From continuum studies it is known that the Coulomb string tension ${\sigma }_C$ gives an upper bound for the physical (Wilson) string tension ${\sigma }_W$ [D. Zwanziger, Phys. Rev. Lett. 90, 102001 (2003)]. How does such a relationship translate to the lattice, however? In this paper we give evidence that on the lattice, while the two string tensions are related at zero temperature, they decouple at finite temperature. More precisely, we show that on the lattice the Coulomb gauge confinement scenario is always tied to the spatial string tension, which is known to survive the deconfinement phase transition and to cause screening effects in the quark-gluon plasma. Our analysis is based on the identification and elimination of center vortices, which allows us to control the physical string tension and study its effect on the Coulomb gauge observables. We also show how alternative definitions of the Coulomb potential may sense the deconfinement transition; however, a true static Coulomb gauge order parameter for the phase transition is still elusive on the lattice.

A new mechanism for the pion production in high energy reactions is suggested. It is related to a possibility for the direct production of the pions induced by instantons, topologically nontrivial gluonic excitations of the QCD vacuum. This mechanism does not require any fragmentation functions for the production of pseudoscalar mesons in high energy reactions with hadrons. We calculate the contribution of the new mechanism to the inclusive ${\pi }^0$-meson production in high energy proton-proton collisions. It is shown that it gives the dominant contribution to the inclusive cross sections in the few GeV region for the transverse momentum of the final pion with large rapidity. We discuss the possible applications of the new mechanism to the phenomenon of large spin effects observed in numerous high energy reactions and to particle productions in the relativistic heavy ion collisions.

We bridge the light-front (infinite momentum) and rest-frame descriptions of a heavy quarkonium, spanning them to any quarkonium momentum. For a relativistically moving system with nonrelativistic internal motion, a relation is established between the potentials describing a heavy quarkonium in the rest and moving reference frames. We explore two regimes: the small coupling and nonperturbative small binding energy approximations. In both cases a consistent picture emerges. The results, in particular, can be applied to the description of the final-state interaction of a heavy quarkonium produced in a nuclear or hot-matter environment. It can also be extended to the description of the final-state interaction of other weakly bound systems, like the deuteron.

We analyze within a nuclear database framework the shoulder observed in the antineutrino spectra in current reactor experiments. We find that the ENDF/B-VII.1 database predicts that the antineutrino shoulder arises from an analogous shoulder in the aggregate fission beta spectra. In contrast, the JEFF-3.1.1 database does not predict a shoulder for two out of three of the modern reactor neutrino experiments, and the shoulder that is predicted by JEFF-3.1.1 arises from ${}^{238}\mathrm{U}$. We consider several possible origins of the shoulder, and find possible explanations. For example, there could be a problem with the measured aggregate beta spectra, or the harder neutron spectrum at a light-water power reactor could affect the distribution of beta-decaying isotopes. In addition to the fissile actinides, we find that ${}^{238}\mathrm{U}$ could also play a significant role in distorting the total antineutrino spectrum. Distinguishing these and quantifying whether there is an anomaly associated with measured reactor neutrino signals will require new short-baseline experiments, both at thermal reactors and at reactors with a sizable epithermal neutron component.

This is a sequel to our previous work on LHC phenomenology of the type II seesaw model in the nondegenerate case. In this work, we further study the pair and associated production of the neutral scalars $H^0/A^0$. We restrict ourselves to the so-called negative scenario characterized by the mass order $M_{H^{\pm \pm }}>M_{H^{\pm }}>M_{H^0/A^0}$, in which the $H^0/A^0$ production receives significant enhancement from cascade decays of the charged scalars $H^{\pm \pm },H^{\pm }$. We consider three important signal channels—$b\overline{b}\gamma \gamma$, $b\overline{b}{\tau }^{+}{\tau }^{-}$, $b\overline{b}{\ell }^{+}{\ell }^{-}{\cancel{E}}_T$—and perform detailed simulations. We find that at the 14 TeV LHC with an integrated luminosity of $3000{\mathrm{fb}}^{-1}$, a $5\sigma$ mass reach of 151, 150, and 180 GeV, respectively, is possible in the three channels from the pure Drell-Yan $H^0{A}^0$ production, while the cascade-decay-enhanced $H^0/A^0$ production can push the mass limit further to 164, 177, and 200 GeV. The neutral scalars in the negative scenario are thus accessible at LHC run II.

