22980504
The Solar Acoustic Spectrum and Eigenmode Parameters
The Global Oscillation Network Group (GONG) project estimates the frequencies, amplitudes, and linewidths of more than 250,000 acoustic resonances of the sun from data sets lasting 36 days. The frequency resolution of a single data set is 0.321 microhertz. For frequencies averaged over the azimuthal order m, the median formal error is 0.044 microhertz, and the associated median fractional error is 1.6 × 10−5. For a 3-year data set, the fractional error is expected to be 3 × 10−6. The GONG m-averaged frequency measurements differ from other helioseismic data sets by 0.03 to 0.08 microhertz. The differences arise from a combination of systematic errors, random errors, and possible changes in solar structure.
46298471
Differential Rotation and Dynamics of the Solar Interior
Splitting of the sun's global oscillation frequencies by large-scale flows can be used to investigate how rotation varies with radius and latitude within the solar interior. The nearly uninterrupted observations by the Global Oscillation Network Group (GONG) yield oscillation power spectra with high duty cycles and high signal-to-noise ratios. Frequency splittings derived from GONG observations confirm that the variation of rotation rate with latitude seen at the surface carries through much of the convection zone, at the base of which is an adjustment layer leading to latitudinally independent rotation at greater depths. A distinctive shear layer just below the surface is discernible at low to mid-latitudes.
14723293
On the recovery of geometrodynamics from two different sets of first principles
Abstract The conventional spacetime formulation of general relativity may be recast as a dynamics of spatial 3-geometries (geometrodynamics). Furthermore, geometrodynamics can be derived from first principles. I investigate two distinct sets of these: (i) Hojman, Kuchař and Teitelboim's, which presuppose that the spatial 3-geometries are embedded in spacetime. (ii) The 3-space approach of Barbour, Foster, O Murchadha and Anderson in which the spatial 3-geometries are presupposed but spacetime is not. I consider how the constituent postulates of the conventional approach to relativity emerge or are to be built into these formulations. I argue that the 3-space approach is a viable description of classical physics (fundamental matter fields included), and one which affords considerable philosophical insight because of its ‘relationalist’ character. From these assumptions of less structure, it is also interesting that conventional relativity can be recovered (albeit as one of several options). However, contrary to speculation in the earlier 3-space approach papers, I also argue that this approach is not selective over which sorts of fundamental matter physics it admits. In particular, it does not imply the equivalence principle.
122864304
Direct measurement of the lifetime of the neutral pion
Abstract The lifetime of the neutral pion ( π 0 ) has been directly measured. The lifetime has been found to be τ π 0 = (0.897±0.022±0.017) × 10 −16 s. The systematic error results from uncertainties in the momentum spectrum of the π 0 used for the measurement. This measurement yields a decay width of the π 0 of (7.34±0.18±0.11) eV. An axial anomaly calculation, which neglects the finite mass of the π 0 , predicts a value of 7.87 eV.
120381541
Experimental study of pi- p ---> pi- n* at 8 and 16 gev/c
119252014
Relational Quadrilateralland. I. The Classical Theory
Relational particle mechanics models bolster the relational side of the absolute versus relational motion debate, and are additionally toy models for the dynamical formulation of General Relativity and its Problem of Time. They cover two aspects that the more commonly studied minisuperspace General Relativity models do not: 1) by having a nontrivial notion of structure and thus of cosmological structure formation and of localized records. 2) They have linear as well as quadratic constraints, which is crucial as regards modelling many Problem of Time facets. 
I previously solved relational triangleland classically, quantum mechanically and as regards a local resolution of the Problem of Time. This rested on triangleland's shape space being S^2 with isometry group SO(3), allowing for use of widely-known Geometry, Methods and Atomic/Molecular Physics analogies. I now extend this work to the relational quadrilateral, which is far more typical of the general N-a-gon, represents a `diagonal to nondiagonal Bianchi IX minisuperspace' step-up in complexity, and encodes further Problem of Time subtleties. The shape space now being CP^2 with isometry group SU(3)/Z_3, I now need to draw on Geometry, Shape Statistics and Particle Physics to solve this model; this is therefore an interdisciplinary paper. This Paper treats quadrilateralland at the classical level, and then Paper II provides a quantum treatment.
121752579
Precision Lifetime Measurements on Positive and Negative Muons
An experiment to measure and compare the free decay rates of positive and negative muons is described. Muons from the Nevis synchrocyclotron were stopped in a liquid-hydrogen target containing less than 1 ppm ${\mathrm{D}}_{2}$ and less than 1 part in ${10}^{9}$ of other impurities. In this situation, the rate of ${\ensuremath{\mu}}^{\ensuremath{-}}$ capture in ${\mathrm{H}}_{2}$ was the only significant correction to the free decay rate of ${\ensuremath{\mu}}^{\ensuremath{-}}$ and was measured in a separate experiment. The lifetimes were monitored by measuring the time intervals between muon stops and decay electrons using a transistorized digitron of 30-nsec channel width. Electronic circuitry of the "interference remover" type was employed to eliminate time-dependent background. ${\ensuremath{\mu}}^{\ensuremath{-}}$ and ${\ensuremath{\mu}}^{+}$ lifetimes were measured with the same apparatus and under essentially the same conditions of rate and geometry. The ratio of the lifetimes is expected to be particularly insensitive to any systematic errors. We have obtained: ${\ensuremath{\tau}}_{{\ensuremath{\mu}}^{\ensuremath{-}}}=2.198\ifmmode\pm\else\textpm\fi{}0.002$ \ensuremath{\mu}sec (hydrogen correction made), ${\ensuremath{\tau}}_{{\ensuremath{\mu}}^{+}}=2.197\ifmmode\pm\else\textpm\fi{}0.002$ \ensuremath{\mu}sec, $R=\frac{{\ensuremath{\tau}}_{{\ensuremath{\mu}}^{\ensuremath{-}}}}{{\ensuremath{\tau}}_{{\ensuremath{\mu}}^{+}}}=1.000\ifmmode\pm\else\textpm\fi{}0.001$.