The existence of a dilaton as a pseudo-Nambu-Goldstone boson in spontaneous breaking of scale symmetry is predicted in beyond standard model theories in which electroweak symmetry is broken via strongly coupled conformal dynamics. Such a particle is expected to have a mass below the conformal symmetry breaking scale $f$ and couplings to standard model particles similar to those of the SM Higgs boson. In this paper we estimate, for the first time, the dilaton production in exclusive processes considering Pomeron-Pomeron ($\mathbb{P}\mathbb{P}$) and photon-photon ($\gamma \gamma$) interactions, which are characterized by two rapidity gaps and intact hadrons in the final state. Our results indicate that if the dilaton is massive ($M_{\chi }\ge 2M_W$), the study of dilaton production by $\mathbb{P}\mathbb{P}$ interactions in $pp$ collisions can be useful to determine its mass and the conformal energy scale.

Using the predictive power of the effective field theory approach, we present a physical parametrization of the leading effects beyond the standard model (BSM), which gives us at present the best way to constrain heavy new physics at low energies. We show that other BSM effects are not independent from these ones, and we provide the explicit correlations. This information is useful to know where to primarily look for new physics in future experiments, and to know how this new physics is related to previous measurements, most importantly in electroweak symmetry breaking processes or Higgs physics.

In a recent paper [P. Wang and X.-G. Wang, Phys. Rev. Lett. 111, 042002 (2013)], the charmonium state $X(3872)$ is studied in the framework of an effective field theory. In that work it is claimed that (i) the one-pion exchange (OPE) alone provides sufficient binding to produce the $X$ as a shallow bound state at the $D^0{\overline{D}}^{*0}$ threshold, (ii) short-range dynamics (described by a contact interaction) provides only moderate corrections to the OPE, and (iii) the $X$-pole disappears as the pion mass is increased slightly and therefore the $X$ should not be seen on the lattice, away from the pion physical mass point, if it were a molecular state. In this paper we demonstrate that the results of P. Wang and X.-G. Wang suffer from technical as well as conceptual problems and therefore do not support the conclusions drawn by the authors.

Degenerate neutrino masses are excluded by experiment. The experimentally measured mass squared differences together with the yet undetermined absolute neutrino mass scale allow for a quasidegenerate mass spectrum. For the lightest neutrino mass larger than roughly 0.1 eV, we analyze the influence of threshold corrections at the electroweak scale. We show that typical one-loop corrections can generate the observed neutrino mixing as well as the mass differences starting from exactly degenerate masses at the tree level. Those threshold corrections have to be explicitly flavor violating. Flavor-diagonal, nonuniversal corrections are not sufficient to simultaneously generate the correct mixing and the mass differences. We apply the new insights to an extension of the Minimal Supersymmetric Standard Model with nonminimal flavor violation in the soft breaking terms and discuss the low-energy threshold corrections to the light neutrino mass matrix in that model.

We present midrapidity charged-pion invariant cross sections, the ratio of the ${\pi }^{-}$ to ${\pi }^{+}$ cross sections and the charge-separated double-spin asymmetries in polarized $p+p$ collisions at $\sqrt{s}=200\mathrm{GeV}$. While the cross section measurements are consistent within the errors of next-to-leading-order (NLO) perturbative quantum chromodynamics predictions (pQCD), the same calculations overestimate the ratio of the charged-pion cross sections. This discrepancy arises from the cancellation of the substantial systematic errors associated with the NLO-pQCD predictions in the ratio and highlights the constraints these data will place on flavor-dependent pion fragmentation functions. The charge-separated pion asymmetries presented here sample an $x$ range of $\sim 0.03–0.16$ and provide unique information on the sign of the gluon-helicity distribution.

Geodesic equations of timelike and null charged particles in the Ernst metric are studied. We consider two distinct forms of the Ernst solution where the Maxwell potential represents either a uniform electric or magnetic field. Circular orbits in various configurations are considered, as well as their perturbations and stability. We find that the electric field strength must be below a certain charge-dependent critical value for these orbits to be stable. The case of the magnetic Ernst metric contains a limit which reduces to the Melvin magnetic universe. In this case the equations of motion are solved to reveal cycloidlike or trochoidlike motion, similar to those found by Frolov and Shoom around black holes immersed in test magnetic fields.

