We investigate the low-order Green’s functions of $SU(N)$ Yang-Mills theory in Landau gauge, using a covariant variational principle based on the effective action formalism. Employing an approximation to the Faddeev-Popov determinant established previously in the Hamiltonian approach in Coulomb gauge leads to a closed set of integral equations for the ghost and gluon propagator. We carry out the renormalization and the infrared analysis of this system of equations. Finally, we solve the renormalized system numerically and compare with lattice results and other functional approaches.

We present and discuss explicit solutions to the non-Abelian self-dual string equation as well as to the non-Abelian self-duality equation in six dimensions. These solutions are generalizations of the ’t Hooft–Polyakov monopole and the basic SU(2) instanton to higher gauge theory. We expect that these solutions are relevant to the effective description of M2- and M5-branes.

A shortcoming of current binary black-hole initial data is the generation of spurious gravitational radiation, so-called junk radiation, when they are evolved. This problem is a consequence of an oversimplified modeling of the binary’s physics in the initial data. Since junk radiation is not astrophysically realistic, it contaminates the actual waveforms of interest and poses a numerical nuisance. The work here presents a further step towards mitigating and understanding the origin of this issue by incorporating post-Newtonian results in the construction of constraint-satisfying binary black-hole initial data. Here, we focus on including realistic tidal deformations of the black holes in the initial data by building on the method of superposing suitably chosen black-hole metrics to compute the conformal data. We describe the details of our initial data for an equal-mass and nonspinning binary, compute the subsequent relaxation of horizon quantities in evolutions, and quantify the amount of junk radiation that is generated. These results are contrasted with those obtained with the most common choice of conformally flat (CF) initial data, as well as superposed Kerr-Schild (SKS) initial data. We find that when realistic tidal deformations are included, the early transients in the horizon geometries are significantly reduced, along with smaller deviations in the relaxed black-hole masses and spins from their starting values. Likewise, the junk radiation content in the $l=2$ modes is reduced by a factor of $\sim 1.7$ relative to CF initial data, but only by a factor of $\sim 1.2$ relative to SKS initial data. More prominently, the junk radiation content in the $3\le l\le 8$ modes is reduced by a factor of $\sim 5$ relative to CF initial data, and by a factor of $\sim 2.4$ relative to SKS initial data.

Violating Lorentz invariance, and so implicitly permitting some form of super-luminal communication, necessarily alters the notion of a black hole. Nevertheless, in both Einstein-æther gravity and Hořava-Lifshitz gravity, there is still a causally disconnected region in black-hole solutions, now being bounded by a “universal horizon,” which traps excitations of arbitrarily high velocities. To better understand the nature of these black holes, and their universal horizons, we study ray trajectories in these spacetimes. We find evidence that Hawking radiation is associated with the universal horizon, while the “lingering” of ray trajectories near the Killing horizon hints at reprocessing there. In doing this we solve an apparent discrepancy between the surface gravity of the universal horizon and the associated temperature derived by the tunneling method. These results advance the understanding of these exotic horizons and provide hints for a full understanding of black-hole thermodynamics in Lorentz-violating theories.

We complete the analytical determination, at the 4th post-Newtonian (4PN) approximation, of the conservative dynamics of gravitationally interacting two-point-mass systems. This completion is obtained by resolving the infra-red ambiguity which had blocked a previous 4PN calculation [P. Jaranowski and G. Schäfer, Phys. Rev. D 87, 081503(R) (2013)] by taking into account the 4PN breakdown of the usual near-zone expansion due to infinite-range tail-transported temporal correlations found long ago [L. Blanchet and T. Damour, Phys. Rev. D 37, 1410 (1988)]. This leads to a Poincaré-invariant 4PN-accurate effective action for two masses, which mixes instantaneous interaction terms (described by a usual Hamiltonian) with a (time-symmetric) nonlocal-in-time interaction.

In this paper, we present a complete Noether symmetry analysis in the framework of scalar-tensor cosmology. Specifically, we consider a nonminimally coupled scalar field action embedded in the Friedmann-Lemaître-Robertson-Walker spacetime and provide a full set of Noether symmetries for related minisuperspaces. The presence of symmetries implies that the dynamical system becomes integrable and then we can compute cosmological analytical solutions for specific functional forms of coupling and potential functions selected by the Noether approach.

