The purpose of this paper is to study quasinormal modes (QNM) of the Bardeen black hole due to scalar perturbations. We have done a thorough analysis of the QNM frequencies by varying the charge $q$, mass $M$ and the spherical harmonic index $l$. The unstable null geodesics are used to compute the QNM’s in the eikonal limit. Furthermore, massive scalar field modes are also studied by varying the mass of the field. Comparisons are done with the QNM frequencies of the Reissner-Nordstrom black hole.

Backreaction effects of the large-scale structure on the background dynamics have been claimed to lead to a renormalization of the background dynamics that may account for the late time acceleration of the cosmic expansion. This article emphasizes that generically the averaged flow is locally anisotropic, a property that can be related to observation. Focusing on perturbation theory, the spatially averaged shear, that characterizes the anisotropy of the flow, is computed. It is shown that this shear arising from backreaction differs from a homogeneous shear: its time evolution is different, and its amplitude is completely determined by the cosmological parameters and the matter power spectrum. It ranges within 2% and 37% at a redshift of order 0.5 so that the isotropy of the Hubble flow may allow us to constrain the backreaction approach to dark energy.

Rapidly rotating, slightly nonaxisymmetric neutron stars emit nearly periodic gravitational waves (GWs), quite possibly at levels detectable by ground-based GW interferometers. We refer to these sources as “GW pulsars.” For any given sky position and frequency evolution, the $\mathcal{F}$-statistic is the maximum likelihood statistic for the detection of GW pulsars. However, in “all-sky” searches for previously unknown GW pulsars, it would be computationally intractable to calculate the (fully coherent) $\mathcal{F}$-statistic at every point of (a suitably fine) grid covering the parameter space: the number of grid points is many orders of magnitude too large for that. Therefore, in practice some nonoptimal detection statistic is used for all-sky searches. Here we introduce a “phase-relaxed” $\mathcal{F}$-statistic, which we denote ${\mathcal{F}}_{\mathrm{pr}}$, for incoherently combining the results of fully coherent searches over short time intervals. We estimate (very roughly) that for realistic searches, our ${\mathcal{F}}_{\mathrm{pr}}$ is $\sim 10–15\%$ more sensitive than the “semicoherent” $\mathcal{F}$-statistic that is currently used. Moreover, as a by-product of computing ${\mathcal{F}}_{\mathrm{pr}}$, one obtains a rough determination of the time-evolving phase offset between one’s template and the true signal imbedded in the detector noise. Almost all the ingredients that go into calculating ${\mathcal{F}}_{\mathrm{pr}}$ are already implemented in the LIGO Algorithm Library, so we expect that relatively little additional effort would be required to develop a search code that uses ${\mathcal{F}}_{\mathrm{pr}}$.

We study the real-time behavior of classical Yang-Mills theory under initial conditions with nonperturbatively large, infrared field amplitudes. Our lattice study confirms the cascade of energy toward higher momenta and lower occupancy, which occurs via a scaling solution $f[p,t_1]=(t_0/t_1{)}^{\frac{4}{7}}f[p(t_0/t_1{)}^{\frac{1}{7}},t_0]$. Above a characteristic scale $p_{\max }$, $f$ falls exponentially; below $p_{\max }$, $f[p]\propto p^{\frac{-4}{3}}$. We find no evidence for different infrared exponents or for infrared occupancies in excess of those described by this scaling solution. We also investigate what the fate of large occupancies would be, both in the electric and the magnetic sector.

Motivated by the large like-sign dimuon charge asymmetry observed recently, whose explanation would require an enhanced decay rate of $B_s\to {\tau }^{+}{\tau }^{-}$, we explore how large a branching ratio of this decay mode is allowed by the present constraints. We use bounds from the lifetimes of $B_d$ and $B_s$, constraints from the branching ratios of related $b\to s{\tau }^{+}{\tau }^{-}$ modes, as well as measurements of the mass difference, width difference and $CP$-violating phase in the $B_s\mathrm{\text{−}}{\overline{B}}_s$ system. Using an effective field theory approach, we show that a branching ratio as high as 15% may be allowed while being consistent with the above constraints. The measurement of this decay, therefore, may be within the reach of current experiments and can point toward a specific class of new physics models. We also explore the possible enhancement of this decay in models with leptoquarks and $Z^{\prime }$ and find that, in the latter case, the branching ratio may be as much as 5%, which can alleviate the dimuon anomaly to some extent.

