Extreme mass-ratio inspirals, in which a stellar-mass object orbits a supermassive black hole, are prime sources for space-based gravitational wave detectors because they will facilitate tests of strong gravity and probe the spacetime around rotating compact objects. In the last few years of such inspirals, the total phase is in the millions of radians and details of the waveforms are sensitive to small perturbations. We show that one potentially detectable perturbation is the presence of a second supermassive black hole within a few tenths of a parsec. The acceleration produced by the perturber on the extreme mass-ratio system produces a steady drift that causes the waveform to deviate systematically from that of an isolated system. If the perturber is a few tenths of a parsec from the extreme mass-ratio system (plausible in as many as a few percent of cases) higher derivatives of motion might also be detectable. In that case, the mass and distance of the perturber can be derived independently, which would allow a new probe of merger dynamics.

We present a state-of-the-art primordial recombination code, HYREC, including all the physical effects that have been shown to significantly affect recombination. The computation of helium recombination includes simple analytic treatments of hydrogen continuum opacity in the He I $2^1{P}^o-1^{1}S$ line, the He I] $2^3{P}^o-1^{1}S$ line, and treats feedback between these lines within the on-the-spot approximation. Hydrogen recombination is computed using the effective multilevel atom method, virtually accounting for an infinite number of excited states. We account for two-photon transitions from $2s$ and higher levels as well as frequency diffusion in Lyman-$\alpha$ with a full radiative transfer calculation. We present a new method to evolve the radiation field simultaneously with the level populations and the free electron fraction. These computations are sped up by taking advantage of the particular sparseness pattern of the equations describing the radiative transfer. The computation time for a full recombination history is $\sim 2$ seconds. This makes our code well suited for inclusion in Monte Carlo Markov chains for cosmological parameter estimation from upcoming high-precision cosmic microwave background anisotropy measurements.

Long wavelength oscillations (Tkachenko waves) of the triangular lattice of quantized vortices in superfluid neutron stars have been suggested as one of the possible explanations for the timing noise observed in many radio pulsars, in particular, for the 100–1000 day variations in the spin of PSR 1828-11. Most studies to date have, however, been based on the hydrodynamics developed for superfluid Helium. In this paper we extend the formulation to a two-fluid neutron and proton system, relevant for neutron star interiors and include the effect of chemical coupling, compressibility and mutual friction between the components. In particular we find that chemical coupling and compressibility can have a drastic effect on the mode structure. However, for the slower pulsars rotating at 1–10 Hz (such as PSR B1828-11), most choices of parameters in the equation of state lead to Tkachenko oscillations with frequencies in the correct range to explain the timing noise. We also investigate the case of more rapidly rotating pulsars (above 100 Hz) for which we find that there is a vast portion of parameter space in which there are no Tkachenko modes, but only modified sound waves at much higher frequencies.

In a previous publication we noted that the time dependence of an incoherent $B^0-{\overline{B}}^0$ mixture undergoes a qualitative change when the magnitude of $CP$ violation $\delta$ exceeds a critical value. Requiring, on physical grounds, that the system evolve from an initial incoherent state to a final pure state in a monotonic way yields a new upper limit for $\delta$. The recent measurement of the wrong charge semileptonic asymmetry of $B_s^0$ mesons presented by the D0 collaboration is outside this bound by 1 standard deviation. If this result is confirmed it implies the existence of a new quantum mechanical oscillation phenomenon.

It is shown that the ${\pi }^0$ transition form factor $F(Q_1^2,Q_2^2)$ differs substantially from its one-real-photon limit $F(Q_1^2,0)$ even for rather small values of $Q_2^2$ ($\approx 0.1{\mathrm{GeV}}^2$), which cannot be excluded in experiments with one “untagged” electron. It indicates that the comparison of data with theoretical calculations, which usually assume $Q_2^2=0$, may be untrustworthy. Our phenomenological model of the ${\pi }^0$ transition form factor is based on the vector-meson-dominance hypothesis and all its parameters are fixed by using the experimental data on the decays of vector mesons. The model soundness is checked in the two-real-photon limit, where it provides a good parameter-free description of the ${\pi }^0\to 2\gamma$ decay rate, and in the ${\pi }^0$ Dalitz decay. The dependence of $F(Q_1^2,Q_2^2)$ on $Q_1^2$ at several fixed values of $Q_2^2$ is presented and the comparison with existing data performed.

