We study a class of supersymmetric models with nonuniversal gaugino masses that could arise from $F$-terms in a general combination of the singlet and adjoint representations of $SU(5)$. We explore models that satisfy present Large Hadron Collider and other bounds, showing how the allowed parameter space is divided into distinct “continents.” Regions of parameter space that ameliorate the supersymmetric little hierarchy problem with a small $\mu$ parameter include the usual focus-point scenario, but also natural areas with much lighter squarks and sleptons. These models are continuously connected in parameter space to regions in which stau coannihilation or Higgs exchange is mostly responsible for dark matter annihilation, and to models in which the thermal relic abundance is achieved by slepton-mediated annihilation, reviving the bulk region that is severely restricted in minimal supergravity models. In hybrid or confluence regions, several mechanisms combine to give the requisite dark matter annihilation rate. In each case, we study the prospects for direct detection of dark matter. We also comment briefly on the impact of recent hints for $M_h$ near 125 GeV from the LHC.

Scalar and tensor interactions were once competitors to the now well-established $V-A$ structure of the standard model weak interactions. We revisit these interactions and survey constraints from low-energy probes (neutron, nuclear, and pion decays) as well as collider searches. Currently, the most stringent limit on scalar and tensor interactions arise from $0^{+}\to 0^{+}$ nuclear decays and the radiative pion decay $\pi \to e\nu \gamma$, respectively. For the future, we find that upcoming neutron beta decay and LHC measurements will compete in setting the most stringent bounds. For neutron beta decay, we demonstrate the importance of lattice computations of the neutron-to-proton matrix elements to setting limits on these interactions, and provide the first lattice estimate of the scalar charge and a new average of existing results for the tensor charge. Data taken at the LHC is currently probing these interactions at the ${10}^{-2}$ level (relative to the standard weak interactions), with the potential to reach the $\lesssim {10}^{-3}$ level. We show that, with some theoretical assumptions, the discovery of a charged spin-0 resonance decaying to an electron and missing energy implies a lower limit on the strength of scalar interactions probed at low energy.

The surprising results by the BABAR Collaboration on the $\pi \gamma$ transition form factor require new thoughts about the high-$Q^2$ dependence of the form factors with virtual photons. We make use of the anomaly sum rule [J. Horejsi and O. Teryaev, Z. Phys. C 65, 691 (1995).] which relates the hadron spectral density to the axial anomaly [S. Adler, Phys. Rev. 177, 2426 (1969); J. S. Bell and R. Jackiw, Nuovo Cimento A 60, 47 (1969).]. We study the quark-hadron duality relation for this sum rule and find out that the increase of the rescaled form factor $Q^2{F}_{\pi \gamma }(Q^2)\sim \log (Q^2)$ suggested by the BABAR data requires the presence of a $1/s$-correction term in the relation between the one-loop spectral density and the hadron-continuum spectral density.

In the present paper, we study numerically the equatorial lensing and quasiequatorial lensing by Kerr black holes pierced by a cosmic string in the strong deflection limit. We calculate the strong deflection limit coefficients and the deflection angle, which are found to depend closely on the cosmic string parameter $\beta$ and dimensionless spin $a_{*}$. The magnification and positions of relativistic images are also computed in the strong deflection limit, and a two-dimensional lens equation is derived. The most important and outstanding effect is that the caustics drift away from the optical axis and shift in the clockwise direction with respect to the Kerr black hole. For fixed $a_{*}$ of the black hole, the caustics drift farther away from the optical axis for a large value of $\beta$. And for fixed $\beta$, they drift farther for high $a_{*}$. We also obtain the intersections of the critical curves with the equatorial plane, which decrease with $a_{*}$ and $\beta$. In particular, we obtain a quantity ${\overline{\mu }}_{k+1}/{\overline{\mu }}_k$, which is independent of the black hole spin and mass. Thus, through measuring it, one is allowed to determine the value of $\beta$ from astronomical observations.

