65,015 research outputs found

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

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

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

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 $\sim 10$ nG and a coherence length of
several $\times\ 100\ h^{-1}$ 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 $\sim 1\ {\rm rad\ m^{-2}}$. In addition, we
predicted that the probability distribution function of $|{\rm RM}|$ through
filaments follows the log-normal distribution, and the power spectrum of RM in
the local universe peaks at a scale of $\sim 1\ h^{-1}$ 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

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

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