We have studied the scalar field perturbations on six-dimensional ultraspinning black holes. We have numerically calculated the quasinormal modes of rotating black holes. Our results suggest that such perturbations are stable.

The conservative dynamics of two point masses given in harmonic coordinates up to the third post-Newtonian order is treated within the framework of constrained canonical dynamics. A representation of the approximate Poincaré algebra is constructed with the aid of Dirac brackets. Uniqueness of the generators of the Poincaré group or the integrals of motion is achieved by imposing their action on the point mass coordinates to be identical with that of the usual infinitesimal Poincaré transformations. The second post-Coulombian approximation to the dynamics of two point charges as predicted by Feynman-Wheeler electrodynamics in Lorentz gauge is treated similarly.

Tidal streams of the Sagittarius dwarf spheroidal galaxy (Sgr) may be showering dark matter onto the solar system and contributing $\sim (0.3–23)\%$ of the local density of our galactic halo. If the Sagittarius galaxy contains dark matter in the form of weakly interacting massive particles (WIMPs), the extra contribution from the stream gives rise to a steplike feature in the energy recoil spectrum in direct dark matter detection. For our best estimate of stream velocity (300 km/s) and direction (the plane containing the Sgr dwarf and its debris), the count rate is maximum on June 28 and minimum on December 27 (for most recoil energies), and the location of the step oscillates yearly with a phase opposite to that of the count rate. In the CDMS experiment, for 60 GeV WIMPs, the location of the step oscillates between 35 and 42 keV, and for the most favorable stream density, the stream should be detectable at the $11\sigma$ level in four years of data with 10 keV energy bins. Planned large detectors like XENON, CryoArray, and the directional detector DRIFT may also be able to identify the Sgr stream.

We introduce an extension of the Born-Infeld action for a scalar field and show that it can act as unifying dark matter, providing an explanation for both structure formation and the accelerated expansion of the universe. We investigate the cosmological dynamics of this theory in a particular case, referred to as the “Milne-Born-Infeld” (MBI) Lagrangian. We show that this model, whose equation of state has effectively a single free parameter, is consistent with recent type Ia supernovae data, providing a fit as good as for the $\Lambda \mathrm{C}\mathrm{D}\mathrm{M}$ model with the same number of degrees of freedom. Furthermore, this parameter is tightly constrained by current data, making the model easily testable with other observables. Contrary to previous candidates for unifying dark matter, the sound velocity of the MBI model is vanishing both close to the dark-matter state as well as near the cosmological constant state. This could avoid the problems on the matter power spectrum that were present in previous adiabatic dark-matter/dark-energy unification models. We also present a short discussion on the causal propagation in nonlinear scalar field theories such as the one proposed here.

The allowed range of parameters for supersymmetric hybrid inflation and its extensions are investigated. The lower bound on the reheat temperature $T_r$ in these models with hierarchical right-handed neutrinos is found to be $3\times {10}^7\mathrm{G}\mathrm{e}\mathrm{V}$. ($T_r$ as low as 100 GeV is possible for quasidegenerate right-handed neutrinos.) We also present revised estimates for the scalar spectral index and the symmetry breaking scale associated with inflation.

We present a new general mechanism to generate curvature perturbations after the end of the slow-roll phase of inflation. Our model is based on the simple assumption that the potential driving inflation is characterized by an underlying global symmetry which is slightly broken.

In this paper, we show that the $B\to \pi$ transition form factor can be calculated by using the different approach in the different $q^2$ regions and they are consistent with each other in the whole physical region. For the $B\to \pi$ transition form factor in the large recoil regions, one can apply the perturbative quantum chromodynamics (PQCD) approach, where the transverse momentum dependence for both the hard-scattering part and the nonperturbative wave function, the Sudakov effects and the threshold effects are included to regulate the endpoint singularity and to derive a more reliable PQCD result. Pionic twist-3 contributions are carefully studied with a better endpoint behavior wave function for ${\Psi }_p$ and we find that its contribution is less than the leading twist contribution. Both the two wave functions ${\Psi }_B$ and ${\overline{\Psi }}_B$ of the $B$ meson can give sizable contributions to the $B\to \pi$ transition form factor and should be kept for a better understanding of the $B$ decays. The present obtained PQCD results can match with both the QCD light cone sum rule results and the extrapolated lattice QCD results in the large recoil regions.

