Supersymmetric theories in a 5D orbifold can have Fayet-Iliopoulos (FI) terms on the boundaries. These terms induce a 5D mass for the bulk matter fields. We analyze this effect using $N=1\mathrm{}$ superfields and show how it can be understood as a mixing between the U(1) gauge boson and the graviphoton. We also study the implications of the FI terms in the mass spectrum of theories with Scherk-Schwarz supersymmetry breaking. We present a new 5D supersymmetric model that has the massless spectrum of the standard model and predicts a Higgs boson with a mass around the present experimental limit.

Three dimensional (3D) numerical evolutions of static black holes with excision are presented. These evolutions extend to about $8000M,$ where M is the mass of the black hole. This degree of stability is achieved by using growth-rate estimates to guide the fine tuning of the parameters in a multiparameter family of symmetric hyperbolic representations of the Einstein evolution equations. These evolutions were performed using a fixed gauge in order to separate the intrinsic stability of the evolution equations from the effects of stability-enhancing gauge choices.

We describe in this article a new code for evolving axisymmetric isolated systems in general relativity. Such systems are described by asymptotically flat space-times which have the property that they admit a conformal extension. We are working directly in the extended “conformal” manifold and solve numerically Friedrich’s conformal field equations, which state that Einstein’s equations hold in the physical space-time. Because of the compactness of the conformal space-time the entire space-time can be calculated on a finite numerical grid. We describe in detail the numerical scheme, especially the treatment of the axisymmetry and the boundary.

Several numerical relativity groups are using a modified Arnowitt-Deser-Misner (ADM) formulation for their simulations, which was developed by Nakamura and co-workers (and widely cited as the Baumgarte-Shapiro-Shibata-Nakamura system). This so-called BSSN formulation is shown to be more stable than the standard ADM formulation in many cases, and there have been many attempts to explain why this reformulation has such an advantage. We try to explain the background mechanism of the BSSN equations by using an eigenvalue analysis of constraint propagation equations. This analysis has been applied and has succeeded in explaining other systems in our series of works. We derive the full set of the constraint propagation equations, and study it in the flat background space-time. We carefully examine how the replacements and adjustments in the equations change the propagation structure of the constraints, i.e., whether violation of constraints (if it exists) will decay or propagate away. We conclude that the better stability of the BSSN system is obtained by their adjustments in the equations, and that the combination of the adjustments is in a good balance, i.e., a lack of their adjustments might fail to obtain the present stability. We further propose other adjustments to the equations, which may offer more stable features than the current BSSN equations.

We investigate the prospects of detecting weakly interacting massive particle (WIMP) dark matter by measuring the contribution to the extragalactic gamma-ray radiation induced, in any dark matter halo and at all redshifts, by WIMP pair annihilations into high-energy photons. We perform a detailed analysis of the very distinctive spectral features of this signal, recently proposed in a short letter by three of the authors: The gamma-ray flux which arises from the decay of ${\pi }^0$ mesons produced in the fragmentation of annihilation final states shows a severe cutoff close to the value of the WIMP mass. An even more spectacular signature appears for the monochromatic gamma-ray components, generated by WIMP annihilations into two-body final states containing a photon: the combined effect of cosmological redshift and absorption along the line of sight produces sharp bumps, peaked at the rest frame energy of the lines and asymmetrically smeared to lower energies. The level of the flux depends both on the particle physics scenario for WIMP dark matter (we consider, as our template case, the lightest supersymmetric particle in a few supersymmetry breaking schemes), and on the question of how dark matter clusters. Uncertainties introduced by the latter are thoroughly discussed implementing a realistic model inspired by results of the state-of-the-art N-body simulations and semianalytic modeling in the cold dark matter structure formation theory. We also address the question of the potential gamma-ray background originating from active galaxies, presenting a novel calculation and critically discussing the assumptions involved and the induced uncertainties. Furthermore, we apply a realistic model for the absorption of gamma-rays on the optical and near-IR intergalactic radiation field to derive predictions for both the signal and background. Comparing the two, we find that there are viable configurations, in the combined parameter space defined by the particle physics setup and the structure formation scenario, for which the WIMP induced extragalactic gamma-ray signal will be detectable in the new generation of gamma-ray telescopes such as GLAST.

