Lattice field theories with a complex action can be studied numerically by allowing a complexified configuration space to be explored. Here we compare the recently introduced formulation on a Lefschetz thimble with the result from stochastic quantization (or complex Langevin dynamics) in the case of a simple model and contrast the distributions being sampled. We also study the role of the residual phase on the Lefschetz thimble.

We calculate the magnetic moments of low-lying heavy-flavor bottom baryons using effective quark mass and shielded quark charge scheme. We obtain the magnetic moments of both $J^P=\frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{+}}{}$ and $J^P=\frac{3}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{+}}{}$ baryon states. We compare our predictions with other theoretical approaches.

The processes with oppositely charged spinor particles in initial and/or final states in homogeneous magnetic field $B$ are subject to focusing effects in their relative motion, which yield the amplifying factors in probabilities growing as $eB$. In addition the increasing energy of some Landau levels influences the phase space. As a result, some processes in the proper spin states can be enlarged as $\sim \frac{eB}{{\kappa }^2}$, where ${\kappa }^2$ is the characteristic phase space factor available for perpendicular to $\mathbf{B}$ motion. Several examples, including neutron $\beta$ decay, positronium decay, and $e^{+}{e}^{-}$ pair production, are quantitatively considered.

We present a comprehensive analysis of inclusive $W(\to e\nu )+n\mathrm{\text{-jet}}$ ($n\ge 1$, 2, 3, 4) production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Tevatron collider using a $3.7{\mathrm{fb}}^{-1}$ data set collected by the D0 detector. Differential cross sections are presented as a function of the jet rapidities ($y$), lepton transverse momentum ($p_T$) and pseudorapidity ($\eta$), the scalar sum of the transverse energies of the $W$ boson and all jets ($H_T$), leading dijet $p_T$ and invariant mass, dijet rapidity separations for a variety of jet pairings for $p_T$-ordered and angular-ordered jets, dijet opening angle, dijet azimuthal angular separations for $p_T$-ordered and angular-ordered jets, and $W$ boson transverse momentum. The mean number of jets in an event containing a $W$ boson is measured as a function of $H_T$, and as a function of the rapidity separations between the two highest-$p_T$ jets and between the most widely separated jets in rapidity. Finally, the probability for third-jet emission in events containing a $W$ boson and at least two jets is studied by measuring the fraction of events in the inclusive $W+2\mathrm{\text{-jet}}$ sample that contain a third jet over a $p_T$ threshold. The analysis employs a regularized singular value decomposition technique to accurately correct for detector effects and for the presence of backgrounds. The corrected data are compared to particle level next-to-leading-order perturbative QCD predictions, predictions from all-order resummation approaches, and a variety of leading-order and matrix element plus parton shower event generators. Regions of the phase space where there is agreement or disagreement with the data are discussed for the different models tested.

We introduce dissipative effects in the effective field theory of hydrodynamics. We do this in a model-independent fashion by coupling the long-distance degrees of freedom explicitly kept in the effective field theory to a generic sector that “lives in the fluid,” which corresponds physically to the microscopic constituents of the fluid. At linear order in perturbations, the symmetries, the derivative expansion, and the assumption that this microscopic sector is thermalized allow us to characterize the leading dissipative effects at low frequencies via three parameters only, which correspond to bulk viscosity, shear viscosity, and—in the presence of a conserved charge—heat conduction. Using our methods we rederive the Kubo relations for these transport coefficients.

We show that modified Newtonian dynamics (MOND) is equivalent to assuming an isothermal dark matter density profile, with its density related to the enclosed total baryonic mass. This density profile can be deduced by physical laws if a dark matter core exists and if the baryonic component is spherically symmetric, isotropic, and isothermal. All the usual predictions of MOND, as well as the universal constant $a_0$, can be derived in this model. Since the effects of baryonic matter are larger in galaxies than in galaxy clusters, this result may explain why MOND appears to work well for galaxies but poorly for clusters. As a consequence of the results presented here, MOND can be regarded as a misinterpretation of a particular dark matter density profile.

We revisit minimal supersymmetric extension of the Standard Model scenarios with light neutralino as a dark matter candidate in view of the latest LHC and dark matter direct and indirect detection experiments. We show that scenarios with a very light neutralino ($\sim 10\mathrm{GeV}$) and a scalar bottom quark close in mass can satisfy all the available constraints from LEP, Tevatron, LHC, flavor and low energy experiments and provide solutions in agreement with the bulk of dark matter direct detection experiments, and in particular with the recent CDMS results.

We analyze three-jet production in the central-forward and forward rapidity regions in proton-proton and proton-lead collisions at LHC energies. Our calculation relies on high-energy factorization with a single off-shell gluon obeying small $x$ evolution equation which includes saturation. The calculations are made using two independent Monte Carlo codes implementing tree-level gauge invariant off-shell matrix elements. We calculate differential cross sections for azimuthal decorrelations and unbalanced jet transverse momenta and discuss them in the context of differences in the evolution of the unintegrated gluon densities.