We show that the charge asymmetry in $t\overline{t}$ production at the LHC, $A_C$, and the forward-backward asymmetry at the Tevatron, $A_{\mathrm{FB}}$, are in general not tightly correlated. They can even have opposite signs if the underlying new physics (NP) model is general enough. We demonstrate this using two examples of NP: a light axigluon, and a vector that is a color octet and electroweak triplet. The small value of $A_C$ measured at the LHC is thus shown not to exclude a NP interpretation of the anomalously large $A_{\mathrm{FB}}$ at the Tevatron. We identify two observables where significant NP effects are still expected at the Tevatron and the LHC, the $b\overline{b}$ production forward-backward asymmetry and spin polarizations of the pair-produced tops and antitops.

Within the framework of nonrelativistic QCD, we present a detailed discussion on doubly heavy baryon production through the $e^{+}{e}^{-}$ annihilation channel, $e^{+}{e}^{-}\to \gamma /Z^0\to {\Xi }_{Q{Q}^{\prime }}+\overline{Q}+{\overline{Q}}^{\prime }$, at a high luminosity $e^{+}{e}^{-}$ collider. Here $Q^{(\prime )}$ stands for the heavy $b$ or $c$ quark. In addition to the channel through the usually considered diquark state $(Q{Q}^{\prime })[{}^{3}S_1{]}_{\overline{\mathbf{3}}}$, contributions from the channels through other equally important diquark states such as $(Q{Q}^{\prime })[{}^{1}S_0{]}_{\mathbf{6}}$ are also discussed. Uncertainties for the total cross sections are predicted by taking $m_c=1.80\pm 0.30\mathrm{GeV}$ and $m_b=5.10\pm 0.40\mathrm{GeV}$. At a super-$Z$ factory running around the $Z^0$ mass and with a high luminosity up to $\mathcal{L}\propto {10}^{34}\sim {10}^{36}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$, we estimate that about $1.1\times {10}^{5–7}$ ${\Xi }_{cc}$ events, $2.6\times {10}^{5–7}$ ${\Xi }_{bc}$ events, and $1.2\times {10}^{4–6}$ ${\Xi }_{bb}$ events can be generated in one operation year. Such a $Z$ factory, thus, will provide a good platform for studying doubly heavy baryons in a manner comparable to the CERN Large Hadron Collider.

We present a quantitative assessment of the impact a future electron-ion collider will have on determinations of helicity quark and gluon densities and their contributions to the proton spin. Our results are obtained by performing a series of global QCD analyses at next-to-leading order accuracy based on realistic sets of pseudo-data for the inclusive and semi-inclusive deep-inelastic scattering of longitudinally polarized electrons and protons at different, conceivable center-of-mass system energies.

The pattern of lepton mixing can emerge from breaking a flavor symmetry in different ways in the neutrino and charged lepton Yukawa sectors. In this framework, we derive the model-independent conditions imposed on the mixing matrix by the structure of discrete groups of the von Dyck type which include ${\mathbf{A}}_4$, ${\mathbf{S}}_4$, and ${\mathbf{A}}_5$. We show that, in general, these conditions lead to at least two equations for the mixing parameters (angles and $CP$ phase $\delta$). These constraints, which correspond to unbroken residual symmetries, are consistent with nonzero 13 mixing and deviations from maximal 2–3 mixing. For the simplest case, which leads to an ${\mathbf{S}}_4$ model and reproduces the allowed values of the mixing angles, we predict $\delta =(90°–120°)$.

The MiniBooNE and SciBooNE collaborations report the results of a joint search for short baseline disappearance of ${\overline{\nu }}_{\mu }$ at Fermilab’s Booster Neutrino Beamline. The MiniBooNE Cherenkov detector and the SciBooNE tracking detector observe antineutrinos from the same beam, therefore the combined analysis of their data sets serves to partially constrain some of the flux and cross section uncertainties. Uncertainties in the ${\nu }_{\mu }$ background were constrained by neutrino flux and cross section measurements performed in both detectors. A likelihood ratio method was used to set a 90% confidence level upper limit on ${\overline{\nu }}_{\mu }$ disappearance that dramatically improves upon prior limits in the $\Delta m^2=0.1–100{\mathrm{eV}}^2$ region.