A first search is reported for a standard model Higgs boson ($H$) that is produced through vector boson fusion and decays to a bottom-quark pair. Two data samples, corresponding to integrated luminosities of $19.8{\mathrm{fb}}^{-1}$ and $18.3{\mathrm{fb}}^{-1}$ of proton-proton collisions at $\sqrt{s}=8\mathrm{TeV}$ were selected for this channel at the CERN LHC. The observed significance in these data samples for a $H\to b\overline{b}$ signal at a mass of 125 GeV is 2.2 standard deviations, while the expected significance is 0.8 standard deviations. The fitted signal strength $\mu =\sigma /{\sigma }_{\mathrm{SM}}=2.8_{-1.4}^{+1.6}$. The combination of this result with other CMS searches for the Higgs boson decaying to a $b$-quark pair yields a signal strength of $1.0\pm 0.4$, corresponding to a signal significance of 2.6 standard deviations for a Higgs boson mass of 125 GeV.

We consider a family of exact boost invariant solutions of the transport equation for free-streaming massless particles, where the one-particle distribution function is defined in terms of a function of a single variable. The evolution of second and third moments of the one-particle distribution function [the second moment being the energy momentum tensor (EMT) and the third moment the nonequilibrium current (NEC)] depends only on two moments of that function. Given those two moments, we show how to build a nonlinear hydrodynamic theory which reproduces the early time evolution of the EMT and the NEC. The structure of these theories may give insight on nonlinear hydrodynamic phenomena on short time scales.

We report on the calculation of the threshold soft function for heavy quark pair production in $e^{+}{e}^{-}$ annihilation at two-loop order. Our main result is a generalization of the familiar Drell-Yan threshold soft function to the case of nonzero primary quark mass. We set up a framework based on the method of differential equations which allows for the straightforward calculation of the bare soft function to arbitrarily high orders in the dimensional regularization parameter. Remarkably, we find that we can obtain the bare two-loop Drell-Yan soft function from the heavy quark soft function to the order in epsilon required for a two-loop calculation by making simple replacements. We expect that our results will be of use, both as an important input for precision physics calculations at linear colliders and, more formally, as a first step toward a better understanding of the connection between vacuum matrix elements of massive soft Wilson lines and vacuum matrix elements of massless soft Wilson lines.

We give a consistent quantum description of time, based on Page and Wootters’s conditional probabilities mechanism, which overcomes the criticisms that were raised against similar previous proposals. In particular we show how the model allows one to reproduce the correct statistics of sequential measurements performed on a system at different times.

We construct the gauge invariant three-photon decay amplitude of particle-antiparticle bound states modeled by the Dyson-Schwinger and Bethe-Salpeter equations. Application to the quark-antiquark ($q\overline{q}$) bound states is emphasized. An essential aspect of our formulation is that it applies to any underlying quantum field theoretic model of the $q\overline{q}$ system, and not just to models, like exact QCD, where the quark self-energy $\mathrm{\Sigma }$ couples to the electromagnetic field solely via dressed quark propagators. In this way, applications to effective field theories and other QCD motivated models are envisioned. The three-photon decay amplitude is constructed by attaching currents to all possible places in the Feynman diagrams contributing to the dressed quark propagator. The gauge invariance of our construction is thus a direct consequence of respecting the underlying structure of the quantum field theory determining the dynamics. In the resultant expression for the three-photon decay amplitude, all the basic ingredients consisting of the bound-state wave function, the final-state interaction $q\overline{q}$ $t$ matrix, the dressed quark propagator, and dressed quark currents, are determined by a universal Bethe-Salpeter kernel.

