We consider the Plebański class of electrovacuum solutions to the Einstein equations with a cosmological constant. These space-times, which are also known as the Kerr-Newman-NUT–(anti–)de Sitter space-times, are characterized by a mass $m$, a spin $a$, a parameter $\beta$ that comprises electric and magnetic charge, a NUT parameter $\ell$ and a cosmological constant $\mathrm{\Lambda }$. Based on a detailed discussion of the photon regions in these space-times (i.e., of the regions in which spherical lightlike geodesics exist), we derive an analytical formula for the shadow of a Kerr-Newman-NUT–(anti–)de Sitter black hole for an observer at given Boyer-Lindquist coordinates $(r_O,{\vartheta }_O)$ in the domain of outer communication. We visualize the photon regions and the shadows for various values of the parameters.

If Lorentz and $CPT$ violations exist, they could affect the decays of scalar and pseudoscalar particles. For a decay into a fermion and an antifermion (not necessarily of the same mass), both the total decay rate and the outgoing particle distribution may be modified, through interference between the conventional decay mechanism and a separate Lorentz-violating mechanism. The modifications are sensitive to forms of Lorentz violation that are otherwise rather difficult to study, since at tree level they do not affect particle propagation, but only interaction vertices. Using existing experimental data on charged pion decay, it is possible to constrain three parameters in the modified pion-muon-neutrino coupling at better than the ${10}^{-9}$ level; these are the first bounds on these quantities.

The gross structure of compact stars composed of pion superfluid quark matter is investigated in the frame of the Nambu–Jona-Lasinio model. Under the Pauli-Villars regularization scheme, the uncertainty of the thermodynamic functions for inhomogeneous states is cured, and the Larkin-Ovchinnikov-Fulde-Ferrel state that appeared in the hard cutoff scheme is removed from the phase diagram of the pion superfluid. Different from the unpaired quark matter and color superconductor, the strongly coupled pion superfluid is a possible candidate of compact stars with mass $M\simeq 3M_{\odot }$ and radius $R\simeq 14\mathrm{km}$.

Following the recent confirmation of the $Z^{+}(4430)$ resonance with $J^{PG}=1^{++}$, we have re-examined the model of $S$- and $P$-wave tetraquarks. We propose a “type-II” diquark-antidiquark model which shows to be very effective at producing a simple and comprehensive picture of the $J^{PG}=1^{++}$ and $1^{--}$ sectors of the recently discovered charged tetraquarks and of the observed $Y$ resonances. The model is still faced with the unresolved difficulty of explaining why some states seem to have incomplete isospin multiplets.

We define three orthogonal axes to investigate the top-quark polarization in the $t$-channel single-top process. We provide expressions for the polarization in these axes in terms of anomalous $Wtb$ couplings. It is found that the polarizations in the two axes orthogonal to the spectator quark axis are very sensitive to an anomalous coupling involving a ${\overline{b}}_L{\sigma }^{\mu \nu }{t}_R$ dipole term. In particular, an asymmetry based on the polarization normal to the production plane is more sensitive to the imaginary part of this coupling than previously studied observables.

Evidence is presented for the baryonic $B$ meson decay ${\overline{B}}^0\to D^0\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ based on a data sample of $471\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric $e^{+}{e}^{-}$ collider located at the SLAC National Accelerator Laboratory. The branching fraction is determined to be $\mathcal{B}({\overline{B}}^0\to D^0\mathrm{\Lambda }\overline{\mathrm{\Lambda }})=({9.8}_{-2.6}^{+2.9}\pm 1.9)\times {10}^{-6}$, corresponding to a significance of 3.4 standard deviations including additive systematic uncertainties. A search for the related baryonic $B$ meson decay ${\overline{B}}^0\to D^0{\mathrm{\Sigma }}^0\overline{\mathrm{\Lambda }}$ with ${\mathrm{\Sigma }}^0\to \mathrm{\Lambda }\gamma$ is performed and an upper limit $\mathcal{B}({\overline{B}}^0\to D^0{\mathrm{\Sigma }}^0\overline{\mathrm{\Lambda }}+{\overline{B}}^0\to D^0\mathrm{\Lambda }{\overline{\mathrm{\Sigma }}}^0)<3.1\times {10}^{-5}$ is determined at 90% confidence level.