We reexamine our previous calculation on the Collins effect in the semi-inclusive deeply inelastic scattering process with a ${}^3\mathrm{He}$ target, and find that our previous treatment on the dilution factors may cause the results to be larger than the realistic situation. We thus modify our calculation in an improved treatment with an updated prediction on the $\sin ({\varphi }_h+{\varphi }_S)$ asymmetry for the JLab 12 GeV under the transverse momentum dependent factorization framework. Meanwhile, we also provide the prediction of such asymmetry for the JLab 6 GeV and the prediction of the $\sin (3{\varphi }_h-{\varphi }_S)$ asymmetry related to pretzelosity.

The mass of a $P$-wave $cs$-scalar-diquark $\overline{c}\overline{s}$-scalar-antidiquark state is computed in the framework of QCD sum rules. The result $4.69\pm 0.36\mathrm{GeV}$ is in good agreement with the experimental value of $Y(4660)$ but higher than $Y(4260)$’s, which supports the $P$-wave $[cs][\overline{c}\overline{s}]$ configuration for $Y(4660)$ while disfavors the interpretation of $Y(4260)$ as the $P$-wave $[cs][\overline{c}\overline{s}]$ state. In the same picture, the mass of $P$-wave $[bs][\overline{b}\overline{s}]$ is predicted to be $11.19\pm 0.49\mathrm{GeV}$.

We examine the potential of the $pp\to p\gamma p\to pWqX$ reaction to probe anomalous $WW\gamma$ couplings at the LHC. We find 95% confidence level bounds on the anomalous coupling parameters with various values of the integrated luminosity. We show that the reaction $pp\to p\gamma p\to pWqX$ at the LHC highly improves the current limits.

Based on a supersymmetric Yukawaon model with O(3) family symmetry, possible forms of quark and lepton mixing matrices are systematically investigated under a condition that the up-quark mass matrix form leads to the observed nearly tribimaximal mixing in the lepton sector. Although the previous model could not provide a good fitting of the observed quark mixing, the present model can give a reasonably good fitting not only for lepton mixing but also for the quark mixing by using a different origin of the $CP$ violation from one in the previous model.

This paper investigates a new experimental framework to test the braneworld hypothesis. Recent theoretical results have shown the possibility of matter exchange between branes under the influence of suitable magnetic vector potentials. It is shown that the required conditions might be achieved with present-day technology. The experiment uses a source of pulsed and coherent electromagnetic radiation and relies on the Hänsch frequency comb technique well-known in ultrahigh-precision spectroscopy. A good matter candidate for testing the hypothesis is a polarized ultracold neutron gas for which the number of swapped neutrons is measured.

We propose a new method to discover light top squarks (stops) in the co-annihilation region at the Large Hadron Collider (LHC). The bino-like neutralino is the lightest supersymmetric particle (LSP) and the lighter stop is the next-to-LSP. Such scenarios can be consistent with electroweak baryogenesis and also with dark matter constraints. We consider the production of two stops in association with two $b$-quarks, including pure QCD as well as mixed electroweak-QCD contributions. The stops decay into a charm quark and the LSP. For a higgsino-like light chargino, the electroweak contributions can exceed the pure QCD prediction. We show the size of the electroweak contributions as a function of the stop mass and present the LHC discovery reach in the stop-neutralino mass plane.