The differential cross section for the production of charged hadrons with high transverse momenta in the scattering of $160\mathrm{GeV}/c$ muons off nucleons at low photon virtualities has been measured at the COMPASS experiment at CERN. The results, which cover transverse momenta from $1.1\mathrm{GeV}/c$ to $3.6\mathrm{GeV}/c$, are compared to a perturbative quantum chromodynamics (pQCD) calculation, in order to evaluate the applicability of pQCD to this process in the kinematic domain of the experiment. The shape of the calculated differential cross section as a function of transverse momentum is found to be in good agreement with the experimental data, but the absolute scale is underestimated by next-to-leading order pQCD. The inclusion of all-order resummation of large logarithmic threshold corrections reduces the discrepancy from a factor of 3 to 4 to a factor of 2. The dependence of the cross section on the pseudorapidity and on the virtual photon energy fraction is investigated. Finally the dependence on the charge of the hadrons is discussed.

We calculate the conductivity matrix of a weakly coupled quark-gluon plasma at the leading-log order. By setting all quark chemical potentials to be identical, the diagonal conductivities become degenerate and positive, while the off-diagonal ones become degenerate but negative (or zero when the chemical potential vanishes). This means a potential gradient of a certain fermion flavor can drive backward currents of other flavors. A simple explanation is provided for this seemingly counterintuitive phenomenon. It is speculated that this phenomenon is generic even beyond the leading-log order, and it is most easily measured in cold atom experiments.

A four-parametric exact solution describing a two-body system of identical Kerr-Newman counterrotating black holes endowed with opposite electric/magnetic charges is presented. The axis conditions are solved in order to really describe two black holes separated by a massless strut. Moreover, the explicit form of the horizon half length parameter $\sigma$ in terms of physical Komar parameters, i.e., Komar’s mass $M$, electric charge $Q_E$, angular momentum $J$, and a coordinate distance $R$ is derived. Additionally, magnetic charges $Q_B$ arise from the rotation of electrically charged black holes. As a consequence, in order to account for the contribution to the mass of the magnetic charge, the usual Smarr mass formula should be generalized, as it is proposed by A. Tomimatsu, Prog. Theor. Phys. 72, 73 (1984).

Being able to measure each merger’s sky location, distance, component masses, and conceivably spins, ground-based gravitational-wave detectors will provide an extensive and detailed sample of coalescing compact binaries in the local and, with third-generation detectors, distant universe. By applying conventional Bayesian methods to an array of competing progenitor formation models, these measurements will distinguish between competing scenarios. First, however, each progenitor formation scenario must be calculated, typically at great computational cost. In practice, a sparse sample of costly scenarios will be gradually refined, guided by observations. This iterative procedure requires physically motivated and data-driven parametrizations of the model space, to quantify the similarities between a given sparse sample of scenarios; the ability for observations to distinguish between them; and to identify plausible new scenarios meriting detailed evaluation. In this paper we develop practical tools to characterize the amount of experimentally accessible information available, to distinguish between two a priori progenitor models. Using a simple time-independent model, we demonstrate the information content scales strongly with the number of observations. The exact scaling depends on how significantly mass distributions change between similar models. We develop phenomenological diagnostics to estimate how many models can be distinguished, using first-generation and future instruments. Finally, we emphasize that multiobservable distributions can be fully exploited only with very precisely calibrated detectors, search pipelines, parameter estimation, and Bayesian model inference.

We present the field equations governing the equilibrium of rapidly rotating neutron stars in scalar-tensor theories of gravity, as well as representative numerical solutions. The conditions for the presence of a nontrivial scalar field and the deviations from the general relativistic solutions are studied. Two examples of scalar-tensor theories are examined—one case that is equivalent to the Brans-Dicke theory and a second case that is perturbatively equivalent to Einstein’s general relativity in the weak field regime, but can differ significantly for strong fields. Our numerical results show that rapidly rotating neutron star models with a nontrivial scalar field exist in both cases and that the effect of the scalar field is stronger for rapid rotation. If we consider values of the coupling parameters in accordance with current observations, only the second example of scalar-tensor theories has significant influence on the neutron star structure. We show that scalarized, rapidly rotating neutron stars exist for a larger range of the parameters than in the static case, since a nontrivial scalar field is present even for values of the coupling constant $\beta >-4.35$, and that these solutions are energetically more favorable than the general relativistic ones. In addition, the deviations of the rapidly rotating scalar-tensor neutron stars from the general-relativistic solutions is significantly larger than in the static case.

We consider cosmological dynamics in the theory of gravity with the scalar field possessing a nonminimal kinetic coupling to gravity, $\kappa G_{\mu \nu }{\varphi }^{\mu }{\varphi }^{\nu }$, and the power-law potential $V(\varphi )=V_0{\varphi }^N$. Using the dynamical system method, we analyze all possible asymptotical regimes of the model under investigation and show that for sloping potentials with $0<N<2$ there exists a quasi–de Sitter asymptotic $H=1/\sqrt{9\kappa }$ corresponding to an early inflationary Universe. In contrast to the standard inflationary scenario, the kinetic coupling inflation does not depend on a scalar field potential and is only determined by the coupling parameter $\kappa$. We obtain that there exist two different late-time asymptotical regimes. The first one leads to the usual powerlike cosmological evolution with $H=1/3t$, while the second one represents the late-time inflationary Universe with $H=1/\sqrt{3\kappa }$. This secondary inflationary phase depends only on $\kappa$ and is a specific feature of the model with nonminimal kinetic coupling. Additionally, an asymptotical analysis shows that for the quadric potential with $N=2$, the asymptotical regimes remain qualitatively the same, while the kinetic coupling inflation is impossible for steep potentials with $N>2$. Using a numerical analysis, we also construct exact cosmological solutions and find initial conditions leading to the initial kinetic coupling inflation followed either by a “graceful” oscillatory exit or by the secondary inflation.

