It has long been known that dissipation is a crucial ingredient in the superradiant amplification of wave packets off rotating objects. We show that, once appropriate dissipation mechanisms are included, stars are also prone to superradiance and superradiant instabilities. In particular, ultralight dark matter with small interaction cross section with the star material or self-annihilation can trigger a superradiant instability. On long time scales, the instability strips the star of most of its angular momentum. Whether or not new stationary configurations surrounded by scalar condensates exist remains to be seen.

We study the stability and the scattering properties of a spacetime with a topological defect along a spherical bubble. This bubble connects two flat spacetimes which are asymptotically Minkowski, so that the resulting universe may be regarded as containing a wormhole. Its distinguished feature is the absence of exotic matter, i.e., its matter content respects all the energy conditions. Although this wormhole is nontraversable, waves and quantum particles can tunnel between both universes. Interestingly enough, the wave equation alone does not uniquely determine the evolution of scalar waves on this background, and the theory of self-adjoint extensions of symmetric operators is required to find the relevant boundary conditions in this context. Here we show that, for a particular boundary condition, this spacetime is stable and gives rise to a scattering pattern which is identical to the more usual thin-shell wormhole composed of exotic matter. Other boundary conditions of interest are also analyzed, including an unstable configuration with sharp resonances at well-defined frequencies.

Using black hole perturbation theory and arbitrary-precision computer algebra, we obtain the post-Newtonian expansions of the linear-in-mass-ratio corrections to the spin-precession angle and tidal invariants for a particle in circular orbit around a Schwarzschild black hole. We extract coefficients up to 20 post-Newtonian order from numerical results that are calculated with an accuracy greater than 1 part in ${10}^{500}$. These results can be used to calibrate parameters in effective-one-body models of compact binaries, specifically the spin-orbit part of the effective Hamiltonian and the dynamically significant tidal part of the main radial potential of the effective metric. Our calculations are performed in a radiation gauge, which is known to be singular away from the particle. To overcome this irregularity, we define suitable Detweiler–Whiting singular and regular fields in this gauge, and we compute the invariants using mode-sum regularization in combination with averaging from two sides of the particle. The detailed justification of this regularization procedure will be presented in a forthcoming companion paper.

A profound assumption in peculiar velocity cosmology is $b_v=1$ at sufficiently large scales, where $b_v$ is the volume-weighted halo(galaxy) velocity bias with respect to the matter velocity field. However, this fundamental assumption has not been robustly verified in numerical simulations. Furthermore, it is challenged by structure formation theory (Bardeen, Bond, Kaiser and Szalay, Astrophys. J. 304, 15 (1986); Desjacques and Sheth, Phys. Rev D 81, 023526 (2010), which predicts the existence of velocity bias (at least for proto-halos) due to the fact that halos reside in special regions (local density peaks). The major obstacle to measuring the volume-weighted velocity from N-body simulations is an unphysical sampling artifact. It is entangled in the measured velocity statistics and becomes significant for sparse populations. With recently improved understanding of the sampling artifact (Zhang, Zheng and Jing, 2015, PRD; Zheng, Zhang and Jing, 2015, PRD), for the first time we are able to appropriately correct this sampling artifact and then robustly measure the volume-weighted halo velocity bias. (1) We verify $b_v=1$ within 2% model uncertainty at $k\lesssim 0.1h/\mathrm{Mpc}$ and $z=0–2$ for halos of mass $\sim {10}^{12}–{10}^{13}{h}^{-1}{M}_{\odot }$ and, therefore, consolidate a foundation for the peculiar velocity cosmology. (2) We also find statistically significant signs of $b_v\ne 1$ at $k\gtrsim 0.1h/\mathrm{Mpc}$. Unfortunately, whether this is real or caused by a residual sampling artifact requires further investigation. Nevertheless, cosmology based on the $k\gtrsim 0.1h/\mathrm{Mpc}$ velocity data should be careful with this potential velocity bias.

In canonical quantum cosmology, the wave function of the Universe lacks explicit time dependence. However, time evolution may be present implicitly through the semiclassical superspace variables, which themselves depend on time in classical dynamics. In this paper, we apply this approach to an oscillating universe model recently introduced by Graham et al. [A simple harmonic universe, J. High Energy Phys. 02 (2014) 029.] By extending the model to include a massless, minimally coupled scalar field $\varphi$ which has little effect on the dynamics but can play the role of a “clock,” we determine the decay rate of the oscillating universe.