At finite $N$, the number of restricted Schur polynomials is greater than or equal to the number of generalized restricted Schur polynomials. In this note, we study this discrepancy and explain its origin. We conclude that for quiver gauge theories, in general, the generalized restricted Shur polynomials correctly account for the complete set of finite $N$ constraints, and they provide a basis, while the restricted Schur polynomials only account for a subset of the finite $N$ constraints and are thus overcomplete. We identify several situations in which the restricted Schur polynomials do in fact account for the complete set of finite $N$ constraints. In these situations, the restricted Schur polynomials and the generalized restricted Schur polynomials both provide good bases for the quiver gauge theory. Finally, we demonstrate situations in which the generalized restricted Schur polynomials reduce to the restricted Schur polynomials.

In this paper, we first compute the Killing spinors of ${\mathrm{AdS}}_4\times Q^{1,1,1}$ and its certain orbifolds. Based on this, two classes of $M2$-brane solutions are found. The first class of solutions includes $M2$-branes dual to Wilson loops in the fundamental representation as a special case. The second class includes the candidates of the holographic description of vortex loops in the dual field theories.

We determine the shear viscosity of a hot and dense Yukawa-Fermi gas, using the standard Green-Kubo relation, according to which the shear viscosity is given by the retarded correlator of the traceless part of the viscous energy-momentum tensor. We approximate this retarded correlator using a one-loop skeleton expansion, and express the bosonic and fermionic shear viscosities, ${\eta }_b$ and ${\eta }_f$, in terms of bosonic and fermionic spectral widths, ${\mathrm{\Gamma }}_b$ and ${\mathrm{\Gamma }}_{\pm }$. Here, the subscripts $\pm$ correspond to normal and collective (plasmino) excitations of fermions. We study, in particular, the effect of these excitations on thermal properties of ${\eta }_f[{\mathrm{\Gamma }}_{\pm }]$. To do this, we determine first the dependence of ${\mathrm{\Gamma }}_b$ and ${\mathrm{\Gamma }}_{\pm }$ on momentum $p$, temperature $T$, chemical potential $\mu$ and ${\xi }_0\equiv m_b^0/m_f^0$, in a one-loop perturbative expansion in the orders of the Yukawa coupling. Here, $m_b^0$ and $m_f^0$ are $T$- and $\mu$-independent bosonic and fermionic masses, respectively. We then numerically determine ${\eta }_b[{\mathrm{\Gamma }}_b]$ and ${\eta }_f[{\mathrm{\Gamma }}_{\pm }]$, and study their thermal properties. It turns out that whereas ${\mathrm{\Gamma }}_b$ and ${\mathrm{\Gamma }}_{+}$ decrease with increasing $T$ or $\mu$, ${\mathrm{\Gamma }}_{-}$ increases with increasing $T$ or $\mu$. This behavior qualitatively changes by adding thermal corrections to $m_b^0$ and $m_f^0$, while the difference between ${\mathrm{\Gamma }}_{+}$ and ${\mathrm{\Gamma }}_{-}$ keeps increasing with increasing $T$ or $\mu$. Moreover, ${\eta }_b$ (${\eta }_f$) increases (decreases) with increasing $T$ or $\mu$. We show that the effect of plasminos on ${\eta }_f$ becomes negligible with increasing (decreasing) $T$ ($\mu$).

We use heat-kernel techniques in order to compute the one-loop effective action in the cubic Galileon theory for a background that realizes the Vainshtein mechanism. We find that the UV divergences are suppressed relative to the predictions of standard perturbation theory at length scales below the Vainshtein radius.

