Hydrogen thermal conductivity at temperatures from 2000 to 4000 deg F Final report

Hydrogen thermal conductivity at temperatures from 2000 to 4600 deg

Dynamics and Transport in Random Antiferromagnetic Spin Chains

We present the first results on the low-frequency dynamical and transport properties of random antiferromagnetic spin chains at low temperature ($T$). We obtain the momentum and frequency dependent dynamic structure factor in the Random Singlet (RS) phases of both spin-1/2 and spin-1 chains, as well as in the Random Dimer phase of spin-1/2 chains. We also show that the RS phases are unusual `spin-metals' with divergent low-frequency conductivity at T=0, and follow the spin conductivity through `metal-insulator' transitions tuned by the strength of dimerization or Ising anisotropy in the spin-1/2 case, and by the strength of disorder in the spin-1 case.Comment: 4 pages (two-column format). Presentation substantially revised to accomodate new result

Thermal properties of solid and porous tungsten at temperatures to 5000 deg F

Thermal properties of solid and porous tungsten at high temperature

Global unions: chasing the dream or building the reality?

This article takes as its theme the global restructuring of capital and its impact on worker organization. It argues for a reassertion of class in any analysis of global solidarity, and assesses the opportunities and barriers to effective global unionization. Rooted in the UK experience, the article analyzes the impact of the European social dimension on trade unions, before taking the discussion into a global dimension. It concludes by suggesting that there are reasons for cautious optimism in terms of solidarity building, despite difficult historical legacies and the common replacement of action with rhetoric

Thermal conductivity of hydrogen from 2000 deg to 4700 deg F

Thermal conductivity of hydrogen from 2000 to 4700 degrees Fahrenhei

Density Matrix Renormalization Group Study of the Haldane Phase in Random One-Dimensional Antiferromagnets

It is conjectured that the Haldane phase of the S=1 antiferromagnetic Heisenberg chain and the $S=1/2$ ferromagnetic-antiferromagnetic alternating Heisenberg chain is stable against any strength of randomness, because of imposed breakdown of translational symmetry. This conjecture is confirmed by the density matrix renormalization group calculation of the string order parameter and the energy gap distribution.Comment: 4 Pages, 7 figures; Considerable revisions are made in abstract and main text. Final accepted versio

A Search for the Near-Infrared Counterpart to GCRT J1745-3009

We present an optical/near-infrared search for a counterpart to the perplexing radio transient GCRT J1745-3009, a source located ~1 degree from the Galactic Center. Motivated by some similarities to radio bursts from nearby ultracool dwarfs, and by a distance upper limit of 70 pc for the emission to not violate the 1e12 K brightness temperature limit for incoherent radiation, we searched for a nearby star at the position of GCRT J1745-3009. We found only a single marginal candidate, limiting the presence of any late-type star to >1 kpc (spectral types earlier than M9), >200 pc (spectral types L and T0-T4), and >100 pc (spectral types T4-T7), thus severely restricting the possible local counterparts to GCRT J1745-3009. We also exclude any white dwarf within 1 kpc or a supergiant star out to the distance of the Galactic Center as possible counterparts. This implies that GCRT J1745-3009 likely requires a coherent emission process, although whether or not it reflects a new class of sources is unclear.Comment: 10 pages, 5 figures. Accepted for publication in the Astrophysical Journa

Dynamics and transport in random quantum systems governed by strong-randomness fixed points

We present results on the low-frequency dynamical and transport properties of random quantum systems whose low temperature ($T$), low-energy behavior is controlled by strong disorder fixed points. We obtain the momentum and frequency dependent dynamic structure factor in the Random Singlet (RS) phases of both spin-1/2 and spin-1 random antiferromagnetic chains, as well as in the Random Dimer (RD) and Ising Antiferromagnetic (IAF) phases of spin-1/2 random antiferromagnetic chains. We show that the RS phases are unusual `spin metals' with divergent low-frequency spin conductivity at T=0, and we also follow the conductivity through novel `metal-insulator' transitions tuned by the strength of dimerization or Ising anisotropy in the spin-1/2 case, and by the strength of disorder in the spin-1 case. We work out the average spin and energy autocorrelations in the one-dimensional random transverse field Ising model in the vicinity of its quantum critical point. All of the above calculations are valid in the frequency dominated regime \omega \agt T, and rely on previously available renormalization group schemes that describe these systems in terms of the properties of certain strong-disorder fixed point theories. In addition, we obtain some information about the behavior of the dynamic structure factor and dynamical conductivity in the opposite `hydrodynamic' regime $\omega < T$ for the special case of spin-1/2 chains close to the planar limit (the quantum x-y model) by analyzing the corresponding quantities in an equivalent model of spinless fermions with weak repulsive interactions and particle-hole symmetric disorder.Comment: Long version (with many additional results) of Phys. Rev. Lett. {\bf 84}, 3434 (2000) (available as cond-mat/9904290); two-column format, 33 pages and 8 figure

Real Space Renormalization Group Study of the S=1/2 XXZ Chains with Fibonacci Exchange Modulation

Ground state properties of the S=1/2 antiferromagnetic XXZ chain with Fibonacci exchange modulation are studied using the real space renormalization group method for strong modulation. The quantum dynamical critical behavior with a new universality class is predicted in the isotropic case. Combining our results with the weak coupling renormalization group results by Vidal et al., the ground state phase diagram is obtained.Comment: 9 pages, 9 figure