Recently, the Auger group has extracted the proton-air cross section from observations of air showers produced by cosmic ray protons (and nuclei) interacting in the atmosphere, and converted it into measurements of the total and inelastic $pp$ cross sections ${\sigma }_{\mathrm{tot}}$ and ${\sigma }_{\mathrm{inel}}$ at the super-LHC energy of 57 TeV. Their results reinforce our earlier conclusions that the proton becomes a black disk at asymptotic energies, a prediction reached on the basis of sub-LHC $\overline{p}p$ and $pp$ measurements of ${\sigma }_{\mathrm{tot}}$ and $\rho$, the ratio of the real to the imaginary part of the forward scattering amplitude [M. M. Block and F. Halzen, Phys. Rev. Lett. 107, 212002 (2011)]. The same black disk description of the proton anticipated the values of ${\sigma }_{\mathrm{tot}}$ and ${\sigma }_{\mathrm{inel}}$ measured by the TOTEM experiment at the LHC c.m. (center of mass) energy of $\sqrt{s}=7\mathrm{TeV}$, as well as those of ${\sigma }_{\mathrm{inel}}$ measured by ALICE, ATLAS and CMS, as well as the ALICE measurement at 2.76 TeV. All data are consistent with a proton that is asymptotically a black disk of gluons: (i) both ${\sigma }_{\mathrm{tot}}$ and ${\sigma }_{\mathrm{inel}}$ behave as ${ln}^{2}s$, saturating the Froissart bound; (ii) the forward scattering amplitude becomes pure imaginary; (iii) the ratio ${\sigma }_{\mathrm{inel}}/{\sigma }_{\mathrm{tot}}=0.509\pm 0.021$, compatible with the black disk value of $\frac{1}{2}$; and (iv) proton interactions become flavor blind.

Direct detection experiments searching for weakly interacting massive particle (WIMP) dark matter typically use a simplified model of the Galactic halo to derive parameter constraints. However, there is strong evidence that this Standard Halo Model is not a good approximation to our Galaxy. We discuss previous attempts to extract the WIMP mass, cross section and speed distribution from direct detection data and show that these lead to significant biases in the reconstructed parameter values. We develop and test an alternative model-independent method based on parametrizing the momentum distribution of the WIMPs. This allows us to limit the analysis only to those regions of momentum space to which the experiments are sensitive. The method can be applied to a single experiment to extract information about the distribution function, as well as information on the degenerate WIMP mass and interaction cross section combined in a single parameter. This degeneracy can be broken by including data from additional experiments, meaning that the WIMP mass and speed distribution can be recovered. We test the momentum parametrization method using mock data sets from proposed ton-scale direct detection experiments, showing that it exhibits improved coverage properties over previous methods, as well as significantly reduced bias. We are also able to accurately reconstruct the shape of the WIMP speed distribution but distinguishing between different underlying distributions remains difficult.

We provide an explicit construction for Gazeau-Klauder coherent states related to non-Hermitian Hamiltonians with discrete bounded below and nondegenerate eigenspectrum. The underlying spacetime structure is taken to be of a noncommutative type with associated uncertainty relations implying minimal lengths. The uncertainty relations for the constructed states are shown to be saturated in a Hermitian as well as a non-Hermitian setting for a perturbed harmonic oscillator. The computed value of the Mandel parameter dictates that the coherent wave packets are assembled according to sub-Poissonian statistics. Fractional revival times, indicating the superposition of classical-like sub-wave packets, are clearly identified.

We show how the relativistic matter and velocity power spectra behave in different gauges. We construct a new gauge where both spectra coincide with Newtonian theory on all scales. However, in this gauge there are geometric quantities present which do not exist in Newtonian theory, for example the local variation of the Hubble parameter. Comparing this quantity to second-order Newtonian quantities, we find that Newtonian theory is inaccurate on scales larger than 10 Mpc. This stresses the importance of relativistic corrections to Newtonian cosmological $N$-body simulations on these scales.

