Connecting the Micro-dynamics to the Emergent Macro-variables: Self-Organized Criticality and Absorbing Phase Transitions in the Deterministic Lattice Gas

We reinvestigate the Deterministic Lattice Gas introduced as a paradigmatic model of the 1/f spectra (Phys. Rev. Lett. V26, 3103 (1990)) arising according to the Self-Organized Criticality scenario. We demonstrate that the density fluctuations exhibit an unexpected dependence on systems size and relate the finding to effective Langevin equations. The low density behavior is controlled by the critical properties of the gas at the absorbing state phase transition. We also show that the Deterministic Lattice Gas is in the Manna universality class of absorbing state phase transitions. This is in contrast to expectations in the literature which suggested that the entirely deterministic nature of the dynamics would put the model in a different universality class. To our knowledge this is the first fully deterministic member of the Manna universality class.Comment: 8 pages, 12 figures. Changes in the new version: Reference list has been correcte

Tracking and data systems support for the Helios project. Volume 3: DSN support of Project Helios May 1976 - June 1977

Spacecraft extended mission coverage does not generally carry a high priority, but Helios was fortunate in that a combination of separated viewperiods and unique utilization of the STDN Goldstone antenna have provided a considerable amount of additional science data return, particularly at key times such a perihelion and/or solar occultation

Young Binary Stars and Associated Disks

The typical product of the star formation process is a binary star. Binaries have provided the first dynamical measures of the masses of pre-main-sequence (PMS) stars, providing support for the calibrations of PMS evolutionary tracks. Surprisingly, in some star-forming regions PMS binary frequencies are higher than among main-sequence solar-type stars. The difference in PMS and main-sequence binary frequencies is apparently not an evolutionary effect; recent attention has focussed on correlations between binary frequency and stellar density or cloud temperatures. Accretion disks are common among young binary stars. Binaries with separations between 1 AU and 100 AU have substantially less submillimeter emission than closer or wider binaries, suggesting that they have truncated their disks. Evidence of dynamical clearing has been seen in several binaries. Remarkably, PMS binaries of all separations show evidence of circumstellar disks and continued accretion. This suggests that the circumstellar disks are replenished from circumbinary disks or envelopes. The frequent presence of disks suggests that planet formation can occur in binary environments, and formation of planets in wide binaries is already established by their discovery. Circumbinary disk masses around very short period binaries are ample to form planetary systems such as our own. The nature of planetary systems among the most common binaries, with separations between 10 AU and 100 AU, is less clear given the observed reduction in disk mass, though they may have disk masses adequate for the formation of terrestrial-like planets.Comment: 32 pages, including 6 Postscript figures (TeX, uses psfig.sty); to appear in "Protostars & Planets IV". Gif figures with captions and high-res Postscript color figure available at http://hven.swarthmore.edu/~jensen/preprints/ppiv.htm

Charge Transport Transitions and Scaling in Disordered Arrays of Metallic Dots

We examine the charge transport through disordered arrays of metallic dots using numerical simulations. We find power law scaling in the current-voltage curves for arrays containing no voids, while for void-filled arrays charge bottlenecks form and a single scaling is absent, in agreement with recent experiments. In the void-free case we also show that the scaling exponent depends on the effective dimensionality of the system. For increasing applied drives we find a transition from 2D disordered filamentary flow near threshold to a 1D smectic flow which can be identified experimentally using characteristics in the transport curves and conduction noise.Comment: 4 pages, 4 postscript figure

Strongly interacting confined quantum systems in one dimension

In one dimension, the study of magnetism dates back to the dawn of quantum mechanics when Bethe solved the famous Heisenberg model that describes quantum behaviour in magnetic systems. In the last decade, one-dimensional systems have become a forefront area of research driven by the realization of the Tonks-Girardeau gas using cold atomic gases. Here we prove that one-dimensional fermionic and bosonic systems with strong short-range interactions are solvable in arbitrary confining geometries by introducing a new energy-functional technique and obtaining the full spectrum of energies and eigenstates. As a first application, we calculate spatial correlations and show how both ferro- and anti-ferromagnetic states are present already for small system sizes that are prepared and studied in current experiments. Our work demonstrates the enormous potential for quantum manipulation of magnetic correlations at the microscopic scale.Comment: 11 pages, 2 figures, including methods, final versio

Fractional energy states of strongly-interacting bosons in one dimension

We study two-component bosonic systems with strong inter-species and vanishing intra-species interactions. A new class of exact eigenstates is found with energies that are {\it not} sums of the single-particle energies with wave functions that have the characteristic feature that they vanish over extended regions of coordinate space. This is demonstrated in an analytically solvable model for three equal mass particles, two of which are identical bosons, which is exact in the strongly-interacting limit. We numerically verify our results by presenting the first application of the stochastic variational method to this kind of system. We also demonstrate that the limit where both inter- and intra-component interactions become strong must be treated with extreme care as these limits do not commute. Moreover, we argue that such states are generic also for general multi-component systems with more than three particles. The states can be probed using the same techniques that have recently been used for fermionic few-body systems in quasi-1D.Comment: 6 pages, 4 figures, published versio

Interdependence of magnetism and superconductivity in the borocarbide TmNi2B2C

We have discovered a new antiferromagnetic phase in TmNi2B2C by neutron diffraction. The ordering vector is Q_A = (0.48,0,0) and the phase appears above a critical in-plane magnetic field of 0.9 T. The field was applied in order to test the assumption that the zero-field magnetic structure at Q_F = (0.094,0.094,0) would change into a c-axis ferromagnet if superconductivity were destroyed. We present theoretical calculations which show that two effects are important: A suppression of the ferromagnetic component of the RKKY exchange interaction in the superconducting phase, and a reduction of the superconducting condensation energy due to the periodic modulation of the moments at the wave vector Q_A