In this paper, we study the existence of universal horizons in a given static spacetime and find that the test khronon field can be solved explicitly when its velocity becomes infinitely large, at which point the universal horizon coincides with the sound horizon of the khronon. Choosing the timelike coordinate aligned with the khronon, the static metric takes a simple form, from which it can be seen clearly that the metric is free of singularity at the Killing horizon, but becomes singular at the universal horizon. Applying such developed formulas to three well-known black hole solutions, the Schwarzschild, Schwarzschild–anti–de Sitter, and Reissner-Nordström, we find that in all these solutions universal horizons exist and are always inside the Killing horizons. In particular, in the Eddington-Finkelstein and Painleve-Gullstrand coordinates, in which the metrics are not singular when crossing both of the Killing and universal horizons, the peeling-off behavior of the khronon is found only at the universal horizons, whereby we show that the values of surface gravity of the universal horizons calculated from the peeling-off behavior of the khronon match with those obtained from the covariant definition given recently by Cropp, Liberati, Mohd and Visser.

In the Carlip-Majhi-Padmanabhan approach, we calculate the microscopic entropy of the trapping (apparent) horizon of the Friedmann-Robertson-Walker metric. We solve Killing equations for the $t,r$ part of the metric without fixing a priori the form of the scaling factor $a(t)$ which is determined from the requirement of consistency of the Killing equations. Further restrictions on the form of the Killing vector follow from the requirement that the Killing vector is null at the trapping horizon at all $t$. The $r,t$ part of the Killing vector extended by zero $\vartheta$ and $\phi$ components forms an approximate Killing vector in the vicinity of the horizon and satisfies the Killing equations at the horizon. Applying the technique used to calculate the microscopic entropy of the Killing horizons, we calculate the microscopic entropy of the trapping horizon. Using the explicit form of the Killing vector, we verify that the identities used in the calculation of the central term of the Virasoro algebra for the Killing horizons of black holes are valid in the present case.

Accurately modeling astrophysical extreme-mass-ratio inspirals requires calculating the gravitational self-force for orbits in Kerr spacetime. The necessary calculation techniques are typically very complex and, consequently, toy scalar-field models are often developed in order to establish a particular calculational approach. To that end, I present a calculation of the scalar-field self-force for a particle moving on a (fixed) inclined circular geodesic of a background Kerr black hole. I make the calculation in the frequency domain and demonstrate how to apply the mode-sum regularization procedure to all four components of the self-force. I present results for a number of strong-field orbits which can be used as benchmarks for emerging self-force calculation techniques in Kerr spacetime.

In this paper I derive the flat space limit of the modified Cardy formula associated with inner horizons and show that it reproduces the correct Galilean conformal field theory counting of flat space cosmology microstates. l also determine the entropy of flat space cosmologies in flat space chiral gravity in this way. In addition, I derive a Cardy-like expression for flat space cosmologies with spin-3 charges and, thus, give a prediction for the corresponding Galilean conformal field theory counting of flat space cosmology microstates with spin-3 charges.

Three new observables for $Z$ factory to measure the weak dipole moment of $\tau$ lepton ($d_w^{\tau }$) are proposed. As those observables are employed at LEP-I, the new observables depend on the real and imaginary parts of $d_w^{\tau }$ linearly; thus, we calculate the slopes, i.e., the linear coefficients of the dependence, precisely and find that the obtained slopes are much lager than those employed at LEP-I. It means that the signal for the weak dipole moment $d_w^{\tau }$ may be enhanced quite a lot if one employs the new observables. Being superior to those at LEP-I, we recommend measuring the weak dipole moment $d_w^{\tau }$ in terms of the new observables if reanalyzing the data of LEP-I or doing the measurement at a possible $Z$ factory in the near future.

We study F-theory duals of singular heterotic K3 models that correspond to Abelian toroidal orbifolds $T^4/{\mathbb{Z}}_N$. While our focus is on the standard embedding, we also comment on models with Wilson lines and more general gauge embeddings. In the process of constructing the duals, we work out a Weierstrass description of the heterotic toroidal orbifold models, which exhibit singularities of Kodaira type $I_0^{*}$, ${IV}^{*}$, ${III}^{*}$, and ${II}^{*}$. This construction unveils properties like the instanton number per fixed point and a correlation between the orbifold order and the multiplicities in the Dynkin diagram. The results from the Weierstrass description are then used to restrict the complex structure of the F-theory Calabi–Yau threefold such that the gauge group and the matter spectrum of the heterotic theories are reproduced. We also comment on previous approaches that have been employed to construct the duality and point out the differences and limitations in our case. Our results show explicitly how the various orbifold models are connected and described in F-theory.

The effects induced by the quantum vacuum fluctuations of one massless real scalar field on a configuration of two partially transparent plates are investigated. The physical properties of the infinitely thin plates are simulated by means of Dirac-$\delta -{\delta }^{\prime }$ point interactions. It is shown that the distortion caused on the fluctuations by this external background gives rise to a generalization of Robin boundary conditions. The $T$ operator for potentials concentrated on points with nondefined parity is evaluated with total generality. The quantum vacuum interaction energy between the two plates is computed in several dimensions using the $TGTG$ formula to find positive, negative, and zero Casimir energies. The parity properties of the $\delta -{\delta }^{\prime }$ potential demands that one distinguish between opposite and identical objects. It is shown that between identical sets of $\delta -{\delta }^{\prime }$ plates, repulsive, attractive, or null quantum vacuum forces arise. However, there is always attraction between a pair of opposite $\delta -{\delta }^{\prime }$ plates.

