One of the main bottlenecks in gravitational wave (GW) astronomy is the high cost of performing parameter estimation and GW searches on the fly. We propose a novel technique based on reduced order quadratures (ROQs), an application and data-specific quadrature rule, to perform fast and accurate likelihood evaluations. These are the dominant cost in Markov chain Monte Carlo algorithms, which are widely employed in parameter estimation studies, and so ROQs offer a new way to accelerate GW parameter estimation. We illustrate our approach using a four-dimensional GW burst model embedded in noise. We build an ROQ for this model and perform four-dimensional Markov chain Monte Carlo searches with both the standard and ROQ rules, showing that, for this model, the ROQ approach is around 25 times faster than the standard approach with essentially no loss of accuracy. The speed-up from using ROQs is expected to increase for more complex GW signal models and therefore has significant potential to accelerate parameter estimation of GW sources such as compact binary coalescences.

We provide a simple, unified approach to describing the impact of super-sample covariance, or beat coupling, on power spectrum estimation in a finite-volume survey. For a wide range of survey volumes, the sample variance that arises from modes that are larger than the survey dominates the covariance of power spectrum estimators for modes much smaller than the survey. The deeply nonlinear version of this effect is known as halo sample variance. We show that all variants are unified by the matter trispectrum of squeezed configurations and that such configurations obey a consistency relation which relates them to the response of the power spectrum to a change in the background density. Our method also applies to statistics that are based on radial projections of the density field such as weak lensing shear. While we use the halo model for an analytic description to expose the nature of the effect, the consistency description enables an accurate calibration of the full effect directly from simulations. It also suggests that super-sample covariance may be viewed as an additional interesting signal rather than excess noise.

Kinematical and dynamical properties of a generic inhomogeneous cosmological model, spatially averaged with respect to free-falling (generalized fundamental) observers, are investigated for the matter model “irrotational dust.” Paraphrasing a previous Newtonian investigation, we present a relativistic generalization of a backreaction model based on volume-averaging the “relativistic Zel’dovich approximation.” In this model we investigate the effect of “kinematical backreaction” on the evolution of cosmological parameters as they are defined in an averaged inhomogeneous cosmology, and we show that the backreaction model interpolates between orthogonal symmetry properties by covering subcases of the plane-symmetric solution, the Lemaître-Tolman-Bondi solution and the Szekeres solution. We so obtain a powerful model that lays the foundations for quantitatively addressing curvature inhomogeneities as they would be interpreted as “dark energy” or “dark matter” in a quasi-Newtonian cosmology. The present model, having a limited architecture due to an assumed Friedmann-Lemaître-Robertson-Walker background, is nevertheless capable of replacing $1/4$ of the needed amount for dark energy on domains of 200 Mpc in diameter for typical (one-sigma) fluctuations in a cold dark matter initial power spectrum. However, the model is far from explaining dark energy on larger scales (spatially), where a 6% effect on 400 Mpc domains is identified that can be traced back to an on average negative intrinsic curvature today. One drawback of the quantitative results presented is the fact that the epoch when backreaction is effective on large scales and leads to volume acceleration lies in the future. We discuss this issue in relation to the initial spectrum, the dark matter problem, the coincidence problem, and the fact that large-scale dark energy is an effect on the past light cone (not spatial), and we pinpoint key elements of future research.

Sources of isocurvature perturbations and large non-Gaussianities include field degrees of freedom whose vacuum expectation values are smaller than the expansion rate of inflation. The inhomogeneities in the energy density of such fields are quadratic in the fields to leading order in the inhomogeneity expansion. Although it is often assumed that such isocurvature perturbations and inflaton-driven curvature perturbations are uncorrelated, this is not obvious from a direct computational point of view due to the form of the minimal gravitational interactions. We thus compute the irreducible gravitational contributions to the quadratic isocurvature-curvature cross-correlation. We find a small but nondecaying cross-correlation, which in principle serves as a measurable prediction of this large class of isocurvature perturbations. We apply our cross-correlation result to two dark matter isocurvature perturbation scenarios: QCD axions and wimpzillas. On the technical side, we utilize a gravitational Ward identity in a novel manner to demonstrate the gauge invariance of the computation. Furthermore, the detailed computation is interpreted in terms of a soft-$\zeta$ theorem and a gravitational Ward identity. Finally, we also identify explicitly all the counterterms that are necessary for renormalizing the isocurvature perturbation composite operator in inflationary cosmological backgrounds.

