We present a search for a new heavy vector boson $Z^{\prime }$ that decays to gluons. Decays to on-shell gluons are suppressed, leading to a dominant decay mode of $Z^{\prime }\to g^{*}g$. We study the case where the off-shell gluon $g^{*}$ converts to a pair of top quarks, leading to a final state of $t\overline{t}g$. In a sample of events with exactly one charged lepton, large missing transverse momentum and at least five jets, corresponding to an integrated luminosity of $8.7{\mathrm{fb}}^{-1}$ collected by the CDF II detector, we find the data to be consistent with the standard model. We set upper limits on the production cross section times branching ratio of this chromophilic $Z^{\prime }$ at 95% confidence level from 300 to 40 fb for $Z^{\prime }$ masses ranging from 400 to $1000\mathrm{GeV}/c^2$, respectively.

In this paper, we consider the acoustic black hole metrics obtained from a relativistic fluid under the influence of constant background that violates the Lorentz symmetry to study the analogue of the Aharonov-Bohm (AB) effect. We show that the scattering of planar waves by a draining bathtub vortex leads to a modified AB effect and due to the Lorentz symmetry breaking, the phase shift persists even in the limit where the parameters associated with the circulation and draining vanish. In this limit, the Lorentz-violating background forms a conical defect, which is also responsible for the appearance of the analogue AB effect.

We study the renormalization flow of axion electrodynamics, concentrating on the nonperturbative running of the axion-photon coupling and the mass of the axion(-like) particle. Due to a nonrenormalization property of the axion-photon vertex, the renormalization flow is controlled by photon and axion anomalous dimensions. As a consequence, momentum-independent axion self-interactions are not induced by photon fluctuations. The nonperturbative flow towards the ultraviolet exhibits a Landau-pole-type behavior, implying that the system has a scale of maximum UV extension and that the renormalized axion-photon coupling in the deep infrared is bounded from above. Even though gauge invariance guarantees that photon fluctuations do not decouple in the infrared, the renormalized couplings remain finite even in the deep infrared and even for massless axions. Within our truncation, we also observe the existence of an exceptional renormalization group trajectory, which is extendable to arbitrarily high scales, without being governed by a UV fixed point.

Most calculations in cosmological perturbation theory, including those dealing with the inflationary generation of perturbations, their time evolution, and their observational consequences, decompose those perturbations into plane waves (Fourier modes). However, for some calculations, particularly those involving observations performed on a spherical sky, a decomposition into waves of fixed total angular momentum (TAM) may be more appropriate. Here we introduce TAM waves—solutions of fixed total angular momentum to the Helmholtz equation—for three-dimensional scalar, vector, and tensor fields. The vector TAM waves of given total angular momentum can be decomposed further into a set of three basis functions of fixed orbital angular momentum, a set of fixed helicity, or a basis consisting of a longitudinal ($L$) and two transverse ($E$ and $B$) TAM waves. The symmetric traceless rank-2 tensor TAM waves can be similarly decomposed into a basis of fixed orbital angular momentum or fixed helicity, or a basis that consists of a longitudinal ($L$), two vector ($VE$ and $VB$, of opposite parity), and two tensor ($TE$ and $TB$, of opposite parity) waves. We show how all of the vector and tensor TAM waves can be obtained by applying derivative operators to scalar TAM waves. This operator approach then allows one to decompose a vector field into three covariant scalar fields for the $L$, $E$, and $B$ components and symmetric-traceless-tensor fields into five covariant scalar fields for the $L$, $VE$, $VB$, $TE$, and $TB$ components. We provide projections of the vector and tensor TAM waves onto vector and tensor spherical harmonics. We provide calculational detail to facilitate the assimilation of this formalism into cosmological calculations. As an example, we calculate the power spectra of the deflection angle for gravitational lensing by density perturbations and by gravitational waves. We comment on an alternative approach to cosmic microwave background fluctuations based on TAM waves. An accompanying paper will work out three-point functions in terms of TAM waves and their relation to the usual Fourier-space bispectra. Our work may have applications elsewhere in field theory and in general relativity.

We show that the variations of the ground state entanglement in linear, higher spatial derivative field theories at zero temperature have signatures of phase transition. Around the critical point, when the dispersion relation changes from linear to nonlinear, there is a fundamental change in the reduced density matrix leading to a change in the scaling of entanglement entropy. We suggest possible explanations involving both kinematical and dynamical effects. We discuss the implication of our work for 2D condensed matter systems, black-hole entropy, and models of quantum gravity.