If vector type perturbations are present in the primordial plasma before recombination, the generation of magnetic fields is known to be inevitable through the Harrison mechanism. In the context of the standard cosmological perturbation theory, nonlinear couplings of first-order scalar perturbations create second-order vector perturbations, which generate magnetic fields. Here we reinvestigate the generation of magnetic fields at second-order in cosmological perturbations on the basis of our previous study, and extend it by newly taking into account the time evolution of purely second-order vector perturbations with a newly developed second-order Boltzmann code. We confirm that the amplitude of magnetic fields from the product-terms of the first-order scalar modes is consistent with the result in our previous study. However, we find, both numerically and analytically, that the magnetic fields from the purely second-order vector perturbations partially cancel out the magnetic fields from one of the product-terms of the first-order scalar modes, in the tight coupling regime in the radiation dominated era. Therefore, the amplitude of the magnetic fields on small scales, $k\gtrsim 10h{\mathrm{Mpc}}^{-1}$, is smaller than the previous estimates. The amplitude of the generated magnetic fields at cosmological recombination is about $B_{\text{rec}}=5.0\times {10}^{-24}\text{Gauss}$ on $k=5.0\times {10}^{-1}h{\mathrm{Mpc}}^{-1}$. Finally, we discuss the reason for the discrepancies that exist in estimates of the amplitude of magnetic fields among other authors.

A 3 sigma excess has been recently announced by ATLAS in events with $Z$-peaked dilepton pairs, jets, and large transverse missing energy. We interpret this finding in the context of composite Higgs/Randall-Sundrum theories. We find that composite Higgs theories with custodial symmetry protection to the $Zb\overline{b}$ coupling predict a significant contribution to $ZZbb$ (and to $hhbb$) final states coming from heavy gluon decays to pairs of bottom partner vectorlike quarks. The heavy gluon to vectorlike quark signal is largely accepted by the ATLAS selection if one of the $Z$ bosons in the $ZZbb$ final state decays leptonically and the other to neutrinos. For a bottom partner of $\sim 900\mathrm{GeV}$, we find that the ATLAS excess can be reproduced by composite Higgs models, in an experimentally allowed parameter space, for heavy gluon masses roughly in a range 1.87–2.15 TeV and for heavy gluon couplings to light quarks within $\sim (0.3–0.65)g_S$. We briefly discuss the implication of this result for future experimental tests.

Determination of Higgs self-interactions through the double Higgs production from gluon fusion is a major goal of current and future collider experiments. We point out this channel could help disentangle and resolve the nature of ultraviolet contributions to Higgs couplings to two gluons. Analytic properties of the double Higgs amplitudes near kinematic threshold are used to study features resulting from scalar and fermionic loop particles mediating the interaction. Focusing on the $hh$ invariant mass spectrum, we consider the effect from anomalous top and bottom Yukawa couplings, as well as from scalar and fermionic loop particles. In particular, the spectrum at high $hh$ invariant mass is sensitive to the spin of the particles in the loop.

LHCb measurements of $B_{d,s}\to J/\psi +X$ are shown to be consistent with historical data on scalar and axial mesons below 2 GeV. This is in contrast to some recent interpretations of these data. Further tests of our hypotheses in other $B_{u,d,s}\to J/\psi +X$ decay modes are suggested.

We suggest that the observed properties of the charmonium-like resonance $X(3915)$ can possibly be explained if it is an $S$-wave molecular bound state of the $D_s{\overline{D}}_s$ meson pair with a binding energy of about 18 MeV. In particular, the decays of $X(3915)$ to pairs of nonstrange $D$ mesons are suppressed and proceed at a rate comparable to that of the decay $X(3915)\to \omega J/\psi$, whose branching fraction can be as large as about 0.3. Other major types of decay of $X(3915)$ with a comparable (or slightly smaller) rate are the transition $X(3915)\to \eta {\eta }_c$ and the decays into light hadrons due to the annihilation of the $c\overline{c}$ quark pair. The existence of a bound state should lead to an enhancement in the spectrum of the invariant mass for the $D_s{\overline{D}}_s$ near threshold in $B$ decays, e.g. in $B\to K{D}_s{\overline{D}}_s$ the enhancement of which can be tested experimentally.

