998 research outputs found
Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR105 and 2003 VB12
Explaining the origin of the orbit of 2000 CR105 (a ~ 230AU, q ~ 45AU) is a
major test for our understanding of the primordial evolution of the outer Solar
System. Gladman et al. (2001) showed that this objects could not have been a
normal member of the scattered disk that had its perihelion distance increased
by chaotic diffusion. In this paper we explore four seemingly promising
mechanisms for explaining the origin of the orbit of this peculiar object: (i)
the passage of Neptune through a high-eccentricity phase, (ii) the past
existence of massive planetary embryos in the Kuiper belt or the scattered
disk, (iii) the presence of a massive trans-Neptunian disk at early epochs
which exerted tides on scattered disk objects, and (iv) encounters with other
stars. Of all these mechanisms, the only one giving satisfactory results is the
passage of a star. Indeed, our simulations show that the passage of a solar
mass star at about 800 AU only perturbs objects with semi-major axes larger
than roughly 200 AU to large perihelion distances. This is in good agreement
with the fact that 2000 CR105 has a semi-major axis of 230AU and no other
bodies with similar perihelion distances but smaller semi-major axes have yet
been discovered. The discovery of 2003 VB12, (a=450AU, q=75AU) announced a few
days before the submission of this paper, strengthen our conclusions.Comment: AJ submitted. 27 pages, 6 figure
Modeling galactic halos with predominantly quintessential matter
This paper discusses a new model for galactic dark matter by combining an
anisotropic pressure field corresponding to normal matter and a quintessence
dark energy field having a characteristic parameter such that
. Stable stellar orbits together with an attractive
gravity exist only if is extremely close to , a result
consistent with the special case studied by Guzman et al. (2003). Less
exceptional forms of quintessence dark energy do not yield the desired stable
orbits and are therefore unsuitable for modeling dark matter.Comment: 12 pages, 1 figur
Anisotropic interactions of a single spin and dark-spin spectroscopy in diamond
The nitrogen-vacancy (N-V) center in diamond is a promising atomic-scale
system for solid-state quantum information processing. Its spin-dependent
photoluminescence has enabled sensitive measurements on single N-V centers,
such as: electron spin resonance, Rabi oscillations, single-shot spin readout
and two-qubit operations with a nearby 13C nuclear spin. Furthermore, room
temperature spin coherence times as long as 58 microseconds have been reported
for N-V center ensembles. Here, we have developed an angle-resolved
magneto-photoluminescence microscopy apparatus to investigate the anisotropic
electron spin interactions of single N-V centers at room temperature. We
observe negative peaks in the photoluminescence as a function of both magnetic
field magnitude and angle that are explained by coherent spin precession and
anisotropic relaxation at spin level anti-crossings. In addition, precise field
alignment unmasks the resonant coupling to neighboring dark nitrogen spins that
are not otherwise detected by photoluminescence. The latter results demonstrate
a means of investigating small numbers of dark spins via a single bright spin
under ambient conditions.Comment: 13 pages, 4 figure
Galois covers of the open p-adic disc
This paper investigates Galois branched covers of the open -adic disc and
their reductions to characteristic . Using the field of norms functor of
Fontaine and Wintenberger, we show that the special fiber of a Galois cover is
determined by arithmetic and geometric properties of the generic fiber and its
characteristic zero specializations. As applications, we derive a criterion for
good reduction in the abelian case, and give an arithmetic reformulation of the
local Oort Conjecture concerning the liftability of cyclic covers of germs of
curves.Comment: 19 pages; substantial organizational and expository changes; this is
the final version corresponding to the official publication in Manuscripta
Mathematica; abstract update
Dark matter effects in vacuum spacetime
We analyze a toy model describing an empty spacetime in which the motion of a
test mass (and the trajectories of photons) evidence the presence of a
continuous and homogeneous distribution of matter; however, since the
energy-momentum tensor vanishes, no real matter or energy distribution is
present at all. Thus, a hypothetical observer will conclude that he is immersed
in some sort of dark matter, even though he has no chance to directly detect
it. This suggests yet another possibility of explaining the elusive dark matter
as a purely dynamical effect due to the curvature of spacetime.Comment: 5 pages, 2 figures, expanded with comments about the exact motion and
curvature invariant
The a-number of hyperelliptic curves
It is known that for a smooth hyperelliptic curve to have a large -number,
the genus must be small relative to the characteristic of the field, ,
over which the curve is defined. It was proven by Elkin that for a genus
hyperelliptic curve to have , the genus is bounded by
. In this paper, we show that this bound can be lowered to . The method of proof is to force the Cartier-Manin matrix to have rank one
and examine what restrictions that places on the affine equation defining the
hyperelliptic curve. We then use this bound to summarize what is known about
the existence of such curves when and .Comment: 7 pages. v2: revised and improved the proof of the main theorem based
on suggestions from the referee. To appear in the proceedings volume of Women
in Numbers Europe-
Лекарственный анафилактический и псевдоаллергический шок: патогенез, клиника, дифференциальная диагностика, подходы к терапии
Представлены особенности патогенеза анафилактического и псевдоаллергического шока, обусловленного лекарственными средствами, сходства и различия в клиническом их течении, субъективные и объективные признаки дифференциальной диагностики, подходы к терапии.The peculiarities of the pathogenesis of anaphylactic and pseudoallergic shock caused by medications, similarity and differences of the clinical course, subjective and objective signs of differential diagnosis, approaches to therapy are presented
Tannakian approach to linear differential algebraic groups
Tannaka's Theorem states that a linear algebraic group G is determined by the
category of finite dimensional G-modules and the forgetful functor. We extend
this result to linear differential algebraic groups by introducing a category
corresponding to their representations and show how this category determines
such a group.Comment: 31 pages; corrected misprint
Local Surface Density of the Galactic Disk from a 3-D Stellar Velocity Sample
We have re-estimated the surface density of the Galactic disk in the solar
neighborhood within 0.4 kpc of the Sun using parallaxes and proper
motions of a kinematically and spatially unbiased sample of 1476 old bright red
giant stars from the Hipparcos catalog with measured radial velocities from
Barbier-Brossat & Figon (2000). We determine the vertical distribution of the
red giants as well as the vertical velocity dispersion of the sample, (14.4
0.26 km/sec), and combine these to derive the surface density of
gravitating matter in the Galactic disk as a function of the galactic
coordinate . The surface density of the disk increases from 10.5 0.5
/ pc within 50 pc to 42 6 / pc
within 350 pc. The estimated volume density of the galactic disk within
50 pc is about 0.1 / pc which is close to the volume
density estimates of the observed baryonic matter in the solar neighborhood.Comment: 24 pages, 15 figures, AJ in pres
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