50,029 research outputs found
Redistribution of particle and anti-particle entanglement in non-inertial frames
We analyse the entanglement tradeoff between particle and anti-particle modes
of a Dirac field from the perspective of inertial and uniformly accelerated
observers. Our results show that a redistribution of entanglement between
particle and anti-particle modes plays a key role in the survival of fermionic
field entanglement in the infinite acceleration limit.Comment: 10 pages, 5 figures, revtex4. Added journal referenc
Boxy/peanut bulges : formation, evolution and properties
We discuss the formation and evolution of boxy/peanut bulges (B/Ps) and
present new simulations results. Orbital structure studies show that B/Ps are
parts of bars seen edge-on, they have their origin in vertical instabilities of
the disc material and they are somewhat shorter in extent than bars. When the
bar forms it is vertically thin, but after a time of the order of a Gyr it
experiences a vertical instability and buckles. At that time the strength of
the bar decreases, its inner part becomes thicker, so that, seen edge-on, it
acquires a peanut or boxy shape. A second buckling episode is seen in
simulations with strong bars, accompanied by a further thickening of the B/P
and a weakening of the bar. Quantitatively, this evolution depends considerably
on the properties of the halo and particularly on the extent of its core. This
influences the amount of angular momentum exchanged within the galaxy, emitted
by near-resonant material in the bar region and absorbed by near-resonant
material in the halo and in the outer disc. Haloes with small cores generally
harbour stronger bars and B/Ps and they often witness double buckling.Comment: 7 pages, 3 figures, contribution to the conference "Chaos in
Astronomy", Athens, sept. 2007, eds. G. Contopoulos & P.A. Patsi
Boxy/Peanut bulges, vertical buckling and galactic bars
Boxy/peanut bulges in disk galaxies have been associated to stellar bars. In
this talk, we discuss the different properties of such bulges and their
relation with the corresponding bar, using a very large sample of a few hundred
numerical N-body simulations. We present and inter-compare various methods of
measuring the boxy/peanut bulge properties, namely its strength, shape and
possible asymmetry. Some of these methods can be applied to both simulations
and observations. Our final goal is to get correlations that will allow us to
obtain information on the boxy/peanut bulge for a galaxy viewed face-on as well
as information on the bars of galaxies viewed edge-on.Comment: 4 pages. To appear in the proceedings of IAU Symposium 245 "Formation
and Evolution of Galaxy Bulges", M. Bureau, E. Athanassoula, and B. Barbuy,
ed
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