17,907 research outputs found

    Three-Point Functions at Finite Temperature

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    We study 3-point functions at finite temperature in the closed time path formalism. We give a general decomposition of the eight component tensor in terms of seven vertex functions. We derive a spectral representation for these seven functions in terms of two independent real spectral functions. We derive relationships between the seven functions and obtain a representation of the vertex tensor that greatly simplifies calculations in real time.Comment: 21 pages LaTeX; one ps-figure; Revised version, contains more references and discussio

    Evaporation Prescription for Time-Dependent Density Functional Calculations

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    Collisions between 248^{248}Cm and 48^{48}Ca are systematically calculated by time-dependent density functional calculations with evaporation prescription. Depending on the incident energy and impact parameter, fusion, fusion-fission, and quasi-fission events are expected to appear. In this paper, the evaporation prescription is introduced, which is expected to be rather important to heavy-ion reactions producing superheavy nuclei, where the heavier total mass can be related to the higher total excitation energy.Comment: To appear in the NN2012 Proceedings in Journal of Physics: Conference Series; revised based on the referee's comment (ver. 2, 09/2012

    Shock heating by FR I radio sources in galaxy clusters

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    Feedback by active galactic nuclei (AGN) is frequently invoked to explain the cut-off of the galaxy luminosity function at the bright end and the absence of cooling flows in galaxy clusters. Meanwhile, there are recent observations of shock fronts around radio-loud AGN. Using realistic 3D simulations of jets in a galaxy cluster, we address the question what fraction of the energy of active galactic nuclei is dissipated in shocks. We find that weak shocks that encompass the AGN have Mach numbers of 1.1-1.2 and dissipate at least 2% of the mechanical luminosity of the AGN. In a realistic cluster medium, even a continuous jet can lead to multiple shock structures, which may lead to an overestimate of the AGN duty cycles inferred from the spatial distribution of waves.Comment: accepted by MNRAS Letter

    A systematic comparison of jet quenching in different fluid-dynamical models

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    Comparing four different (ideal and viscous) hydrodynamic models for the evolution of the medium created in 200 AGeV Au-Au collisions, combined with two different models for the path length dependence of parton energy loss, we study the effects of jet quenching on the emission-angle dependence of the nuclear suppression factor R_AA(phi) and the away-side per trigger yield I_AA(phi). Each hydrodynamic model was tuned to provide a reasonable description of the single-particle transverse momentum spectra for all collision centralities, and the energy loss models were adjusted to yield the same pion nuclear suppression factor in central Au-Au collisions. We find that the experimentally measured in-plane vs. out-of-plane spread in R_AA(phi) is better reproduced by models that shift the weight of the parton energy loss to later times along its path. Among the models studied here, this is best achieved by energy loss models that suppress energy loss at early times, combined with hydrodynamic models that delay the dilution of the medium density due to hydrodynamic expansion by viscous heating. We were unable to identify a clear tomographic benefit of a measurement of I_AA(phi) over that of R_AA(phi).Comment: 17 pages, 11 figure

    Psychopharmacological Procedures

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    Psychopharmacology has opened the door to many previously blocked parts of psychiatric therapy. It has been a welcome catalyst for a long awaited rapprochement between psychiatry and the rest of medicine. Even if psychopharmacological research is not likely to produce another revolutionary breakthrough type of drug in the near future, there is good reason to expect many more useful therapeutic tools to issue from such research in the years to come

    Parametric Feedback Resonance in Chaotic Systems

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    If one changes the control parameter of a chaotic system proportionally to the distance between an arbitrary point on the strange attractor and the actual trajectory, the lifetime τ of the most stable unstable periodic orbit in the vicinity of this point starts to diverge with a power law. The volume in parameter space where τ becomes infinite is finite and from its nonfractal boundaries one can determine directly the local Liapunov exponents. The experimental applicability of the method is demonstrated for two coupled diode resonators

    Thermodynamics of nuclei in thermal contact

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    The behaviour of a di-nuclear system in the regime of strong pairing correlations is studied with the methods of statistical mechanics. It is shown that the thermal averaging is strong enough to assure the application of thermodynamical methods to the energy exchange between the two nuclei in contact. In particular, thermal averaging justifies the definition of a nuclear temperature.Comment: 9 pages, 1 figur

    Elliptic flow of thermal photons and dileptons

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    In this talk we describe the recently discovered rich phenomenology of elliptic flow of electromagnetic probes of the hot matter created in relativistic heavy-ion collisions. Using a hydrodynamic model for the space-time dynamics of the collision fireball created in Au+Au collisions at RHIC, we compute the transverse momentum spectra and elliptic flow of thermal photons and dileptons. These observables are shown to provide differential windows into various stages of the fireball expansion.Comment: 8 pages, including 9 figures. Invited talk at the Hard Probes 2006 Conference (Asilomar, June 9-16, 2006), to appear in the Proceedings (Elsevier
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