Hybrid inflation is a two-field model where inflation ends because of a tachyonic instability, the duration of which is determined by stochastic effects and has important observational implications. Making use of the recursive approach to the stochastic formalism presented in [L. P. Levasseur, preceding article, Phys. Rev. D 88, 083537 (2013)], these effects are consistently computed. Through an analysis of backreaction, this method is shown to converge in the valley but points toward an (expected) instability in the waterfall. It is further shown that the quasistationarity of the auxiliary field distribution breaks down in the case of a short-lived waterfall. We find that the typical dispersion of the waterfall field at the critical point is then diminished, thus increasing the duration of the waterfall phase and jeopardizing the possibility of a short transition. Finally, we find that stochastic effects worsen the blue tilt of the curvature perturbations by an $\mathcal{O}(1)$ factor when compared with the usual slow-roll contribution.

We present a new, recursive approach to stochastic inflation which is self-consistent and solves multiple problems that plagued a certain number of previous studies, in particular, in realistic contexts where the background spacetime is taken to be dynamical, where there is more than one field present (especially with a mass hierarchy), or where the role played by backreaction is suspected to be important. We first review the formalism of stochastic inflation as it is usually heuristically presented, that is, deriving the Langevin equations from the field equations of motion, and summarize previous results on the subject. We demonstrate where inconsistent approximations to the Langevin equations are commonly made and show how these can be avoided. This setup shares many similarities with quantum Brownian motion and out-of-equilibrium statistical quantum dynamics. We hence review how path integral techniques can be applied to the stochastic inflationary context. We show that this formalism is consistent with the standard approach. We then develop a natural perturbative expansion and use it to calculate the one-loop corrected Langevin equations.

The basic constituent of many space-borne gravitational missions, in particular, for interferometric gravitational-wave detectors, is the so-called “link” made out of a satellite sending an electromagnetic beam to a second satellite. We illustrate how, by measuring the time derivative of the frequency of the received beam, the link behaves as a differential, time-delayed dynamometer in which the effect of gravity is exactly equivalent to an effective differential force applied to the two satellites. We also show that this differential force gives an integrated measurement of curvature along the beam. Finally, we discuss how this approach can be implemented to benefit the data analysis of gravitational-wave detectors.

Based on the full BABAR data sample, we report improved measurements of the ratios $\mathcal{R}(D)=\mathcal{B}(\overline{B}\to D{\tau }^{-}{\overline{\nu }}_{\tau })/\mathcal{B}(\overline{B}\to D{\ell }^{-}{\overline{\nu }}_{\ell })$ and $\mathcal{R}(D^{*})=\mathcal{B}(\overline{B}\to D^{*}{\tau }^{-}{\overline{\nu }}_{\tau })/\mathcal{B}(\overline{B}\to D^{*}{\ell }^{-}{\overline{\nu }}_{\ell })$, where $\ell$ refers to either an electron or muon. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure $\mathcal{R}(D)=0.440\pm 0.058\pm 0.042$ and $\mathcal{R}(D^{*})=0.332\pm 0.024\pm 0.018$, which exceed the standard model expectations by $2.0\sigma$ and $2.7\sigma$, respectively. Taken together, the results disagree with these expectations at the $3.4\sigma$ level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model. Kinematic distributions presented here exclude large portions of the more general type III two-Higgs-doublet model, but there are solutions within this model compatible with the results.

We report new constraints on flavor-changing non-standard neutrino interactions from the MINOS experiment, in which neutrino versus antineutrino interactions can be distinguished on an event-by-event basis. We analyzed a combined set of beam neutrino and antineutrino data from the well-understood NuMI beam, and found no evidence for deviations from standard neutrino mixing. The observed energy spectra constrain the non-standard neutrino interactions parameter to the range $-0.20<{\epsilon }_{\mu \tau }<0.07(90\%\mathrm{C}.\mathrm{L}.)$.

We present results for matrix elements of $\Delta S=2$ four-fermion operators arising generically in models of new physics. These are needed to constrain such models using the measured values of ${\epsilon }_K$ and $\Delta M_K$. We use lattice QCD with $2+1$ flavors of improved staggered fermions on lattices generated by the MILC Collaboration. We extrapolate to the continuum from three lattice spacings ranging down to $a\approx 0.045\mathrm{fm}$. Total errors are $\sim 5\%–6\%$, arising primarily from our use of one-loop matching between lattice and continuum operators. For two of the matrix elements, our results disagree significantly from those obtained using different fermion discretizations.