Quantum ballistic transport in in-plane-gate transistors showing onset of a novel ferromagnetic phase transition

We study one-dimensional transport in focused-ion-beam written in-plane-gate transistors on III-V heterostructures at moderately low temperatures at zero bias without any external magnetic field applied. In accordance with a recent proposal of A. Gold and L. Calmels, Valley- and spin-occupancy instability in the quasi-one-dimensional electron gas, Phil. Mag. Lett. 74, 33-42 (1996) and earlier experimental data, we observe plateaux in the source-drain conductivity considered as a function of the gate voltage, not only at multliples of 2e^2/h but also clearly at e^2/h, just before the channel closes to zero conductivity. This may be interpreted as a many electron effect, namely as a novel ballistic ferromagnetic ground state evading standard descriptions and theorems.Comment: 19 pages, 9 figures, 22 reference

Linear growth of the trace anomaly in Yang-Mills thermodynamics

In the lattice work by Miller [1,2] and in the work by Zwanziger [3] a linear growth of the trace anomaly for high temperatures was found in pure SU(2) and SU(3) Yang-Mills theories. These results show the remarkable property that the corresponding systems are strong interacting even at high temperatures. We show that within an analytical approach to Yang-Mills thermodynamics this linear rise is obtained and is directly connected to the presence of a temperature-dependent ground state, which describes (part of) the nonperturbative nature of the Yang-Mills system. Our predictions are in approximate agreement with [1,2,3]Comment: 9 pages and 2 figure

ISO_q(3) and ISO_q(2,1)

We prove the embedding of ISO_q(3) \hook ISU^{ex}_{\sqrt{q}}(2) and ISO_q(2,1) \hook ISL^{ex}_q(2,R) as $^*$-algebras and give a Hilbert space representation of $ISU^{ex}_{\sqrt{q}}(2)$Comment: 10 pages, 12 figures, Late

Nonperturbative screening of the Landau pole

Based on the trace anomaly for the energy-momentum tensor, an effective theory for the thermodynamics of the deconfining phase, and by assuming the asymptotic behavior to be determined by one-loop perturbation theory we compute the nonperturbative beta function for the fundamental coupling $g$ in SU(2) and SU(3) Yang-Mills theory. With increasing temperature we observe a very rapid approach to the perturbative running. The Landau pole is nonperturbatively screened.Comment: 11 pages, 3 figure

Heavy-Quark Probes of the Quark-Gluon Plasma at RHIC

Thermalization and collective flow of charm (c) and bottom (b) quarks in ultra-relativistic heavy-ion collisions are evaluated based on elastic parton rescattering in an expanding quark-gluon plasma (QGP). We show that resonant interactions in a strongly interacting QGP (sQGP), as well as the effects of parton coalescence, can play an essential role in the interpretation of recent data from the Relativistic Heavy-Ion Collider (RHIC), and thus illuminate the nature of the sQGP and its hadronization. Our main assumption, motivated by recent findings in lattice computations of Quantum Chromodynamics, is the existence of D- and B-meson states in the sQGP, providing resonant cross sections for heavy quarks up to temperatures of sim 2 T_c. Pertinent drag and diffusion coefficients are implemented into a relativistic Langevin simulation to compute transverse-momentum spectra and azimuthal asymmetries (v_2) of b- and c-quarks in Au-Au collisions at RHIC. Hadronization into D- and B-mesons is calculated from a combination of coalescence with light quarks and fragmentation, and associated electron-decay spectra and v_2 are compared to recent RHIC data. We also comment on the relative importance of radiative and elastic energy loss of heavy quarks in the QGP.Comment: 4 pages, 3 figures, v2: 1 reference updated, v3: replaced comparison to data to more recent data, references added, contents unchange

Evaluation of different sources of uncertainty in climate change impact research using a hydro-climatic model ensemble

The international research project QBic3 (Quebec-Bavarian Collaboration on Climate Change) aims at investigating the potential impacts of climate change on the hydrology of regional scale catchments in Southern Quebec (Canada) and Bavaria (Germany). Yet, the actual change in river runoff characteristics during the next 70 years is highly uncertain due to a multitude of uncertainty sources. The so-called hydro-climatic ensemble that is constructed to describe the uncertainties of this complex model chain consists of four different global climate models, downscaled by three different regional climate models, an exchangeable bias correction algorithm, a separate method to scale RCM outputs to the hydrological model scale and several hydrological models of differing complexity to assess the impact of different hydro model concepts. This choice of models and scenarios allows for the inter-comparison of the uncertainty ranges of climate and hydrological models, of the natural variability of the climate system as well as of the impact of scaling and correction of climate data on mean, high and low flow conditions. A methodology to display the relative importance of each source of uncertainty is proposed and results for past runoff and potential future changes are presented

Coupled dynamics of RNA folding and nanopore translocation

The translocation of structured RNA or DNA molecules through narrow pores necessitates the opening of all base pairs. Here, we study the interplay between the dynamics of translocation and base-pairing theoretically, using kinetic Monte Carlo simulations and analytical methods. We find that the transient formation of basepairs that do not occur in the ground state can significantly speed up translocation.Comment: 4 pages, 3 figures, to appear in Physical Review Letter

Search for rare leptonic B decays at the Tevatron

Results of a search for the Flavor-Changing Neutral Current decay $B^0_{s,d} \to \mu^+ \mu^-$ using $p\bar{p}$ collision data at $\sqrt{s}=1.96$ TeV collected at Fermilab Tevatron collider by the CDF and D{\O}detectors are presented. CDF reports upper limits on ${\cal B} (B^0_{s} \to \mu^+ \mu^-) \leq 7.5 \cdot10^{-7}$ and ${\cal B}(B^0_{d} \to \mu^+ \mu^-) \leq 1.9 \cdot10^{-7}$ at the 95% C.L. using 171 pb$^{-1}$. The D{\O}Collaboration used 240 pb$^{-1}$ to set an even more stringent limit on the branching ratio for $B^0_{s} \to \mu^+ \mu^-$ of $5.0\cdot 10^{-7}$ at the 95% C.L.Comment: 5 pages, 2 figures, submitted to DPF 2004 conference proceedings, UC Riverside, C