Government Data and the Invisible Hand

If President Barack Obama\u27s new administration really wants to embrace the potential of Internet-enabled government transparency, it should follow a counter-intuitive but ultimately compelling strategy: reduce the federal role in presenting important government information to citizens. Today, government bodies consider their own Web sites to be a higher priority than technical infrastructures that open up their data for others to use. We argue that this understanding is a mistake. It would be preferable for government to understand providing reusable data, rather than providing Web sites, as the core of its online publishing responsibility. During the presidential campaign, all three major candidates indicated that they thought the federal government could make better use of the Internet. Barack Obama\u27s platform went the furthest and explicitly endorsed maling government data available online in universally accessible formats. Hillary Clinton, meanwhile, remarked that she wanted to see much more government information online. John McCain\u27s platform called for a new Office of Electronic Government. But the situation to which these candidates were responding-the wide gap between the exciting uses of Internet technology by private parties, on the one hand, and the government\u27s lagging technical infrastructure, on the other-is not new. A minefield of federal rules and a range of other factors, prevent government Web masters from keeping pace with the evergrowing potential of the Internet

N-body simulations in modified Newtonian dynamics

We describe some results obtained with N-MODY, a code for N-body simulations of collisionless stellar systems in modified Newtonian dynamics (MOND). We found that a few fundamental dynamical processes are profoundly different in MOND and in Newtonian gravity with dark matter. In particular, violent relaxation, phase mixing and galaxy merging take significantly longer in MOND than in Newtonian gravity, while dynamical friction is more effective in a MOND system than in an equivalent Newtonian system with dark matter.Comment: 4 pages, no figures. To appear in EAS Publication Series (Proceedings of Symposium 7 of the JENAM 2008, Vienna

Solution of the Two-Channel Anderson Impurity Model - Implications for the Heavy Fermion UBe13_{13} -

We solve the two-channel Anderson impurity model using the Bethe-Ansatz. We determine the ground state and derive the thermodynamics, obtaining the impurity entropy and specific heat over the full range of temperature. We show that the low temperature physics is given by a line of fixed points decribing a two-channel non Fermi liquid behavior in the integral valence regime associated with moment formation as well as in the mixed valence regime where no moment forms. We discuss relevance for the theory of UBe$_{13}$.Comment: 4 pages, 2 figures, (to be published in PRL

The Age-Redshift Relation for Standard Cosmology

We present compact, analytic expressions for the age-redshift relation $\tau(z)$ for standard Friedmann-Lema\^ \itre-Robertson-Walker (FLRW) cosmology. The new expressions are given in terms of incomplete Legendre elliptic integrals and evaluate much faster than by direct numerical integration.Comment: 13 pages, 3 figure

The inverse-Compton ghost HDF 130 and the giant radio galaxy 6C 0905+3955: matching an analytic model for double radio source evolution

We present new GMRT observations of HDF 130, an inverse-Compton (IC) ghost of a giant radio source that is no longer being powered by jets. We compare the properties of HDF 130 with the new and important constraint of the upper limit of the radio flux density at 240 MHz to an analytic model. We learn what values of physical parameters in the model for the dynamics and evolution of the radio luminosity and X-ray luminosity (due to IC scattering of the cosmic microwave background (CMB)) of a Fanaroff-Riley II (FR II) source are able to describe a source with features (lobe length, axial ratio, X-ray luminosity, photon index and upper limit of radio luminosity) similar to the observations. HDF 130 is found to agree with the interpretation that it is an IC ghost of a powerful double-lobed radio source, and we are observing it at least a few Myr after jet activity (which lasted 5--100 Myr) has ceased. The minimum Lorentz factor of injected particles into the lobes from the hotspot is preferred to be $\gamma\sim10^3$ for the model to describe the observed quantities well, assuming that the magnetic energy density, electron energy density, and lobe pressure at time of injection into the lobe are linked by constant factors according to a minimum energy argument, so that the minimum Lorentz factor is constrained by the lobe pressure. We also apply the model to match the features of 6C 0905+3955, a classical double FR II galaxy thought to have a low-energy cutoff of $\gamma\sim10^4$ in the hotspot due to a lack of hotspot inverse-Compton X-ray emission. The models suggest that the low-energy cutoff in the hotspots of 6C 0905+3955 is $\gamma\gtrsim 10^3$, just slightly above the particles required for X-ray emission.Comment: 9 pages, 3 figure

