We present theoretical arguments and strong phenomenological evidence that hadronic Regge trajectories are essentially nonlinear and can be well approximated, for phenomenological purposes, by a specific square-root form.

We present the first numerical QCD bound state calculation based on a renormalization group-improved light-front Hamiltonian formalism. The QCD Hamiltonian is determined to second order in the coupling, and it includes two-body confining interactions. We make a momentum expansion, obtaining an equal-time-like Schrődinger equation. This is solved for quark-antiquark constituent states, and we obtain a set of self-consistent parameters by fitting B meson spectra.

A constituent parton picture of hadrons with logarithmic confinement naturally arises in weak coupling light-front QCD. Confinement provides a mass gap that allows the constituent picture to emerge. The effective renormalized Hamiltonian is computed to ${\cal O}(g^2)$, and used to study charmonium and bottomonium. Radial and angular excitations can be used to fix the coupling $\alpha$, the quark mass $M$, and the cutoff $\Lambda$. The resultant hyperfine structure is very close to experiment.Comment: 9 pages, 1 latex figure included in the text. Published version (much more reader-friendly); corrected error in self-energ

Using the "glueball dominance" picture of the mixing between qq mesons of different hidden flavors, we establish new glueball-meson mass relations which serve as a basis for glueball spectral systematics. For the tensor glueball mass 2.3 ± 0.1 GeV used as an input parameter, these relations predict the following glueball masses: M (0 ++ ) ≃ 1.65 ± 0.05 GeV, M (1 −− ) ≃ 3.2 ± 0.2 GeV, M (2 −+ ) ≃ 2.95 ± 0.15 GeV, M (3 −− ) ≃ 2.8 ± 0.15 GeV. We briefly discuss the failure of such relations for the pseudoscalar sector. Our results are consistent with (quasi)-linear Regge trajectories for glueballs with slope ≃ 0.3 ± 0.1 GeV −2 .

We consider a class of cosmological models in which the universe is filled with a (non-electric) charge density that repels itself by means of a force carried by a vector boson with a tiny mass. When the vector's mass depends upon other fields, the repulsive interaction gives rise to an electromagnetic barrier which prevents these fields from driving the mass to zero. This can modify the cosmology dramatically. We present a very simple realization of this idea in which the vector's mass arises from a scalar field. The electromagnetic barrier prevents this field from rolling down its potential and thereby leads to accelerated expansion. 98.80.Cq,04.62.+v,98.80.Hw