Although theoretically expected to be statistically isotropic (SI), the observed cosmic microwave background (CMB) temperature and polarization field would exhibit SI violation due to various inevitable effects like weak lensing, Doppler boost, and practical limitations of observations like noncircular beam, masking, etc. However, the presence of any SI violation beyond these effects may lead to a discovery of inherent cosmic SI violation in the CMB temperature and polarization field. Recently, Planck presented strong evidence of SI violation as a dipolar power asymmetry of the CMB temperature field in two hemispheres. Statistical studies of SI violation effect require non-SI (nSI) Gaussian realizations of the CMB temperature field. The nSI Gaussian temperature field leads to nonzero off-diagonal terms in the spherical harmonics (SH) space covariance matrix encoded in the coefficients of the bipolar spherical harmonics (BipoSH) representation. We discuss an effective numerical algorithm, code for nonisotropic Gaussian sky (CoNIGS) to generate nSI realizations of the Gaussian CMB temperature field of Planck-like resolution with specific cases of SI violation. Realizations of nSI CMB temperature field are obtained for nonzero quadrupolar ($L=2$) BipoSH measurements by WMAP, dipolar asymmetry (resembles $L=1$ BipoSH coefficients) with a scale-dependent modulation field as measured by Planck and for Doppler-boosted CMB temperature field which also leads to $L=1$ BipoSH spectra. Our method, CoNIGS can incorporate any kind of SI violation and can produce nSI realizations efficiently.

We model the observed $J^{++}$ mesonic mass spectrum in terms of energies for tightly knotted and linked chromoelectric QCD flux tubes. The data is fit with one- and two-parameter models. We predict a possible new state at approximately 1190 MeV and a plethora of new states above 1690 MeV.

We calculate the Sivers function in semi-inclusive deep inelastic scattering (SIDIS) and in the Drell-Yan process (DY) by employing the quasiclassical Glauber-Mueller/McLerran-Venugopalan approximation. Modeling the hadron as a large “nucleus” with nonzero orbital angular momentum (OAM), we find that its Sivers function receives two dominant contributions: one contribution is due to the OAM, while another one is due to the local Sivers function density in the nucleus. While the latter mechanism, being due to the “lensing” interactions, dominates at large transverse momentum of the produced hadron in SIDIS or of the dilepton pair in DY, the former (OAM) mechanism is leading in saturation power counting and dominates when the above transverse momenta become of the order of the saturation scale. We show that the OAM channel allows for a particularly simple and intuitive interpretation of the celebrated sign flip between the Sivers functions in SIDIS and DY.

We present an analysis of the lowest-lying decuplet baryon masses in the covariant baryon chiral perturbation theory with the extended-on-mass-shell scheme up to next-to-next-to-next-to-leading order. In order to determine the 14 low-energy constants, we perform a simultaneous fit of the $n_f=2+1$ lattice QCD data from the PACS-CS, QCDSF-UKQCD, and HSC Collaborations, taking finite-volume corrections into account self-consistently. We show that up to next-to-next-to-next-to-leading order one can achieve a good description of the lattice QCD and experimental data. Surprisingly, we note that the current lattice decuplet baryon masses can be fitted rather well by the next-to-leading order baryon chiral perturbation theory, which, however, misses the experimental data a little bit. Furthermore, we predict the pion- and strangeness-sigma terms of the decuplet baryons by use of the Feynman-Hellmann theorem.

From the matching of soft-wall AdS/QCD and light-front QCD for electromagnetic form factors of hadrons with arbitrary twist, we derive an effective light-front wave function (LFWF). The scale at which such matching is performed is set as an initial scale. Together with the LFWF, we also obtain expressions for parton distribution functions (PDFs) and generalized parton distributions (GPDs) at this scale. Doing the hard evolution of PDFs and GPDs, we show that these quantities obey model-independent constraints imposed, e.g., by the Drell-Yan-West duality at large $x$ and large scales, while the hadronic form factors at large momenta are in full agreement with quark counting rules. We finally propose a phenomenological light-front wave function for hadrons with arbitrary twist dimension (mesons, baryons, and multiquark states). It explicitly depends on the scale. The wave function evolves from the expression at the initial scale predicted by soft-wall AdS/QCD to high scales, where it gives the correct scaling behavior of PDFs, GPDs, and form factors for both pions and nucleons. For other hadronic states, the proposed wave function produces form factors consistent with quark counting rules and gives predictions for parton distributions. As an application, we build a light-front quark model for nucleons based on the proposed wave function.

