We analytically calculate to leading order the asymptotic form of quasinormal frequencies of Kerr black holes in four, five, and seven dimensions. All the relevant quantities can be explicitly expressed in terms of elliptical integrals. In four dimensions, we confirm the results obtained by Keshest and Hod by comparing the analytic results to the numerical ones.

We calculate all of the 2 to 2 scattering process in Yang-Mills theory in the light cone gauge, with the dimensional regulator as the UV regulator. The IR is regulated with a cutoff in $q^{+}$. It supplements our earlier work, where a Lorentz noncovariant regulator was used, and the final results bear some problems in gauge fixing. Supersymmetry relations among various amplitudes are checked by using the light cone superfields.

Baryons in the massive Nambu-Jona-Lasinio model in $1+1$ dimensions (the massive chiral Gross-Neveu model) are studied in the limit of an infinite number of flavors. The baryon mass is evaluated for a wide range of bare fermion masses and filling fractions, combining analytical asymptotic expansions with a full numerical Hartree-Fock calculation.

A recent work has investigated the possibility that the mass scale for the ultraviolet (UV) brane in the Randall-Sundrum (RS) model is of the order ${10}^3\mathrm{TeV}$. In this so called “little Randall-Sundrum” (LRS) model the bounds on the gauge sector are less severe, permitting a lower Kaluza-Klein scale and cleaner discovery channels. However employing a low UV scale nullifies one major appeal of the RS model, namely, the elegant explanation of the hierarchy between the Planck and weak scales. In this work we show that by localizing the gauge, fermion, and scalar sector of the LRS model on a five dimensional slice of a doubly warped spacetime one may obtain the low UV brane scale employed in the LRS model and motivate the weak-Planck hierarchy. We also consider the generalization to an $n$-warped spacetime.

We use the functional renormalization group equation for quantum gravity to construct a nonperturbative flow equation for modified gravity theories of the form $S=\int d^{d}x\sqrt{g}f(R)$. Based on this equation we show that certain gravitational interaction monomials can be consistently decoupled from the renormalization group (RG) flow and reproduce recent results on the asymptotic safety conjecture. The nonperturbative RG flow of nonlocal extensions of the Einstein-Hilbert truncation including $\int d^{d}x\sqrt{g}\ln (R)$ and $\int d^{d}x\sqrt{g}{R}^{-n}$ interactions is investigated in detail. The inclusion of such interactions resolves the infrared singularities plaguing the RG trajectories with positive cosmological constant in previous truncations. In particular, in some $R^{-n}$ truncations all physical trajectories emanate from a non-Gaussian (UV) fixed point and are well-defined on all RG scales. The RG flow of the $\ln (R)$ truncation contains an infrared attractor which drives a positive cosmological constant to zero dynamically.

Most of the properties of black holes can be mimicked by horizonless compact objects such as gravastars and boson stars. We show that these ultracompact objects develop a strong ergoregion instability when rapidly spinning. Instability time scales can be of the order of 0.1 seconds to 1 week for objects with mass $M=1-{10}^6{M}_{\odot }$ and angular momentum $J>0.4M^2$. This provides a strong indication that ultracompact objects with large rotation are black holes. Explosive events due to ergoregion instability have a well-defined gravitational-wave signature. These events could be detected by next-generation gravitational-wave detectors such as Advanced LIGO or LISA.

The expectation-value equations for the collapse of a macroscopic, spherically symmetric, and uncharged body are integrated up to the limit of validity of semiclassical theory. The collapse finishes with a true stable black hole of the mass microscopically exceeding the vacuum-induced charge. The apparent horizon is almost closed. The most important feature of the solution is the presence of an irremovable Cauchy horizon.

The bending of light due to the curvature of spacetime close to a black hole is so strong that light can even return to the point of emittance yielding an Einstein ring. Using the analytic solution of the geodesic equation in Schwarzschild spacetime and a distant star or a flash of light, we will be able to determine the mass of a black hole as well as the distance of the observer to this black hole, at least in principle.

Nonbirefringent modified-Maxwell theory, coupled to standard Dirac particles, involves nine dimensionless parameters, which can be bounded by the inferred absence of vacuum Cherenkov radiation for ultrahigh-energy cosmic rays (UHECRs). With selected UHECR events, two-sided bounds on the eight nonisotropic parameters are obtained at the ${10}^{-18}$ level, together with an improved one-sided bound on the single isotropic parameter at the ${10}^{-19}$ level.

In this article we aim to estimate the bounds on the noncommutative scale ${\Lambda }_{\mathrm{NC}}$ and to extract the 95% exclusion contours for some ${\theta }_{\mu \nu }$ components using the recent measurements of the top quark width and the $W$ boson polarization in top pair events from CDF experiments at Tevatron.

If the observed light neutrino masses are induced by their Yukawa couplings to singlet right-handed neutrinos, the natural smallness of those makes direct collider tests of the electroweak scale neutrino mass mechanisms difficult in the simplest models. In the triplet Higgs seesaw scenario the smallness of light neutrino masses may come from the smallness of $B-L$ breaking parameters, allowing sizable Yukawa couplings even for a TeV scale triplet. We show that, in this scenario, measuring the branching fractions of doubly charged Higgs to different same-charged lepton flavors at CERN LHC and/or ILC experiments will allow one to measure the neutrino mass parameters that neutrino oscillation experiments are insensitive to, including the neutrino mass hierarchy, lightest neutrino mass, and Majorana phases.

