The helicity of a photon traversing a magnetized plasma can flip when the $B$ field along the trajectory slowly reverses. Broderick and Blandford have recently shown that this intriguing effect can profoundly change the usual Faraday effect for radio waves. We study this phenomenon in a formalism analogous to neutrino flavor oscillations: the evolution is governed by a Schrödinger equation for a two-level system consisting of the two photon helicities. Our treatment allows for a transparent physical understanding of this system and its dynamics. In particular, it allows us to investigate the nature of transitions at intermediate adiabaticities.

We study the couplings of a $CP$-even neutral Higgs boson $h$ in a model containing one scalar $\mathrm{SU}(2{)}_L$ doublet, one real triplet, and one complex triplet with hypercharge 1. Because the two triplets contribute to the $\rho$ parameter with opposite signs, the triplet vacuum expectation values can be sizable. We show that (i) the $hWW$ and $hZZ$ couplings can be larger than the corresponding values in the standard model, and (ii) the ratio of the $WW$ and $ZZ$ couplings of $h$ can be different than the corresponding ratio in the standard model. Neither of these results can occur in models containing only Higgs doublets. We also compute the rates for $gg\to h\to WW$ and $gg\to h\to ZZ$ and find that, for reasonable parameter values and $M_h\sim 140–180\mathrm{GeV}$, the hadron collider rate for $gg\to h\to WW$ ($ZZ$) can be up to 20% (5 times) larger than in the standard model. We discuss implications for Higgs coupling extraction at the LHC.

The inclusive production of light mesons in $pp$-scattering is considered in the framework of Reggeon phenomenology with supercritical Pomeron. Available low-energy data can be explained with three Reggeon particles taken into account. With the results obtained rapidity and pseudorapidity distributions for light-meson production at the LHC energies are predicted.

At $\sqrt{s}=7\mathrm{TeV}$, the standard model (SM) needs at least $10(\mathrm{fb}{)}^{-1}$ integrated luminosity at LHC to make a definitive discovery of the Higgs boson. Using binary tetrahedral ($T^{\prime }$) discrete flavor symmetry, we discuss how the decay of the lightest $T^{\prime }$ Higgs into $\gamma \gamma$ can be effectively enhanced and dominate over its decay into $b\overline{b}$. Since the two-photon final state allows for a clean reconstruction, a decisive Higgs discovery may be possible at 7 TeV with the integrated luminosity only of $\sim 1(\mathrm{fb}{)}^{-1}$.

In this paper we study one-dimensional static self-dual solitons with compact support in an Abelian-Higgs Chern-Simons model with a noncanonical kinetic term. We present an analytical solution which corresponds to a compacton located in a region with a linear electric charge density and where the scalar field gets maximum. We then consider a sequence of these compactons to construct periodic chains. In particular, one can construct a chain of multi-non-interacting compactons which is electrically neutral. This may have applications to planar models in condensed matter.

In this, the first of two companion papers, we present a method for finding the gravitational self-force in a modified radiation gauge for a particle moving on a geodesic in a Schwarzschild or Kerr spacetime. An extension of an earlier result by Wald is used to show the spin weight $\pm 2$ perturbed Weyl scalar (${\psi }_0$ or ${\psi }_4$) determines the metric perturbation outside the particle up to a gauge transformation and an infinitesimal change in mass and angular momentum. A Hertz potential is used to construct the part of the retarded metric perturbation that involves no change in mass or angular momentum from ${\psi }_0$ in a radiation gauge. The metric perturbation is completed by adding changes in the mass and angular momentum of the background spacetime outside the radial coordinate $r_0$ of the particle in any convenient gauge. The resulting metric perturbation is singular only on the trajectory of the particle. A mode-sum method is then used to renormalize the self-force. Gralla shows that the renormalized self-force can be used to find the correction to a geodesic orbit in a gauge for which the leading, $O({\rho }^{-1})$, term in the metric perturbation has spatial components even under a parity transformation orthogonal to the particle trajectory, and we verify that the metric perturbation in a radiation gauge satisfies that condition. We show that the singular behavior of the metric perturbation and the expression for the bare self-force have the same power-law behavior in $L=\ell +1/2$ as in a Lorenz gauge (with different coefficients). We explicitly compute the singular Weyl scalar and its mode-sum decomposition to subleading order in $L$ for a particle in circular orbit in a Schwarzschild geometry and obtain the renormalized field. Because the singular field can be defined as this mode sum, the coefficients of each angular harmonic in the sum must agree with the large $L$ limit of the corresponding coefficients of the retarded field. One may therefore compute the singular field by numerically matching the retarded field to a power series in $L$. To check the accuracy of the numerical method, we analytically compute leading and subleading terms in the singular expansion of ${\psi }_0$ and compare the numerical and analytic values of the renormalization constants, finding agreement to high precision. Details of the numerical computation of the perturbed metric, the self-force, and the quantity $h_{\alpha \beta }{u}^{\alpha }{u}^{\beta }$ (gauge invariant under helically symmetric gauge transformations) are presented for this test case in the companion paper.