Gravitational waves (GWs) emitted by generic black-hole binaries show a rich structure that directly reflects the complex dynamics introduced by the precession of the orbital plane, which poses a real challenge to the development of generic waveform models. Recent progress in modelling these signals relies on an approximate decoupling between the nonprecessing secular inspiral and a precession-induced rotation. However, the latter depends in general on all physical parameters of the binary which makes modelling efforts as well as understanding parameter-estimation prospects prohibitively complex. Here we show that the dominant precession effects can be captured by a reduced set of spin parameters. Specifically, we introduce a single effective precession spin parameter, ${\chi }_p$, which is defined from the spin components that lie in the orbital plane at some (arbitrary) instant during the inspiral. We test the efficacy of this parameter by considering binary inspiral configurations specified by the physical parameters of a corresponding nonprecessing-binary configuration (total mass, mass ratio, and spin components (anti)parallel to the orbital angular momentum), plus the effective precession spin applied to the larger black hole. We show that for an overwhelming majority of random precessing configurations, the precession dynamics during the inspiral are well approximated by our equivalent configurations. Our results suggest that in the comparable-mass regime waveform models with only three spin parameters faithfully represent generic waveforms, which has practical implications for the prospects of GW searches, parameter estimation and the numerical exploration of the precessing-binary parameter space.

In conformally flat background geometries the long-wavelength gravitons can be described in the fluid approximation and they induce scalar fluctuations both during inflation and in the subsequent radiation-dominated epoch. While this effect is minute and suppressed for a de Sitter stage of expansion, the fluctuations of the energy-momentum pseudotensor of the graviton fluid lead to curvature perturbations that increase with time all along the post-inflationary evolution. An explicit calculation of these effects is presented for a standard thermal history and it is shown that the growth of the curvature perturbations caused by the long-wavelength modes is approximately compensated by the slope of the power spectra of the energy density, pressure and anisotropic stress of the relic gravitons.

We present a new, comprehensive global analysis of parton-to-pion fragmentation functions at next-to-leading-order accuracy in QCD. The obtained results are based on the latest experimental information on single-inclusive pion production in electron-positron annihilation, lepton-nucleon deep-inelastic scattering, and proton-proton collisions. An excellent description of all data sets is achieved, and the remaining uncertainties in parton-to-pion fragmentation functions are estimated based on the Hessian method. Extensive comparisons to the results from our previous global analysis are performed.

In this paper, we use the latest Higgs measurements from ATLAS and CMS to constrain the parameter space of the model of Schmaltz, Stolarski, and Thaler, a little Higgs model with two Higgs doublets, which we will refer to as the BLH model. We account for all production and decay modes explored at ATLAS and CMS in two scenarios: a general case, which assumes the $h_0$ state is light ($m_{h_0}\approx 125\mathrm{GeV}$) and the masses of the other neutral scalars ($H_0$ and $A_0$) are allowed to vary, and a case with a near-degeneracy between the masses of the $h_0$ and $A_0$ and, for some choices of parameters, the $H_0$ states. The near-degeneracy scenario can result in an enhanced diphoton rate, as measured by ATLAS, but is largely ruled out by a combination of the $h_0\to {\tau }^{+}{\tau }^{-}$ and the heavy $H_0\to W^{+}{W}^{-}$ measurements. In the general case, we find large regions of parameter space that are in better agreement with either the ATLAS or CMS results than is the SM. However, a significantly enhanced diphoton rate is only possible through large contributions to the $h_0\gamma \gamma$ effective coupling from charged Higgs bosons in a region of parameter space that borders on violation of perturbativity in the scalar sector.

We study properties of effective temperature of nonequilibrium steady states by using the anti–de Sitter spacetime/conformal field theory ($\mathrm{AdS}/\mathrm{CFT}$) correspondence. We consider nonequilibrium systems with a constant flow of current along an electric field, in which the current is carried by both the doped charges and those pair created by the electric field. We find that the effective temperature agrees with that of the Langevin systems if we take the limit where the pair creation is negligible. The effect of pair creation raises the effective temperature whereas the current by the doped charges contributes to lower the effective temperature in a wide range of the holographic models.

We calculate the one-loop effective potential for Horava-Lifshitz-like QED with an arbitrary critical exponent within different approaches and discuss its gauge dependence.