We consider all perturbative radiative corrections to the total $e^{+}{e}^{-}$ annihilation cross section $R_{e^{+}{e}^{-}}$ showing how the renormalization group (RG) equation associated with the radiatively induced mass scale $\mu$ can be used to sum the logarithmic contributions in two ways. First of all, one can sum leading-log, next-to-leading-log, etc., contributions to $R_{e^{+}{e}^{-}}$ using in turn the one-loop, two-loop, etc., contributions to the RG function $\beta$. A second summation shows how all logarithmic corrections to $R_{e^{+}{e}^{-}}$ can be expressed entirely in terms of the log-independent contributions when one employs the full $\beta$-function. Next, using Stevenson’s characterization of any choice of renormalization scheme by the use of the contributions to the $\beta$-function arising beyond two-loop order, we examine the RG scheme dependence in $R_{e^{+}{e}^{-}}$ when using the second way of summing logarithms. The renormalization scheme invariants that arise are then related to the renormalization scheme invariants found by Stevenson. We next consider two choices of the renormalization scheme, one which can be used to express $R_{e^{+}{e}^{-}}$ solely in terms of two powers of a running coupling, and the second which can be used to express $R_{e^{+}{e}^{-}}$ as an infinite series in the two-loop running coupling (i.e., a Lambert $W$-function). In both cases, $R_{e^{+}{e}^{-}}$ is expressed solely in terms of renormalization scheme invariant parameters that are to be computed by a perturbative evaluation of $R_{e^{+}{e}^{-}}$. We then establish how in general the coupling constant arising in one renormalization scheme can be expressed as a power series of the coupling arising in any other scheme. We then establish how, by using a different renormalization mass scale at each order of perturbation theory, all renormalization scheme dependence can be absorbed into these mass scales when one uses the second way of summing logarithmic corrections to $R_{e^{+}{e}^{-}}$. We then employ the approach to renormalization scheme dependency that we have applied to $R_{e^{+}{e}^{-}}$ to a RG summed expression for the Coleman-Weinberg effective potential $V$ in a massless scalar model with quartic self-coupling, showing that the previously derived result that $V$ is independent of the background field $\varphi$ if $V^{\prime }(\varphi \ne 0)=0$ is renormalization scheme independent. The way in which Stevenson’s “principle of minimal sensitivity” can be applied to the RG summed form of $R_{e^{+}{e}^{-}}$ is then discussed. The significance of our results is considered in a concluding section.

We construct rotating boson stars in ($4+1$)-dimensional asymptotically anti–de Sitter space-time with two equal angular momenta that are composed out of a massive and self-interacting scalar field. These solutions possess a single Killing vector field. We construct explicit solutions of the equations in the case of a fixed anti–de Sitter background and vanishing self-coupling of the scalar field. These are the generalizations of the oscillons discussed previously in the literature, now taking the mass of the scalar field into account. We study the evolution of the spectrum of massive oscillons when taking backreaction and/or the self-coupling into account numerically. We observe that very compact boson stars possess an ergoregion.

This paper presents a new technique for achieving spectral accuracy and fast computational performance in a class of black hole perturbation and gravitational self-force calculations involving extreme mass ratios and generic orbits. Called spectral source integration (SSI), this method should see widespread future use in problems that entail (i) a point-particle description of the small compact object, (ii) frequency domain decomposition, and (iii) the use of the background eccentric geodesic motion. Frequency domain approaches are widely used in both perturbation theory flux-balance calculations and in local gravitational self-force calculations. Recent self-force calculations in Lorenz gauge, using the frequency domain and method of extended homogeneous solutions, have been able to accurately reach eccentricities as high as $e\simeq 0.7$. We show here SSI successfully applied to Lorenz gauge. In a double precision Lorenz gauge code, SSI enhances the accuracy of results and makes a factor of 3 improvement in the overall speed. The primary initial application of SSI—for us its the raison d’être—is in an arbitrary precision mathematica code that computes perturbations of eccentric orbits in the Regge–Wheeler gauge to extraordinarily high accuracy (e.g., 200 decimal places). These high-accuracy eccentric orbit calculations would not be possible without the exponential convergence of SSI. We believe the method will extend to work for inspirals on Kerr and will be the subject of a later publication. SSI borrows concepts from discrete-time signal processing and is used to calculate the mode normalization coefficients in perturbation theory via sums over modest numbers of points around an orbit. A variant of the idea is used to obtain spectral accuracy in a solution of the geodesic orbital motion.

The geometry of a spacetime containing a wormhole generated by a spherically symmetric electric field is investigated in detail. These solutions arise in high-energy extensions of general relativity formulated within the Palatini approach and coupled to Maxwell electrodynamics. Even though curvature divergences generically arise at the wormhole throat, we find that these spacetimes are geodesically complete. This provides an explicit example where curvature divergences do not imply spacetime singularities.