In this paper we formulate the restricted-foliation-preserving diffeomorphism invariant $f(R)$ Hořava-Lifshitz gravity and we show that it is related to the ghost condensation in the projectable version of Hořava-Lifshitz gravity.

A Lagrangian density is provided that allows the recovery of the Z4 evolution system from an action principle. The resulting system is then strongly hyperbolic when supplemented by gauge conditions like “$1+\log $” or “freezing shift,” suitable for numerical evolution. The physical constraint $Z_{\mu }=0$ can be imposed just on the initial data. The corresponding canonical equations are also provided. This opens the door to analogous results for other numerical-relativity formalisms, like BSSN (Baumgarte-Shapiro-Shibata-Nakamura), that can be derived from Z4 by a symmetry-breaking procedure. The harmonic formulation can be easily recovered by a slight modification of the procedure. This provides a mechanism for deriving both the field evolution equations and the gauge conditions from the action principle, with a view on using symplectic integrators for a constraint-preserving numerical evolution. The gauge sources corresponding to the “puncture gauge” conditions are identified in this context.

We investigate possible modifications on the gravitational deflection of light. Two forms of deformation of the Schwarzschild spacetime are proposed. The first ansatz is a given Finslerian line element; it could be regarded as a weak quantum gravity effect on the Schwarzschild spacetime. Starting from this ansatz, we deduce the deflection angle of the light ray which passes a weak gravitational source. The second ansatz could be regarded as a quantum vacuum effect on the Schwarzschild spacetime. The deflection angle of the light ray which passes a weak gravitational source is deduced in this Riemannian spacetime. This vacuum effect may distinguish the mixed light rays in the absence of gravitational source by a “spectroscope” (the gravitational source). The solutions of the gravitational field equation in this Riemannian spacetime imply this issue.

Detecting the dark matter annihilation signal from Galactic substructure, or subhalos, is an important challenge for high-energy gamma-ray experiments. In this paper we discuss detection prospects by combining two different aspects of the gamma-ray signal: the angular distribution and the photon counts probability distribution function (PDF). The true PDF from subhalos has been shown recently (by Lee et al.) to deviate from Poisson; we extend this analysis and derive the signal PDF from a detailed $\Lambda \mathrm{CDM}$-based model for the properties of subhalos. We combine our PDF with a model for Galactic and extra-Galactic diffuse gamma-ray emission to obtain an estimator and projected error on dark matter particle properties (mass and annihilation cross section) using the Fermi gamma-ray space telescope. We compare the estimator obtained from the true PDF to that obtained from the simpler Poisson analysis. We find that, although both estimators are unbiased in the presence of backgrounds, the error on dark matter properties derived from the true PDF is $\sim 50\%$ smaller than when utilizing the Poisson-based analysis.

We construct the gauge invariant free action for cosmological perturbations for the nonminimally coupled inflaton field in the Jordan frame. For this the phase space formalism is used, which keeps track of all the dynamical and constraint fields. We perform explicit conformal transformations to demonstrate the physical equivalence between the Jordan and Einstein frames at the level of quadratic perturbations. We show how to generalize the formalism to the case of a more complicated scalar sector with an internal symmetry, such as Higgs inflation. This work represents a first step in developing gauge invariant perturbation theory for nonminimally coupled inflationary models.

The light curve of a type Ia supernova decays at a rate set by the $\beta$-decay lifetimes of the ${}^{56}\mathrm{Ni}$ and ${}^{56}\mathrm{Co}$ produced in the explosion. This makes such a light curve sensitive to the value of the Fermi constant $G_F$ at the time of the supernova. Using data from the CfA Supernova Archive, we measure the dependence of the light curve decay rate on redshift and place a bound on the time variation of $G_F$ of $|\frac{{\dot{G}}_F}{G_F}|<{10}^{-9}{\mathrm{yr}}^{-1}$.

We examine a well-motivated nonuniversal supergravity model where the Higgs boson masses are not unified with the other scalars at the grand unified scale at the LHC. The dark matter content can easily be satisfied in this model by having a larger Higgsino component in the lightest neutralino. Typical final states in such a scenario at the LHC involve $W$ bosons. We develop a bi-event subtraction technique to reduce a huge combinatorial background to identify $W\to jj$ decays. This is also a key technique to reconstruct supersymmetric particle masses in order to determine the model parameters. With the model parameters, we find that the dark matter content of the Universe can be determined in agreement with existing experimental results.

We investigate leptonic decays $D_s\to \tau {\nu }_{\tau }$ and $B^{+}\to \tau {\nu }_{\tau }$ in the $R$-parity violating (RPV) supersymmetric standard model. Accounting for the interference between the $s$-channel slepton exchange and the $t$-channel squark exchange diagrams, we find that the supersymmetric contributions are cancelled between two diagrams so that the RPV couplings could be sizable under the experimental bounds. Constraints on the relative sign between the RPV couplings in $s$- and $t$-channel diagrams are also discussed.

