7,838 research outputs found
Detecting filaments at z=3
We present the detection of a filament of Ly-alpha emitting galaxies in front
of the quasar Q1205-30 at z=3.04 based on deep narrow band imaging and
follow-up spectroscopy obtained at the ESO NTT and VLT. We argue that Ly-alpha
selection of high redshift galaxies with relatively modest amounts of observing
time allows the detection and redshift measurement of galaxies with
sufficiently high space densities that we can start to map out the large scale
structure at z=2-3 directly. Even more interesting is it that a 3D map of the
filaments will provide a new cosmological test for the value of the
cosmological constant, Omega_Lambda.Comment: 7 pages, 4 figures, contribution to the procedings of the conference
``Lighthouses of the Universe'' held in Garching (Germany), August 200
Gravitational Lensing of the SDSS High-Redshift Quasars
We predict the effects of gravitational lensing on the color-selected
flux-limited samples of z~4.3 and z>5.8 quasars, recently published by the
Sloan Digital Sky Survey (SDSS). Our main findings are: (i) The lensing
probability should be 1-2 orders of magnitude higher than for conventional
surveys. The expected fraction of multiply-imaged quasars is highly sensitive
to redshift and the uncertain slope of the bright end of the luminosity
function, beta_h. For beta_h=2.58 (3.43) we find that at z~4.3 and i*<20.0 the
fraction is ~4% (13%) while at z~6 and z*<20.2 the fraction is ~7% (30%). (ii)
The distribution of magnifications is heavily skewed; sources having the
redshift and luminosity of the SDSS z>5.8 quasars acquire median magnifications
of med(mu_obs)~1.1-1.3 and mean magnifications of ~5-50. Estimates of
the quasar luminosity density at high redshift must therefore filter out
gravitationally-lensed sources. (iii) The flux in the Gunn-Peterson trough of
the highest redshift (z=6.28) quasar is known to be f_lambda<3 10^-19
erg/sec/cm^2/Angstrom. Should this quasar be multiply imaged, we estimate a 40%
chance that light from the lens galaxy would have contaminated the same part of
the quasar spectrum with a higher flux. Hence, spectroscopic studies of the
epoch of reionization need to account for the possibility that a lens galaxy,
which boosts the quasar flux, also contaminates the Gunn-Peterson trough. (iv)
Microlensing by stars should result in ~1/3 of multiply imaged quasars in the
z>5.8 catalog varying by more than 0.5 magnitudes over the next decade. The
median equivalent width would be lowered by ~20% with respect to the intrinsic
value due to differential magnification of the continuum and emission-line
regions.Comment: 27 pages, 10 figures. Expansion on the discussion in
astro-ph/0203116. Replaced with version accepted for publication in Ap
Walter Campbell:A distinguished life
An efficient and simple synthesis approach to form stable (68) Ga-labeled nanogels is reported and their fundamental properties investigated. Nanogels are obtained by self-assembly of amphiphilic statistical prepolymers derivatised with chelating groups for radiometals. The resulting nanogels exhibit a well-defined spherical shape with a diameter of 290 +/- 50 nm. The radionuclide (68) Ga is chelated in high radiochemical yields in an aqueous medium at room temperature. The phagocytosis assay demonstrates a highly increased internalization of nanogels by activated macrophages. Access to these (68) Ga-nanogels will allow the investigation of general behavior and clearance pathways of nanogels in vivo by nuclear molecular imaging
Constraints on (Omega_m,Omega_Lambda) using distributions of inclination angles for high redshift filaments
In this paper we present a scale free method to determine the cosmological
parameters (Omega_m, Omega_Lambda). The method is based on the requirement of
isotropy of the distribution of orientations of cosmological filaments. The
current structure formation paradigm predicts that the first structures to form
are voids and filaments, causing a web-like structure of the matter
distribution at high redshifts. Recent observational evidence suggests that the
threads, or filaments, of the cosmic web most easily are mapped in Ly-alpha
emission. We describe how such a 3D map can be used to constrain the
cosmological parameters in a way which, contrary to most other cosmological
tests, does not require the use of a standard rod or a standard candle. We
perform detailed simulations in order to define the optimal survey parameters
for the definition of an observing programme aimed to address this test, and to
investigate how statistical and observational errors will influence the
results. We conclude that observations should target filaments of comoving size
15-50 Mpc in the redshift range 2-4, and that each filament must be defined by
at least four Ly-alpha emitters. Detection of 20 filaments will be sufficient
to obtain a result, while 50 filaments will make it possible to place
significant new constraints on the values of Omega_m and Omega_Lambda permitted
by the current supernova observations. In a future paper we study how robust
these conclusions are to systematic velocities in the survey box.Comment: 8 pages, 6 figures, accepted for publication in A&
The Article III Party and the Originalist Case Against Corporate Diversity Jurisdiction
Federal courts control an outsize share of big-ticket corporate litigation. And that control rests, to a significant degree, on the Supreme Court’s extension of Article III’s Diversity of Citizenship Clause to corporations. Yet, critics have questioned the constitutionality of corporate diversity jurisdiction from the beginning.