The frequencies of three separate Cs fountain clocks and one Rb fountain clock have been compared to various hydrogen masers to search for periodic changes correlated with the changing solar gravitational potential at the Earth and boost with respect to the cosmic microwave background rest frame. The data sets span over more than 8 yr. The main sources of long-term noise in such experiments are the offsets and linear drifts associated with the various H-masers. The drift can vary from nearly immeasurable to as high as $1.3\times {10}^{-15}$ per day. To circumvent these effects, we apply a numerical derivative to the data, which significantly reduces the standard error when searching for periodic signals. We determine a standard error for the putative local position invariance coefficient with respect to gravity for a Cs-fountain H-maser comparison of $|{\beta }_{\mathrm{H}}-{\beta }_{\mathrm{Cs}}|\le 4.8\times {10}^{-6}$ and $|{\beta }_{\mathrm{H}}-{\beta }_{\mathrm{Rb}}|\le {10}^{-5}$ for a Rb-Fountain H-maser comparison. From the same data, the putative boost local position invariance coefficients were measured to a precision of up to parts in ${10}^{11}$ with respect to the cosmic microwave background rest frame. By combining these boost invariance experiments to a cryogenic sapphire oscillator vs H-maser comparison, independent limits on all nine coefficients of the boost-violation vector with respect to fundamental constant invariance, ${\mathit{B}}_{\alpha }$, ${\mathit{B}}_e$, and ${\mathit{B}}_q$ (fine structure constant, electron mass, and quark mass, respectively), were determined to a precision of parts up to ${10}^{10}$.

We constrain generic nonstandard neutrino interactions with existing experimental data on neutrino transition magnetic moments and derive strong bounds on tensorial couplings of neutrinos to charged fermions. We also discuss how some of these tensorial couplings can be constrained by other experiments, e.g., on neutrino-electron and neutrino-nucleus scattering.

We consider scenarios where strong conformal dynamics constitutes the ultraviolet completion of the physics that drives electroweak symmetry breaking. We show that in theories where the operator responsible for the breaking of conformal symmetry is close to marginal at the breaking scale, the dilaton mass can naturally lie below the scale of the strong dynamics. However, in general, this condition is not satisfied in the scenarios of interest for electroweak symmetry breaking, and so the presence of a light dilaton in these theories is associated with mild tuning. We construct the effective theory of the light dilaton in this framework and determine the form of its couplings to Standard Model states. We show that corrections to the form of the dilaton interactions arising from conformal symmetry violating effects are suppressed by the square of the ratio of the dilaton mass to the strong coupling scale and are under good theoretical control. These corrections are generally subleading, except in the case of dilaton couplings to marginal operators, when symmetry violating effects can sometimes dominate. We investigate the phenomenological implications of these results for models of technicolor, and for models of the Higgs as a pseudo-Nambu-Goldstone boson, that involve strong conformal dynamics in the ultraviolet.

The Large Hadron Collider has recently discovered a Higgs-like particle having a mass around 125 GeV and also indicated that there is an enhancement in the Higgs to diphoton decay rate as compared to that in the standard model. We have studied implications of these discoveries in the bilinear $R$-parity violating supersymmetric model, whose main motivation is to explain the nonzero masses for neutrinos. The $R$-parity violating parameters in this model are $ϵ$ and $b_{ϵ}$, and these parameters determine the scale of neutrino masses. If the enhancement in the Higgs to diphoton decay rate is true, then we have found $ϵ\gtrsim 0.01\mathrm{GeV}$ and $b_{ϵ}\sim 1{\mathrm{GeV}}^2$ in order to be compatible with the neutrino oscillation data. Also, in the above mentioned analysis, we can determine the soft masses of sleptons ($m_L$) and $CP$-odd Higgs boson mass ($m_A$). We have estimated that $m_L\gtrsim 300\mathrm{GeV}$ and $m_A\gtrsim 700\mathrm{GeV}$. We have also commented on the allowed values of $ϵ$ and $b_{ϵ}$, in case there is no enhancement in the Higgs to diphoton decay rate. Finally, we present a model to explain the smallness of $ϵ$ and $b_{ϵ}$.

We demonstrate that in supersymmetry with relatively light top superpartners, $h\to b\overline{b}$ can be a very promising channel to discover the Standard Model (SM)-like Higgs resonance at the LHC; although in general contexts, it is thought to be challenging because of its huge QCD background. In this scenario, the SM-like Higgs boson is mainly produced via cascade decays initiated by pair-produced stop or sbottom squarks. The good sensitivity to $h\to b\overline{b}$ owes a great deal to the application of multiple ($\ge 4$) $b$-jet tagging in removing the QCD background and color-flow variables for reconstructing the Higgs resonance. We show in two benchmark points that a SM-like Higgs resonance can be discovered at the 14 TeV LHC (with a signal-to-background ratio as high as 0.35), with $\sim 40{\mathrm{fb}}^{-1}$ of data. Potentially, this strategy can be also applied to nonsupersymmetry theories with cascade decays of top partners for the SM-like Higgs search, such as little Higgs, composite Higgs, and Randall-Sundrum models.