Sneutrino-antisneutrino oscillation can be a very useful probe to look for signatures of lepton number violation ($\Delta L=2$) at the LHC. Here, we discuss the effect of the Lorentz factor $\gamma$ and the travelling distance $L$ on the probability of the oscillation. We demonstrate that these two parameters can significantly alter the probability of the oscillation when the sneutrinos are ultrarelativistic and have a very small total decay width. We propose a scenario where these requirements are fulfilled and which produces interesting signals at the LHC even for a mass splitting $\Delta m$ as small as ${10}^{-14}\mathrm{GeV}$ between the sneutrino mass eigenstates.

We study the hierarchy of the coefficients in the $1/N_c$ expansion for the negative parity $L=1$ excited baryons from the perspective of the constituent quark model. This is related to the problem of determining the spin-flavor structure of the quark interaction. The most general two-body scalar interaction between quarks contains the spin-flavor structures $t_1^a{t}_2^a,{\overrightarrow{s}}_1·{\overrightarrow{s}}_2$ and ${\overrightarrow{s}}_1·{\overrightarrow{s}}_2{t}_1^a{t}_2^a$. We show that in the limit of a zero range interaction all these structures are matched onto the same hadronic mass operator $S_c^2$, which gives a possible explanation for the dominance of this operator in the $1/N_c$ expansion for the $L=1$ states and implies that in this limit it is impossible to distinguish between these different spin-flavor structures. Modeling a finite range interaction through the exchange of a vector and pseudoscalar meson, we propose a test for the spin-flavor dependence of the quark forces. For the scalar part of the quark interaction, we find that both pion exchange and gluon exchange are compatible with the data.

Analytic QCD models are those versions of QCD in which the running coupling parameter $a(Q^2)$ has the same analytic properties as the spacelike physical quantities, i.e., no singularities in the complex $Q^2$ plane except on the timelike semiaxis. In such models, $a(Q^2)$ usually differs from its perturbative analog by power terms $\sim ({\Lambda }^2/Q^2{)}^k$ for large momenta, introducing thus nonperturbative terms $\sim ({\Lambda }^2/Q^2{)}^k$ in spacelike physical quantities whose origin is the UV regime. Consequently, it contradicts the ITEP operator product expansion philosophy which states that such terms can come only from the IR regimes. We investigate whether it is possible to construct analytic QCD models which respect the aforementioned ITEP philosophy and, at the same time, reproduce not just the high-energy QCD observables, but also the low-energy ones, among them the well-measured semihadronic $\tau$ decay ratio.

We calculate the contained and upward muon and shower fluxes due to neutrinos produced via dark matter annihilation or decay in the Galactic center. We consider dark matter models in which the dark matter particle is a gravitino, a Kaluza-Klein particle and a particle in leptophilic models. The Navarro-Frenk-White profile for the dark matter density distribution in the Galaxy is used. We incorporate neutrino oscillations by assuming maximal mixing and parametrize our results for muon and shower distributions. The muon and shower event rates and the minimum observation times in order to reach $2\sigma$ detection significance are evaluated. We illustrate how observation times vary with the cone half angle chosen about the Galactic center, with the result that the optimum angles are about 10° and 50° for the muon events and shower events, respectively. We find that for the annihilating dark matter models such as the leptophilic and Kaluza-Klein models, upward and contained muon as well as showers are promising signals for dark matter detection in just a few years of observation, whereas for decaying dark matter models, the same observation times can only be reached with showers. We also illustrate for each model the parameter space probed with the $2\sigma$ signal detection in five years. We discuss how the shape of the parameter space probed change with significance and the observation time.

As the vacuum state of a quantum field is not an eigenstate of the Hamiltonian density, the vacuum energy density can be represented as a random variable. We present an analytical calculation of the probability distribution of the vacuum energy density for real and complex massless scalar fields in Minkowski space. The obtained probability distributions are broad and the vacuum expectation value of the Hamiltonian density is not fully representative of the vacuum energy density.

New exact results are given for the interior Casimir energies of infinitely long waveguides of triangular cross section (equilateral, hemiequilateral, and isosceles right triangles). Results for cylinders of rectangular cross section are rederived. In particular, results are obtained for interior modes belonging to Dirichlet and Neumann boundary conditions (TM and TE modes). These results are expressed in rapidly convergent series using the Chowla-Selberg formula, and in fact may be given in closed form, except for general rectangles. The energies are finite because only the first three heat-kernel coefficients can be nonzero for the case of polygonal boundaries. What appears to be a universal behavior of the Casimir energy as a function of the shape of the regular or quasiregular cross-sectional figure is presented. Furthermore, numerical calculations for arbitrary right triangular cross sections suggest that the universal behavior may be extended to waveguides of general polygonal cross sections. The new exact and numerical results are compared with the proximity force approximation (PFA).