9,083 research outputs found
Stellar escapers from M67 can reach solar-like Galactic orbits
We investigate the possibility that the Sun could have been born in M67 by
carrying out -body simulations of M67-like clusters in a time-varying
Galactic environment, and following the galactic orbits of stars that escape
from them. We find that model clusters that occupy similar orbits to M67 today
can be divided up into three groups. Hot clusters are born with a high initial
-velocity, depleted clusters are born on cold orbits but are destroyed by
GMC encounters in the Galactic disc, and scattered clusters are born on cold
orbits and survive with more than 1000 stars at an age of 4.6 Gyr. We find that
all cluster models in all three cluster groups have stellar escapers that are
kinematicaly similar to the Sun. Hot clusters having the lowest such fraction
%, whilst depleted clusters have the highest fraction,
%. We calculate that clusters that are destroyed in the
Galactic disc have a specific frequency of escapers that end up on solar-like
orbits that is 2 times that of escapers from clusters that survive their
journey
A Pulse Shaping Algorithm of a Coherent Matter Wave. Controlling Reaction Dynamics
A pulse shaping algorithm for a matter wave with the purpose of controlling a
binary reaction has been designed. The scheme is illustrated for an Eley-Rideal
reaction where an impinging matter-wave atom recombines with an adsorbed atom
on a metal surface. The wave function of the impinging atom is shaped such that
the desorbing molecule leaves the surface in a specific vibrational state.Comment: 4 pages, 5 figure
The news model of asset price determination: An empirical examination of the Danish football club Brøndby IF
According to the news model of asset price determination, only the unexpected component of an information should drive the stock price. We use the Danish publicly listed football club Brøndby IF to analyze how match outcome impacts the stock price. To disentangle gross news from net news, betting odd information is used to control for the expected match outcome. --news model,football industry,betting odds,stock market,market efficiency,event study
The fundamental plane of elliptical galaxies with modified Newtonian dynamics
The modified Newtonian dynamics (MOND), suggested by Milgrom as an
alternative to dark matter, implies that isothermal spheres with a fixed
anisotropy parameter should exhibit a near perfect relation between the mass
and the fourth power of the velocity dispersion. This is consistent with the
observed Faber-Jackson relation for elliptical galaxies-- a luminosity-velocity
dispersion relation with large scatter. However, the observable global
properties of elliptical galaxies comprise a three parameter family; they lie
on a ``fundamental plane'' in a logarithmic space consisting of central
velocity dispersion, effective radius, and luminosity. The scatter
perpendicular to this plane is significantly less than that about the
Faber-Jackson relation. I show here that, in order to match the observed global
properties of elliptical galaxies with MOND, models must deviate from being
strictly isothermal and isotropic; such objects can be approximated by
high-order polytropic spheres with a radial orbit anisotropy in the outer
regions. MOND imposes boundary conditions on the inner Newtonian regions which
restrict these models to a dynamical fundamental plane which may differ from
that implied by the traditional virial theorem. Scatter about this plane is
relatively insensitive to the necessary deviations from homology.Comment: 9 pages, 6 eps figures, mn style. Shortened and revised version
includes more recent data on elliptical galaxies. Accepted for publication in
MNRA
A deeply embedded young protoplanetary disk around L1489 IRS observed by the submillimeter array
Circumstellar disks are expected to form early in the process that leads to
the formation of a young star, during the collapse of the dense molecular cloud
core. It is currently not well understood at what stage of the collapse the
disk is formed or how it subsequently evolves. We aim to identify whether an
embedded Keplerian protoplanetary disk resides in the L1489 IRS system. Given
the amount of envelope material still present, such a disk would respresent a
very young example of a protoplanetary disk. Using the Submillimeter Array
(SMA) we have observed the HCO 3--2 line with a resolution of about
1. At this resolution a protoplanetary disk with a radius of a few hundred
AUs should be detectable, if present. Radiative transfer tools are used to
model the emission from both continuum and line data. We find that these data
are consistent with theoretical models of a collapsing envelope and Keplerian
circumstellar disk. Models reproducing both the SED and the interferometric
continuum observations reveal that the disk is inclined by 40 which is
significantly different to the surrounding envelope (74). This
misalignment of the angular momentum axes may be caused by a gradient within
the angular momentum in the parental cloud or if L1489 IRS is a binary system
rather than just a single star. In the latter case, future observations looking
for variability at sub-arcsecond scales may be able to constrain these
dynamical variations directly. However, if stars form from turbulent cores, the
accreting material will not have a constant angular momentum axis (although the
average is well defined and conserved) in which case it is more likely to have
a misalignment of the angular momentum axes of the disk and the envelope.Comment: 11 pages, 13 figures, accepted by A&
MOND and the lensing Fundamental Plane: No need for dark matter on galaxy scales
Bolton et al. (2007) have derived a mass-based fundamental plane using
photometric and spectroscopic observations of 36 strong gravitational lenses.
The lensing allows a direct determination of the mass-surface density and so
avoids the usual dependence on mass-to-light ratio. We consider this same
sample in the context of modified Newtonian dynamics (MOND) and demonstrate
that the observed mass-based fundamental plane coincides with the MOND
fundamental plane determined previously for a set of high-order polytropic
spheres chosen to match the observed range of effective radii and velocity
dispersions in elliptical galaxies. Moreover, the observed projected mass
within one-half an effective radius is consistent with the mass in visible
stars plus a small additional component of ``phantom dark matter'' resulting
from the MOND contribution to photon deflection.Comment: Minor revisions in response to referee. Revised title. Accepted in
MNRA
Single wall carbon nanotube double quantum dot
We report on two top-gate defined, coupled quantum dots in a semiconducting
single wall carbon nanotube, constituting a tunable double quantum dot system.
The single wall carbon nanotubes are contacted by titanium electrodes, and
gated by three narrow top-gate electrodes as well as a back-gate. We show that
a bias spectroscopy plot on just one of the two quantum dots can be used to
extract the addition energy of both quantum dots. Furthermore, honeycomb charge
stability diagrams are analyzed by an electrostatic capacitor model that
includes cross capacitances, and we extract the coupling energy of the double
quantum dot.Comment: Published in Applied Physics Letters 4 December 2006.
http://link.aip.org/link/?APL/89/23211
Optimizing the CLIC Beam Delivery System
The optimization of the new CLIC Final Focus System (FFS) with L*=3.5m is presented for a collection of CLIC beam parameters. The final performance is computed for the full Beam Delivery System including the new diagnostics section. A comparison to previous designs is also presented
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