Building upon our recent study [G. S. Bali et al., “Eur. Phys. J. C 78, 217 (2018)], we investigate the feasibility of calculating the pion distribution amplitude from suitably chosen Euclidean correlation functions at large momentum. We demonstrate in this work the advantage of analyzing several correlation functions simultaneously and extracting the pion distribution amplitude from a global fit. This approach also allows us to study higher-twist corrections, which are a major source of systematic error. Our result for the higher-twist parameter ${\delta }_2^{\pi }$ is in good agreement with estimates from QCD sum rules. Another novel element is the use of all-to-all propagators, calculated using stochastic estimators, which enables an additional volume average of the correlation functions, thereby reducing statistical errors.

We explore the recently observed ${\mathrm{\Xi }}_b(6227{)}^{-}$ resonance to fix its quantum numbers. To this end, we consider various possible scenarios: It can be considered as either a $1P$ or $2S$ excitation of the ${\mathrm{\Xi }}_b^{-}$ and ${\mathrm{\Xi }}_b^{\prime }(5935)$ ground-state baryons with spin-$\frac{1}{2}$ or the $1P$ or $2S$ excitation of the ground-state ${\mathrm{\Xi }}_b(5955)$ with spin-$\frac{3}{2}$. We calculate the masses of the possible angular-orbital $1P$ and $2S$ excited states corresponding to each channel employing the QCD sum rule technique. It is seen that all the obtained masses are in agreement with the experimentally observed value, implying that the mass calculations are not enough to determine the quantum numbers of the state under question. Therefore, we extend the analysis to investigate the possible decays of the excited states into ${\mathrm{\Lambda }}_b^0{K}^{-}$ and ${\mathrm{\Xi }}_b^{-}\pi$. Using the light cone QCD sum rule method, we calculate the corresponding strong coupling constants, which are used to extract the decay widths of the modes under consideration. Our results on decay widths indicate that the ${\mathrm{\Xi }}_b(6227{)}^{-}$ is a $1P$ angular-orbital excited state of the ${\mathrm{\Xi }}_b(5955)$ baryon with quantum numbers $J^P={\frac{3}{2}}^{-}$.

Results are reported from a search for long-lived particles in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ delivered by the CERN LHC and collected by the CMS experiment. The data sample, which was recorded during 2015 and 2016, corresponds to an integrated luminosity of $38.5{\mathrm{fb}}^{-1}$. This search uses benchmark signal models in which long-lived particles are pair-produced and each decays into two or more quarks, leading to a signal with multiple jets and two displaced vertices composed of many tracks. No events with two well-separated high-track-multiplicity vertices are observed. Upper limits are placed on models of $R$-parity violating supersymmetry in which the long-lived particles are neutralinos or gluinos decaying solely into multijet final states or top squarks decaying solely into dijet final states. For neutralino, gluino, or top squark masses between 800 and 2600 GeV and mean proper decay lengths between 1 and 40 mm, the analysis excludes cross sections above 0.3 fb at 95% confidence level. Gluino and top squark masses are excluded below 2200 and 1400 GeV, respectively, for mean proper decay lengths between 0.6 and 80 mm. A method is provided for extending the results to other models with pair-produced long-lived particles.

We show that second-generation gravitational-wave detectors at their design sensitivity will allow us to directly probe the ringdown phase of binary black hole coalescences. This opens the possibility to test the so-called black hole no-hair conjecture in a statistically rigorous way. Using state-of-the-art numerical relativity-tuned waveform models and dedicated methods to effectively isolate the quasistationary perturbative regime where a ringdown description is valid, we demonstrate the capability of measuring the physical parameters of the remnant black hole and subsequently determining parameterized deviations from the ringdown of Kerr black holes. By combining information from $\mathcal{O}(5)$ binary black hole mergers with realistic signal-to-noise ratios achievable with the current generation of detectors, the validity of the no-hair conjecture can be verified with an accuracy of $\sim 1.5\%$ at 90% confidence.

We revisit in the framework of the classical theory the problem of accelerated motion of an electron, taking into account the effect of radiation emission. We present results for the momentum and energy of the electromagnetic field of an accelerated electron for a spatial region excluding a vicinity of the electron and a procedure to compensate their singularities in the limit of the point electron. From them we infer expressions for the observables momentum and energy of the electron. They lead, together with those corresponding to the emitted radiation, to an equation of motion of the electron that coincides, in the case of an external electromagnetic field, with the Lorentz-Dirac equation. Based on the results for the linear momentum and using the same calculation method, we obtain the equations corresponding to the angular momentum of the electron and its field. While the formalism used is not wholly manifestly covariant, arguments based on relativistic covariance are invoked and used at appropriate places, where they play an essential role.

