We quantify the slow-roll corrections to primordial density perturbations arising from inflation driven by a four-dimensional scalar field with a monomial potential in a five-dimensional noncompact bulk space-time. Although the difference between the classical brane-world solutions and standard four-dimensional solutions is large at early times, the change to the amplitude at late times of perturbations generated from quantum fluctuations is first order in slow-roll parameters, leading to second-order slow-roll corrections to the spectral index. This confirms that the leading-order effects are correctly given by previous work in the literature.

We update our recent calculation of quarkonium Euclidean correlators at finite temperatures in a potential model by including the effect of zero modes in the lattice spectral functions. These contributions cure most of the previously observed discrepancies with lattice calculations, supporting the use of potential models at finite temperature as an important tool to complement lattice studies.

We study the $B$ meson spectroscopy allowing the mixture of conventional $P$ wave quark-antiquark states and four-quark components. A similar picture was used to describe the new $D_J$ and $D_{sJ}$ open-charm mesons. The four-quark components shift the masses of some positive parity $B_{sJ}$ states below their corresponding isospin preserving two-meson threshold and therefore they are expected to be narrow. Electromagnetic decay widths are analyzed.

A particularly simple Lorentz-violating modification of the Maxwell theory of photons maintains gauge invariance, $CPT$, and renormalization. This modified Maxwell theory, coupled to standard Dirac particles, involves 19 dimensionless “deformation parameters.” Ten of these parameters lead to birefringence and are already tightly constrained by astrophysics. New bounds on the remaining nine nonbirefringent parameters can be obtained from the absence of vacuum Cherenkov radiation for ultrahigh-energy cosmic rays (UHECRs). Using selected UHECR events recorded at the Pierre Auger Observatory and assigning pseudorandom directions (i.e., assuming large-scale isotropy), Cherenkov bounds are found at the ${10}^{-18}$ level, which improve considerably upon current laboratory bounds. Future UHECR observations may reduce these Cherenkov bounds to the ${10}^{-23}$ level.

Several extended supersymmetric models, motivated by either grand unification, or by neutrino mass generation, predict light doubly charged Higgsinos. We study the production of a single doubly charged Higgsino and its decay channels at the International Linear Collider (ILC) operating in the $e^{-}{e}^{-}$ mode. We analyze the production cross section for $e^{-}{e}^{-}\to {\tilde{\Delta }}_{L,R}^{--}{\chi }_1^0$ as a function of different kinematic variables, followed by the decay, through several channels, of the doubly charged Higgsino into a final state of two leptons plus missing energy. We include the standard model background and discuss how kinematic cuts could be used effectively to limit this background. Single production of these exotics could provide a spectacular signal for a new underlying symmetry and for physics beyond the minimal supersymmetric standard model.

We calculate the transverse-momentum ($p_T$) distribution for the inclusive hadroproduction of $B$ mesons at intermediate values of $p_T$ at next-to-leading order (NLO) in a dedicated finite-mass scheme using realistic nonperturbative fragmentation functions that are obtained through a global fit to $e^{+}{e}^{-}$ data from CERN LEP1 and SLAC SLC exploiting their universality and scaling violations. We find that finite-mass effects moderately enhance the cross section, by about 20% at $p_T=2m_b$, and rapidly fade out with increasing value of $p_T$, so that the zero-mass prediction is reached. We also perform comparisons with recent $p\overline{p}$ data taken by the CDF Collaboration in run II at the Fermilab Tevatron and comment on the usefulness of the fixed-flavor-number scheme.

In this work, we study the isospin-violating decay of $\varphi \to \omega {\pi }^0$ and quantify the electromagnetic (EM) transitions and intermediate meson exchanges as two major sources of the decay mechanisms. In the EM decays, the present datum status allows a good constraint on the EM decay form factor in the vector meson dominance model, and it turns out that the EM transition can only account for about $1/4\sim 1/3$ of the branching ratio for $\varphi \to \omega {\pi }^0$. The intermediate meson exchanges, $K\overline{K}(K^{*})$ (intermediate $K\overline{K}$ interaction via $K^{*}$ exchanges), $K{\overline{K}}^{*}(K)$ (intermediate $K{\overline{K}}^{*}$ rescattering via kaon exchanges), and $K{\overline{K}}^{*}(K^{*})$ (intermediate $K{\overline{K}}^{*}$ rescattering via $K^{*}$ exchanges), which evade the naive Okubo-Zweig-Iizuka rule, serve as another important contribution to the isospin violations. They are evaluated with effective Lagrangians where explicit constraints from experiment can be applied. Combining these three contributions, we obtain results in good agreement with the experimental data. This approach is also extended to $J/\psi ({\psi }^{\prime })\to \omega {\pi }^0$, where we find contributions from the $K\overline{K}(K^{*})$, $K{\overline{K}}^{*}(K)$, and $K{\overline{K}}^{*}(K^{*})$ loops are negligibly small, and the isospin violation is likely to be dominated by the EM transition.

