The muon anomalous magnetic moment is discussed within the model based on the $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$-gauge group. The contributions of the neutrinos having the dipole magnetic moment are calculated. The cases of the Majorana and Dirac neutrinos are considered. It is shown that, to account for the $(g-2{)}_{\mu }$ anomaly, dipole magnetic moments connected with heavy neutrinos should be on the order of $\mathrm{few}\times {10}^{-8}{\mu }_B$, that is, at variance with the theoretically predicted values.

We propose a subtraction scheme for a massive Yang-Mills theory realized via a nonlinear representation of the gauge group [here $SU(2)$]. It is based on the subtraction of the poles in $D-4$ of the amplitudes, in dimensional regularization, after a suitable normalization has been performed. Perturbation theory is in the number of loops, and the procedure is stable under iterative subtraction of the poles. The unphysical Goldstone bosons, the Faddeev-Popov ghosts, and the unphysical mode of the gauge field are expected to cancel out in the unitarity equation. The spontaneous symmetry breaking parameter is not a physical variable. We use the tools already tested in the nonlinear sigma model: hierarchy in the number of Goldstone boson legs and weak-power-counting property (finite number of independent divergent amplitudes at each order). It is intriguing that the model is naturally based on the symmetry $SU(2{)}_L$ local $\otimes$ $SU(2{)}_R$ global. By construction the physical amplitudes depend on the mass and on the self-coupling constant of the gauge particle and moreover on the scale parameter of the radiative corrections. The Feynman rules are in the Landau gauge.

We study a 5d gravity theory with a warped metric and show that two $N=2$ supersymmetric quantum-mechanical systems are hidden in the 4d spectrum. The supersymmetry can be regarded as a remnant of higher-dimensional general coordinate invariance and turns out to become a powerful tool to determine the physical 4d spectrum and the allowed boundary conditions. Possible extensions of the $N=2$ supersymmetry are briefly discussed.

We test the accuracy of our recently proposed empirical formula to model the recoil velocity imparted to the merger remnant of spinning, unequal-mass black-hole binaries. We study three families of black-hole binary configurations, all with mass ratio $q=3/8$ (to nearly maximize the unequal-mass contribution to the kick) and spins aligned (or counter-aligned) with the orbital angular momentum, two with spin configurations chosen to minimize the spin-induced tangential and radial accelerations of the trajectories, respectively, and a third family where the trajectories are significantly altered by spin-orbit coupling. We find good agreement between the measured and predicted recoil velocities for the first two families, and reasonable agreement for the third. We also reexamine our original generic binary configuration that led to the discovery of extremely large spin-driven recoil velocities and inspired our empirical formula, and find rough agreement between the predicted and measured recoil speeds.

We present an investigation into how sensitive the last orbits and merger of binary black hole systems are to the presence of spurious radiation in the initial data. Our numerical experiments consist of a binary black hole system starting the last couple of orbits before merger with additional spurious radiation centered at the origin and fixed initial angular momentum. As the energy in the added spurious radiation increases, the binary is invariably hardened for the cases we tested; i.e., the merger of the two black holes is hastened. The change in merger time becomes significant when the additional energy provided by the spurious radiation increases the Arnowitt-Deser-Misner mass of the spacetime by about 1%. While the final masses of the black holes increase due to partial absorption of the radiation, the final spins remain constant to within our numerical accuracy. We conjecture that the spurious radiation is primarily increasing the eccentricity of the orbit and secondarily increasing the mass of the black holes while propagating out to infinity.