Invoking an initial symmetry between the time $t$ and some extra spatial dimension $y$, we discuss a novel scenario where the dynamical formation of the 4 dimensional brane and its cosmological evolution are induced simultaneously by a common $t\leftrightarrow y$ symmetry breaking mechanism. The local maximum of the underlying scalar potential is mapped onto a “watershed” curve in the $(t,y)$ plane; the direction tangent to this curve is identified as the cosmic time, whereas the perpendicular direction serves locally as the extra spatial dimension. Special attention is devoted to the so-called slinky configurations, whose brane cosmology is characterized by a decaying cosmological constant along the watershed curve. Such a slinky solution is first constructed within a simplified case where the watershed is constrained by $y=0$. The physical requirements for a slinky configuration to generate a realistic model of cosmological evolution are then discussed in a more elaborated framework.

It has recently been shown that the graviton can consistently gain a constant mass without introducing the Boulware-Deser ghost. We propose a gravity model where the graviton mass is set by a scalar field and prove that this model is free of the Boulware-Deser ghost by analyzing its constraint system and showing that two constraints arise. We also initiate the study of the model’s cosmic background evolution and tentatively discuss possible cosmological implications of this model. In particular, we consider a simple scenario where the scalar field setting the graviton mass is identified with the inflaton and the graviton mass evolves from a high to a low energy scale, giving rise to the current cosmic acceleration.

By combining a standard symmetric, symplectic integrator with a new step size controller, we provide an integration scheme that is symmetric, reversible and conserves the values of the constants of motion. This new scheme is appropriate for long-term numerical integrations of geodesic orbits in spacetime backgrounds, whose corresponding Hamiltonian system is nonintegrable, and, in general, for any nonintegrable Hamiltonian system whose kinetic part depends on the position variables. We show by numerical examples that the new integrator is faster and more accurate (i) than the standard symplectic integration schemes with or without standard adaptive step size controllers and (ii) than an adaptive step Runge-Kutta scheme.

We derive the gravitational radiation-reaction force modifying the Effective One Body description of the conservative dynamics of binary systems. Our result is applicable to general orbits (elliptic or hyperbolic) and keeps terms of fractional second post-Newtonian order (but does not include tail effects). Our derivation of radiation-reaction is based on a new way of requiring energy and angular momentum balance. We give several applications of our results, notably the value of the (minimal) ‘‘Schott” contribution to the energy, the radial component of the radiation-reaction force, and the radiative contribution to the angle of scattering during hyperbolic encounters. We present also new results about the conservative relativistic dynamics of hyperbolic motions.

We consider a simulated population of isolated Galactic neutron stars. The rotational frequency of each neutron star evolves through a combination of electromagnetic and gravitational-wave emission. The magnetic field strength dictates the dipolar emission, and the ellipticity (a measure of a neutron star’s deformation) dictates the gravitational-wave emission. Through both analytic and numerical means, we assess the detectability of the Galactic neutron star population and bound the magnetic field strength and ellipticity parameter space of Galactic neutron stars with or without a direct gravitational-wave detection. While our simulated population is primitive, this work establishes a framework by which future efforts can be conducted.

We obtain the self-interaction for a point charge in the space-time of a cylindrical thin-shell wormhole connecting two identical locally flat geometries with a constant deficit angle. Although this wormhole geometry is locally indistinguishable from a cosmic string background, the corresponding self-forces are different even at the qualitative level. In fact, in the cosmic string geometry the force is always repulsive while for the wormhole background we find that the force may point outward or toward the wormhole throat depending on the parameters of the configuration. These results suggest that the study of the electromagnetic fields of charged particles is a useful tool for testing the global properties of a given background.

We perform the Hamiltonian analysis of the specific model of the nonlinear massive gravity in Stückelberg formalism where the square root structure is replaced by introducing auxiliary fields. Following Hassan et al. [J. High Energy Phys. 06 (2012) 170], we show that given theory possesses an additional primary constraint. Then we perform analysis of the consistency of all constraints during the time development of the system and we argue for the existence of the additional constraint. As a result, the theory possesses the correct number of physical degrees of freedom corresponding to the massive gravity.

Coupling the Galileons to a curved background has been a tradeoff between maintaining second order equations of motion and the Galilean shift symmetries, and allowing the background metric to be dynamical. We propose a construction which can achieve all three for a novel class of Galilean invariant models by coupling a scalar with the Galilean symmetry to a massive graviton. This generalizes the brane construction for Galileons by adding to the brane a dynamical metric (nonuniversally) interacting with the Galileon field. Alternatively, it can be thought of as an extension of the ghost-free massive gravity, or as a massive graviton-Galileon scalar-tensor theory. In the decoupling limit of these theories, new kinds of Galileon invariant interactions arise between the scalar and the longitudinal mode of the graviton. These have higher order equations of motion and infinite powers of the field, yet are ghost free.

The particles of a dark matter deviate from straight trajectories in the vicinity of a massive body. This causes their density to become inhomogeneous. The developed density contrast causes a gravitation attraction force acting upon the body proportional to its mass squared. Since this effect depends on the body’s velocity, it causes a specific reference frame to stand out. The force is similar to an anisotropic drag, which can be negative in some directions. The mean drag force, averaged over all direction, is nonpositive. We can expect some observational manifestation of the considered effect for supermassive black holes in galaxies.