We report new limits on the ${\pi }^0\to \gamma X$ decay of the neutral pion into a photon and a new gauge boson $X$ followed by the decay $X\to e^{+}{e}^{-}$. If this process exists, one would expect a flux of high energy $X$’s produced from ${\pi }^0$’s generated by the proton beam in a neutrino target. The $X$’s would then penetrate the downstream shielding and be observed in a neutrino detector via their decays. Using bounds from the NOMAD and PS191 neutrino experiments at CERN that searched for an excess of $e^{+}{e}^{-}$ pairs from heavy neutrino decays, stringent limits on the branching ratio as small as $\mathrm{Br}({\pi }^0\to \gamma X)\lesssim {10}^{-15}$ are obtained. These limits are several orders of magnitude smaller than the previous experimental and cosmological bounds. The obtained results are used to constrain models, where the $X$ interacts with quarks and leptons, or it is a new vector boson mixing with photons that transmits interaction between our world and hidden sectors consisting of $SU(3{)}_C\times SU(2{)}_L\times U(1{)}_Y$ singlet fields.

The neutral triplet scalars ($H^0$, $A^0$) in the Higgs triplet model are difficult to detect at the LHC for the case of mass degeneracy with the singly charged ($H^{\pm }$) and doubly charged ($H^{\pm \pm }$) scalars. A nonzero value of a specific quartic coupling in the scalar potential removes this degeneracy, and positive values of this coupling would give rise to the mass hierarchy $m_{A^0,H^0}>m_{H^{\pm }}>m_{H^{\pm \pm }}$. In this scenario the decays $H^0\to H^{\pm }{W}^{*}$ and $A^0\to H^{\pm }{W}^{*}$, followed by $H^{\pm }\to H^{\pm \pm }{W}^{*}$, can proceed with large branching ratios, even for small mass splittings among the triplet scalars. Such a cascade process would lead to production of $H^{++}{H}^{--}$ accompanied by several virtual $W$ bosons, and would provide a way of observing $H^0$ and $A^0$ with a signature which is different from that of the conventional production process for doubly charged scalars, $q\overline{q}\to {\gamma }^{*}$, $Z^{*}\to H^{++}{H}^{--}$. Assuming the decay $H^{\pm \pm }\to {\ell }^{\pm }{\ell }^{\prime \pm }$, we quantify the magnitude of the five-lepton and six-lepton signals in these channels, which have essentially negligible backgrounds at the LHC.

Results of a high-statistics, multivolume lattice QCD exploration of the deuteron, the dineutron, the H-dibaryon, and the ${\Xi }^{-}{\Xi }^{-}$ system at a pion mass of $m_{\pi }\sim 390\mathrm{MeV}$ are presented. Calculations were performed with an anisotropic $n_f=2+1$ clover discretization in four lattice volumes of spatial extent $L\sim 2.0$, 2.5, 2.9, and 3.9 fm, with a lattice spacing of $b_s\sim 0.123\mathrm{fm}$ in the spatial direction and $b_t\sim b_s/3.5$ in the time direction. Using the results obtained in the largest two volumes, the ${\Xi }^{-}{\Xi }^{-}$ is found to be bound by $B_{{\Xi }^{-}{\Xi }^{-}}0=14.0(1.4)(6.7)\mathrm{MeV}$, consistent with expectations based upon phenomenological models and low-energy effective field theories constrained by nucleon-nucleon and hyperon-nucleon scattering data at the physical light-quark masses. Further, we find that the deuteron and the dineutron have binding energies of $B_d=11(05)(12)\mathrm{MeV}$ and $B_{nn}=7.1(5.2)(7.3)\mathrm{MeV}$, respectively. With an increased number of measurements and a refined analysis, the binding energy of the H-dibaryon is $B_H=13.2(1.8)(4.0)\mathrm{MeV}$ at this pion mass, updating our previous result.

We compute the effective Lagrangian of static gravitational fields interacting with thermal fields. Our approach employs the usual imaginary time formalism as well as the equivalence between the static and space-time independent external gravitational fields. This allows to obtain a closed form expression for the thermal effective Lagrangian in $d$ space-time dimensions.