We present a complete 1-loop study of the electroweak corrections to the process $ug\to d{W}^{+}$ in the minimal supersymmetric standard model and the standard model. The occurrence of a number of remarkable properties in the behavior of the helicity amplitudes at high energies is stressed, and the crucial role of the virtual supersymmetric (SUSY) contributions in establishing them is emphasized. The approach to asymptopia of these amplitudes is discussed, comparing the effects of the logarithmic and constant contributions to the mass-suppressed ones, which are relevant at lower energies. Applying crossing to $ug\to d{W}^{+}$, we obtain all subprocesses needed for the 1-loop electroweak corrections to $W^{\pm }$-production at LHC. The SUSY model dependence of such a production is then studied, and illustrations are given for the transverse $W^{\pm }$ momentum distribution, as well as the angular distribution in the subprocess center of mass.

The radiative corrections of the strong and electroweak interactions are calculated at next-to-leading order for Higgs-boson production in the weak-boson-fusion channel at hadron colliders. Specifically, the calculation includes all weak-boson fusion and quark-antiquark annihilation diagrams to Higgs-boson production in association with two hard jets, including all corresponding interferences. The results on the QCD corrections confirm that previously made approximations of neglecting $s$-channel diagrams and interferences are well suited for predictions of Higgs production with dedicated vector-boson fusion cuts at the LHC. The electroweak corrections, which also include real corrections from incoming photons and leading heavy Higgs-boson effects at two-loop order, are of the same size as the QCD corrections, viz. typically at the level of 5%–10% for a Higgs-boson mass up to $\sim 700\mathrm{GeV}$. In general, both types of corrections do not simply rescale differential distributions, but induce distortions at the level of 10%. The discussed corrections have been implemented in a flexible Monte Carlo event generator.

We evaluate both the tau-lepton energy loss produced by photonuclear interactions and the neutrino charged current cross section at ultrahigh energies, relevant to neutrino bounds with Earth-skimming tau neutrinos, using different theoretical and phenomenological models for nucleon and nucleus structure functions. The theoretical uncertainty is estimated by taking different extrapolations of the structure function $F_2$ to very low values of $x$, in the low and moderate $Q^2$ range for the tau-lepton interaction and at high $Q^2$ for the neutrino-nucleus inelastic cross section. It is at these extremely low values of $x$ where nuclear shadowing and parton saturation effects are unknown and could be stronger than usually considered. For tau and neutrino energies $E={10}^9\mathrm{GeV}$ we find uncertainties of a factor 4 for the tau energy loss and of a factor 2 for the charged current neutrino-nucleus cross section.

We present results of a search for the decays $B^0\to {\ell }^{+}{\ell }^{-}\gamma$ ($\ell =e$ or $\mu$). The search is performed using $320\times {10}^6$ $B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the BABAR detector at the PEP-II $B$ Factory at SLAC. We find no significant signal and set the following branching fraction upper limits at the 90% confidence level: $\mathcal{B}(B^0\to e^{+}{e}^{-}\gamma )<1.2\times {10}^{-7}$ and $\mathcal{B}(B^0\to {\mu }^{+}{\mu }^{-}\gamma )<1.6\times {10}^{-7}$.

We use ($1+1$)-dimensional large $N$ Gross-Neveu models as a laboratory to derive microscopically effective Lagrangians for positive energy fermions only. When applied to baryons, the Euler-Lagrange equation for these effective theories assumes the form of a nonlinear Dirac equation. Its solution reproduces the full semiclassical results including the Dirac sea to any desired accuracy. Dynamical effects from the Dirac sea are encoded in higher order derivative terms and multifermion interactions with perturbatively calculable, finite coefficients. Characteristic differences between models with discrete and continuous chiral symmetry are observed and clarified.

We describe a new paradox for ideal fluids. It arises in the accretion of an ideal fluid onto a black hole, where, under suitable boundary conditions, the flow can violate the generalized second law of thermodynamics. The paradox indicates that there is in fact a lower bound to the correlation length of any real fluid, the value of which is determined by the thermodynamic properties of that fluid. We observe that the universal bound on entropy, itself suggested by the generalized second law, puts a lower bound on the correlation length of any fluid in terms of its specific entropy. With the help of a new, efficient estimate for the viscosity of liquids, we argue that this also means that viscosity is bounded from below in a way reminiscent of the conjectured Kovtun-Son-Starinets lower bound on the ratio of viscosity to entropy density. We conclude that much light may be shed on the Kovtun-Son-Starinets bound by suitable arguments based on the generalized second law.