The quantum $O(2)$ model in $2+1$ dimensions is studied by simulating the 3D $O(2)$ model near criticality. Finite densities are introduced by a nonzero chemical potential $\mu$, and the worm algorithm is used to circumvent the sign problem. The renormalization is discussed in some detail. We find that the onset value of the chemical potential coincides with the mass gap. The $\mu$ dependence of the density rules out Bose-Einstein condensation and might be compatible with an interacting Fermi gas. The $\mu \mathrm{\text{−}}T$ phase diagram is explored using the density and the magnetic susceptibility. In the cold but dense regime of the phase diagram, we find a superfluid phase.

Phenomenological Tsallis fits to the CMS, ATLAS, and ALICE transverse momentum spectra of hadrons for $pp$ collisions at LHC were recently found to extend over a large range of the transverse momentum. We investigate whether the few degrees of freedom in the Tsallis parametrization may arise from the relativistic parton-parton hard-scattering and related processes. The effects of the multiple hard-scattering and parton showering processes on the power law are discussed. We find empirically that whereas the transverse spectra of both hadrons and jets exhibit power-law behavior of $1/p_T^n$ at high $p_T$, the power indices $n$ for hadrons are systematically greater than those for jets, for which $n\sim 4–5$.

We present results for the production of a $Z$ boson in association with single top at next-to-leading order (NLO), including the decay of the top quark and the $Z$ boson. This electroweak process gives rise to the trilepton signature $l^{+}{l}^{-}{l}^{\prime \pm }+\mathrm{\text{jets}}+\mathrm{\text{missing energy}}$. We present results for this signature and show that the rate is competitive with the contribution of the mixed strong and electroweak production process, $t\overline{t}Z$. As such it should be observable in the full data sample from LHC running at $\sqrt{s}=8\mathrm{TeV}$. The single $\mathrm{\text{top}}+Z$ process is a hitherto unconsidered irreducible background in searches for flavor changing neutral current decays of the top quark in $t\overline{t}$ production. For a selection of cuts used at the LHC involving a $b$-tag it is the dominant background. In the Appendices we also briefly discuss the impact of NLO corrections on the related $tH$ process.

By means of effective field theory techniques, we study the modifications of some properties of weakly coupled heavy quarkonium states propagating through a quark-gluon plasma at temperatures much smaller than the heavy quark mass, $m_Q$. Two different cases are considered, corresponding to two different hierarchies between the typical size of the bound state, $r$, the binding energy, $E$, the temperature, $T$, and the screening mass, $m_D$. The first case corresponds to the hierarchy $m_Q\gg 1/r\gg T\gg E\gg m_D$, relevant for moderate temperatures, and the second one to the hierarchy $m_Q\gg T\gg 1/r$, $m_D\gg E$, relevant for studying the dissociation mechanism. In the first case we determine the perturbative correction to the binding energy and to the decay width of states with arbitrary angular momentum, finding that the width is a decreasing function of the velocity. A different behavior characterizes the second kinematical case, where the width of $s$-wave states becomes a nonmonotonic function of the velocity, increasing at moderate velocities and decreasing in the ultrarelativistic limit. We obtain a simple analytical expression of the decay width for $T\gg 1/r\gg m_D\gg E$ at moderate velocities, and we derive the $s$-wave spectral function for the more general case $T\gg 1/r$, $m_D\gg E$. A brief discussion of the possible experimental signatures as well as a comparison with the relevant lattice data are also presented.

The formulas directly connecting parton distribution functions and fragmentation functions at the next-to-leading-order QCD with the same quantities at the leading order are derived. These formulas are universal, i.e., have the same form for all kinds of parton distribution functions and fragmentation functions, differing only in the respective splitting functions entering there.