We consider a self-interacting, massive scalar field (non)minimally coupled to new massive gravity in three dimensions. For this model, we first derive a family of black hole solutions depending on a unique integration constant and parametrized in terms of the nonminimal coupling parameter. Imposing the absence of naked singularities restricts the parameters in such a way that the field vanishes at infinity and fixes the metric to be asymptotically AdS. Within this family of solutions it is possible to find a black hole supported by a minimally coupled scalar field, and therefore the existence of these solutions is not inherent to the presence of the nonminimal coupling. The Wald formula for the entropy, being proportional to the lapse function evaluated at the horizon, yields a zero entropy in spite of the fact that the solution has a nonzero temperature. As a consequence, the unique integration constant may be interpreted as a sort of gravitational hair. As in the source-free case, we show that the same field equations also admit asymptotically Lifshitz black hole solutions in a different region of the space of parameters. These Lifshitz solutions are divided into three families for which all the parameters entering in the action may be expressed in terms of the dynamical exponent.

For a narrow band of values of the top quark and Higgs boson masses, the standard model Higgs potential develops a shallow local minimum at energies of about ${10}^{16}\mathrm{GeV}$, where primordial inflation could have started in a cold metastable state. For each point of that band, the highness of the Higgs potential at the false minimum is calculable, and there is an associated prediction for the inflationary gravitational wave background, namely, for the tensor to scalar ratio $r$. We show that the recent measurement of $r$ by the BICEP2 collaboration, $r=0.16_{-0.05}^{+0.06}$ at $1\sigma$, combined with the most up-to-date measurements of the top quark and Higgs boson masses, reveals that the hypothesis that a standard model shallow false minimum was the source of inflation in the early Universe is viable.

Aberration kernels describe how harmonic-space multipole coefficients of cosmic microwave background (CMB) observables transform under Lorentz boosts of the reference frame. For spin-weighted CMB observables, transforming like the CMB temperature (i.e., Doppler weight $d=1$), we show that the aberration kernels are the matrix elements of a unitary boost operator in harmonic space. Algebraic properties of the rotation and boost generators then give simple, exact recursion relations that allow us to raise or lower the multipole quantum numbers $\ell$ and $m$ and the spin weight $s$. Further recursion relations express kernels of other Doppler weights $d\ne 1$ in terms of the $d=1$ kernels. From those we show that on the full sky, to all orders in $\beta =v/c$, $E$- and $B$-mode polarization observables do not mix under aberration if and only if $d=1$. The new relations, fully nonlinear in the boost velocity $\beta$, form the basis of a practical recursive algorithm to accurately compute any aberration kernel. In addition, we develop a second, fast algorithm in which aberration kernels are obtained using a set of ordinary differential equations. This system can also be approximately solved at small scales, providing simple asymptotic formulas for the aberration kernels. The results of this work will be useful for further studying the effect of aberration on future CMB temperature and polarization analysis and might provide a basis for relativistic radiative transfer schemes.

The recent BICEP2 detection of degree scale cosmic microwave background (CMB) $B$-mode polarization, coupled with a deficit of observed power in large angle temperature anisotropy, suggest that the slow-roll parameter ${\epsilon }_H$, the fractional variation in the Hubble rate per $e$-fold, is both relatively large and may evolve from an even larger value on scales greater than the horizon at recombination. The relatively large tensor contribution implied also requires finite matching features in the tensor power spectrum for any scalar power spectrum feature proposed to explain anomalies in the temperature data. We extend the generalized slow-roll approach for computing power spectra, appropriate for such models where the slow-roll parameters vary, to tensor features where scalar features are large. This approach also generalizes the tensor-scalar consistency relation to be between the ratio of tensor and scalar sources and features in the two power spectra. Features in the tensor spectrum are generically suppressed by ${\epsilon }_H$ relative those in the scalar spectrum and by the smoothness of the Hubble rate, which must obey covariant conservation of energy, versus its derivatives. Their detection in near future CMB data would indicate a fast roll period of inflation where ${\epsilon }_H$ approaches order unity, allowed but not required by inflationary explanations of temperature anomalies.

