15,572 research outputs found
Variability and polarization in the inner jet of 3C395
We present new results on the parsec-scale jet of the quasar 3C395, derived
from VLBI polarization sensitive observations made in 1995.91 and 1998.50 at
8.4, 15.4 and 22.2 GHz. The observations show a complex one-sided jet extending
up to 20 mas, with a projected magnetic field essentially aligned with the
radio jet. The emission is strongly dominated, in total intensity and
polarization, by the core and the inner jet region (of ~3 mas length). We have
studied the details of this dominant region finding clear structural variations
during this ~2.5 years period, in contrast with the apparent quietness of the
jet structure inferred from lower resolution VLBI observations. We observe the
ejection of a new component from the core and variations in the degree of
polarization of the inner jet components. We estimate a high Faraday Rotation
Measure close to the core, with a strong decrease along the inner jet.Comment: 7 pages, 4 figures, A&A in pres
Revisiting the optical -symmetric dimer
Optics has proved a fertile ground for the experimental simulation of quantum
mechanics. Most recently, optical realizations of -symmetric
quantum mechanics have been shown, both theoretically and experimentally,
opening the door to international efforts aiming at the design of practical
optical devices exploiting this symmetry. Here, we focus on the optical
-symmetric dimer, a two-waveguide coupler were the materials show
symmetric effective gain and loss, and provide a review of the linear and
nonlinear optical realizations from a symmetry based point of view. We go
beyond a simple review of the literature and show that the dimer is just the
smallest of a class of planar -waveguide couplers that are the optical
realization of Lorentz group in 2+1 dimensions. Furthermore, we provide a
formulation to describe light propagation through waveguide couplers described
by non-Hermitian mode coupling matrices based on a non-Hermitian generalization
of Ehrenfest theorem.Comment: 25 pages, 12 figure
Physical processes leading to surface inhomogeneities: the case of rotation
In this lecture I discuss the bulk surface heterogeneity of rotating stars,
namely gravity darkening. I especially detail the derivation of the omega-model
of Espinosa Lara & Rieutord (2011), which gives the gravity darkening in
early-type stars. I also discuss the problem of deriving gravity darkening in
stars owning a convective envelope and in those that are members of a binary
system.Comment: 23 pages, 11 figure, Lecture given to the school on the cartography
of the Sun and the stars (May 2014 in Besan\c{c}on), to appear in LNP, Neiner
and Rozelot edts V2: typos correcte
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