198,157 research outputs found

    Mass Hierarchy and Trapping of Gravity

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    We construct a model consisting of many D3-branes with only positive tension in a five-dimensional anti-de Sitter space-time geometry. It is shown that this type of model naturally realizes not only exponential mass hierarchy between the Planck scale and the electroweak scale but also trapping of the graviton on the D3-branes. It is pointed out that our model may have a flexibility to explain the existence of more than one disparate mass scales, such as the electroweak scale and the GUT scale, on the same D3-brane.Comment: 11 pages, LaTex 2

    Modified Slim-Disk Model Based on Radiation-Hydrodynamic Simulation Data: The Conflict Between Outflow and Photon Trapping

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    Photon trapping and outflow are two key physics associated with the supercritical accretion flow. We investigate the conflict between these two processes based on two-dimensional radiation-hydrodynamic (RHD) simulation data and construct a simplified (radially) one-dimensional model. Mass loss due to outflow, which is not considered in the slim-disk model, will reduce surface density of the flow, and if very significant, it will totally suppress photon trapping effects. If the photon trapping is very significant, conversely, outflow will be suppressed because radiation pressure force will be reduced. To see what actually occurs, we examine the RHD simulation data and evaluate the accretion rate and outflow rate as functions of radius. We find that the former monotonically decreases, while the latter increases, as the radius decreases. However, the former is kept constant at small radii, inside several Schwarzschild radii, since the outflow is suppressed by the photon trapping effects. To understand the conflict between the photon trapping and outflow in a simpler way, we model the radial distribution of the accretion rate from the simulation data and build up a new (radially) one-dimensional model, which is similar to the slim-disk model but incorporates the mass loss effects due to the outflow. We find that the surface density (and, hence, the optical depth) is much reduced even inside the trapping radius, compared with the case without outflow, whereas the effective temperature distribution hardly changes. That is, the emergent spectra do not sensitively depend on the amount of mass outflow. We conclude that the slim-disk approach is valid for interpreting observations, even if the outflow is taken into account.Comment: 15 pages, 5 figures, accepted for publication in PAS

    Variations on a theme of AGN-driven outflows: luminosity evolution and ambient density distribution

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    Galactic outflows are now commonly observed in starburst and active galactic nuclei (AGN) host galaxies. Yet, there is no clear consensus on their physical driving mechanism(s). We have previously shown that AGN radiative feedback, driven by radiation pressure on dust, can account for the observed dynamics and energetics of galactic outflows, provided that radiation trapping is taken into account. Here we generalise our model results by explicitly considering the temporal evolution of the central AGN luminosity, and the shell mass evolution in different ambient density distributions. In the case of fixed-mass shells, the high observed values of the momentum ratio (ζ=p˙/(L/c)\zeta = \dot{p}/(L/c)) and energy ratio (ϵk=E˙k/L\epsilon_k = \dot{E}_{k}/L) may be attributed to either radiation trapping or AGN luminosity decay. In contrast, for expanding shells sweeping up mass from the surrounding environment, a decay in AGN luminosity cannot account for the observed high energetics, and radiation trapping is necessarily required. Indeed, strong radiation trapping, e.g. due to high dust-to-gas ratios, can considerably boost the outflow energetics. We obtain a distinct radial dependence for the outflow energetics (ζ(r)\zeta(r), ϵk(r)\epsilon_k(r)) in the case of radiation trapping and luminosity decay, which may help discriminate between the two scenarios. In this framework, the recently discovered `fossil' outflows, with anomalously high values of the energetics, may be interpreted as relics of past AGN activity. The observed outflow properties may therefore provide useful constraints on the past history of AGN activity and/or the physical conditions of the outflow launch region.Comment: accepted for publication in MNRA

    Efficient single photon absorption by a trapped moving atom

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    The influence of the center of mass motion of a trapped two level system on efficient resonant single photon absorption is investigated. It is shown that this absorption process depends strongly on the ratio between the characteristic time scales of spontaneous photon emission and of the two level system's center of mass motion. In particular, if the spontaneous photon emission process occurs almost instantaneously on the time scale of the center of mass motion coherent control of the center of mass motion offers interesting perspectives for optimizing single photon absorption. It is demonstrated that this way time dependent modulation of a harmonic trapping frequency allows to squeeze the two level system's center of mass motion so strongly that high efficient single photon absorption is possible even in cases of weak confinement by a trapping potential.Comment: 9 pages, 5 figure

    The Electrostatic Ion Beam Trap : a mass spectrometer of infinite mass range

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    We study the ions dynamics inside an Electrostatic Ion Beam Trap (EIBT) and show that the stability of the trapping is ruled by a Hill's equation. This unexpectedly demonstrates that an EIBT, in the reference frame of the ions works very similar to a quadrupole trap. The parallelism between these two kinds of traps is illustrated by comparing experimental and theoretical stability diagrams of the EIBT. The main difference with quadrupole traps is that the stability depends only on the ratio of the acceleration and trapping electrostatic potentials, not on the mass nor the charge of the ions. All kinds of ions can be trapped simultaneously and since parametric resonances are proportional to the square root of the charge/mass ratio the EIBT can be used as a mass spectrometer of infinite mass range

    High resolution threshold photoelectron spectroscopy by electron attachment

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    A system is provided for determining the stable energy levels of a species ion, of an atomic, molecular, or radical type, by application of ionizing energy of a predetermined level, such as through photoionization. The system adds a trapping gas to the gaseous species to provide a technique for detection of the energy levels. The electrons emitted from ionized species are captured by the trapping gas, only if the electrons have substantially zero kinetic energy. If the electrons have nearly zero energy, they are absorbed by the trapping gas to produce negative ions of the trapping gas that can be detected by a mass spectrometer. The applied energies (i.e. light frequencies) at which large quantities of trapping gas ions are detected, are the stable energy levels of the positive ion of the species. SF6 and CFCl3 have the narrowest acceptance bands, so that when they are used as the trapping gas, they bind electrons only when the electrons have very close to zero kinetic energy

    Pheromones in pest control on currants : experiences of monitoring, disruption and mass trapping

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    Pheromones; current practice for monitoring of moths in Finland, control experiments in Finland: mating disruption and mass trapping

    Self-Trapping of Polarons in the Rashba-Pekar Model

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    We performed quantum Monte Carlo study of the exciton-polaron model which features the self-trapping phenomenon when the coupling strength and/or particle momentum is varied. For the first time accurate data for energy, effective mass, the structure of the polaronic cloud, dispersion law, and spectral function are available throughout the crossover region. We observed that self-trapping can not be reduced to hybridization of two states with different lattice deformation, and that at least three states are involved in the crossover from light- to heavy-mass regimes.Comment: 5 pages, 5 figures, Accepted to Phys. Rev. B Rapid Communication

    Coherent molecule formation in anharmonic potentials near confinement-induced resonances

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    We perform a theoretical and experimental study of a system of two ultracold atoms with tunable interaction in an elongated trapping potential. We show that the coupling of center-of-mass and relative motion due to an anharmonicity of the trapping potential leads to a coherent coupling of a state of an unbound atom pair and a molecule with a center of mass excitation. By performing the experiment with exactly two particles we exclude three-body losses and can therefore directly observe coherent molecule formation. We find quantitative agreement between our theory of inelastic confinement-induced resonances and the experimental results. This shows that the effects of center-of-mass to relative motion coupling can have a significant impact on the physics of quasi-1D quantum systems.Comment: 7 pages, 4 figure
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