The multiple Doppler readouts available on the Laser Interferometer Space Antenna (LISA) permit simultaneous formation of several interferometric observables. All these observables are independent of laser frequency fluctuations and have different couplings to gravitational waves and to the various LISA instrumental noises. Within the functional space of interferometric combinations LISA will be able to synthesize, we have identified a triplet of interferometric combinations that show optimally combined sensitivity. As an application of the method, we computed the sensitivity improvement for sinusoidal sources in the nominal, equal-arm LISA configuration. In the part of the Fourier band where the period of the wave is longer than the typical light travel-time across LISA, the sensitivity gain over a single Michelson interferometer is equal to $\sqrt{2}.$ In the mid-band region, where the LISA Michelson combination has its best sensitivity, the improvement over the Michelson sensitivity is slightly better than $\sqrt{2},$ and the frequency band of best sensitivity is broadened. For frequencies greater than the reciprocal of the light travel-time, the sensitivity improvement is oscillatory and $\sim \sqrt{3},$ but can be greater than $\sqrt{3}$ near frequencies that are integer multiples of the inverse of the one-way light travel-time in the LISA arm.

At energies higher than the brane tension, the dynamics of a scalar field rolling down a potential are modified relative to the predictions of general relativity. The modifications imply, among other things, that steeper potentials can be used to drive an epoch of slow-roll inflation. We investigate the evolution of entropy and adiabatic modes during inflation driven by two scalar fields confined on the brane. We show that the amount of entropy perturbations produced during inflation is suppressed compared to the predictions made by general relativity. As a consequence, the initial conditions do not matter in multiple field inflation in brane worlds if inflation is driven at energies much higher than the brane tension.

We investigate the associated production of heavy quarkonia, with angular-momentum quantum numbers ${}^{2S+1}{L}_J{=}^1{S}_0{,}^3{S}_1{,}^1{P}_1{,}^3{P}_J$ $\mathrm{}(J=0,1,2\mathrm{}),$ and photons, Z bosons, and W bosons in photon-photon, photon-hadron, and hadron-hadron collisions within the factorization formalism of nonrelativistic quantum chromodynamics providing all contributing partonic cross sections in analytic form. In the case of photoproduction, we also include the resolved-photon contributions. We present numerical results for the processes involving $J/\psi$ and ${\chi }_{\mathrm{cJ}}$ mesons appropriate for the Fermilab Tevatron, CERN LHC, DESY TESLA, operated in the $e^{+}{e}^{-}$ and $\gamma \gamma$ modes, and DESY THERA.

A new flavor changing electron neutrino interaction with matter would always dominate the ${\nu }_e$ oscillation probability at sufficiently high neutrino energies. Being suppressed by ${\theta }_{13},$ the energy scale at which the new effect starts to be relevant may be within the reach of realistic experiments, where the peculiar dependence of the signal with energy could give rise to a clear signature in the ${\nu }_e\to {\nu }_{\tau }$ channel. The latter could be observed by means of a coarse large magnetized detector exploiting $\overrightarrow{\tau }\mu$ decays. We discuss the possibility of identifying or constraining such effects with a high energy neutrino factory. We also comment on the model independent limits on them.

The $\mathrm{sl}\left(2\right)\mathrm{}$ affine Toda model coupled to matter is shown to describe various features, such as the spectrum and string tension, of the low-energy effective Lagrangian of two-dimensional QCD (one flavor and N colors). The corresponding string tension is computed when the dynamical quarks are in the fundamental representation of $\mathrm{SU}\left(N\right)\mathrm{}$ and in the adjoint representation of $\mathrm{SU}\left(2\right).$

We analyze the emergence of a minimal length for a large class of generalized commutation relations, preserving commutation of the position operators and translation invariance as well as rotation invariance (in dimensions higher than one). We show that the construction of the maximally localized states based on squeezed states generally fails. Rather, one must resort to a constrained variational principle.

In extra dimensions the infrared attractive force of gauge interactions is amplified. We find that this force can align in the infrared limit the soft-supersymmetry breaking terms out of their anarchical disorder at a fundamental scale in such a way that flavor-changing neutral currents as well as dangerous $\mathrm{CP}$-violating phases are sufficiently suppressed at the unification scale. The main assumption is that the matter and Higgs supermultiplets and the flavor-dependent interactions such as Yukawa interactions are stuck at the four-dimensional boundary. As a concrete example we consider the minimal model based on $\mathrm{SU}\left(5\right)\mathrm{}$ in six dimensions.