The Bethe-Salpeter equation in QCD connects the gauge-dependent gluon and quark degrees of freedom with the gauge-invariant properties of mesons. We study the $\rho$ meson mass and decay constant for various versions of the gauge-dependent input functions discussed in the literature, which start to differ generically below the hadronic scale and show qualitative different infrared behavior. We find that, once the gauge-dependent quark-gluon vertex is permitted to vary as well, the $\rho$ mass and decay constant is reproduced equally well for all forms investigated. A possible conclusion from this is that these $\rho$-meson properties are only sensitive to changes in the input at scales above a few hundred MeV.

We present a general, model independent argument demonstrating that gluons produced in high energy hadronic collision are necessarily correlated in rapidity and also in the emission angle. The strength of the correlation depends on the process and on the structure/model of the colliding particles. In particular we argue that it is strongly affected (and underestimated) by factorized approximations frequently used to quantify the effect.

The absence of backscattering in metallic nanotubes as well as perfect Klein tunneling in potential barriers in graphene are the prominent electronic characteristics of carbon nanostructures. We show that the phenomena can be explained by a peculiar supersymmetry generated by a first order Hamiltonian and zero-order supercharge operators. Like the supersymmetry associated with second order reflectionless finite-gap systems, it relates here the low-energy behavior of the charge carriers with the free-particle dynamics.

Pair creation of scalar particles in a boost-invariant electric field which is confined in the forward light cone is studied. We present the proper-time evolution of momentum distributions of created particles, which preserve the boost invariance of the background field. The two-particle correlation of the created particles is also calculated. We find that long-range rapidity correlations may arise from the Schwinger mechanism in the boost-invariant electric field.

We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length $L=2.1\mathrm{fm}$ and $L=2.8\mathrm{fm}$. Cut-off effects are investigated using three different values of the lattice spacings, namely $a=0.089\mathrm{fm}$, $a=0.070\mathrm{fm}$ and $a=0.056\mathrm{fm}$. The nucleon axial charge is obtained in the continuum limit and chirally extrapolated to the physical pion mass enabling comparison with experiment.

Galileon models, which were developed in the context of modified gravity, give a class of Lagrangians containing derivative interactions without introducing higher order derivatives in the equations of motion. Here we extend the analysis to an arbitrary number of scalars, and examine the restrictions imposed by an internal symmetry, focusing in particular on SU(N) and SO(N). This therefore extends the possible gradient terms that may be included when constructing topological objects such as sigma model lumps.

It has recently been suggested that the presence of a plenitude of light axions, an Axiverse, is evidence for the extra dimensions of string theory. We discuss the observational consequences of these axions on astrophysical black holes through the Penrose superradiance process. When an axion Compton wavelength is comparable to the size of a black hole, the axion binds to the black hole “nucleus” forming a gravitational atom in the sky. The occupation number of superradiant atomic levels, fed by the energy and angular momentum of the black hole, grows exponentially. The black hole spins down and an axion Bose-Einstein condensate cloud forms around it. When the attractive axion self-interactions become stronger than the gravitational binding energy, the axion cloud collapses, a phenomenon known in condensed matter physics as “bosenova”. The existence of axions is first diagnosed by gaps in the mass vs spin plot of astrophysical black holes. For young black holes the allowed values of spin are quantized, giving rise to “Regge trajectories” inside the gap region. The axion cloud can also be observed directly either through precision mapping of the near-horizon geometry or through gravitational waves coming from the bosenova explosion, as well as axion transitions and annihilations in the gravitational atom. Our estimates suggest that these signals are detectable in upcoming experiments, such as Advanced LIGO, AGIS, and LISA. Current black hole spin measurements imply an upper bound on the QCD axion decay constant of $2\times {10}^{17}\mathrm{GeV}$, while Advanced LIGO can detect signals from a QCD axion cloud with a decay constant as low as the GUT scale. We finally discuss the possibility of observing the $\gamma$-rays associated with the bosenova explosion and, perhaps, the radio waves from axion-to-photon conversion for the QCD axion.