Calculations of $1\to N$ amplitudes in scalar field theories at very high multiplicities exhibit an extremely rapid growth with the number $N$ of final state particles. This either indicates an end of perturbative behavior, or possibly even a breakdown of the theory itself. It has recently been proposed that in the Standard Model this could even lead to a solution of the hierarchy problem in the form of a “Higgsplosion” [1]. To shed light on this question we consider the quantum mechanical analogue of the scattering amplitude for $N$ particle production in ${\varphi }^4$ scalar quantum field theory, which corresponds to transitions $⟨N|\widehat{x}|0⟩$ in the anharmonic oscillator with quartic coupling $\lambda$. We use recursion relations to calculate the $⟨N|\widehat{x}|0⟩$ amplitudes to high order in perturbation theory. Using this we provide evidence that the amplitude can be written as $⟨N|\widehat{x}|0⟩\sim \exp (F(\lambda N)/\lambda )$ in the limit of large $N$ and $\lambda N$ fixed. We go beyond the leading order and provide a systematic expansion in powers of $1/N$. We then resum the perturbative results and investigate the behavior of the amplitude in the region where tree-level perturbation theory violates unitarity constraints. The resummed amplitudes are in line with unitarity as well as stronger constraints derived by Bachas [2]. We generalize our result to arbitrary states and powers of local operators $⟨N|{\widehat{x}}^q|M⟩$ and confirm that, to exponential accuracy, amplitudes in the large $N$ limit are independent of the explicit form of the local operator, i.e., in our case $q$.

New extended interpolating operators made of quenched three-dimensional fermions are introduced in the context of lattice QCD. The mass of the 3D fermions can be tuned in a controlled way to find a better overlap of the extended operators with the states of interest. The extended operators have good renormalization properties and are easy to control when taking the continuum limit. Moreover, the short distance behavior of the two point functions built from these operators is greatly improved with respect to Jacobi smeared sources and point sources. A numerical comparison with point sources and Jacobi smeared sources on dynamical $2+1$ flavor configurations is presented.

We report searches for the processes $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0{\chi }_{bJ}$ and $e^{+}{e}^{-}\to \varphi {\chi }_{bJ}$ ($\mathrm{J}=1$, 2) based on data samples collected by the Belle experiment at the KEKB collider. We report the first observation of the process $e^{+}{e}^{-}\to ({\pi }^{+}{\pi }^{-}{\pi }^0{)}_{\mathrm{non}-\omega }{\chi }_{b1}$ and first evidence for $e^{+}{e}^{-}\to \omega {\chi }_{bJ}$ in the vicinity of the $\mathrm{\Upsilon }(11020)$ resonance, with center-of-mass energies from 10.96 to 11.05 GeV. The significances for $({\pi }^{+}{\pi }^{-}{\pi }^0{)}_{\mathrm{non}-\omega }{\chi }_{b1}$ and $\omega {\chi }_{bJ}$ are greater than $5.3\sigma$ and $4.0\sigma$, respectively. We also investigate the energy dependence of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0{\chi }_{bJ}$ cross section, but we cannot determine whether the contributions are from the $\mathrm{\Upsilon }(10860)$ and $\mathrm{\Upsilon }(11020)$ resonances or nonresonant continuum processes. The signals for $e^{+}{e}^{-}\to \varphi {\chi }_{bJ}$ are not significant, and the upper limits of the Born cross sections at the 90% confidence level are 0.7 and 1.0 pb for $e^{+}{e}^{-}\to \varphi {\chi }_{b1}$ and $\varphi {\chi }_{b2}$, respectively, for center-of-mass energies from 10.96 to 11.05 GeV.

We apply the relation between deep learning (DL) and the $\mathrm{AdS}/\mathrm{CFT}$ correspondence to a holographic model of QCD. Using lattice QCD data of the chiral condensate at a finite temperature as our training data, the deep learning procedure holographically determines an emergent bulk metric as neural network weights. The emergent bulk metric is found to have both a black hole horizon and a finite-height IR wall, so it shares both the confining and the deconfining phases, signaling the crossover thermal phase transition of QCD. In fact, a quark-antiquark potential holographically calculated by the emergent bulk metric turns out to possess both the linear confining part and the Debye screening part, as is often observed in lattice QCD. From this we argue the discrepancy between the chiral symmetry breaking and the quark confinement in the holographic QCD. The DL method is shown to provide a novel data-driven holographic modeling of QCD, and sheds light on the mechanism of emergence of the bulk geometries in the $\mathrm{AdS}/\mathrm{CFT}$ correspondence.