Probing the phase diagram of CeRu_2Ge_2 by thermopower at high pressure

The temperature dependence of the thermoelectric power, S(T), and the electrical resistivity of the magnetically ordered CeRu_2Ge_2 (T_N=8.55 K and T_C=7.40 K) were measured for pressures p < 16 GPa in the temperature range 1.2 K < T < 300 K. Long-range magnetic order is suppressed at a p_c of approximately 6.4 GPa. Pressure drives S(T) through a sequence of temperature dependences, ranging from a behaviour characteristic for magnetically ordered heavy fermion compounds to a typical behaviour of intermediate-valent systems. At intermediate pressures a large positive maximum develops above 10 K in S(T). Its origin is attributed to the Kondo effect and its position is assumed to reflect the Kondo temperature T_K. The pressure dependence of T_K is discussed in a revised and extended (T,p) phase diagram of CeRu_2Ge_2.Comment: 7 pages, 6 figure

Non-Fermi liquid normal state of the Heavy Fermion superconductor UBe13

Non-Fermi liquid (NFL) behavior in the normal state of the heavy-fermion superconductor UBe13 is studied by means of low-temperature measurements of the specific heat, C, and electrical resistivity, \rho, on a high-quality single crystal in magnetic fields up to 15.5 T. At B=0, unconventional superconductivity forms at Tc=0.9 K out of an incoherent state, characterized by a large and strongly temperature dependent \rho(T). In the magnetic field interval 4 T \leq B \leq 10 T, \rho(T) follows a T^3/2 behavior for Tc(B)\leq T \leq 1 K, while \rho is proportional to T at higher temperatures. Corresponding Non-Fermi liquid behavior is observed in C/T as well and hints at a nearby antiferromagnetic (AF) quantum critical point (QCP) covered by the superconducting state. We speculate that the suppression of short-range AF correlations observed by thermal expansion and specific heat measurements below T_L \simeq 0.7 K (B=0) yields a field-induced QCP, T_L \to 0, at B=4.5 T.Comment: Presented at the M2S-2003 conference in Rio / Brazi

Mixed-valent regime of the two-channel Anderson impurity as a model for UBe_13

We investigate the mixed-valent regime of a two-configuration Anderson impurity model for uranium ions, with separate quadrupolar and magnetic doublets. With a new Monte Carlo approach and the non-crossing approximation we find: (i) A non-Fermi-liquid fixed point with two-channel Kondo model critical behavior; (ii) Distinct energy scales for screening the low-lying and excited doublets; (iii) A semi-quantitative explanation of magnetic-susceptibility data for U$_{1-x}$Th$_x$Be$_{13}$ assuming 60-70% quadrupolar doublet ground-state weight, supporting the quadrupolar-Kondo interpretation.Comment: 4 Pages, 3 eps figures; submitted to Phys. Rev. Let

Superconductivity and Antiferromagnetism: Hybridization Impurities in a Two-Band Spin-Gapped Electron System

We present the exact solution of a one-dimensional model of a spin-gapped correlated electron system with hybridization impurities exhibiting both magnetic and mixed-valence properties. The host supports superconducting fluctuations, with a spin gap. The localized electrons create a band of antiferromagnetic spin excitations inside the gap for concentrations x of the impurities below some critical value x_c. When x = x_c the spin gap closes and a ferrimagnetic phase appears. This is the first example of an exactly solvable model with coexisting superconducting and antiferromagnetic fluctuations which in addition supports a quantum phase transition to a (compensated) ferrimagnetic phase. We discuss the possible relevance of our results for experimental systems, in particular the U-based heavy-fermion materials.Comment: 4 page

Managing risks to drivers in road transport

This report presents a number of case studies in managing risks to road transport drivers. The cases feature a variety of initiatives and interventions to protect drivers.In the road transport sector, as with any other, it is important to pay attention to working conditions in order to ensure a skilled and motivated workforce. Certain characteristics of the sector make it more difficult to practice risk management than in other sectors. But by taking account of how the sector operates in practice, and the characteristics of drivers themselves and the way they work, risks can be successfully manage