8,959 research outputs found

    Stellar escapers from M67 can reach solar-like Galactic orbits

    Full text link
    We investigate the possibility that the Sun could have been born in M67 by carrying out NN-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 zz-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 f=0.06f_{\odot} = 0.06 %, whilst depleted clusters have the highest fraction, f=6.61f_{\odot} = 6.61 %. 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 \sim 2 times that of escapers from clusters that survive their journey

    A Pulse Shaping Algorithm of a Coherent Matter Wave. Controlling Reaction Dynamics

    Full text link
    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

    Get PDF
    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

    Get PDF
    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

    Full text link
    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+^+ J=J= 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^\circ which is significantly different to the surrounding envelope (74^\circ). 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

    Get PDF
    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

    Full text link
    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

    Get PDF
    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
    corecore