We study the impact of primordial non-Gaussianity generated during inflation on the bias of halos using excursion set theory. We recapture the familiar result that the bias scales as $k^{-2}$ on large scales for local type non-Gaussianity but explicitly identify the approximations that go into this conclusion and the corrections to it. We solve the more complicated problem of nonspherical halos, for which the collapse threshold is scale-dependent.

The Fermi-LAT telescope has unexpectedly discovered GeV $\gamma$-ray emission from the symbiotic Nova V407 Cygni. We investigate the radiation processes due to electrons and hadrons accelerated during the explosion of this nova. We consider a scenario in which GeV $\gamma$-ray emission observed by Fermi is produced by the electrons with energies of a few tens of GeV in the inverse Compton scattering of stellar radiation. On the other hand, the hadrons are expected to reach larger energies, due to the lack of radiation losses during acceleration process, producing TeV $\gamma$ rays and neutrinos. We predict the fluxes of very high energy $\gamma$ rays and neutrinos from novas of the V407 type for two models of hadron acceleration and discuss their possible detectability by the present and future telescopes (e.g., IceCube, CTA).

Within the 3-3-1 model framework, we consider the production and decay of fermionic leptoquarks into a striking experimental signature at the LHC: a narrow resonance at the $b$ jet plus same-sign dileptons channel. The data already accumulated by the LHC collaborations may hide a large number of events associated to the production and decay of such exotic quarks, allowing one to investigate large portions of the parameters space of the model. The observation or not of such events would shed light on the construction of models presenting heavy exotic quarks.

We investigate the effects of gluon number fluctuations on the total $\gamma \gamma$, ${\gamma }^{*}{\gamma }^{*}$ cross sections and the photon structure function $F_2^{\gamma }(x,Q^2)$. Considering a model which relates the dipole-dipole and dipole-hadron scattering amplitudes, we estimate these observables by using event-by-event and physical amplitudes. We demonstrate that both analyses are able to describe the LEP data, but predict different behaviors for the observables at high energies, with the gluon fluctuations effects decreasing the cross sections. We conclude that the study of $\gamma \gamma$ interactions can be useful to constrain the QCD dynamics.

In conventional treatments, predictions from fixed-order perturbative QCD calculations cannot be fixed with certainty because of ambiguities in the choice of the renormalization scale as well as the renormalization scheme. In this paper we present a general discussion of the constraints of the renormalization group (RG) invariance on the choice of the renormalization scale. We adopt the RG-based equations, which incorporate the scheme parameters, for a general exposition of RG invariance, since they simultaneously express the invariance of physical observables under both the variation of the renormalization scale and the renormalization scheme parameters. We then discuss the self-consistency requirements of the RG, such as reflexivity, symmetry, and transitivity, which must be satisfied by the scale-setting method. The principle of minimal sensitivity requires the slope of the approximant of an observable to vanish at the renormalization point. This criterion provides a scheme-independent estimation, but it violates the symmetry and transitivity properties of the RG and does not reproduce the Gell-Mann-Low scale for QED observables. The principle of maximum conformality (PMC) satisfies all of the deductions of the RG invariance—reflectivity, symmetry, and transitivity. Using the PMC, all nonconformal $\{{\beta }_i^{\mathcal{R}}\}$ terms ($\mathcal{R}$ stands for an arbitrary renormalization scheme) in the perturbative expansion series are summed into the running coupling, and one obtains a unique, scale-fixed, scheme-independent prediction at any finite order. The PMC scales and the resulting finite-order PMC predictions are both to high accuracy independent of the choice of initial renormalization scale, consistent with RG invariance. Moreover, after PMC scale setting, the residual initial scale dependence at fixed order owing to unknown higher-order $\{{\beta }_i\}$ terms can be substantially suppressed. The PMC thus eliminates a serious systematic scale error in perturbative quantum chromodynamics predictions, greatly improving the precision of tests of the Standard Model and the sensitivity to new physics at collider and other experiments.