In the framework of designing laboratory tests of relativistic gravity, we investigate the gravitational field produced by the magnetic field of a solenoid. Observing this field might provide a means of testing whether stresses gravitate as predicted by Einstein’s theory. A previous study of this problem by Braginsky, Caves, and Thorne predicted that the contribution to the gravitational field resulting from the stresses of the magnetic field and of the solenoid walls would cancel the gravitational field produced by the mass-energy of the magnetic field, resulting in a null magnetically generated gravitational force outside the solenoid. They claim that this null result, once proved experimentally, would demonstrate the stress contribution to gravity. We show that this result is incorrect, as it arises from an incomplete analysis of the stresses, which neglects the axial stresses in the walls. Once the stresses are properly evaluated, we find that the gravitational field outside a long solenoid is in fact independent of Maxwell and material stresses, and it coincides with the Newtonian field produced by the linear mass distribution equivalent to the density of magnetic energy stored in a unit length of the solenoid. We argue that the gravity of Maxwell stress can be directly measured in the vacuum region inside the solenoid, where the Newtonian noise is absent in principle, and the gravity generated by Maxwell stresses is not screened by the negative gravity of magnetic-induced stresses in the solenoid walls.

The reheating of the Universe after hybrid inflation proceeds through the nucleation and subsequent collision of large concentrations of energy density in the form of bubblelike structures moving at relativistic speeds. This generates a significant fraction of energy in the form of a stochastic background of gravitational waves, whose time evolution is determined by the successive stages of reheating: First, tachyonic preheating makes the amplitude of gravity waves grow exponentially fast. Second, bubble collisions add a new burst of gravitational radiation. Third, turbulent motions finally sets the end of gravitational waves production. From then on, these waves propagate unimpeded to us. We find that the fraction of energy density today in these primordial gravitational waves could be significant for grand unified theory (GUT)-scale models of inflation, although well beyond the frequency range sensitivity of gravitational wave observatories like LIGO, LISA, or BBO. However, low-scale models could still produce a detectable signal at frequencies accessible to BBO or DECIGO. For comparison, we have also computed the analogous gravitational wave background from some chaotic inflation models and obtained results similar to those found by other groups. The discovery of such a background would open a new observational window into the very early universe, where the details of the process of reheating, i.e. the big bang, could be explored. Moreover, it could also serve in the future as a new experimental tool for testing the inflationary paradigm.

We present a scenario in which a remarkably simple relation linking dark matter properties and neutrino masses naturally emerges. This framework points towards a low energy theory where the neutrino mass originates from the existence of a light scalar dark matter particle in the keV-MeV mass range. We discuss different ways to constrain and test this scenario by means of astrophysical and cosmological observations as well as laboratory experiments. Finally, we point out that one interesting aspect is that the implied mass range is compatible with the one required for the explanation of the mysterious emission of 511 keV photons from the center of our galaxy in terms of dark matter annihilation into $e^{+}{e}^{-}$ pairs.

We discuss the consequences of the accretion of dark matter (DM) particles on compact stars such as white dwarfs and neutron stars. We show that in large regions of the DM parameter space, these objects are sensitive probes of the presence of DM and can be used to set constraints both on the DM density and on the physical properties of DM particles.

Cosmological observations have revealed the existence of a dark matter sector, which is commonly assumed to be made up of one particle species only. However, this sector might be more complicated than we currently believe: there might be more than one dark matter species (for example, two components of cold dark matter or a mixture of hot and cold dark matter) and there may be new interactions between these particles. In this paper we study the possibility of multiple dark matter species and interactions mediated by a dark energy field. We study both the background and the perturbation evolution in these scenarios. We find that the background evolution of a system of multiple dark matter particles (with constant couplings) mimics a single fluid with a time-varying coupling parameter. However, this is no longer true on the perturbative level. We study the case of attractive and repulsive forces as well as a mixture of cold and hot dark matter particles.

The existence of a primordial magnetic field (PMF) would affect both the temperature and polarization anisotropies of the cosmic microwave background (CMB). It also provides a plausible explanation for the possible disparity between observations and theoretical fits to the CMB power spectrum. Here we report on calculations of not only the numerical CMB power spectrum from the PMF, but also the correlations between the CMB power spectrum from the PMF and the primary curvature perturbations. We then deduce a precise estimate of the PMF effect on all modes of perturbations. We find that the PMF affects not only the CMB TT (temperature fluctuation), TE (cross correlation as temperature—E-type polarization) modes on small angular scales, but also on large angular scales. The introduction of a PMF leads to a better fit to the CMB power spectrum for the higher multipoles, and the fit at lowest multipoles can be used to constrain the correlation of the PMF with the density fluctuations for large negative values of the spectral index. Our prediction for the BB (B-type polarization) mode for a PMF average field strength $|B_{\lambda }|=4.0\mathrm{nG}$ is consistent with the upper limit on the BB mode deduced from the latest CMB observations. We find that the BB mode is dominated by the vector mode of the PMF for higher multipoles. We also show that by fitting the complete power spectrum one can break the degeneracy between the PMF amplitude and its power spectral index.

