A Ramsey theorem for trees

We prove a Ramsey theorem for trees. The infinite version of this theorem can be stated: if T is a rooted tree of infinite height with each node of T having at least one but finitely many immediate successors, if n is a positive integer, and if the collection of all strongly embedded, height-n subtrees of T is partitioned into finitely many classes, then there must exist a strongly embedded subtree S of T with S having infinite height and with all the strongly embedded, height-n subtrees of S in the same class.     

De haas-van alphen effect in stage 2 graphite-AsF5

We have observed dHvA frequencies in several samples of stage 2 graphite-AsF₅ intercalation compound. A consistent interpretation is given in terms of two nested hole surfaces located at each of the 6 corners of the 2D graphite zone. A fractional ionization f = 0.42 is obtained, consistent with spin susceptibility, with the Blinowski-Rigaux analysis of reflectivity, and with recent chemical results.     

Direct measurement of the lifetime of the neutral pion

The lifetime of the neutral pion (π⁰) has been directly measured. The lifetime has been found to be τ_π⁰ = (0.897±0.022±0.017) × 10^?16 s. The systematic error results from uncertainties in the momentum spectrum of the π⁰ used for the measurement. This measurement yields a decay width of the π⁰ of (7.34±0.18±0.11) eV. An axial anomaly calculation, which neglects the finite mass of the π⁰, predicts a value of 7.87 eV.     

Experimental demonstration of an oscillator stabilized Josephson flux qubit

We experimentally demonstrate the use of a superconducting transmission line, shorted at both ends, to stabilize the operation of a tunable flux qubit. Using harmonic-oscillator stabilization and pulsed dc operation, we have observed Larmor oscillations with a single shot visibility of 90%. In another qubit, the visibility was 60% and there was no measurable visibility reduction after 35 ns.     

Electrical Characteristics of an Aluminum: Trans- (Ch)X Photodiode and Possible Defect-Related Current Transport

We have measured the electrical characteristics of photodiodes made by vacuum deposition of aluminum onto fibrous trans-(CH)_x. The trans-(CH)_x was not intentionally doped. The polymer surface was rough, so the Al overlayers were irregular. They were thick, to have low resistance, and had gaps that allowed some light into the junction. A simple equivalent circuit was fitted to the dark and illuminated current-voltage characteristics. The room temperature diode quality factor, n, was 1.9 for the junction in this circuit. This result is consistent with several mechanisms for the forward diode current, including that of charge carrier recombination at defects in the junction space charge region of the trans-(CH)_x.     

Hindman's theorem and groups

We prove a theorem which limits the possible uncountable generalizations of Hindman's theorem.