1,068 research outputs found
Exact vortex nucleation and cooperative vortex tunneling in dilute BECs
With the imminent advent of mesoscopic rotating BECs in the lowest Landau
level (LLL) regime, we explore LLL vortex nucleation. An exact many-body
analysis is presented in a weakly elliptical trap for up to 400 particles.
Striking non-mean field features are exposed at filling factors >>1 . Eg near
the critical rotation frequency pairs of energy levels approach each other with
exponential accuracy. A physical interpretation is provided by requantising a
mean field theory, where 1/N plays the role of Planck's constant, revealing two
vortices cooperatively tunneling between classically degenerate energy minima.
The tunnel splitting variation is described in terms of frequency, particle
number and ellipticity.Comment: 4 pages,4 figure
Exporting Vector Muscles for Facial Animation
In this paper we introduce a method of exporting vector muscles from one 3D face to another for facial animation. Starting from a 3D face with an extended version of Waters' linear muscle system, we transfer the linear muscles to a target 3D face. We also transfer the region division, which is used to increase the performance of the muscle as well as to control the animation. The human involvement is just as simple as selecting the faces which shows the most natural facial expressions in the animator's view. The method allows the transfer of the animation to a new 3D model within a short time. The transferred muscles can then be used to create new animations
Optimal Spin Basis in Polarized Photon Linear Colliders
We analyze the spin correlations of the top quark pairs produced at Photon
Linear Colliders. We employ the circular polarized photon beams and general
spin basis for the top quark pair. We consider general spin bases to find a
strong spin correlation between produced top quark and anti-top quark. We show
the cross-section in these bases and discuss the characteristics of results.Comment: RevTeX, 16 pages, 6 figures, psfig.sty and here.sty are require
Discovery of a New Transient Magnetar Candidate: XTE J1810-197
We report the discovery of a new X-ray pulsar, XTE J1810-197. The source was
serendipitously discovered on 2003 July 15 by the Rossi X-ray Timing Explorer
(RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a
5.54 s spin-period and a soft spectrum (photon index ~ 4). We detect the source
in earlier RXTE observations back to 2003 January. These show that a transient
outburst began between 2002 November 17 and 2003 January 23 and that the pulsar
has been spinning down since then, with a high rate Pdot ~ 10^-11 s/s showing
significant timing noise, but no evidence for Doppler shifts due to a binary
companion. The rapid spin-down rate and slow spin-period imply a super-critical
magnetic field B=3x10^14 G and a young characteristic age < 7600 yr. These
properties are strikingly similar to those of anomalous X-ray pulsars and soft
gamma repeaters, making the source a likely new magnetar. A follow-up Chandra
observation provided a 2".5 radius error circle within which the 1.5 m
Russian-Turkish Optical Telescope RTT150 found a limiting magnitude of
R_c=21.5, in accord with other recently reported limits. The source is present
in archival ASCA and ROSAT data as well, at a level 100 times fainter than the
\~ 3 mCrab seen in 2003. This suggests that other X-ray sources that are
currently in a state similar to the inactive phase of XTE J1810-197 may also be
unidentified magnetars awaiting detection via a similar activity.Comment: Submitted to ApJL; 4 pages; 4 figure
QCD Corrections to Spin Correlations in Top Quark Production at Lepton Colliders
Spin correlations, using a generic spin basis, are investigated to leading
order in QCD for top quark production at lepton colliders. Even though, these
radiative corrections induce an anomalous gamma/Z magnetic moment for the top
quarks and allow for single, real gluon emission, their effects on the top
quark spin orientation are very small. The final results are that the top (or
anti-top) quarks are produced in an essentially unique spin configuration in
polarized lepton collisions even after including the O(alpha_{s}) QCD
corrections.Comment: 32 pages, REVTeX, 13 Postscript figures, psfig.sty and here.sty are
required. Several references added, Tables 3, 4 and 5 are change
Microscopic description of the beta delayed deuteron emission from \bbox{^6}He
The beta delayed deuteron emission from He is studied in a dynamical
microscopic cluster model. This model gives a reasonably good description for
all the subsystems of He and Li in a coherent way, without any free
parameter. The beta decay transition probability to the Li ground state is
underestimated by a few percents. The theoretical beta delayed deuteron
spectrum is close to experiment but it is also underestimated by about a factor
1.7. We argue that, in spite of their different magnitudes, both
underestimations might have a common origin. The model confirms that the
neutron halo part of the He wave function plays a crucial role in quenching
the beta decay toward the + d channel.Comment: LATEX with REVTEX, Submitted to Phys. Rev. C, 11 pages, 3 figures
(not included) are available upon request. ATOMKI-93/
Identifying risk and mitigating gambling-related harm in online poker
The present paper conducts a critical analysis of the potential for gambling-related harm in relation to online poker participation, and a theoretical evaluation of current responsible gambling strategies employed to mitigate harm in online gambling and applies the evaluation of these strategies specifically to online poker gambling. Theoretically, the primary risk for harm in online poker is the rapid and continuous nature of poker provisions online, and has been demonstrated to be associated with disordered gambling behaviour, including the chasing of monetary losses. The following responsible gambling features were deemed relevant for consideration: informed player choice, voluntary self-exclusion, employee intervention, pre-commitment, in-game feedback, behavioural tracking tools, and age restriction and verification. Although current responsible gambling features are evaluated as theoretically robust, there remains a fundamental need for experimental validation of their effectiveness. Furthermore, despite online poker gamblers perceiving the responsible gambling features as valuable tools, in reality very few players regularly use available responsible gambling features. Ultimately, for the online poker gambling industry to retain market credibility and avoid substantial top-down regulation, it is imperative to demonstrate effectiveness of responsible gambling approaches, and increase customer utilisation of available harm-mitigation features
The neutron halo of He in a microscopic model
The two--neutron separation energy of He has been reproduced for the
first time in a realistic parameter--free microscopic multicluster model
comprising the and clusterizations, with cluster
breathing excitations included. The contribution of the channel is
substantial. A very thick (0.85 fm) neutron halo has been found in full
agreement with the results of the latest phenomenological analysis.Comment: Submitted to Phys. Rev. C, 8 pages, Latex with Revtex, 2 figures (not
included) available on request, 08-03-9
Angular Correlations in Top Quark Pair Production and Decay at Hadron Colliders
We show how to observe sizable angular correlations between the decay
products of the top quark and those of the anti-top quark in top quark pair
production and decay at hadron colliders. These correlations result from the
large asymmetry in the rate for producing like-spin versus unlike-spin top
quark pairs provided the appropriate spin axes are used. The effects of new
physics at production or decay on these correlations are briefly discussed.Comment: 34 pages, revtex, including 12 uuencoded postscript figure
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