The cosmological constant $\Lambda$ affects gravitational lensing phenomena. The contribution of $\Lambda$ to the observable angular positions of multiple images and to their amplification and time delay is here computed through a study of the weak deflection limit of the equations of motion in the Schwarzschild–de Sitter metric. Because of $\Lambda$ the unresolved images are slightly demagnified, the radius of the Einstein ring decreases, and the time delay increases. The effect is however negligible for near lenses. In the case of a null cosmological constant, we provide some updated results on lensing by a Schwarzschild black hole.

Coupling the scale invariant unparticle sector to flavor physics and assuming that it remains scale invariant I investigate its consequences in heavy flavor physics. A characteristic feature of unparticle physics is a $CP$-even phase leading to novel $CP$ violating phenomena. The phase is large, based on the assumption that the unparticle sector is strongly self-coupled. I consider the $CP$ asymmetry in the leptonic decay $B^{+}\to {\tau }^{+}\nu$ and the hadronic decay $B_d\to D^{+}{D}^{-}$, taking into account constraints of branching ratios and time dependent $CP$ asymmetries. It turns out that the $CP$ asymmetry can be very large even for small couplings because the unparticle interaction term has a lower scaling dimension than the four-Fermi weak interaction term. $CP$ asymmetries in leptonic decays such as $B^{+}\to {\tau }^{+}\nu$ are neither experimentally searched for nor predicted by any other model. I show that the novel $CP$ violation is consistent with the $CPT$ theorem. I identify the $CP$ compensating mode in the unparticle sector and explicitly demonstrate the exact cancellation as demanded by the $CPT$ theorem.

We consider cosmological implications of supersymmetric models with right-handed (s)neutrinos where the neutrino masses are purely Dirac type. We pay particular attention to the case where the gravitino is the lightest superparticle while one of the right-handed sneutrinos is next-to-the-lightest superparticle. We study constraints from big-bang nuleosynthesis and show that the constraints could be relaxed compared to the case without right-handed sneutrinos. As a result, the gravitino-dark-matter scenario becomes viable with a relatively large value of the gravitino mass. We also discuss constraints from the structure formation; in our model, the free-streaming length of the gravitino dark matter may be as long as $O(1\mathrm{Mpc})$, which is comparable to the present observational upper bound on the scale of free-streaming.

The electromagnetic bremsstrahlung produced by a quark interacting with nucleons or nuclei is azimuthally asymmetric. In the light-cone dipole approach this effect is related to the orientation dependent dipole cross section. Such a radiation anisotropy is expected to contribute to the azimuthal asymmetry of direct photons in $pA$ and $AA$ collisions, as well as in deep-inelastic scattering and in the production of dileptons.

We investigate the QCD effects in the associated production of the chargino and the neutralino, ${\tilde{\chi }}_1^{\pm }$ and ${\tilde{\chi }}_2^0$, in the minimal supersymmetric standard model at both the Fermilab Tevatron and the CERN Large Hadron Collider. We include the next-to-leading order (NLO) QCD corrections (including supersymmetric QCD) and the threshold resummation effects. Our results show that, compared to the NLO predictions, the threshold resummation effects can increase the total cross sections by 3.6% and 3.9% for the associated production of ${\tilde{\chi }}_1^{+}{\tilde{\chi }}_2^0$ and ${\tilde{\chi }}_1^{-}{\tilde{\chi }}_2^0$ at the LHC, respectively, and by 4.7% for those of ${\tilde{\chi }}_1^{\pm }{\tilde{\chi }}_2^0$ at the Tevatron. In the invariant mass distributions the resummation effects are significant for large invariant mass. The threshold resummation reduces the dependence of the total cross sections at the LHC (Tevatron) on the renormalization/factorization scales to 5% (4%) from up to 7% (11%) at NLO.