We study the decay $B\to X_s\gamma$ within the framework of the minimal 331 model, taking into account both new experimental and theoretical developments that allow us to update and improve on an existing 10 yr old analysis. In contrast to several other flavor changing observables that are modified already at tree level from a new $Z^{\prime }$ gauge boson, we have only one loop contributions in this case. Nevertheless, these are interesting, as they may be enhanced and can shed light on the charged gauge boson and Higgs sector of the model. Numerically, we find that the Higgs sector, which is well approximated by a 2 Higgs doublet model (2HDM), dominates, since the gauge contributions are already very strongly constrained. With respect to $B\to X_s\gamma$, the signal of the minimal 331 model is therefore nearly identical to the 2HDM one, which allows us to obtain a lower bound on the charged Higgs mass. Further, we observe, in analogy to the 2HDM model, that the branching fraction can be rather strongly increased for small values of $\tan \beta$. Also, we find that $B\to X_s\gamma$ has no impact on the bounds obtained on rare $K$ and $B$ decays in an earlier analysis.

We examine the eigenvalues and eigenvectors of the staggered Dirac operator on thermal ensembles created in QCD with two flavors of staggered quarks. We see that across the phase transition a gap opens in the spectrum. For finite volume lattices in the low-temperature phase the eigenvectors are extended, but generic field configurations in the high temperature phase give rise to localized eigenstates. We examine measures of the stability of such localization and find that at finite volumes localization occurs through Mott’s mechanism of the formation of mobility edges. However, the band gap between the localized and extended states seem to scale to zero in the limit of large volume.

We present one-loop matching coefficients between continuum and lattice QCD for the heavy-light four-fermion operators relevant for neutral $B$ meson mixing both within and beyond the standard model. For the lattice theory we use nonrelativistic QCD (NRQCD) to describe $b$ quarks and improved staggered fermions (AsqTad) for light quarks. The gauge action is the tree-level Symanzik improved gauge action. Matching to full QCD is carried out through order ${\alpha }_s$, ${\Lambda }_{\mathrm{QCD}}/M_b$, and ${\alpha }_s/(a{M}_b)$.

The nonvanishing of gluonic pole matrix elements can explain the appearance of single spin asymmetries in high-energy scattering processes. We use a spectator framework approach to investigate the spectral properties of quark-quark-gluon correlators and use this to study gluonic pole matrix elements. Such matrix elements appear in principle both for distribution functions such as the Sivers function and fragmentation functions such as the Collins function. We find that for a specific class of spectator models, the contribution of the gluonic pole matrix element in fragmentation functions vanishes. This outcome is important in the study of universality for fragmentation functions and confirms findings using a different approach.

In this paper, we examine $B\to VT$ decays ($V$ is a vector and $T$ is a tensor meson), whose final-state particles can have transverse or longitudinal polarization. Measurements have been made of $B\to \varphi K_2^{*}$, and it is found that $f_T/f_L$ is small, where $f_T$ ($f_L$) is the fraction of transverse (longitudinal) decays. We find that the standard model naively predicts that $f_T/f_L\ll 1$. The two extensions of the naive standard model which have been proposed to explain the large $f_T/f_L$ in $B\to \varphi K^{*}$—penguin annihilation and rescattering—make no firm predictions for the polarization in $B\to \varphi K_2^{*}$. The two new-physics scenarios, which explain the data in $B\to \pi K$ and the $\varphi (\rho )K^{*}$ polarization measurements, can reproduce the $f_T/f_L$ data in $B\to \varphi K_2^{*}$ only if the $B\to T$ form factors obey a certain hierarchy. Finally, we present the general angular analysis which can be used to get helicity information using two- and three-body decays.

The rare $B_c\to D_{s,d}^{*}{l}^{+}{l}^{-}$ decays are investigated in the framework of the three-point QCD sum rules approach. Considering the gluon condensate corrections to the correlation function, the form factors relevant to these transitions are calculated. The total decay width and branching ratio for these decays are also evaluated. The results for the branching ratios are in good agreement with the quark models.

Parity-violating deep inelastic scattering (PVDIS) has been proposed as an important new tool to extract the flavor and isospin dependence of parton distributions in the nucleon. We discuss finite-$Q^2$ effects in PVDIS asymmetries arising from subleading kinematical corrections and longitudinal contributions to the $\gamma Z$ interference. For the proton, these need to be accounted for in order to accurately extract the $d/u$ ratio at large $x$; for the deuteron they are important to consider when searching for evidence of charge symmetry violation in parton distributions or signals for physics beyond the standard model. We further explore the dependence of PVDIS asymmetries for polarized targets on the $u$ and $d$ helicity distributions at large $x$.

In the past decade, lattice QCD has been able to compute the low-lying glueball spectrum with accuracy. Like other effective approaches of QCD, potential models still have difficulties to cope with gluonic hadrons. Assuming that glueballs are bound states of valence gluons with zero current mass, it is readily understood that the use of a potential model, intrinsically noncovariant, could be problematic in this case. The main challenge for this kind of model is actually to find a way to introduce properly the more relevant degree of freedom of the gluon: spin or helicity. In this work, we use the so-called helicity formalism of Jacob and Wick to describe two-gluon glueballs. We show, in particular, that this helicity formalism exactly reproduces the $J^{PC}$ numbers which are observed in lattice QCD when the constituent gluons have a helicity-1, without introducing extra states as is the case in most of the potential models. These extra states appear when gluons are seen as spin-1 particles. Using a simple spinless Salpeter model with Cornell potential within the helicity formalism, we obtain a glueball mass spectrum which is in good agreement with lattice QCD predictions for helicity-1 gluons provided instanton-induced interactions are taken into account.

A completely model-independent method of obtaining information on the spin using the quantum interference effect among various helicity states was proposed in a recent paper. Here we point out that this effect should be demonstrable in the existing data on $e^{-}{e}^{+}\to W^{+}{W}^{-}$ at LEP-II and $p\overline{p}\to Z^0+j$ at Tevatron.