Modern Physics Letters A

Polarization measurements are the best instrument to understand how quark and antiquark combine into the different quarkonium states, but no model has so far succeeded in explaining the measured J/ψ and ϒ polarizations. On the other hand, the experimental data in proton–antiproton and proton–nucleus collisions are inconsistent, incomplete and ambiguous. New analyses will have to properly address often underestimated issues: the existence of azimuthal anisotropies, the dependence on the reference frame, the influence of the experimental acceptance on the comparison with other measurements and with theory. Additionally, a recently developed frame-invariant formalism will provide an alternative and often more immediate physical viewpoint and, at the same time, will help probing systematic effects due to experimental biases. The role of feed-down decays from heavier states, a crucial missing piece in the current experimental knowledge, will have to be investigated. Ultimately, quarkonium polarization measurements will also offer new possibilities in the study of the properties of the quark–gluon plasma.

Motivated by recent physical interpretation on quasinormal modes presented by Maggiore [Phys. Rev. Lett. 100, 141301 (2008)], the adiabatic quantity method given by Kunstatter [Phys. Rev. Lett. 90, 161301 (2003)] is used to calculate the spectrums of a non-extremal Schwarzschild de Sitter black hole in this paper, as well as electrically charged case. According to highly damped Konoplya and Zhidenko's numerical observational results for high overtone modes [JHEP 06, 037 (2004)], we found that the asymptotic non-flat spacetime structure leads to two interesting facts: (i) near inner event horizon, the area and entropy spectrums, which are given by A_en = 8 n₁ πℏ, S_en = 2πn₁ℏ, are equally spaced accurately. (ii) However, near outer cosmological horizon the spectrums, which are in the form of , are not markedly equidistant. Finally, we also discuss the electrically charged case and find that the black holes in de Sitter spacetime have similar quantization behavior no matter with or without charge.

New spherical scalar modes on the expanding part of Sitter spacetime, eigenfunctions of a conserved Hamiltonian-like operator are found by solving the Klein–Gordon equation in the appropriate coordinate chart, with the help of a time evolution picture technique specially developed for spatially flat Friedmann–Lemaître–Robertson–Walker (FLRW) charts. Transition coefficients are computed between these modes and the rest of the scalar spherical and plane wave modes, either momentum or energy eigenfunctions on the spatially flat FLRW chart.

We analyze the potential of Compact Linear Colliders (CLIC) based on the γe^- collisions to search for the radion in the Randall–Sundrum (RS) model, where compactification radius of the extra dimension is stabilized by the radion, which is a scalar field lighter than the graviton Kaluza–Klein states. The radion production in high energy γe^- colliders with the polarization of the electron beams are calculated in detail. Numerical evaluation shows that if the radion mass is not too heavy with the mass order of GeV, then the reaction can give observable cross-section in future colliders at the high degree of polarization.

Effective field theory (EFT) of massive Yang–Mills fields interacting with fermions is considered. Perturbative renormalizability in the framework of EFT is shown. It is argued that the limit of vanishing vector boson mass leads to massless gauge EFT. Possible relevance for the solution to the strong CP problem is discussed.

Traditional geometry employs idealized concepts like that of a point or a curve, the operational definition of which relies on the availability of classical point particles as probes. Real, physical objects are quantum in nature though, leading us to consider the implications of using realistic probes in defining an effective spacetime geometry. As an example, we consider de Sitter spacetime and employ the centroid of various composite probes to obtain its effective sectional curvature, which is found to depend on the probe's internal energy, spatial extension, and spin. Possible refinements of our approach are pointed out and remarks are made on the relevance of our results to the quest for a quantum theory of gravity.

We linearize the field equations for higher order theories of gravity that contain scalar invariants other than the Ricci scalar. We find that besides a massless spin-2 field (the standard graviton), the theory contains also spin-0 and spin-2 massive modes with the latter being, in general, ghost modes. The rate at which such particles would emit gravitational Cherenkov radiation is calculated for some interesting physical cases.