Owing to the fact that $m_c^2\sim m_b{\Lambda }_{\mathrm{Q}\mathrm{C}\mathrm{D}}$, the end point region of the charged lepton energy spectrum in the inclusive decay $B\to X_c\ell {\overline{\nu }}_{\ell }$ is affected by the Fermi motion of the initial-state $b$ quark bound in the $B$ meson. This effect is described in QCD by shape functions. Including the mass of the final-state quark, we find that a different set of operators as employed in previous work is needed for a consistent matching, when incorporating the subleading contributions in $B\to X_q\ell {\overline{\nu }}_{\ell }$ for both $q=u$ and $q=c$. In addition, we modify the usual twist expansion in such a way that it yields a description of the lepton energy spectrum which is not just valid in the end point region, but over the entire phase space.

Latest measurements have revealed that the deviation from a maximal solar mixing angle is approximately the Cabibbo angle [i.e., quark-lepton complementarity (QLC) relation]. We argue that it is not plausible that this deviation from maximality, be it a coincidence or not, comes from the charged lepton mixing. Consequently we have calculated the required corrections to the exactly bimaximal neutrino mass matrix ansatz necessary to account for the solar mass difference and the solar mixing angle. We point out that the relative size of these two corrections depends strongly on the hierarchy case under consideration. We find that the inverted hierarchy case with opposite $CP$ parities, which is known to guarantee the renormalization group equations stability of the solar mixing angle, offers the most plausible scenario for a high-energy origin of a QLC-corrected bimaximal neutrino mass matrix. This possibility may allow us to explain the QLC relation in connection with the origin of the charged fermion mass matrices.

We present results on $B\to J/\psi K\pi$ decays using $e^{+}{e}^{-}$annihilation data collected with the BABAR detector at the ${\rm Y}(4S)$ resonance. The detector is located at the PEP-II asymmetric-energy storage ring facility at the Stanford Linear Accelerator Center. Using approximately $88\times {10}^6$ $B\overline{B}$ pairs, we measure the decay amplitudes for the flavor eigenmodes and observe strong-phase differences indicative of final-state interactions with a significance of 7.6 standard deviations. We use the interference between the $K\pi$ $S$-wave and $P$-wave amplitudes in the region of the $K^{*}(892)$ to resolve the ambiguity in the determination of these strong phases. We then perform an ambiguity-free measurement of $\cos 2\beta$ using the angular and time-dependent asymmetry in $B\to J/\psi K^{*0}(K_S^0{\pi }^0)$ decays. With $\sin 2\beta$ fixed at its measured value and $\cos 2\beta$ treated as an independent parameter, we find $\cos 2\beta ={2.72}_{-0.79}^{+0.50}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.27(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$, determining the sign of $\cos 2\beta$ to be positive at 86% C.L.

A family of states built from the uncertainty principle on the fuzzy sphere has been shown to reproduce the stereographic projection in the large $j$ limit. These generalized squeezed states are used to construct an associative star product which involves a finite number of derivatives on its primary functional space. It is written in terms of a variable on the complex plane. We show that it actually coincides with the one found by Gross and Presnajder in the simplest cases, endowing the later with a supplementary physical interpretation. We also show how the spherical harmonics emerge in this setting.

Great efforts are currently being channeled into ground- and balloon-based CMB experiments, mainly to explore polarization and anisotropy on small angular scales. To optimize instrumental design and assess experimental prospects, it is important to understand in detail the atmosphere-related systematic errors that limit the science achievable with new instruments. As a step in this direction, we spatially compare the 648 square degree ground- and balloon-based QMASK map with the atmosphere-free WMAP map, finding beautiful agreement on all angular scales where both are sensitive. Although much work remains on quantifying atmospheric effects on CMB experiments, this is a reassuring quantitative assessment of the power of the state-of-the-art fast-Fourier-transform- and matrix-based mapmaking techniques that have been used for QMASK and virtually all subsequent experiments.

