13,265 research outputs found
Reflexivity of the automorphism and isometry groups of the suspension of
The aim of this paper is to show that the automorphism and isometry groups of
the suspension of , being a separable infinite dimensional Hilbert
space, are algebraically reflexive. This means that every local automorphism,
respectively local surjective isometry of is an
automorphism, respectively a surjective isometry
Linear maps on the space of all bounded observables preserving maximal deviation
In this paper we determine all the bijective linear maps on the space of
bounded observables which preserve a fixed moment or the variance. Nonlinear
versions of the corresponding results are also presented.Comment: 27 pages. To appear in J. Funct. Ana
Metal line blanketing and opacity in the ultraviolet of alpha 2 Canum Venaticorum
Ultraviolet photometry by OAO-2 was made of alpha 2 CVn covering the entire 5.5d period of this magnetic Ap variable. The light curves ranging from 1330 A to 3320 A indicate the dominant role of rare-earth line-blanketing in redistributing flux. In a broad depression of the continuum covering 2300-2600 A, scanner observations possibly identify strong lines of Eu III as major contributors to this feature. At maximum intensity of the rare-earth lines, the ultraviolet continuum shortward of 2900 A is greatly diminished while the longer wavelength regions into the visual become brighter. In addition, there is evidence that the hydrogen line opacity is variable and the photoionization edge of Si I at 1680 A is identified
Shocks and Tides Quantified in the "Sausage" Cluster, CIZA J2242.8+5301, using N-body/hydro-dynamical Simulations
The colliding cluster, CIZA J2242.8+5301, displays a spectacular, almost 2
Mpc long shock front with a radio based Mach number M ~ 5, that is puzzlingly
large compared with the X-ray estimate of M ~ 2.5. The extent to which the
X-ray temperature jump is diluted by cooler unshocked gas projected through the
cluster currently lacks quantification. Thus, here we apply our self-consistent
N-body/hydro-dynamical code (based on FLASH) to model this binary cluster
encounter. We can account for the location of the shock front and also the
elongated X-ray emission by tidal stretching of the gas and dark matter between
the two cluster centers. The required total mass is Msun
with a 1.3:1 mass ratio favoring the southern cluster component. The relative
velocity we derive is km/s initially between the two main cluster
components, with an impact parameter of 120 kpc. This solution implies that the
shock temperature jump derived from the low angular resolution X-ray satellite
SUZAKU is underestimated by a factor of two, due to cool gas in projection,
bringing the observed X-ray and radio estimates into agreement. We propose that
the complex southern relics in CIZA J2242.8+5301, have been broken up as the
southerly moving "back" shocked gas impacts the gas still falling in along the
collision axis. Finally, we use our model to generate Compton-y maps to
estimate the reduction in radio flux caused by the thermal Sunyaev-Zel'dovich
(SZ) effect. At 30 GHz, this amounts to mJy/arcmin
and mJy/arcmin at the locations of the northern and
southern shock fronts respectively. Our model estimate agrees with previous
empirical estimates that have inferred the measured radio spectra can be
significantly affected by the SZ effect, with implications for charged particle
acceleration models of the radio relics.Comment: 8 pages, 7 figures and 1 table, submitted to the Astrophysical
Journal for publication on March
Multi-Phenomena Modeling of the New Bullet Cluster, ZwCl008.8+52, using N-body/hydrodynamical Simulations
We use hydrodynamical/N-body simulations to interpret the newly discovered
Bullet-cluster-like merging cluster, ZwCl 0008.8+5215 (ZwCl 0008 hereafter),
where a dramatic collision is apparent from multi-wavelength observations. We
have been able to find a self-consistent solution for the radio, X-ray, and
lensing phenomena by projecting an off-axis, binary cluster encounter viewed
just after first core passage. A pair radio relics traces well the leading and
trailing shock fronts that our simulation predict, providing constraints on the
collision parameters. We can also account for the observed distinctive
comet-like X-ray morphology and the positions of the X-ray peaks relative to
the two lensing mass centroids and the two shock front locations. Relative to
the Bullet cluster, the total mass is about 70% lower, ( Msun, with a correspondingly lower infall velocity, km/s,
and an impact parameter of kpc. As a result, the gas component of
the infalling cluster is not trailing significantly behind the associated dark
matter as in the case of the Bullet cluster. The degree of agreement we find
between all the observables provides strong evidence that dark matter is
effectively collisionless on large scales calling into question other claims
and theories that advocate modified gravity.Comment: 9 pages, 3 figures, and 1 table, submitted to the Astrophysical
Journal for publicationon on December 18. Coments are welcom
A Hydrodynamical Solution for the "Twin-Tailed" Colliding Galaxy Cluster "El Gordo"
The distinctive cometary X-ray morphology of the recently discovered massive
galaxy cluster "El Gordo" (ACT-CT J0102-4915; z=0.87) indicates that an
unusually high-speed collision is ongoing between two massive galaxy clusters.
A bright X-ray "bullet" leads a "twin-tailed" wake, with the SZ centroid at the
end of the Northern tail. We show how the physical properties of this system
can be determined using our FLASH-based, N-body/hydrodynamic model, constrained
by detailed X-ray, Sunyaev-Zel'dovich (SZ), and Hubble lensing and dynamical
data. The X-ray morphology and the location of the two Dark Matter components
and the SZ peak are accurately described by a simple binary collision viewed
about 480 million years after the first core passage. We derive an impact
parameter of ~300 kpc, and a relative initial infall velocity of ~2250 km/sec
when separated by the sum of the two virial radii assuming an initial total
mass of 2.15x10^(15) Msun and a mass ratio of 1.9. Our model demonstrates that
tidally stretched gas accounts for the Northern X-ray tail along the collision
axis between the mass peaks, and that the Southern tail lies off axis,
comprising compressed and shock heated gas generated as the massive component
plunges through the main cluster. The challenge for LCDM will be to find out if
this physically extreme event can be plausibly accommodated when combined with
the similarly massive, high infall velocity case of the "Bullet cluster" and
other such cases being uncovered in the new SZ based surveys.Comment: 9 pages, 5 Figures and 1 Table, accepted for publication in the
Astrophysical Journa
Flavor ordering of elliptic flows at high transverse momentum
Based on the quark coalescence model for the parton-to-hadron phase
transition in ultra-relativistic heavy ion collisions, we relate the elliptic
flow () of high \pt hadrons to that of high \pt quarks. For high \pt
hadrons produced from an isospin symmetric and quark-antiquark symmetric
partonic matter, magnitudes of their elliptic flows follow a flavor ordering as
if strange quarks have a
smaller elliptic flow than light quarks. The elliptic flows of high \pt
hadrons further follow a simple quark counting rule if strange quarks and light
quarks have same high \pt spectrum and coalescence probability.Comment: 4 pages, 1 figure, revte
Geophysical study of the structure and processes of the continental convergence zones: Alpine-Himalayan belt
Studies of the structure of the continental collision zones using seismic and body waves, theoretical modelling of the thermal regime of the convergence processes, and studies of earthquake mechanisms and deformation aspects of the model are covered
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