We employ the diluted instanton liquid model and the Green-Kubo formula to investigate the shear viscosity of the SU(2) light-flavor quark matter at finite temperature under an external strong magnetic field $e|\mathit{B}|\sim m_{\pi }^2$. We apply the Schwinger method to calculate the effect of the external magnetic field. We find that the shear viscosity increases as temperature increases even beyond the transition temperature $T_0=170\mathrm{MeV}$ if temperature-dependent model parameters are used. On the other hand, with temperature-independent ones the shear viscosity starts to drop when the temperature goes beyond $T_0$. Furthermore, we find that the presence of an external magnetic field will reduce the shear viscosity. However, this effect is almost negligible in the chiral-restored phase even for a very strong magnetic field, $e|\mathit{B}|\approx {10}^{20}\mathrm{gauss}$. We also compute the ratio of the shear viscosity and the entropy density $\eta /s$ and our results are well compatible with the other theoretical results for a wide temperature range. We also provide the parametrization of the temperature-dependent ratio $\eta /s$ from our numerical result as $\eta /s=0.27-0.87/t+1.19/t^2-0.28/t^3$ with $t\equiv T/T_0$ for $T=(100\sim 350)\mathrm{MeV}$ when $e|\mathit{B}|=0$.

We search for the flavor-changing neutral-current decays $B\to K^{(*)}\nu \overline{\nu }$, and the invisible decays $J/\psi \to \nu \overline{\nu }$ and $\psi (2S)\to \nu \overline{\nu }$ via $B\to K^{(*)}J/\psi$ and $B\to K^{(*)}\psi (2S)$, respectively, using a data sample of $471\times {10}^6$ $B\overline{B}$ pairs collected by the BABAR experiment. We fully reconstruct the hadronic decay of one of the $B$ mesons in the ${\rm Y}(4S)\to B\overline{B}$ decay, and search for the $B\to K^{(*)}\nu \overline{\nu }$ decay in the rest of the event. We observe no significant excess of signal decays over background and report branching fraction upper limits of $\mathcal{B}(B^{+}\to K^{+}\nu \overline{\nu })<3.7\times {10}^{-5}$, $\mathcal{B}(B^0\to K^0\nu \overline{\nu })<8.1\times {10}^{-5}$, $\mathcal{B}(B^{+}\to K^{*+}\nu \overline{\nu })<11.6\times {10}^{-5}$, $\mathcal{B}(B^0\to K^{*0}\nu \overline{\nu })<9.3\times {10}^{-5}$, and combined upper limits of $\mathcal{B}(B\to K\nu \overline{\nu })<3.2\times {10}^{-5}$ and $\mathcal{B}(B\to K^{*}\nu \overline{\nu })<7.9\times {10}^{-5}$, all at the 90% confidence level. For the invisible quarkonium decays, we report branching fraction upper limits of $\mathcal{B}(J/\psi \to \nu \overline{\nu })<3.9\times {10}^{-3}$ and $\mathcal{B}(\psi (2S)\to \nu \overline{\nu })<15.5\times {10}^{-3}$ at the 90% confidence level. Using the improved kinematic resolution achieved from hadronic reconstruction, we also provide partial branching fraction limits for the $B\to K^{(*)}\nu \overline{\nu }$ decays over the full kinematic spectrum.

We consider different realizations for the momentum sector of $\kappa$-Poincaré-Hopf algebra, which is associated with a curved momentum space. We show that the notion of the particle mass as introduced recently by Amelino-Camelia et al. in the context of relative locality is realization independent for a wide class of realizations, up to linear order in the deformation parameter $l$. On the other hand, the time delay formula clearly shows a dependence on the choice of realization.

In this paper we determine the exact fermionic spectral function of the Bloch-Nordsieck model at finite temperature. Analytic results are presented for some special parameters; for other values we have numerical results. The spectral function is finite and normalizable for any nonzero temperature value. The real time dependence of the retarded Green’s function is powerlike for small times and exhibits exponential damping for large times. Treating the temperature as an infrared regulator, we can also give a safe interpretation of the zero temperature result.

We study supersymmetric boundary conditions in three-dimensional $\mathcal{N}=2$ Landau-Ginzburg models and Abelian gauge theories. In the Landau-Ginzburg model the boundary conditions that preserve (1,1) supersymmetry (A-type) and (2,0) supersymmetry (B-type) on the boundary are classified in terms of subspaces of the target space (“brane”). An A-type brane is a Lagrangian submanifold on which the imaginary part of the superpotential is constant, while a B-type brane is a holomorphic submanifold on which the superpotential is constant. We also consider the $\mathcal{N}=2$ Maxwell theory with boundary and the Abelian duality. Finally we make some comments on $\mathcal{N}=2$ SQED with boundary condition and the mirror symmetry.

Force between static point particles coupled to a classical ultramassive scalar field is calculated. The field potential is proportional to the modulus of the field. It turns out that the force exactly vanishes when the distance between the particles exceeds certain finite value. Moreover, each isolated particle is surrounded by a compact cloud of the scalar field that completely screens its scalar charge.