We obtain bounds on the stability of various self-gravitating astrophysical objects using a new measure of shape complexity known as configurational entropy. We apply the method to Newtonian polytropes, neutron stars with an Oppenheimer-Volkoff equation of state, and to self-gravitating configurations of complex scalar field (boson stars) with different self couplings, showing that the critical stability region of these stellar configurations obtained from traditional perturbation methods correlates well with critical points of the configurational entropy with accuracy of a few percent or better.

We study incomplete relaxation to quantum equilibrium at long wavelengths, during a preinflationary phase, as a possible explanation for the reported large-scale anomalies in the cosmic microwave background. Our scenario makes use of the de Broglie–Bohm pilot-wave formulation of quantum theory, in which the Born probability rule has a dynamical origin. The large-scale power deficit could arise from incomplete relaxation for the amplitudes of the primordial perturbations. We show, by numerical simulations for a spectator scalar field, that if the preinflationary era is radiation dominated then the deficit in the emerging power spectrum will have a characteristic shape (an inverse-tangent dependence on wave number $k$, with oscillations). It is found that our scenario is able to produce a power deficit in the observed region and of the observed (approximate) magnitude for an appropriate choice of cosmological parameters. We also discuss the large-scale anisotropy, which might arise from incomplete relaxation for the phases of the primordial perturbations. We present numerical simulations for phase relaxation, and we show how to define characteristic scales for amplitude and phase nonequilibrium. The extent to which the data might support our scenario is left as a question for future work. Our results suggest that we have a potentially viable model that might explain two apparently independent cosmic anomalies by means of a single mechanism.

We investigate the effects of a K-mouflage modification of gravity on the dynamics of clusters of galaxies. We extend the description of K-mouflage to situations where the scalar field responsible for the modification of gravity is coupled to a perfect fluid with pressure. We describe the coupled system at both the background cosmology and cosmological perturbations levels, focusing on cases where the pressure emanates from small-scale nonlinear physics. We derive these properties in both the Einstein and Jordan frames, as these two frames already differ by a few percents at the background level for K-mouflage scenarios, and next compute cluster properties in the Jordan frame that is better suited to these observations. Galaxy clusters are not screened by the K-mouflage mechanism and therefore feel the modification of gravity in a maximal way. This implies that the halo mass function deviates from $\mathrm{\Lambda }$-CDM by a factor of order 1 for masses $M\gtrsim {10}^{14}{h}^{-1}{M}_{\odot }$. We then consider the hydrostatic equilibrium of gases embedded in galaxy clusters and the consequences of K-mouflage on the x-ray cluster luminosity, the gas temperature, and the Sunyaev–Zel’dovich effect. We find that the cluster temperature function, and more generally number counts, are largely affected by K-mouflage, mainly due to the increased cluster abundance in these models. Other scaling relations such as the mass-temperature and the temperature-luminosity relations are only modified at the percent level due to the constraints on K-mouflage from local Solar System tests.

We introduce a new paradigm for dark matter (DM) interactions in which the interaction strength is asymptotically safe. In models of this type, the coupling strength is small at low energies but increases at higher energies, and asymptotically approaches a finite constant value. The resulting phenomenology of this “asymptotically safe DM” is quite distinct. One interesting effect of this is to partially offset the low-energy constraints from direct detection experiments without affecting thermal freeze-out processes which occur at higher energies. High-energy collider and indirect annihilation searches are the primary ways to constrain or discover safe dark matter.

Compact astrophysical objects are a window for the study of strongly interacting nuclear matter given the conditions in their interiors, which are not reproduced in a laboratory environment. Much has been debated about their composition with possibilities ranging from a simple mixture of mostly protons and neutrons to deconfined quark matter. Recent observations on the mass of two pulsars, PSR $\mathrm{J}1614-2230$ and PSR $\mathrm{J}0348+0432$, have posed a great restriction on their composition, since the equation of state must be hard enough to support masses of about at least two solar masses. The onset of quarks tends to soften the equation of state, but it can get substantially stiffer since in the high-dense medium a repulsive vector interaction channel is opened. Nevertheless, we show that once gluon effects are considered, the equation of state of strange stars formed by quark matter in the color-flavor-locked (CFL) phase of color superconductivity becomes softer decreasing the maximum stellar mass that can be reached. This may indicate that strange stars made entirely of CFL matter can only be favored if other interactions, as the one corresponding to the vector channel, are taken into consideration and are large enough.