A novel refinement of the conventional treatment of Kadanoff-Baym equations is suggested. In addition to the Boltzmann equation, another differential equation is used for calculating the evolution of the nonequilibrium two-point function. Although it was usually interpreted as a constraint on the solution of the Boltzmann equation, we argue that its dynamics is relevant to the determination and resummation of the particle production cut contributions. The differential equation for this new contribution is illustrated in the example of the cubic scalar model. The analogue of the relaxation time approximation is suggested. It results in the shift of the threshold location and in a smearing out of the nonanalytic threshold behavior of the spectral function. The possible consequences for the dilepton production are discussed.

Certain spontaneously broken gauge theories contain massless magnetic monopoles. These are realized classically as clouds of non-Abelian fields surrounding one or more massive monopoles. In order to gain a better understanding of these clouds, we study BPS solutions with four massive and six massless monopoles in an SU(6) gauge theory. We develop an algebraic procedure, based on the Nahm construction, that relates these solutions to previously known examples. Explicit implementation of this procedure for a number of limiting cases reveals that the six massless monopoles condense into four distinct clouds, of two different types. By analyzing these limiting solutions, we clarify the correspondence between clouds and massless monopoles, and infer a set of rules that describe the conditions under which a finite size cloud can be formed. Finally, we identify the parameters entering the general solution and describe their physical significance.

We develop a simplified method for obtaining higher orders in the perturbative expansion of the singular term $A\left({\alpha }_s\right)/[1-x{]}_{+}$ of nonsinglet partonic splitting functions. Our method is based on the calculation of eikonal diagrams. The key point is the observation that the corresponding cross sections exponentiate in the case of two eikonal lines, and that the exponent is directly related to the functions $A\left({\alpha }_s\right)$ due to the factorization properties of parton distribution functions. As examples, we rederive the one- and two-loop coefficients $A^{\mathrm{}\left(1\right)\mathrm{}}$ and $A^{\mathrm{}\left(2\right)\mathrm{}}.$ We go on to derive the known general formula for the contribution to $A^{\mathrm{}\left(n\right)\mathrm{}}$ proportional to $N_f^{n-1},$ where $N_f$ denotes the number of flavors. Finally, we determine the previously uncalculated term proportional to $N_f$ of the three-loop coefficient $A^{\mathrm{}\left(3\right)\mathrm{}}$ to illustrate the method. Our answer agrees with the existing numerical estimate. The exact knowledge of the coefficients $A^{\mathrm{}\left(n\right)\mathrm{}}$ is important for the resummations of large logarithmic corrections due to soft radiation. Although only the singular part of the splitting functions is calculable within our method, higher-order computations are much less complex than within conventional methods, and even the calculation of $A^{\mathrm{}\left(4\right)\mathrm{}}$ may be possible.

The response of an interferometer becomes complicated for a gravitational wave shorter than the armlength of the detector, as the nature of the wave appears strongly. We study how the parameter estimation for merging massive-black-hole binaries is affected by this complicated effect in the case of LISA. It is shown that the three-dimensional positions of some binaries might be determined much more accurately than in past estimations that use the long wave approximation. For equal mass binaries this improvement is most prominent at $\sim {10}^5{M}_{\odot }.$

The model of inflation with a single tachyon field generates larger anisotropy and has difficulties in describing the formation of the Universe [L. Kofman and A. Linde, J. High Energy Phys. 07, 004 (2002)]. In this paper we consider a model with multitachyon fields and study the assisted inflationary solution. Our results show that this model satisfies the observations.

The relativistic five-quark equations are found in the framework of the dispersion relation technique. The behavior of the low-energy five-particle amplitude is determined by its leading singularities in the pair invariant masses. The solutions of these equations using the method based on the extraction of leading singularities of the amplitudes are obtained. The mass spectra of nucleon and Δ-isobar hybrid baryons are calculated. The calculations of hybrid baryon amplitudes estimate the contributions of four subamplitudes. The main contributions to the hybrid baryon amplitude are determined by the subamplitudes, which include the excited gluon states.

We calculate one-loop matching factors for bilinear operators composed of improved staggered fermions. We compare the results for different improvement schemes used in the recent literature, all of which involve the use of smeared links. These schemes aim to reduce, though not completely eliminate, ${O(a}^2)$ discretization errors. We find that all these improvement schemes substantially reduce the size of matching factors compared to unimproved staggered fermions. The resulting corrections are comparable to, or smaller than, those found with Wilson and domain-wall fermions. In the best case (“Fat-7” and mean-field improved hypercubic fat links) the corrections are $10\%$ or smaller at $1/a=2\mathrm{GeV}.$