We examine the accuracy of the quasistatic approximation and a parametric form commonly employed for evolving linear perturbations in $f(R)$ gravity theories and placing cosmological constraints. In particular, we analyze the nature and the importance of the near-horizon effects that are often neglected. We find that for viable models, with a small present value of the scalaron field, such corrections are entirely negligible with no impact on observables. We also find that the one-parameter form, commonly used to represent the modified equations for linear perturbations in $f(R)$, leads to theoretical systematic errors that are relatively small and, therefore, is adequate for placing constraint on $f(R)$ models.

We make a perturbative calculation of neutrino scattering and absorption in hot and dense hyperonic neutron-star matter in the presence of a strong magnetic field. We calculate that the absorption cross-sections in a fully relativistic mean-field theory. We find that there is a remarkable angular dependence, i.e., the neutrino absorption strength is reduced in a direction parallel to the magnetic field and enhanced in the opposite direction. This asymmetry in the neutrino absorption is estimated to be as much as 2.2% of the entire neutrino momentum for an interior magnetic field of $\sim 2\times {10}^{17}\mathrm{G}$. The pulsar kick velocities associated with this asymmetry are shown to be comparable to observed velocities.

We show that the eigenvectors of the $\mathcal{P}\mathcal{T}$-symmetric imaginary cubic oscillator are complete, but do not form a Riesz basis. This results in the existence of a bounded metric operator having intrinsic singularity reflected in the inevitable unboundedness of the inverse. Moreover, the existence of nontrivial pseudospectrum is observed. In other words, there is no quantum-mechanical Hamiltonian associated with it via bounded and boundedly invertible similarity transformations. These results open new directions in physical interpretation of $\mathcal{P}\mathcal{T}$-symmetric models with intrinsically singular metric, since their properties are essentially different with respect to self-adjoint Hamiltonians, for instance, due to spectral instabilities.

We apply a recently constructed model of analytic QCD in the operator product expansion (OPE) analysis of the $\tau$ lepton decay data in the $V+A$ channel. The model has the running coupling ${\mathcal{A}}_1(Q^2)$ with no unphysical singularities, i.e., it is analytic. It differs from the corresponding perturbative QCD coupling $a(Q^2)$ at high squared momenta $|Q^2|$ by terms $\propto (1/Q^2{)}^5$; hence it does not contradict the OPE philosophy of ITEP School (Institute of Theoretical and Experimental Physics) and can be consistently applied with OPE up to terms of dimension $D=8$. In evaluations for the Adler function we use a Padé-related renormalization-scale-independent resummation, applicable in any analytic QCD model. Applying the Borel sum rules in the $Q^2$ plane along rays of the complex Borel scale and comparing with ALEPH data of 1998, we obtain the gluon condensate value $⟨({\alpha }_s/\pi )G^2⟩=0.0055\pm 0.0047{\mathrm{GeV}}^4$. Consideration of the $D=6$ term gives us the result $⟨O_6^{(V+A)}⟩=(-0.5\pm 1.1)\times {10}^{-3}{\mathrm{GeV}}^6$, not incompatible with positive values. The real Borel transform then gives us, for the central values of the two condensates, a good agreement with the experimental results in the entire considered interval of the Borel scales $M^2$. In perturbative QCD in the minimal subtraction scheme we deduce similar results for the gluon condensate, $0.0059\pm 0.0049{\mathrm{GeV}}^4$, but the value of the $D=6$ condensate is negative, $⟨O_6^{(V+A)}⟩=(-1.8\pm 0.9)\times {10}^{-3}{\mathrm{GeV}}^6$, and the resulting real Borel transform for the central values is close to the lower bound of the experimental band.

High-luminosity experiments are able to search for new physics at low energies, which could have evaded detection thus far due to very weak couplings to the Standard Model. The DarkLight experiment at Jefferson Lab is designed to search for a new U(1) vector boson $A^{\prime }$ in the mass range 10–100 MeV through its decay $A^{\prime }\to e^{+}{e}^{-}$. In this paper, we demonstrate that DarkLight is also sensitive to an $A^{\prime }$ decaying to invisible final states. We analyze the DarkLight reach for invisible $A^{\prime }$ bosons assuming a nominal two month running time, including the possibility of augmenting the DarkLight design to include photon detection. We also propose two new analysis techniques that might prove useful for other high-luminosity searches: a cut on missing energy to improve the invariant mass resolution, and a cut on the sign of the missing invariant mass-squared to mitigate pileup. We compare the DarkLight reach to existing experimental proposals, including a complementary search using the VEPP-3 positron beam.