \nu }+h_{\mu \nu }$, assuming these Green’s functions are known in the background spacetime ${\overline{g}}_{\mu \nu }$. In particular, we elaborate on the theory in perturbed Minkowski spacetime in significant detail; and we apply our techniques to compute the retarded Green’s functions in the weak field limit of the Kerr spacetime to first order in the black hole’s mass $M$ and angular momentum $S$. Our methods build on and generalize work appearing in the literature on this topic to date, and lay the foundation for a thorough, first-principles-based, investigation of how light propagates over cosmological distances, within a spatially flat inhomogeneous Friedmann-Lemaître-Robertson-Walker universe. This perturbative scheme applied to the graviton Green’s function, when pushed to higher orders, may provide approximate analytic (or semianalytic) results for the self-force problem in the weak field limits of the Schwarzschild and Kerr black hole geometries.

Generically, massive gravity gives a nonunique gravitational field around a star. For a special family of massive gravity theories, we show that the stellar gravitational field is unique and observationally acceptable, that is close to Einsteinian. The black hole solutions in this family of theories are also studied and shown to be peculiar. Black holes have a near-horizon throat and the curvature diverging at the horizon. We show that there exists a subfamily of these massive gravity theories with nonsingular at horizon black holes.

We propose an underground experiment to detect the general relativistic effects due to the curvature of space-time around the Earth (de Sitter effect) and to the rotation of the planet (dragging of the inertial frames or Lense-Thirring effect). It is based on the comparison between the IERS value of the Earth rotation vector and corresponding measurements obtained by a triaxial laser detector of rotation. The proposed detector consists of six large ring lasers arranged along three orthogonal axes. In about two years of data taking, the 1% sensitivity required for the measurement of the Lense-Thirring drag can be reached with square rings of 6 m side, assuming a shot noise limited sensitivity ($20\mathrm{prad}/\mathrm{s}/\sqrt{\mathrm{Hz}}$). The multigyros system, composed of rings whose planes are perpendicular to one or the other of three orthogonal axes, can be built in several ways. Here, we consider cubic and octahedral structures. It is shown that the symmetries of the proposed configurations provide mathematical relations that can be used to ensure the long term stability of the apparatus.

We study the $Z^{\prime }\to \overline{q}q,ggg$ decays in the context of a manifest left-right symmetric gauge theory with three and four generations. The $Z^{\prime }$ couplings to quarks are fixed essentially by the parameters of the standard model and we obtain $\Gamma (Z^{\prime }\to q\overline{q})\approx 14\mathrm{GeV}$ for $M_{Z^{\prime }}\approx 1\mathrm{TeV}$. For the $Z^{\prime }\to ggg$ decay and three families we obtain a branching ratio $\mathrm{BR}(Z^{\prime }\to ggg)=\frac{\Gamma (Z^{\prime }\to ggg)}{\Gamma (Z^{\prime }\to q\overline{q})}=1.2-2.8\times {10}^{-5}$ for $m_{Z^{\prime }}=700–1500\mathrm{GeV}$. The fourth generation produces an enhancement in the branching ratio for $Z^{\prime }$ masses close to the ${\overline{b}}^{\prime }{b}^{\prime }$ threshold and a dip for $Z^{\prime }$ masses close to the ${\overline{t}}^{\prime }{t}^{\prime }$ threshold. Using the values of the fourth-generation quark masses allowed by electroweak precision data, we obtain a branching ratio $\mathrm{BR}(Z^{\prime }\to ggg)=(1-6)\times {10}^{-5}$ for $m_{Z^{\prime }}=(700–1500)\mathrm{GeV}$.

We investigate the phenomenology of the gravitino dark matter scenario with a stau as the next-to-lightest supersymmetric particle at the LHC. For a wide range of gravitino masses the lighter stau is stable on the scale of a detector and gives rise to a prominent signature as a “slow muon.” The direct stau production via the Drell-Yan process is always present and independent of the mass spectrum of the other superparticles, thus providing a lower bound for the discovery potential of this scenario. Performing a careful analysis with particular emphasis on the criteria for observing stau pairs and for distinguishing them from the background, we find that the 14 TeV run of the LHC has a promising potential for finding long-lived staus from Drell-Yan production up to very large stau masses.

Chiral effective field theory can provide valuable insight into the chiral physics of hadrons when used in conjunction with nonperturbative schemes such as lattice quantum chromodynamics (QCD). In this discourse, the attention is focused on extrapolating the mass of the $\rho$ meson to the physical pion mass in quenched QCD. With the absence of a known experimental value, this serves to demonstrate the ability of the extrapolation scheme to make predictions without prior bias. By using extended effective field theory developed previously, an extrapolation is performed using quenched lattice QCD data that extends outside the chiral power-counting regime. The method involves an analysis of the renormalization flow curves of the low-energy coefficients in a finite-range regularized effective field theory. The analysis identifies an optimal regularization scale, which is embedded in the lattice QCD data themselves. This optimal scale is the value of the regularization scale at which the renormalization of the low-energy coefficients is approximately independent of the range of quark masses considered. By using recent precision, quenched lattice results, the extrapolation is tested directly by truncating the analysis to a set of points above 380 MeV, while temporarily disregarding the simulation results closer to the chiral regime. This tests the ability of the method to make predictions of the simulation results, without phenomenologically motivated bias. The result is a successful extrapolation to the chiral regime.