We study the $O(N{)}^3$ symmetric quantum field theory of a bosonic tensor ${\varphi }^{abc}$ with sextic interactions. Its large $N$ limit is dominated by a positive-definite operator, whose index structure has the topology of a prism. We present a large $N$ solution of the model using Schwinger-Dyson equations to sum the leading diagrams, finding that for $2.81<d<3$ and for $d<1.68$ the spectrum of bilinear operators has no complex scaling dimensions. We also develop perturbation theory in $3-\epsilon$ dimensions including eight $O(N{)}^3$ invariant operators necessary for the renormalizability. For sufficiently large $N$, we find a “prismatic” fixed point of the renormalization group, where all eight coupling constants are real. The large $N$ limit of the resulting $\epsilon$ expansions of various operator dimensions agrees with the Schwinger-Dyson equations. Furthermore, the $\epsilon$ expansion allows us to calculate the $1/N$ corrections to operator dimensions. The prismatic fixed point in $3-\epsilon$ dimensions survives down to $N\approx 53.65$, where it merges with another fixed point and becomes complex. We also discuss the $d=1$ model where our approach gives a slightly negative scaling dimension for $\varphi$, while the spectrum of bilinear operators is free of complex dimensions.

We show how to systematically apply the Faddeev-Jackiw symplectic method to general relativity (GR) and to GR extensions. This provides a new coherent frame for Hamiltonian analyses of gravitational theories. The emphasis is on the classical dynamics, uncovering the constraints, the gauge transformations and the number of degrees of freedom; but the method results are also relevant for canonical quantization approaches. We illustrate the method with three applications: GR and to two Brans-Dicke cases (the standard case $\omega \ne -3/2$ and the case with one less degree of freedom, $\omega =-3/2$). We clarify subtleties of the symplectic approach and comment on previous symplectic-based Hamiltonian analyses of extended theories of gravity, pointing out that the present approach is systematic, complete and robust.

We analyze the electromagnetic-gravity interaction in a pure Hořava-Lifshitz framework. To do so we formulate the Hořava-Lifshitz gravity in $4+1$ dimensions and perform a Kaluza-Klein reduction to $3+1$ dimensions. We use this reduction as a mathematical procedure to obtain the $3+1$ coupled theory, which at the end is considered as a fundamental, self-consistent theory. The critical value of the dimensionless coupling constant in the kinetic term of the action is $\lambda =1/4$. It is the kinetic conformal point for the nonrelativistic electromagnetic-gravity interaction. In distinction, the corresponding kinetic conformal value for pure Hořava-Lifshitz gravity in $3+1$ dimensions is $\lambda =1/3$. We analyze the geometrical structure of the critical and noncritical cases, they correspond to different theories. The physical degrees of freedom propagated by the noncritical theory are the transverse traceless graviton, the transverse gauge vector and two scalar fields. In the critical theory one of the scalars is absent, only the dilaton scalar field is present. The gravity and vector excitations propagate with the same speed, which at low energy can be taken to be the speed of light. The field equations for the gauge vector in the nonrelativistic theory have exactly the same form as the relativistic electromagnetic field equations arising from the Kaluza-Klein reduction of general relativity, and are equal to them for a particular value of one of the coupling constants. The potential in the Hamiltonian is a polynomial of finite degree in the gauge vector and its covariant derivatives.

The gravitational waves of Hořava gravity, their polarization states, and their possible observational signatures are discussed. Using the gauge-invariant variable formalism, we find the three polarization modes in Hořava gravity excited by the three physical degrees of freedom contained in this theory. In particular, the scalar degree of freedom excites a mix of the transverse breathing and the longitudinal polarizations. The constraints from the previous experimental observations are taken into account, especially including the speed bound from the observations of GW170817 and GRB 170817A. We find that the Hořava theory is highly constrained. Within the experimentally allowed parametric space, we study whether the pulsar timing arrays and the Gaia mission can be used to distinguish the different polarizations. After calculating the cross-correlation functions between the redshifts of photons and the astrometric positions of stars, we conclude that it is possible to use pulsar timing arrays and the Gaia mission to tell whether the scalar polarization exists.

A nonlinear equation obtained by adding gravitational self-interaction terms to the Poisson equation for Newtonian gravity is here employed in order to analyze a static spherically symmetric homogeneous compact source of given proper mass and radius and the outer vacuum. The main feature of this picture is that, although the freedom of shifting the potential by an arbitrary constant is of course lost, the solutions remain qualitatively very close to the Newtonian behavior. We also notice that the negative gravitational potential energy is smaller than the proper mass for sources with small compactness, but for sources that should form black holes according to general relativity, the gravitational potential energy becomes of the same order of magnitude of the proper mass, or even larger. Moreover, the pressure overcomes the energy density for large values of the compactness, but it remains finite for finite compactness; hence there exists no Buchdahl limit. This classical description is meant to serve as the starting point for investigating quantum features of (near) black hole configurations within the corpuscular picture of gravity in future developments.

