45,417 research outputs found
Review of “Jurisdictional” Issues Under the Bumpers Amendment
The proposed Bumpers Amendment to the Administrative Procedure Act would encourage courts to be less deferential than they have previously been toward federal agencies\u27 views on issues of law. With regard to jurisdictional questions, the amendment would go further: it would invite courts not only to assert their independence, but also to disfavor agencies\u27 positions. Professor Levin regards this special rule of construction for jurisdictional questions as an attempt to achieve deregulation through judicial review. He criticizes this strategy as poorly conceived and calls attention to several weaknesses in the draftsmanship of the jurisdiction provision
Nonlegislative Rules and the Administrative Open Mind
The author\u27s main purpose here is to discuss the openmindedness that agencies are required to maintain towards the positions that they announce in nonlegislative rules. The author will offer a few observations about the circumstances in which this attitude is required, what agencies should do to maintain it, and how courts might police this obligation
Gluon saturation effects on J/Psi production in heavy ion collisions
We consider a novel mechanism for J/Psi production in nuclear collisions
arising due to the high density of gluons. We calculate the resulting J/Psi
production cross section as a function of rapidity and centrality. We evaluate
the nuclear modification factor and show that the rapidity distribution of the
produced J/Psi's is significantly more narrow in AA collisions due to the gluon
saturation effects. Our results indicate that gluon saturation in the colliding
nuclei is a significant source of J/Psi suppression that can be disentangled
from the quark-gluon plasma effects.Comment: 5 pages, 3 figures; v2: typos corrected; presentation improve
Ejection of high-velocity stars from the Galactic Center by an inspiraling Intermediate-Mass Black Hole
The presence of young stars in the immediate vicinity and strong tidal field
of SgrA* remains unexplained. One currently popular idea for their origin
posits that the stars were bused in by an Intermediate-Mass Black Hole (IMBH)
which has inspiraled into the Galactic Center a few million years ago.
Yu and Tremaine (2003) have argued that in this case some of the old stars in
the SgrA* cusp would be ejected by hard gravitational collisions with the IMBH.
Here we derive a general expression for the phase-space distribution of the
ejected high-velocity stars, given the distribution function of the stars in
the cusp. We compute it explicitly for the Peebles-Young distribution function
of the cusp, and make a detailed model for the time-dependent ejection of stars
during the IMBH inspiral. We find that (1) the stars are ejected in a burst
lasting a few dynamical friction timescales; if the ejected stars are detected
by Gaia they are likely to be produced by a single inspiral event, (2) if the
inspiral is circular than in the beginning of the burst the velocity vectors of
the ejected stars cluster around the inspiral plane, but rapidly isotropise as
the burst proceeds, (3) if the inspiral is eccentric, then the stars are
ejected in a broad jet roughly perpendicular to the Runge-Lenz vector of the
IMBH orbit. In a typical cusp the orbit will precess with a period of \sim 10^5
years, and the rate of ejection into our part of the Galaxy (as defined by e.g.
the Gaia visibility domain) will be modulated periodically. Gaia, together with
the ground-based follow-up observations, will be able to clock many
high-velocity stars back to their ejection from the Galactic Center, thus
measuring some of the above phenomena. This would provide a clear signature of
the IMBH inspiral in the past 10--20 Myr.Comment: 12 pages, including 7 figure
Diffractive dissociation and saturation scale from non-linear evolution in high energy DIS
This paper presents the first numerical solution to the non-linear evolution
equation for diffractive dissociation processes in deep inelastic scattering.
It is shown that the solution depends on one scaling variable , where is the saturation scale for the diffraction
processes. The dependence of the saturation scale on both
and is investigated, ( is a minimal rapidity gap for
the diffraction process). The - dependence of turns out to be the
same as of the saturation scale in the total inclusive DIS cross section. In
our calculations reveals only mild dependence on . The
scaling is shown to hold for but is violated at .Comment: 13 pages, 9 figure
Double coset construction of moduli space of holomorphic bundles and Hitchin systems
We present a description of the moduli space of holomorphic vector bundles
over Riemann curves as a double coset space which is differ from the standard
loop group construction. Our approach is based on equivalent definitions of
holomorphic bundles, based on the transition maps or on the first order
differential operators. Using this approach we present two independent
derivations of the Hitchin integrable systems. We define a "superfree" upstairs
systems from which Hitchin systems are obtained by three step hamiltonian
reductions. A special attention is being given on the Schottky parameterization
of curves.Comment: 19 pages, Late
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