1. I have recorded with tungsten microelectrodes from single cells in the monkey's visual cortex and have specifically studied those neurons which were sensitive to the color of the stimulus. In the primate striate cortex there are four classes of color-coded cells. The cells described in this paper have concentric receptive fields with one red-green… (More)
We discuss lattice methods to obtain the derivatives of a lattice meson mass with respect to the bare sea and valence quark masses. Applications are made to quenched and dynamical fermion configurations. We find evidence for significant differences between quenched and dynamical fermion configurations. We discuss how to relate dependence on the bare lattice… (More)
Lattice QCD determinations appropriate to hadron spectroscopy are reviewed with emphasis on the glueball and hybrid meson states in the quenched approximation. Hybrids are discussed for heavy and for light quarks. The effects of sea quarks (un-quenching) are explored. Heavy-light systems are presented-particularly excited B mesons.
We have examined the patterns of termination of single, physiologically identified optic tract fibers in the dorsal lateral geniculate nucleus (LGNd) of the cat. The axons were impaled with a recording micropipette and characterized by their responses to light and by their conduction latencies to electrical stimulation of the optic nerve. Horseradish… (More)
We present results of dynamical simulations of N f = 2 degenerate Wilson twisted mass quarks at maximal twist in the range of pseudo scalar masses 300 MeV m PS 550 MeV. Reaching such small masses was made possible owing to a recently developed variant of the HMC algorithm. The simulations are performed at one value of the lattice spacing a 0.1 fm. In order… (More)
We review lattice QCD results for glueballs (including a discussion of mixing with scalar mesons), hybrid mesons and exotic mesons (such as B s B s molecules).
We evaluate properties of neutral mesons in N f = 2 dynamical simulations of TMQCD at maximal twist. The pion is explored-establishing the size of the isospin splitting (an order a 2 effect). We investigate the η ′ (the N f = 2 flavour singlet pseudoscalar meson) and neutral ρ and scalar mesons. We show that disconnected diagrams can be evaluated very… (More)
The status of lattice determinations of quarkonia and hybrid meson spectra is presented and compared with experiment. Both quenched and unquenched results are discussed. Hybrid meson decays are considered. T his paper discusses the consequences from first principles of QCD for the heavy quark-antiquark bound states: quarkonia and hybrid mesons. This is… (More)