Recently, the $1/N_c$ expansion has been applied to the study of exotic baryons containing both quarks and antiquarks. We extend this approach to exotic states with mixed-symmetric spin-flavor symmetry, which correspond in the quark model to negative parity pentaquarks, and discuss the large $N_c$ predictions for their mass spectrum. The heavy exotics $\overline{Q}{q}^4$ transform as $\mathbf{3},\overline{\mathbf{6}},\mathbf{15}$ and ${\mathbf{15}}^{\prime }$ under SU(3), while the light states $\overline{q}{q}^4$ include the exotic multiplets $\overline{\mathbf{10}},\mathbf{27},\mathbf{35}$. We give mass relations among these multiplets in the $1/N_c$ expansion. In the quark model, the mass splittings between these states are given by color-spin interactions. Using the observation of an anticharmed exotic by the H1 Collaboration, we give predictions for the masses of other expected heavy pentaquarks.

We present the results of a search for anomalous production of diphoton events with large missing transverse energy using the Collider Detector at Fermilab. In $202\mathrm{p}{\mathrm{b}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{T}\mathrm{e}\mathrm{V}$ we observe no candidate events, with an expected standard model background of $0.27\pm 0.07(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.10(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$ events. The results exclude a lightest chargino of mass less than $167\mathrm{G}\mathrm{e}\mathrm{V}/c^2$, and lightest neutralino of mass less than $93\mathrm{G}\mathrm{e}\mathrm{V}/c^2$ at 95% C.L. in a gauge-mediated supersymmetry-breaking model with a light gravitino.

In a ghost inflationary scenario, we study the observational consequences of a tilt in the potential of the ghost condensate. We show how the presence of a tilt tends to make contact between the natural predictions of ghost inflation and the ones of slow roll inflation. In the case of positive tilt, we are able to build an inflationary model in which the Hubble constant $H$ is growing with time. We compute the amplitude and the tilt of the two-point function, as well as the three-point function, for both cases of positive and negative tilt. We find that a good fraction of the parameter space of the model is within experimental reach.

In the universal extra-dimensions models, Kaluza-Klein excitations of matter are generaly produced in pairs. However, if matter lives on a fat brane embedded in a larger space, gravity-matter interactions do not obey KK number-conservation, thus making possible the production of single KK excitations at colliders. We evaluate the production rates for such excitations at the Tevatron and LHC colliders, and look for ways to detect them.

We discuss the impact of various improvements on simulations of dynamical overlap fermions using the Hybrid Monte Carlo algorithm. We focus on the usage of fat links and multiple pseudofermion fields.

We propose a method to determine the CKM matrix element $|V_{ub}|$ using the global $q^2$ dependence of the dispersive bound on the form factors for $B\to \pi l\nu$ decay. Since the lattice calculation of the $B\to \pi l\nu$ form factor is limited to the large $q^2$ regime, only the experimental data in a limited kinematic range can be used in a conventional method. In our new method which exploits the statistical distributions of the dispersive bound proposed by Lellouch with the quark-hadron duality ansatz, we can utilize the information of the global $q^2$ dependence for all kinematic ranges. As a feasibility study we determine $|V_{ub}|$ by combining the form factors from quenched lattice QCD, the dispersive bounds, and the experimental data by CLEO. We show that the accuracy of $|V_{ub}|$ can be improved by our method.

We show that Dirac neutrino masses of the right size can arise from the Kähler potential of supergravity. They are proportional to the supersymmetry and the electroweak breaking scales. We find that they have the experimentally observed value provided that the ultraviolet cutoff of the Minimal Supersymmetric Standard Model is between the Grand Unification scale and the heterotic string scale. If lepton number is not conserved, then relatively suppressed Majorana masses can also be present, resulting in pseudo-Dirac neutrino masses.