Both neutrino and antineutrino charged-current quasielastic scattering on a carbon target are studied to investigate the nuclear effect on the determination of the axial form factor $F_A(Q^2)$. A method for extraction of $F_A(Q^2)$ from the flux-integrated $d\sigma /d{Q}^2$ cross section of (anti)neutrino scattering on nuclei is presented. Data from the MiniBooNE experiment are analyzed in the relativistic distorted-wave impulse approximation, the Fermi gas model, and the Fermi gas model with enhancements in the transverse cross section. We found that the values of the axial form factor, extracted in the impulse approximation and predicted by the dipole approximation with the axial mass $M_A\approx 1.37\mathrm{GeV}$, are in good agreement. The agreement between the extracted form factor and meson-dominance ansatz also is good. On the other hand, the $Q^2$ dependence of $F_A$ extracted in the approach with the transverse enhancement is found to differ significantly from the dipole approximation.

We compute the entanglement entropy and mutual information for two disjoint intervals in two-dimensional conformal field theories as a function of time after a local quench, using the replica trick and boundary conformal field theory. We obtain explicit formulas for the universal contributions, which are leading in the regimes of, for example, close or well-separated intervals of fixed length. The results are largely consistent with the quasiparticle picture, in which entanglement above that present in the ground state is carried by pairs of entangled freely propagating excitations. We also calculate the mutual information for two disjoint intervals in a proposed holographic local quench, whose holographic energy-momentum tensor matches the conformal field theory one. We find that the holographic mutual information shows qualitative differences from the conformal field theory results and we discuss possible interpretations of this.

We reconsider the quantum vacuum interaction energy between two straight parallel cosmic strings. This problem was discussed several times in an approach treating both strings perturbatively and treating only one perturbatively. Here we point out that a simplifying assumption made by Bordag [Ann. Phys. (Berlin) 47, 93 (1990).] can be justified and show that, despite the global character of the background, the perturbative approach delivers a correct result. We consider the applicability of the scattering methods, developed in the past decade for the Casimir effect, for the cosmic string and find it not applicable. We calculate the scattering $T$-operator on one string. Finally, we consider the vacuum interaction of two strings when each carries a two-dimensional delta function potential.

We report on simulations in general relativity of magnetized disks accreting onto black hole binaries. We vary the binary mass ratio from 1:1 to 1:10 and evolve the systems when they orbit near the binary-disk decoupling radius. We compare (surface) density profiles, accretion rates (relative to a single, nonspinning black hole), variability, effective $\alpha$-stress levels and luminosities as functions of the mass ratio. We treat the disks in two limiting regimes: rapid radiative cooling and no radiative cooling. The magnetic field lines clearly reveal jets emerging from both black hole horizons and merging into one common jet at large distances. The magnetic fields give rise to much stronger shock heating than the pure hydrodynamic flows, completely alter the disk structure, and boost accretion rates and luminosities. Accretion streams near the horizons are among the densest structures; in fact, the 1:10 no-cooling evolution results in a refilling of the cavity. The typical effective temperature in the bulk of the disk is $\sim 10^5(M/10^8{M}_{\odot }{)}^{-1/4}(L/L_{\text{edd}}{)}^{1/4}\mathrm{K}$ yielding characteristic thermal frequencies $\sim 10^{15}(M/10^8{M}_{\odot }{)}^{-1/4}(L/L_{\text{edd}}{)}^{1/4}(1+z{)}^{-1}\mathrm{Hz}$. These systems are thus promising targets for many extragalactic optical surveys, such as the LSST, WFIRST, and PanSTARRS.

We present a framework for discussing the cosmology of dark energy and dark matter based on two scalar degrees of freedom. An effective field theory of cosmological perturbations is employed. A unitary gauge choice renders the dark energy field into the gravitational sector, for which we adopt a generic Lagrangian depending on three-dimensional geometrical scalar quantities arising in the Arnowitt-Deser-Misner decomposition. We add to this dark energy–associated gravitational sector a scalar field $\varphi$ and its kinetic energy $X$ as dark matter variables. Compared to the single-field case, we find that there are additional conditions to obey in order to keep the equations of motion for linear cosmological perturbations at second order. For such a second-order multifield theory, we derive conditions under which ghosts and Laplacian instabilities of the scalar and tensor perturbations are absent. We apply our general results to models with dark energy emerging in the framework of the Horndeski theory and dark matter described by a $k$-essence Lagrangian $P(\varphi ,X)$. We derive the effective coupling between such an imperfect-fluid dark matter and the gravitational sector under the quasistatic approximation on subhorizon scales. By considering the purely kinetic Lagrangian $P(X)$ as a particular case, the formalism is verified to reproduce the gravitational coupling of a perfect-fluid dark matter.

