CHANDRA Observations of X-ray Jet Structure on kpc to Mpc Scales

With its exquisite spatial resolution of better than 0.5 arcsecond, the Chandra observatory is uniquely capable of resolving and studying the spatial structure of extragalactic X-ray jets on scales of a few to a few hundred kilo-parsec. Our analyses of four recent Chandra images of quasar jets interpret the X-ray emission as inverse Compton scattering of high energy electrons on the cosmic microwave background. We infer that these jets are in bulk relativistic motion, carrying kinetic powers upwards of 10^46 ergs/s to distances of hundreds of kpc, with very high efficiency.Comment: 4 pages, 3 figures, to be published in the proceedings of the Bologna jet workshop, "The Physics of Relativistic Jets in the CHANDRA and XMM Era.

Distribution of epicenters in the Olami-Feder-Christensen model

We show that the well established Olami-Feder-Christensen (OFC) model for the dynamics of earthquakes is able to reproduce a new striking property of real earthquake data. Recently, it has been pointed out by Abe and Suzuki that the epicenters of earthquakes could be connected in order to generate a graph, with properties of a scale-free network of the Barabasi-Albert type. However, only the non conservative version of the Olami-Feder-Christensen model is able to reproduce this behavior. The conservative version, instead, behaves like a random graph. Besides indicating the robustness of the model to describe earthquake dynamics, those findings reinforce that conservative and non conservative versions of the OFC model are qualitatively different. Also, we propose a completely new dynamical mechanism that, even without an explicit rule of preferential attachment, generates a free scale network. The preferential attachment is in this case a ``by-product'' of the long term correlations associated with the self-organized critical state. The detailed study of the properties of this network can reveal new aspects of the dynamics of the OFC model, contributing to the understanding of self-organized criticality in non conserving models.Comment: 7 pages, 7 figure

Summary of International Transport Energy Modeling Workshop

The NextSTEPS program at ITS-Davis convened a one-day workshop on international transportation energy modeling (iTEM), focused on comparing the frameworks and scenario projections from four major global transport models: -- Global Change Assessment Model (GCAM) by Pacific Northwest National Laboratory (PNNL) and ITS-Davis, -- MESSAGE-Transport (Model for Energy Supply Strategy Alternatives and their General Environmental Impact) by the International Institute for Applied Systems Analysis (IIASA), -- Mobility Model (MoMo) by the International Energy Agency, and -- Roadmap by the International Council on Clean Transportation (ICCT). Highlights: -- Projections of "baseline" global transportation energy use rise from 98 EJ in 2010 to 160-250 EJ by 2050. -- There are considerable differences in historical data for some modes, both globally and for individual countries (particularly non-OECD countries). Variability in estimates of transportation activity are in most cases much larger than energy differences. -- Global average vehicle ownership rates are projected to range from 270 to 450 per 1,000 people by 2050 with wide ranges across countries: 700-1,075 for the US by the middle of the century (US is around 700 today), 100-650 for China, and 80-380 for India across four models. -- All models rely mainly on GDP to estimate the future demand for freight and hold the base year modal shares (e.g. truck v. rail) roughly constant through 2050. In reality, future evolution will depend on characteristics of products (e.g. type of commodities) being shipped, technologies available for freight and their efficiencies, and policies and infrastructure. -- Current policy commitments toward EVs, PHEVs and H2FCVs (and thus baseline projections) maybe below the numbers suggested by iTEM models as required for meeting climate targets (e.g., 2 degrees C). -- Improvements in data quality and the representation of car ownership and use across the models were identified as priorities. Modeling transport energy use can either be done by estimating how far people travel and what mode of transportation they choose or by estimating how many vehicles there are and how far each one travels. These are complementary approaches, and in theory they should both lead to the same answer. The former approach, used in "service demand" models, seem more intuitive when one wants to model societal shifts in modes of transportation, either in emerging economies as they develop or in developed economies as they decarbonize; but collecting data on service demand is notoriously difficult. In contrast, vehicle stock models use readily-available vehicle sales data, but are harder to use in future-state, what-if scenarios (particularly in estimating modal shift behaviors) and thus require special attention by experts. The four iTEM models are different in terms of scope (GCAM and MESSAGE cover all sectors of the energy system vs. MoMo and Roadmap which cover transportation only) and model structure (GCAM and MESSAGE rely on internal drivers, particularly the costs of technology and travel, to project future changes whereas MoMo and Roadmap rely on experts' judgments and detailed analysis of technology and policies to drive long-term changes). Yet, owing to these differences, the models are highly complementary and in some cases can be used jointly to answer questions that no single model can tackle on its own. The following summary shares some of the comparisons and findings from the workshop

