Michael S. Mahoney, 1939–2008

Perhaps the clearest testimony to the scholarly range and depth of Princeton's now‐lamented Michael S. Mahoney lies in the dismay of his colleagues in the last few years, as they contemplated his imminent retirement. How to maintain coverage of his fields? Fretting over this question, the program in history of science that he did so much to build recently found itself sketching a five-year plan that involved replacing him with no fewer than four new appointments: a historian of mathematics with the ability to handle the course on Greek antiquity, a historian of the core problems of the Scientific Revolution, a historian of technology who could cover the nineteenth‐century United States and Britain, and, finally, a historian of the computer-and-media revolution. In his passing we have lost a small department

Probing States in the Mott Insulator Regime

We propose a method to probe states in the Mott insulator regime produced from a condensate in an optical lattice. We consider a system in which we create time-dependent number fluctuations in a given site by turning off the atomic interactions and lowering the potential barriers on a nearly pure Mott state to allow the atoms to tunnel between sites. We calculate the expected interference pattern and number fluctuations from such a system and show that one can potentially observe a deviation from a pure Mott state. We also discuss a method in which to detect these number fluctuations using time-of-flight imaging.Comment: 4 pages, 3 figures. Send correspondence to [email protected]

Global Properties of Locally Spatially Homogeneous Cosmological Models with Matter

The existence and nature of singularities in locally spatially homogeneous solutions of the Einstein equations coupled to various phenomenological matter models is investigated. It is shown that, under certain reasonable assumptions on the matter, there are no singularities in an expanding phase of the evolution and that unless the spacetime is empty a contracting phase always ends in a singularity where at least one scalar invariant of the curvature diverges uniformly. The class of matter models treated includes perfect fluids, mixtures of non-interacting perfect fluids and collisionless matter.Comment: 18 pages, MPA-AR-94-

The Dilemma of Direct Democracy

The dilemma of direct democracy is that voters may not always be able to make welfare- improving decisions. Lupia’s seminal work has led us to believe that voters can substitute voting cues for substantive policy knowledge. Lupia, however, emphasized that cues were valuable under certain conditions and not others. In what follows, we present three main findings regarding voters and what they know about California’s Proposition 7. First, much like Lupia reported, we show voters who are able to recall endorsements for or against a ballot measure vote similarly to people who recall certain basic facts about the initiative. We show, second, that voters whose stated policy preferences would otherwise suggest they would favor the “no” position cast their ballots with far less error than do people who favor the “yes” position. One thing this suggests is that many voters may employ a “defensive no” strategy when faced with complex policy choices on the ballot. Our third result is a bit surprising: we find that better- informed voters, whether this information is derived from factual knowledge of the initiative or from knowledge of well-publicized voting cues, are no more likely to make reasoned decisions than those who are, by our measure, uninformed. This suggests that existing theories of voter choice, especially in direct democracy, may be inadequate. We conclude with some preliminary policy recommendations that could help improve the information environment for initiatives and referenda by providing key information on the ballot

Quantum imaging of spin states in optical lattices

We investigate imaging of the spatial spin distribution of atoms in optical lattices using non-resonant light scattering. We demonstrate how scattering spatially correlated light from the atoms can result in spin state images with enhanced spatial resolution. Furthermore, we show how using spatially correlated light can lead to direct measurement of the spatial correlations of the atomic spin distribution

Dynamics of the BCS-BEC crossover in a degenerate Fermi gas

We study the short-time dynamics of a degenerate Fermi gas positioned near a Feshbach resonance following an abrupt jump in the atomic interaction resulting from a change of external magnetic field. We investigate the dynamics of the condensate order parameter and pair wavefunction for a range of field strengths. When the abrupt jump is sufficient to span the BCS to BEC crossover, we show that the rigidity of the momentum distribution precludes any atom-molecule oscillations in the entrance channel dominated resonances observed in the 40K and 6Li. Focusing on material parameters tailored to the 40K Feshbach resonance system at 202.1 gauss, we comment on the integrity of the fast sweet projection technique as a vehicle to explore the condensed phase in the crossover regionComment: 5 pages, 4 figure

Formation Times of Meteorites and Lunar Samples

This article summarizes research since the last detailed reviews of meteorite ages by Anders [1963] and Reynolds [1967]. Only crystallization ages based on parent-daughter isotopic relationships resulting from the decay of naturally occurring radioactive nuclei will be discussed. The basic principles and techniques for age determinations are discussed in many of the papers cited and, along with summaries of scientific results, in several recent books [Dalrymple and Lanphere, 1969; Doe 1970; Hamilton, 1965; Schaeffer and Zahringer, 1966; Faul, 1966]. However, developments in the field have made some of the material in the books obsolete

Lunar science: The Apollo Legacy

A general review of lunar science is presented, utilizing two themes: a summary of fundamental problems relating to the composition, structure, and history of the moon and a discussion of some surprising, unanticipated results obtained from Apollo lunar science. (1) The moon has a crust of approximately 60-km thickness, probably composed of feldspar-rich rocks. Such rocks are exposed at the surface in the light-colored lunar highlands. Many highlands rocks are complex impact breccias, perhaps produced by large basin-forming impacts. Most highlands rocks have ages of ∼3.9 × 10^9 yr; the record of igneous activity at older times is obscured by the intense bombardment. The impact rate decreased sharply at 3.8–3.9 × 10^9 yr ago. The impact basins were filled by flows of Fe- and, locally, Ti-rich volcanic rocks creating the dark mare regions and providing the strong visual color contrast of the moon, as viewed from earth. Crustal formation has produced enrichments in many elements, e.g., Ba, Sr, rare earths, and U, analogous to terrestrial crustal rocks. Compared with these elements, relatively volatile elements like Na, K, Rb, and Pb are highly depleted in the source regions for lunar surface rocks. These source regions were also separated from a metal phase, probably before being incorporated into the moon. The physical properties of the lunar mantle are compatible with mixtures of olvine and pyroxene, although Ca- and Al-rich compositions cannot be ruled out. Deeper regions, below ∼1000 km, are probably partially molten. (2) Lunar rocks cooled in the presence of a magnetic field very much stronger than the one that exists today, owing either to dynamo action in an ancient molten core or to an external magnetization of the moon. Lunar soil properties cannot be explained strictly by broken-up local rocks. Distant impacts throw in exotic material from other parts of the moon. About 1% of the soil appears to be of meteoritic origin. Vertical mixing by impacts is important; essentially all material sampled from lunar cores shows evidence of surface residence. The surface layers of lunar material exposed to space contain a chemical record of implanted solar material (rare gases, H) and constituents of a lunar atmosphere (^(40)Ar, Pb). Large isotopic fractionation effects for O, Si, S, and K are present. Physical properties of the surface layers are dominated by radiation damage effects. Lunar rocks have impact craters (≤1 cm) produced by microgram-sized interplanetary particles. The contemporary micrometeorite flux may be much higher than is indicated by the microcrater densities, indicating time variations in the flux. Particle track studies on the returned Surveyor camera filter first showed that the Fe nuclei were preferentially enhanced in solar flares