Fingers of God

Very long wavelength universal gravitational waves cannot now produce in clusters of galaxies velocity dispersions greater than that which these systems would possess if they were expanding with the Universe, if the Universe is not younger than $10^{10}$ yr and Hubble's constant is not less than 50 km/sec/ Mpc. A diagram shows that actual velocity dispersions are significantly greater than this limit.Comment: Published long before the advent of large-scale redshift surveys, as "A Critique of Rees's Theory of Primordial Gravitational Radiation", this paper includes the first presentation of what has come to be known as the fingers-of-god effect. The effect is mentioned several hundred times in arXive papers, rarely with a wrong attribution, usually with none at al

Inflating and Deflating Hot Jupiters: Coupled Tidal and Thermal Evolution of Known Transiting Planets

We examine the radius evolution of close-in giant planets with a planet evolution model that couples the orbital-tidal and thermal evolution. For 45 transiting systems, we compute a large grid of cooling/contraction paths forward in time, starting from a large phase space of initial semi-major axes and eccentricities. Given observational constraints at the current time for a given planet (semi-major axis, eccentricity, and system age) we find possible evolutionary paths that match these constraints, and compare the calculated radii to observations. We find that tidal evolution has two effects. First, planets start their evolution at larger semi-major axis, allowing them to contract more efficiently at earlier times. Second, tidal heating can significantly inflate the radius when the orbit is being circularized, but this effect on the radius is short-lived thereafter. Often circularization of the orbit is proceeded by a long period while the semi-major axis slowly decreases. Some systems with previously unexplained large radii that we can reproduce with our coupled model are HAT-P-7, HAT-P-9, WASP-10, and XO-4. This increases the number of planets for which we can match the radius from 24 (of 45) to as many as 35 for our standard case, but for some of these systems we are required to be viewing them at a special time around the era of current radius inflation. This is a concern for the viability of tidal inflation as a general mechanism to explain most inflated radii. Also, large initial eccentricities would have to be common. We also investigate the evolution of models that have a floor on the eccentricity, as may be due to a perturber. In this scenario we match the extremely large radius of WASP-12b. (Abridged)Comment: 18 pages, 14 figures, 2 tables, Accepted for publication in Ap

Comment on "Classical and Quantum Interaction of the Dipole"

In this paper I have presented Comment on Anandan's paper (J. Anandan, Phys. Rev. Lett. 85, 1354 (2000)) [hep-th/9910018].Comment: 1 page, revtex; small changes, mainly typos, according to the published version in Phys. Rev. Let

Oxidation of GaN: An ab initio thermodynamic approach

GaN is a wide-bandgap semiconductor used in high-efficiency LEDs and solar cells. The solid is produced industrially at high chemical purities by deposition from a vapour phase, and oxygen may be included at this stage. Oxidation represents a potential path for tuning its properties without introducing more exotic elements or extreme processing conditions. In this work, ab initio computational methods are used to examine the energy potentials and electronic properties of different extents of oxidation in GaN. Solid-state vibrational properties of Ga, GaN, Ga2O3 and a single substitutional oxygen defect have been studied using the harmonic approximation with supercells. A thermodynamic model is outlined which combines the results of ab initio calculations with data from experimental literature. This model allows free energies to be predicted for arbitrary reaction conditions within a wide process envelope. It is shown that complete oxidation is favourable for all industrially-relevant conditions, while the formation of defects can be opposed by the use of high temperatures and a high N2:O2 ratio

A legislative bargaining approach to earmarked public expenditures

This paper develops a model of legislative spending in which revenues can be spent through earmarks or a general fund. Legislative choice is modeled as a Baron and Ferejohn style legislative bargaining game. The novel approach is to model the bargaining process as a two-stage game reflecting the reality that earmarked expenditures precede general fund appropriations. This drives the result that all revenue is spent by way of earmarking leaving no revenue in the general fund.Earmarking, legislative bargaining, public goods.