Considering the large value of the top Yukawa coupling, we investigate the leading one-loop Yukawa electroweak corrections that can be induced by the top quark in a process such as Higgs production in association with a tagged bottom-antibottom pair at the LHC. At next-to-leading order these contributions are found to be small at the LHC both for the total cross section and for the distributions. In the limit of vanishing bottom Yukawa coupling where the leading order contribution vanishes, the process can still be induced at one-loop through the top quark transition. Though this contribution which can be counted as part of the next-to-next-to-leading order correction is small for Higgs masses around 120 GeV, it quickly picks up for higher Higgs masses. This contribution represents the rescattering of the top quarks and their decay into $W$’s leading to Higgs production through $WW$ fusion.

We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ and of the parameters ${\rho }^2$, $R_1(1)$, and $R_2(1)$, which fully characterize the form factors for the $B^0\to D^{*-}{\ell }^{+}{\nu }_{\ell }$ decay in the framework of heavy-quark effective field theory. The results, based on a selected sample of about 52 800 $B^0\to D^{*-}{\ell }^{+}{\nu }_{\ell }$ decays, recorded by the BABAR detector, are ${\rho }^2=1.157\pm 0.094\pm 0.027$, $R_1(1)=1.327\pm 0.131\pm 0.043$, $R_2(1)=0.859\pm 0.077\pm 0.021$, and $\mathcal{F}(1)|V_{cb}|=(34.7\pm 0.4\pm 1.0)\times {10}^{-3}$. The first error is the statistical and the second is the systematic uncertainty. Combining these measurements with the previous BABAR measurement of the form factors, which employs a different fit technique on a partial sample of the data, we improve the statistical precision of the result, ${\rho }^2=1.191\pm 0.048\pm 0.028$, $R_1(1)=1.429\pm 0.061\pm 0.044$, $R_2(1)=0.827\pm 0.038\pm 0.022$, and $\mathcal{F}(1)|V_{cb}|=(34.4\pm 0.3\pm 1.1)\times {10}^{-3}$. Using lattice calculations for the axial form factor $\mathcal{F}(1)$, we extract $|V_{cb}|=(37.4\pm 0.3\pm 1.2{\pm }_{1.4}^{1.2})\times {10}^{-3}$, where the third error is due to the uncertainty in $\mathcal{F}(1)$. We also present a measurement of the exclusive branching fraction, $\mathcal{B}=(4.69\pm 0.04\pm 0.34)\%$.

We use the low energy effective $U(1{)}^r$ action on the Coulomb branch of $\mathcal{N}=4$ super Yang-Mills theory to construct approximate field configurations for solitonic dyons in these theories, building on the brane-prong description developed in P. C. Argyres and K. Narayan, J. High Energy Phys. 03 (2001) 047. This dovetails closely with the corresponding description of these dyons as string webs stretched between D-branes in the transverse space. The resulting picture within these approximations shows the internal structure of these dyons (for fixed asymptotic charges) to be moleculelike, with multiple charge cores held together at equilibrium separations, which grow large near lines of marginal stability. Although these techniques do not yield a complete solution for the spatial structure (i.e. all core sizes and separations) of large charge multicenter dyons in high rank gauge theories, approximate configurations can be found in specific regions of moduli space, which become increasingly accurate near lines of marginal stability. We also discuss string webs with internal faces from this point of view.

In this paper we make further refinements to the duality proposed between $N=1$ SQCD and certain string (supergravity plus branes) backgrounds, working in the regime of comparable large number of colors and flavors. Using the string theory solutions, we predict different field theory observables and phenomena like Seiberg duality, gauge coupling and its running, the behavior of Wilson and ’t Hooft loops, anomalous dimensions of the quark superfields, quartic superpotential coupling and its running, continuous and discrete anomaly matching. We also give evidence for the smooth interpolation between the Higgs and confining vacua. We provide several matchings between field theory and string theory computations.