We consider the six-dimensional brane world model, where the brane is described by a localized solution to the baby-Skyrme model extending in the extra dimensions. The branes have a cosmological constant modeled by inflating four-dimensional slices and we further consider a bulk cosmological constant. We focus on the topological number three solutions and discuss the localization mechanism of the fermions on the above 3-branes. We discuss interpretation of the model in term of quark third-generation mass and in terms of the inflation history. We argue that the model can describe various epochs of the early Universe by suitably choosing the parameters. We further discuss the localization properties of gauge fields on the brane and argue that this is achieved only for specific values of the electromagnetic coupling, providing a quantization to the electric charge.

We calculate via the effective field theory (EFT) approach the next-to-next-to-leading order (NNLO) spin1-spin2 conservative potential for a binary. Hereby, we first demonstrate the ability of the EFT approach to go at NNLO in post-Newtonian (PN) corrections from spin effects. The NNLO spin1-spin2 interaction is evaluated at fourth PN order for a binary of maximally rotating compact objects. This sector includes contributions from diagrams, which are not pure spin1-spin2 diagrams, as they contribute through the leading-order spin accelerations and precessions, that should be first taken into account here. The fact that the spin is derivative-coupled adds significantly to the complexity of computations. In particular, for the irreducible two-loop diagrams, which are the most complicated to evaluate in this sector, irreducible two-loop tensor integrals up to order 4 are required. The EFT calculation is carried out in terms of the nonrelativistic gravitational (NRG) fields. However, not all of the benefits of the NRG fields apply to spin interactions, as all possible diagram topologies are realized at each order of $G$ included. Still, the NRG fields remain advantageous, and thus there was no use of automated computations in this work. Our final result can be reduced, and a corresponding Hamiltonian may be derived.

We present a fully nonlinear study of long-wavelength cosmological perturbations within the framework of the projectable Hořava-Lifshitz gravity, coupled to a single scalar field. Adopting the gradient expansion technique, we explicitly integrate the dynamical equations up to any order of the expansion, then restrict the integration constants by imposing the momentum constraint. While the gradient expansion relies on the long-wavelength approximation, amplitudes of perturbations do not have to be small. When the $\lambda \to 1$ limit is taken, the obtained nonlinear solutions exhibit a continuous behavior at any order of the gradient expansion, recovering general relativity in the presence of a scalar field and the “dark matter as an integration constant.” This is in sharp contrast to the results in the literature based on the “standard” (and naive) perturbative approach where in the same limit, the perturbative expansion of the action breaks down and the scalar graviton mode appears to be strongly coupled. We carry out a detailed analysis on the source of these apparent pathologies and determine that they originate from an improper application of the perturbative approximation in the momentum constraint. We also show that there is a new branch of solutions, valid in the regime where $|\lambda -1|$ is smaller than the order of perturbations. In the limit $\lambda \to 1$, this new branch allows the theory to be continuously connected to general relativity, with an effective component which acts like pressureless fluid.

Axions differ from the other cold dark matter candidates in that they form a degenerate Bose gas. It is shown that their huge quantum degeneracy and large correlation length cause cold dark matter axions to thermalize through gravitational self-interactions when the photon temperature reaches approximately 500 eV. When they thermalize, the axions form a Bose-Einstein condensate. Their thermalization occurs in a regime, herein called the “condensed regime,” where the Boltzmann equation is not valid because the energy dispersion of the particles is smaller than their interaction rate. We derive analytical expressions for the thermalization rate of particles in the condensed regime, and check the validity of these expressions by numerical simulation of a toy model. We revisit axion cosmology in light of axion Bose-Einstein condensation. It is shown that axions are indistinguishable from ordinary cold dark matter on all scales of observational interest, except when they thermalize or rethermalize. The rethermalization of axions that are about to fall in a galactic potential well causes them to acquire net overall rotation as they go to the lowest energy state consistent with the total angular momentum they acquired by tidal torquing. This phenomenon explains the occurrence of caustic rings of dark matter in galactic halos. We find that photons may reach thermal contact with axions and we investigate the implications of this possibility for the measurements of cosmological parameters.

