65,015 research outputs found

    Simulations of Nonthermal Electron Transport in Multidimensional Flows: Application to Radio Galaxies

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    We have developed an economical, effective numerical scheme for cosmic-ray transport suitable for treatment of electrons up to a few hundreds of GeV in multidimensional simulations of radio galaxies. The method follows the electron population in sufficient detail to allow computation of synthetic radio and X-ray observations of the simulated sources, including spectral properties (see the companion paper by Tregillis et al. 1999). The cosmic-ray particle simulations can follow the effects of shock acceleration, second-order Fermi acceleration as well as radiative and adiabatic energy losses. We have applied this scheme to 2-D and 3-D MHD simulations of jet-driven flows and have begun to explore links between dynamics and the properties of high energy electron populations in radio lobes. The key initial discovery is the great importance to the high energy particle population of the very unsteady and inhomogeneous flows, especially near the end of the jet. Because of this, in particular, our simulations show that a large fraction of the particle population flowing from the jet into the cocoon never passes through strong shocks. The shock strengths encountered are not simply predicted by 1-D models, and are quite varied. Consequently, the emergent electron spectra are highly heterogeneous. Rates of synchrotron aging in "hot-spots" seem similarly to be very uneven, enhancing complexity in the spectral properties of electrons as they emerge into the lobes and making more difficult the task of comparing dynamical and radiative ages.Comment: 7 pages, 1 figure; to appear in Life Cycles of Radio Galaxies, ed. J. Biretta et al., New Astronomy Review

    Zero-energy edge states and chiral symmetry breaking at edges of graphite sheets

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    Two-dimensional graphite sheets with a certain type of edges are known to support boundary states localized near the edges. Forming a flat band with a sharp peak in the density of states at the Fermi energy, they can trigger a magnetic instability or a distortion of the lattice in the presence of electron-electron or electron-phonon interactions. We shall discuss a relationship between chiral symmetry, which is the origin of the zero-energy edge states, and several types of induced orders such as spin density waves or lattice distortions. We also investigate electron correlation effects on the edge states for a wrapped quasi one-dimensional geometry, i.e., carbon nanotube, by means of the renormalization group and the open boundary bosonization.Comment: 4 pages, Proceedings of EP2DS1

    Faraday Rotation Measure due to the Intergalactic Magnetic Field

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    Studying the nature and origin of the intergalactic magnetic field (IGMF) is an outstanding problem of cosmology. Measuring Faraday rotation would be a promising method to explore the IGMF in the large-scale structure (LSS) of the universe. We investigated the Faraday rotation measure (RM) due to the IGMF in filaments of galaxies using simulations for cosmological structure formation. We employed a model IGMF based on turbulence dynamo in the LSS of the universe; it has an average strength of 10 \sim 10 nG and a coherence length of several × 100 h1\times\ 100\ h^{-1} kpc in filaments. With the coherence length smaller than path length, the inducement of RM would be a random walk process, and we found that the resultant RM is dominantly contributed by the density peak along line of sight. The rms of RM through filaments at the present universe was predicted to be 1 rad m2\sim 1\ {\rm rad\ m^{-2}}. In addition, we predicted that the probability distribution function of RM|{\rm RM}| through filaments follows the log-normal distribution, and the power spectrum of RM in the local universe peaks at a scale of 1 h1\sim 1\ h^{-1} Mpc. Our prediction of RM could be tested with future instruments.Comment: To appear in ApJ. Pdf with full resolution figures can be downloaded from http://canopus.cnu.ac.kr/ryu/ar.pd

    Complete Call-by-Value Calculi of Control Operators II: Strong Termination

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    We provide characterization of the strong termination property of the CCV (complete call-by-value) lambda-mu calculus introduced in the first part of this series of the paper. The calculus is complete with respect to the standard continuation-passing style (CPS) semantics. The union-intersection type systems for the calculus is developed in the previous paper. We characterize the strong normalizability of terms of the calculus in terms of the CPS semantics and typeability