Observations of diffuse Galactic gamma ray emission (DGE) by the Fermi Large Area Telescope (LAT) allow a detailed study of cosmic rays and the interstellar medium. However, diffuse emission models of the inner Galaxy underpredict the Fermi-LAT data at energies above a few GeV and hint at possible nonastrophysical sources including dark matter (DM) annihilations or decays. We present a study of the possible emission components from DM using the high-resolution Via Lactea II N-body simulation of a Milky Way—sized DM halo. We generate full-sky maps of DM annihilation and decay signals that include modeling of the adiabatic contraction of the host density profile, Sommerfeld-enhanced DM annihilations, $p$-wave annihilations, and decaying DM. We compare our results with the DGE models produced by the Fermi-LAT team over different sky regions, including the Galactic center, high Galactic latitudes, and the Galactic anticenter. This work provides possible smooth component templates of DM to fit the observational data. The subhalo contributions can be considered to provide statistically meaningful templates and demonstrate how spatial profiles are significantly modified according to different annihilation or decay scenarios. We argue that a subhalo-based approach can help constrain the DM physics.

We propose a new scenario for early cosmology, where inflationary de Sitter phase dynamically occurs. The effect emerges as a result of dynamics of the topologically nontrivial sectors in the expanding Universe. Technically the effect can be described in terms of the auxiliary fields that effectively describe the dynamics of the topological sectors in a gauge theory. Inflaton in this framework is an auxiliary topological nonpropagating field with no canonical kinetic term, similar to known topologically ordered phases in condensed matter systems. We explain many deep questions in this framework using the so-called weakly coupled “deformed QCD” toy model. While this theory is a weakly coupled gauge theory, it preserves all the crucial elements of strongly interacting gauge theory, including confinement, nontrivial $\theta$ dependence, degeneracy of the topological sectors, etc. We discuss a specific realization of these ideas using a scaled up version of QCD, coined as $\overline{\mathrm{QCD}}$, with the scale $M_{PL}\gg {\mathrm{\Lambda }}_{\overline{\mathrm{QCD}}}\gg \sqrt[3]{M_{EW}^2{M}_{PL}}\sim 10^8\mathrm{GeV}$. If no other fields are present in the system, de Sitter phase will be the final destination of evolution of the Universe. If other interactions are present in the system, the inflationary de Sitter phase lasts for a finite period of time. The inflation starts from the thermal equilibrium state long after the $\overline{\mathrm{QCD}}$-confinement phase transition at temperature $T_i\sim {\mathrm{\Lambda }}_{\overline{\mathrm{QCD}}}\sqrt{\frac{{\mathrm{\Lambda }}_{\overline{\mathrm{QCD}}}}{M_{PL}}}$. The end of inflation is triggered by the coupling with gauge bosons from the standard model. The corresponding interaction is unambiguously fixed by the triangle anomaly. The number of e-folds in the $\overline{\mathrm{QCD}}$-inflation framework is determined by the gauge coupling constant at the moment of inflation, and estimated as $N_{\text{inf}}\sim {\alpha }_s^{-2}\sim 10^2$.

We introduce here a cross-correlation term between CMB lensing and galaxy intrinsic alignment, noted here as $\varphi I$. This effect acts as a contaminant to the cross correlation between CMB lensing and galaxy lensing. The latter cross correlation has recently been detected for the first time, and measurements will greatly improve as the area of overlap between galaxy and CMB surveys increases and measurements of the CMB polarization become more significant. This will constitute a powerful probe for studying the structure and evolution of the universe. The magnitude of the $\varphi I$ term is found to be about 15% of the pure CMB lensing-galaxy lensing component and acts to reduce the magnitude of its measured spectrum. This offset in the spectrum will strongly impact its use for precision cosmological study if left unmitigated. We also propose here a method to calibrate this $\varphi I$ contamination through the use of a scaling relation that allows one to reduce the impact of $\varphi I$ by a factor of 20 or more in all redshift bins, which would reduce its magnitude down to detection limits in almost all cases. This will allow the full use of this probe for precision cosmology.

The problem of searching for unmodeled gravitational-wave bursts can be thought of as a pattern recognition problem: how to find statistically significant clusters in spectrograms of strain power when the precise signal morphology is unknown. In a previous publication, we showed how “seedless clustering” can be used to dramatically improve the sensitivity of searches for long-lived ($\sim 10–1000\mathrm{s}$) gravitational-wave transients. To manage the computational costs, this initial analysis focused on externally triggered searches where the source location and emission time are both known to some degree of precision. In this paper, we show how the principle of seedless clustering can be extended to facilitate computationally feasible, all-sky searches where the direction and emission time of the source are entirely unknown. We further demonstrate that it is possible to achieve a considerable reduction in computation time by using graphical processor units, thereby facilitating more sensitive searches.