We consider a new variant of cosmological perturbation theory that has been designed specifically to include nonlinear density contrasts on scales $\lesssim 100\mathrm{Mpc}$, while still allowing for linear fluctuations on larger scales. This theory is used to derive the relativistic equations of Eulerian hydrodynamics in realistic cosmological scenarios that contain radiation and a cosmological constant, as well as matter that has been allowed to clump into galaxies and clusters of galaxies. These equations can be used to evolve energy densities and velocities in the presences of small-scale nonlinear structures, and on scales all the way up to the horizon and beyond. The leading-order part of these equations reproduces the expected Newtonian equations, while subsequent orders prescribe relativistic corrections. We demonstrate that these evolution equations are consistent with maintaining the Einstein constraints, and hence that the system as a whole is mathematically well posed. The relativistic corrections that we derive are found to exhibit nontrivial interactions between perturbations on different scales, as well as the mixing of scalar, vector and tensor modes. They deviate from those that occur in both post-Friedmann and standard cosmological perturbation theory approaches, and point towards new relativistic effects that could be measurable by upcoming ultra-large-scale surveys.

We study the impact on the galaxy correlation function of the presence of a vector component in the tracers’ peculiar velocities, in the case in which statistical isotropy is violated. We present a general framework—based on the bipolar spherical harmonics expansion—to study this effect in a model independent way, without any hypothesis on the origin or the properties of these vector modes. We construct six new observables, that can be directly measured in galaxy catalogs in addition to the standard monopole, quadrupole, and hexadecapole, and we show that they completely describe any deviations from isotropy. We then perform a Fisher analysis in order to quantify the constraining power of future galaxy surveys. For an example, we show that the SKA2 would be able to detect anisotropic rotational velocities with amplitudes as low as 1% of that of the vorticity generated during shell crossing in standard dark matter scenarios.

We construct a no-scale model of inflation with a single modulus whose real and imaginary parts are fixed by simple power-law corrections to the no-scale Kähler potential. Assuming an uplift of the minimum of the effective potential, the model yields a suitable number of $e$-folds of expansion and values of the tilt in the scalar cosmological density perturbations and of the ratio of tensor and scalar perturbations that are compatible with measurements of the cosmic microwave background radiation.

We present a covariant ray tracing algorithm for computing high-resolution neutrino distributions in general relativistic numerical spacetimes with hydrodynamical sources. Our formulation treats the very important effect of elastic scattering of neutrinos off of nuclei and nucleons (changing the neutrino’s direction but not energy) by incorporating estimates of the background neutrino fields. Background fields provide information about the spectra and intensities of the neutrinos scattered into each ray. These background fields may be taken from a low-order moment simulation or be ignored, in which case the method reduces to a standard state-of-the-art ray tracing formulation. The method handles radiation in regimes spanning optically thick to optically thin. We test the new code, highlight its strengths and weaknesses, and apply it to a simulation of a neutron-star merger to compute neutrino fluxes and spectra, and to demonstrate a neutrino flavor oscillation calculation. In that environment, we find qualitatively different fluxes, spectra, and oscillation behaviors when elastic scattering is included.

The Space Technology 7 Disturbance Reduction System (ST7-DRS) is a NASA technology demonstration payload that operated from January 2016 through July 2017 on the European Space Agency’s (ESA) LISA Pathfinder spacecraft. The joint goal of the NASA and ESA missions was to validate key technologies for a future space-based gravitational wave observatory targeting the source-rich millihertz band. The two primary components of ST7-DRS are a micropropulsion system based on colloidal micro-Newton thrusters (CMNTs) and a control system that simultaneously controls the attitude and position of the spacecraft and the two free-flying test masses (TMs). This paper presents our main experimental results and summarizes the overall performance of the CMNTs and control laws. We find the CMNT performance to be consistent with preflight predictions, with a measured system thrust noise on the order of $100\mathrm{nN}/\sqrt{\mathrm{Hz}}$ in the $1\mathrm{mHz}\le f\le 30\mathrm{mHz}$ band. The control system maintained the TM-spacecraft separation with an RMS error of less than 2 nm and a noise spectral density of less than $3\mathrm{nm}/\sqrt{\mathrm{Hz}}$ in the same band. Thruster calibration measurements yield thrust values consistent with the performance model and ground-based thrust-stand measurements, to within a few percent. We also report a differential acceleration noise between the two test masses with a spectral density of roughly $3\mathrm{fm}/{\mathrm{s}}^2/\sqrt{\mathrm{Hz}}$ in the $1\mathrm{mHz}\le f\le 30\mathrm{mHz}$ band, slightly less than twice as large as the best performance reported with the baseline LISA Pathfinder configuration and below the current requirements for the Laser Interferometer Space Antenna mission.