In this Article and a previous one, we develop the first sustained critique of corporate diversity jurisdiction.
Our previous article demonstrated that corporations are not “citizens” given the original meaning of that word. But we noted this finding alone doesn’t sink general corporate diversity jurisdiction. The ranks of corporate shareholders include many undoubted “citizens.” And so corporate litigants might preserve their access to diversity jurisdiction if that jurisdiction can vest through diverse shareholder citizenship.
In this Article, we consider whether corporations can indeed preserve access to diversity jurisdiction through this route. We conclude they cannot. From an originalist perspective, shareholders are not parties to Article III “controversies” that proceed in the corporate name. In such controversies, shareholder citizenship cannot establish diversity jurisdiction.
The result of our analysis is that corporations are not citizens, and they normally can’t use shareholder citizenship to access diversity jurisdiction either. It follows that general corporate diversity jurisdiction is not authorized by the constitutional text
Single particle calculations for a Woods-Saxon potential with triaxial deformations, and large Cartesian oscillator basis
We present a computer program which solves the Schrodinger equation of the
stationary states for an average nuclear potential of Woods-Saxon type. In this
work, we take specifically into account triaxial (i.e. ellipsoidal) nuclear
surfaces. The deformation is specified by the usual Bohr parameters. The
calculations are carried out in two stages. In the first, one calculates the
representative matrix of the Hamiltonian in the cartesian oscillator basis. In
the second stage one diagonalizes this matrix with the help of subroutines of
the EISPACK library. If it is wished, one can calculate all eigenvalues, or
only the part of the eigenvalues that are contained in a fixed interval defined
in advance. In this latter case the eigenvectors are given conjointly. The
program is very rapid, and the run-time is mainly used for the diagonalization.
Thus, it is possible to use a significant number of the basis states in order
to insure a best convergence of the results.Comment: no figures, but tbles in separate pdf file
The Eastwood-Singer gauge in Einstein spaces
Electrodynamics in curved spacetime can be studied in the Eastwood--Singer
gauge, which has the advantage of respecting the invariance under conformal
rescalings of the Maxwell equations. Such a construction is here studied in
Einstein spaces, for which the Ricci tensor is proportional to the metric. The
classical field equations for the potential are then equivalent to first
solving a scalar wave equation with cosmological constant, and then solving a
vector wave equation where the inhomogeneous term is obtained from the gradient
of the solution of the scalar wave equation. The Eastwood--Singer condition
leads to a field equation on the potential which is preserved under gauge
transformations provided that the scalar function therein obeys a fourth-order
equation where the highest-order term is the wave operator composed with
itself. The second-order scalar equation is here solved in de Sitter spacetime,
and also the fourth-order equation in a particular case, and these solutions
are found to admit an exponential decay at large time provided that
square-integrability for positive time is required. Last, the vector wave
equation in the Eastwood-Singer gauge is solved explicitly when the potential
is taken to depend only on the time variable.Comment: 13 pages. Section 6, with new original calculations, has been added,
and the presentation has been improve
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