In this paper we introduce a novel way to spontaneously localize particles (including gauge bosons) and gravitons kinetic terms on a four-dimensional brane via a gravitational mechanism. The model underlying this localization mechanism can be considered as a high-energy resolution of the so-called braneworlds scenario. In particular, we show how to construct a braneworld with induced gravity without pathologies. Finally, we argue that the brane is only stable if its own mass does not exceed a critical value related to the particles-gravity couplings.

We investigate the capability of directional detectors to probe neutralino dark matter in the minimal supersymmetric standard model and the next-to-minimal supersymmetric standard model with parameters defined at the weak scale. We show that directional detectors such as the future MIMAC detector will probe spin-dependent dark matter scattering on nucleons that are beyond the reach of current spin-independent detectors. The complementarity between indirect searches, in particular, using gamma rays from dwarf spheroidal galaxies, spin-dependent and spin-independent direct search techniques is emphasized. We comment on the impact of the negative results on squark searches at the LHC. Finally, we investigate how the fundamental parameters of the models can be constrained in the event of a dark matter signal.

We calculate in perturbative QCD the transverse momentum imbalance of dijet and dihadron production in high-energy $\mathrm{p}+\mathrm{A}$ ($\mathrm{d}+\mathrm{A}$) collisions. We evaluate the effect of both initial- and final-state multiple scattering, which determines the strength of this transverse momentum imbalance. Combining this new result with the suppression of the cross section in $\mathrm{d}+\mathrm{Au}$ collisions, which arises from cold nuclear matter energy loss and coherent power corrections, we are able to describe the dihadron correlations measured by both PHENIX and STAR collaborations at RHIC, including mid-mid, mid-forward, and forward-forward rapidity hadron pairs.

Radiative effects in the electroproduction of photons in polarized $ep$ scattering are calculated in the leading log approximation and analyzed numerically for kinematical conditions of current measurement at Jefferson Lab. Radiative corrections to the cross sections, their azimuthal distributions, and Fourier coefficients are in particular focus. Kinematical regions where the radiative corrections are considerable are identified.

A recent article [Phys. Rev. D 85, 024040 (2012)] (I) asks if the equivalence of two Lagrangian densities ${\mathcal{L}}_1=P$ and ${\mathcal{L}}_2=-\rho$ for a perfect fluid is also valid for a real scalar field, which is equivalent to a perfect fluid. The treatment has an important error which results in wrong expressions for density and pressure in the case where the field gradient is spacelike. For timelike field gradients, the effective pressure turns out to be equal to the Lagrangian density for both the standard and “phantom” scalar fields, and also the energy density of each field type turns out to be equal to the negative of the Lagrangian density of the other type; but we disagree with the way these equalities are stated in (I). We give the correct density and pressure expressions for the case of spacelike field gradients; such scalar field configurations can serve as one way of realizing effective tachyonic perfect fluids.

We extend the ideas of using AdS/CFT to calculate energy loss of extended defects in strongly coupled systems to general holographic metrics. We find the equations of motion governing uniformly moving defects of various dimension and determine the corresponding energy loss rates in terms of the metric coefficients. We apply our formulae to the specific examples of both bulk geometries created by general $\mathrm{D}p$-branes, as well as to holographic superfluids. For the $\mathrm{D}p$-branes, we find that the energy loss of our defect, in addition to the expected quadratic dependence on velocity, depends on velocity only via an effective blue-shifted temperature—despite the existence of a microscopic length scale in the theory. We also find, for a certain value of $p$ and dimension of the defect, that the energy loss has no dependence on temperature or velocity other than the aforementioned quadratic dependence on velocity. For the superfluid example, we find agreement with previous results on the existence of a cutoff velocity, below which the probe experiences no drag force. For both examples we can easily extend the equations of motion and energy loss to defects of larger dimension.