High Temperature Expansions and Dynamical Systems

We develop a resummed high-temperature expansion for lattice spin systems with long range interactions, in models where the free energy is not, in general, analytic. We establish uniqueness of the Gibbs state and exponential decay of the correlation functions. Then, we apply this expansion to the Perron-Frobenius operator of weakly coupled map lattices.Comment: 33 pages, Latex; [email protected]; [email protected]

The Construction of Double-Ended Classical Trajectories

In the present paper we describe relaxation methods for constructing double-ended classical trajectories. We illustrate our approach with an application to a model anharmonic system, the Henon-Heiles problem. Trajectories for this model exhibit a number of interesting energy-time relationships that appear to be of general use in characterizing the dynamics.Comment: (12 pages, submitted to Chemical Physics Letters. Figures are too large for convenient e-mail access. they are available via anonymous ftp on willie.chem.brown.edu and reside in the directory pub/chem-ph/9407 as the compressed tar file 9407001.tar.Z. If you have difficulty retrieving the figures, please contact J. Doll ([email protected]) for assistance

Intrinsic decoherence and classical-quantum correspondence in two coupled delta-kicked rotors

We show that classical-quantum correspondence of center of mass motion in two coupled delta-kicked rotors can be obtained from intrinsic decoherence of the system itself which occurs due to the entanglement of the center of mass motion to the internal degree of freedom without coupling to external environment

Pure O-sequences and matroid h-vectors

We study Stanley's long-standing conjecture that the h-vectors of matroid simplicial complexes are pure O-sequences. Our method consists of a new and more abstract approach, which shifts the focus from working on constructing suitable artinian level monomial ideals, as often done in the past, to the study of properties of pure O-sequences. We propose a conjecture on pure O-sequences and settle it in small socle degrees. This allows us to prove Stanley's conjecture for all matroids of rank 3. At the end of the paper, using our method, we discuss a first possible approach to Stanley's conjecture in full generality. Our technical work on pure O-sequences also uses very recent results of the third author and collaborators.Comment: Contains several changes/updates with respect to the previous version. In particular, a discussion of a possible approach to the general case is included at the end. 13 pages. To appear in the Annals of Combinatoric

Improved description of charged Higgs boson production at hadron colliders

We present a new method for matching the two twin-processes gb->H+/-t and gg->H+/-tb in Monte Carlo event generators. The matching is done by defining a double-counting term, which is used to generate events that are subtracted from the sum of these two twin-processes. In this way we get a smooth transition between the collinear region of phase space, which is best described by gb->H+/-t, and the hard region, which requires the use of the gg->H+/-tb process. The resulting differential distributions show large differences compared to both the gb-> H+/-t and gg->H+/-tb processes illustrating the necessity to use matching when tagging the accompanying b-jet.Comment: 21 pages, 9 figures. Revised with updated discussion and reference

A 750 mW, continuous-wave, solid-state laser source at 313 nm for cooling and manipulating trapped 9Be+ ions

We present a solid-state laser system that generates 750 mW of continuous-wave single-frequency output at 313 nm. Sum-frequency generation with fiber lasers at 1550 nm and 1051 nm produces up to 2 W at 626 nm. This visible light is then converted to UV by cavity-enhanced second-harmonic generation. The laser output can be tuned over a 495 GHz range, which includes the 9Be+ laser cooling and repumping transitions. This is the first report of a narrow-linewidth laser system with sufficient power to perform fault-tolerant quantum-gate operations with trapped 9Be+ ions by use of stimulated Raman transitions.Comment: 9 pages, 4 figure