We revisit various contributions to neutrinoless double beta decay ($0\nu \beta \beta$) in a TeV-scale left-right symmetric model (LRSM) for type-I seesaw dominance. We show that the momentum-dependent effects due to $W_L-W_R$ exchange ($\lambda$ diagram) and $W_L-W_R$ mixing ($\eta$ diagram) could give dominant contributions to the $0\nu \beta \beta$ amplitude in a wide range of the LRSM parameter space with large left-right neutrino mixing. In particular, for a relatively large $W_L-W_R$ mixing, the $\eta$ contribution by itself could saturate the current experimental limit on the $0\nu \beta \beta$ half-life, thereby providing stringent constraints on the relevant LRSM parameters, complementary to the indirect constraints derived from lepton-flavor-violating observables. In a simplified scenario parametrized by a single light-heavy neutrino mixing, the inclusion of the $\lambda$ and $\eta$ contributions leads to significantly improved $0\nu \beta \beta$ constraints on the light-heavy neutrino mixing as well as on the $W_L-W_R$ mixing parameters. We also present a concrete TeV-scale LRSM setup, where the mixing effects are manifestly enhanced, and discuss the interplay between $0\nu \beta \beta$, lepton flavor violation, and electric dipole moment constraints.

We report the first observation of seasonal modulations in the rates of cosmic ray multiple-muon events at two underground sites, the MINOS Near Detector with an overburden of 225 mwe, and the MINOS Far Detector site at 2100 mwe. At the deeper site, multiple-muon events with muons separated by more than 8 m exhibit a seasonal rate that peaks during the summer, similar to that of single-muon events. In contrast and unexpectedly, the rate of multiple-muon events with muons separated by less than 5–8 m, and the rate of multiple-muon events in the smaller, shallower Near Detector, exhibit a seasonal rate modulation that peaks in the winter.

Using data samples collected with the BESIII detector operating at the BEPCII collider at 17 center-of-mass energies from 3.810 to 4.600 GeV, we perform a study of $e^{+}{e}^{-}\to \eta J/\psi$ and ${\pi }^{0}J/\psi$. The Born cross sections of these two processes are measured at each center-of-mass energy. The measured energy-dependent Born cross section for $e^{+}{e}^{-}\to \eta J/\psi$ shows an enhancement around 4.2 GeV. The measurement is compatible with an earlier measurement by Belle.

Using data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of $e^{+}{e}^{-}\to p\overline{p}$ at 12 center-of-mass energies from 2232.4 to 3671.0 MeV. The corresponding effective electromagnetic form factor of the proton is deduced under the assumption that the electric and magnetic form factors are equal $(|G_E|=|G_M|)$. In addition, the ratio of electric to magnetic form factors, $|G_E/G_M|$, and $|G_M|$ are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at $\sqrt{s}=2232.4$ and 2400.0 MeV and a combined sample at $\sqrt{s}=3050.0$, 3060.0 and 3080.0 MeV, respectively. The measured cross sections are in agreement with recent results from BABAR, improving the overall uncertainty by about 30%. The $|G_E/G_M|$ ratios are close to unity and consistent with BABAR results in the same $q^2$ region, which indicates the data are consistent with the assumption that $|G_E|=|G_M|$ within uncertainties.

Among the so-called classical tests of general relativity (GR), light bending has been confirmed with an accuracy that increases as times goes by. Here we study the gravitational deflection of photons within the framework of classical and semiclassical higher-derivative gravity (HDG)—the only version of GR that is known up to now to be renormalizable along with its matter couplings. Since our computations are restricted to scales much below the Planck cutoff we need not be afraid of the massive spin-2 ghost that haunts HDG. An upper bound on the constant related to the $R_{\mu \nu }^2$ sector of the theory is then found by analyzing—from the classical and semiclassical viewpoints—the deflection angle of a photon passing by the Sun. This upper limit greatly improves that available in the literature.

We use Kaluza-Klein reduction to construct flat-space massive spin-2 Lagrangians based on a kinetic term that has local Weyl and transverse-diffeomorphism gauge symmetries in the massless limit. This yields Lagrangians describing a free massive spin 2 which differ from the usual Fierz-Pauli theory, but are physically equivalent to it. These Lagrangians require the use of auxiliary fields, which appear naturally from the higher-dimensional construction. We discuss how these Lagrangians are related to each other and to the Fierz-Pauli theory through Stückelberg transformations, gauge fixings, and field replacements, and we use this to generalize the construction to spin-2 fields on Einstein manifolds.

The Vainshtein mechanism suppresses the fifth force at astrophysical distances, while enabling it to compete with gravity at cosmological scales. Typically, Vainshtein solutions exhibit superluminal perturbations. However, a restricted class of solutions with special boundary conditions was shown to be devoid of the faster-than-light modes. Here we extend this class by finding solutions in a theory of quasidilaton, amended by derivative terms consistent with its symmetries. Solutions with Minkowski asymptotics are not stable, while the ones that exhibit the Vainshtein mechanism by transitioning to cosmological backgrounds are free of ghosts, tachyons, gradient instability, and superluminality, for all propagating modes present in the theory. These solutions require a special choice of the strength and signs of nonlinear terms, as well as a choice of asymptotic cosmological boundary conditions.