We present a heuristic study on the correlations between harmonic space phase information and higher-order statistics. Using the spherical full-sky maps of the cosmic microwave background as an example, we demonstrate that known phase correlations at large spatial scales can gradually be diminished when subtracting a suitable best-fit (Bianchi-)template map of a given strength. The weaker phase correlations are attended by a vanishing signature of anisotropy when measuring the Minkowski functionals and scaling indices in real space with the aid of surrogate maps being free of phase correlations. Those investigations can open a new road to a better understanding of signatures of non-Gaussianities in complex spatial structures, especially by elucidating the meaning of Fourier phase correlations and their influence on higher-order statistics.

Alignment control in gravitational-wave detectors has consistently proven to be a difficult problem due to the stringent noise contamination requirement for the gravitational wave readout and the radiation-pressure-induced angular instability in Fabry-Perot cavities (Sidles-Sigg instability). We present the analysis of a dual-carrier control scheme that uses radiation pressure to control a suspended mirror, trapping it in the longitudinal degree of freedom and one angular degree of freedom. We show that this scheme can control the Sidles-Sigg angular instability. Its limiting fundamental noise source is the quantum radiation pressure noise, providing an advantage compared to the conventional angular control schemes. In the Appendix we also derive an exact expression for the optical spring constant used in the control scheme.

We consider the nonrelativistic limit of the QCD Hamiltonian in the Coulomb gauge, to describe radiative transitions between conventional charmonium states and from the lowest multiplet of $c\overline{c}$ hybrids to charmonium mesons. The results are compared to potential-quark models and lattice calculations.

Extra scalar fields are common in beyond Standard Model (SM) new physics, and they may mix with the 125 GeV SM-like Higgs boson discovered at the LHC. This fact suggests possible discovery channels for these new scalar fields with their decay modes involving the 125 GeV Higgs boson. In this work, we explore the LHC search potential of the heavy $CP$-even Higgs boson $H$ in the two-Higgs-doublet model. We focus on the channel of $H$ decaying to a pair of light $CP$-even Higgs bosons $h$, with two $h$’s decaying to two $b$ jets and diphoton sequentially. This channel is particularly involved when the relevant cubic coupling is enhanced. We find such enhancement to be possible when taking a large $CP$-odd Higgs mass input for the two-Higgs-doublet model spectrum. Analogous to the SM Higgs self-coupling measurement, the two $b$ jets plus diphoton final states are of particular interest due to the manageable SM background. After performing a cut-based analysis of both signal and background processes, we demonstrate the LHC search sensitivities for the heavy $CP$-even Higgs boson in a broad mass range via the two $b$ jets plus diphoton final states.

With the discovery of a particle that seems rather consistent with the minimal Standard Model Higgs boson, attention turns to questions of naturalness, fine-tuning, and what they imply for physics beyond the Standard Model and its discovery prospects at run II of the LHC. In this article we revisit the issue of naturalness, discussing some implicit assumptions that underly some of the most common statements, which tend to assign physical significance to certain regularization procedures. Vague arguments concerning fine-tuning can lead to conclusions that are too strong and perhaps not as generic as one would hope. Instead, we explore a more pragmatic definition of the hierarchy problem that does not rely on peeking beyond the murky boundaries of quantum field theory: we investigate the fine-tuning of the electroweak scale associated with thresholds from heavy particles, which is both calculable and dependent on the nature of the would-be ultraviolet completion of the Standard Model. We discuss different manifestations of new high-energy scales that are favored by experimental hints for new physics with an eye toward making use of fine-tuning in order to determine natural regions of the new physics parameter spaces.

We investigate the static $\overline{Q}Q$ potential for $N_f=2+1$ QCD at the physical point in the presence of a constant and uniform external magnetic field. The potential is found to be anisotropic and steeper in the directions transverse to the magnetic field than in the longitudinal one. In particular, when compared to the standard case with zero background field, the string tension increases (decreases) in the transverse (longitudinal) direction, while the absolute value of the Coulomb coupling and the Sommer parameter show an opposite behavior.