One of the possible low-energy consequences of string theory is the addition of a Chern-Simons term to the standard Einstein-Hilbert action of general relativity. It can be argued that the quintessence field should couple to this Chern-Simons term, and if so, it drives in the linearized theory a parity-violating interaction between the gravito-electric and gravitomagnetic fields. In this paper, the linearized spacetime for Chern-Simons gravity around a massive spinning body is found to include new modifications to the gravitomagnetic field that have not appeared in previous work. The orbits of test bodies and the precession of gyroscopes in this spacetime are calculated, leading to new constraints on the Chern-Simons parameter space due to current satellite experiments.

We compare waveforms obtained by numerically evolving nonspinning binary black holes to post-Newtonian (PN) template families currently used in the search for gravitational waves by ground-based detectors. We find that the time-domain 3.5PN template family, which includes the inspiral phase, has fitting factors (FFs) $\ge 0.96$ for binary systems with total mass $M=10–20M_{\odot }$. The time-domain 3.5PN effective-one-body template family, which includes the inspiral, merger, and ring-down phases, gives satisfactory signal-matching performance with FFs $\ge 0.96$ for binary systems with total mass $M=10–120M_{\odot }$. If we introduce a cutoff frequency properly adjusted to the final black-hole ring-down frequency, we find that the frequency-domain stationary-phase-approximated template family at 3.5PN order has FFs $\ge 0.96$ for binary systems with total mass $M=10–20M_{\odot }$. However, to obtain high matching performances for larger binary masses, we need to either extend this family to unphysical regions of the parameter space or introduce a 4PN order coefficient in the frequency-domain gravitational wave (GW) phase. Finally, we find that the phenomenological Buonanno-Chen-Vallisneri family has FFs $\ge 0.97$ with total mass $M=10–120M_{\odot }$. The main analyses use the noise-spectral density of LIGO, but several tests are extended to VIRGO and advanced LIGO noise-spectral densities.

Some extensions of the standard model provide dark matter candidate particles which can have a dominant coupling with the lepton sector of the ordinary matter. Thus, such dark matter candidate particles (${\chi }^0$) can be directly detected only through their interaction with electrons in the detectors of a suitable experiment, while they are lost by experiments based on the rejection of the electromagnetic component of the experimental counting rate. These candidates can also offer a possible source of the 511 keV photons observed from the galactic bulge. In this paper this scenario is investigated. Some theoretical arguments are developed and related phenomenological aspects are discussed. Allowed intervals and regions for the characteristic phenomenological parameters of the considered model and of the possible mediator of the interaction are also derived considering the DAMA/NaI data.

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50–1000 Hz and with the frequency’s time derivative in the range $-1\times {10}^{-8}\mathrm{Hz}{\mathrm{s}}^{-1}$ to zero. Data from the fourth LIGO science run (S4) have been used in this search. Three different semicoherent methods of transforming and summing strain power from short Fourier transforms (SFTs) of the calibrated data have been used. The first, known as StackSlide, averages normalized power from each SFT. A “weighted Hough” scheme is also developed and used, which also allows for a multi-interferometer search. The third method, known as PowerFlux, is a variant of the StackSlide method in which the power is weighted before summing. In both the weighted Hough and PowerFlux methods, the weights are chosen according to the noise and detector antenna-pattern to maximize the signal-to-noise ratio. The respective advantages and disadvantages of these methods are discussed. Observing no evidence of periodic gravitational radiation, we report upper limits; we interpret these as limits on this radiation from isolated rotating neutron stars. The best population-based upper limit with 95% confidence on the gravitational-wave strain amplitude, found for simulated sources distributed isotropically across the sky and with isotropically distributed spin axes, is $4.28\times {10}^{-24}$ (near 140 Hz). Strict upper limits are also obtained for small patches on the sky for best-case and worst-case inclinations of the spin axes.

There is a growing appreciation that hidden sector dynamics may affect the supersymmetry breaking parameters in the visible sector (supersymmetric standard model), especially when the dynamics is strong and superconformal. We point out that there are effects that have not been previously discussed in the literature. For example, the gaugino masses are suppressed relative to the gravitino mass. We discuss their implications in the context of various mediation mechanisms. The issues discussed include anomaly mediation with singlets, the $\mu$ ($B\mu$) problem in gauge and gaugino mediation, and distinct mass spectra for the superparticles that have not been previously considered.

We study the Anderson localization effect on the shear viscosity in a system with random medium by Kubo formula. We show that this effect can suppress nonperturbatively the shear viscosity and other transport coefficients. The possible relevancy of such a suppression to the near perfect fluid behavior of the quark-gluon plasma created in heavy-ion collisions is discussed.