11,488 research outputs found

    Synthesizing framework models for symbolic execution

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    Symbolic execution is a powerful program analysis technique, but it is difficult to apply to programs built using frameworks such as Swing and Android, because the framework code itself is hard to symbolically execute. The standard solution is to manually create a framework model that can be symbolically executed, but developing and maintaining a model is difficult and error-prone. In this paper, we present Pasket, a new system that takes a first step toward automatically generating Java framework models to support symbolic execution. Pasket's focus is on creating models by instantiating design patterns. Pasket takes as input class, method, and type information from the framework API, together with tutorial programs that exercise the framework. From these artifacts and Pasket's internal knowledge of design patterns, Pasket synthesizes a framework model whose behavior on the tutorial programs matches that of the original framework. We evaluated Pasket by synthesizing models for subsets of Swing and Android. Our results show that the models derived by Pasket are sufficient to allow us to use off-the-shelf symbolic execution tools to analyze Java programs that rely on frameworks.National Science Foundation (U.S.) (CCF-1139021)National Science Foundation (U.S.) (CCF-1139056)National Science Foundation (U.S.) (CCF-1161775

    Neutron and muon-induced background studies for the AMoRE double-beta decay experiment

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    AMoRE (Advanced Mo-based Rare process Experiment) is an experiment to search a neutrinoless double-beta decay of 100^{100}Mo in molybdate crystals. The neutron and muon-induced backgrounds are crucial to obtain the zero-background level (<10510^{-5} counts/(keV\cdotkg\cdotyr)) for the AMoRE-II experiment, which is the second phase of the AMoRE project, planned to run at YEMI underground laboratory. To evaluate the effects of neutron and muon-induced backgrounds, we performed Geant4 Monte Carlo simulations and studied a shielding strategy for the AMORE-II experiment. Neutron-induced backgrounds were also included in the study. In this paper, we estimated the background level in the presence of possible shielding structures, which meet the background requirement for the AMoRE-II experiment

    A shear spectral sum rule in a non-conformal gravity dual

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    A sum rule which relates a stress-energy tensor correlator to thermodynamic functions is examined within the context of a simple non-conformal gravity dual. Such a sum rule was previously derived using AdS/CFT for conformal N=4\mathcal{N} = 4 Supersymmetric Yang-Mills theory, but we show that it does not generalize to the non-conformal theory under consideration. We provide a generalized sum rule and numerically verify its validity. A useful byproduct of the calculation is the computation of the spectral density in a strongly coupled non-conformal theory. Qualitative features of the spectral densities and implications for lattice measurements of transport coefficients are discussed.Comment: 13 pages, 3 figures. v5: Typos in Eq. (60) fixed. v4: References added, matches published version. v3: Minor typographical corrections. v2: References and some discussion in Appendix A have been added; conclusions unchange

    Particle yield fluctuations and chemical non-equilibrium at RHIC

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    We study charge fluctuations within the statistical hadronization model. Considering both the particle yield ratios and the charge fluctuations we show that it is possible to differentiate between chemical equilibrium and non-equilibrium freeze-out conditions. As an example of the procedure we show quantitatively how the relative yield ratio Λ/K\Lambda/K^- together with the normalized net charge fluctuation v(Q)=\ave{\Delta Q^2}/\ave{\Nch} constrain the chemical conditions at freeze-out. We also discuss the influence of the limited detector acceptance on fluctuation measurements, and show how this can be accounted for within a quantitative analysis.Comment: Accepted for publication by Physical Review

    Low-Temperature Spin Diffusion in a Spin-Polarized Fermi Gas

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    We present a finite temperature calculation of the transverse spin-diffusion coefficient, DD_\bot, in a dilute degenerate Fermi gas in the presence of a small external magnetic field, HH. While the longitudinal diffusion coefficient displays the conventional low-temperature Fermi-liquid behavior, DT2D_\parallel \propto T^{-2}, the corresponding results for DD_\bot show three separate regimes: (a) DH2D_\bot \sim H^{-2} for THT \ll H; (b) DT2D_\bot \sim T^{-2}, D/D1D_\bot /D_\parallel \neq 1 for THT \gg H and large spin-rotation parameter ξ1\xi \gg 1, and (c) D=DT2D_\bot = D_\parallel \propto T^{-2} for THT \gg H and ξ1\xi \ll 1. Our results are qualitatively consistent with the available experimental data in weakly spin-polarized 3He^3{\rm He} and 3He4He^3{\rm He} - ^4{\rm He} mixtures.Comment: 13 pages, REVTEX, 3 figures available upon request, RU-94-4

    Measures of Charge Fluctuations in Nuclear Collisions

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    The properties of two measures of charge fluctuations D and Delta Phi_q are discussed within several toy models of nuclear collisions. In particular their dependence on mean particle multiplicity, multiplicity fluctuations and net electric charge are studied. It is shown that the measure Delta Phi_q is less sensitive to these trivial biasing effects than the originally proposed measure D. Furthermore the influence of resonance decay kinematics is analysed and it is shown that it is likely to shadow a possible reduction of fluctuations due to QGP creation.Comment: 9 pages, 9 figure

    Shear viscosity in ϕ4\phi^4 theory from an extended ladder resummation

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    We study shear viscosity in weakly coupled hot ϕ4\phi^4 theory using the CTP formalism . We show that the viscosity can be obtained as the integral of a three-point function. Non-perturbative corrections to the bare one-loop result can be obtained by solving a decoupled Schwinger-Dyson type integral equation for this vertex. This integral equation represents the resummation of an infinite series of ladder diagrams which contribute to the leading order result. It can be shown that this integral equation has exactly the same form as the Boltzmann equation. We show that the integral equation for the viscosity can be reexpressed by writing the vertex as a combination of polarization tensors. An expression for this polarization tensor can be obtained by solving another Schwinger-Dyson type integral equation. This procedure results in an expression for the viscosity that represents a non-perturbative resummation of contributions to the viscosity which includes certain non-ladder graphs, as well as the usual ladders. We discuss the motivation for this resummation. We show that these resummations can also be obtained by writing the viscosity as an integral equation involving a single four-point function. Finally, we show that when the viscosity is expressed in terms of a four-point function, it is possible to further extend the set of graphs included in the resummation by treating vertex and propagator corrections self-consistently. We discuss the significance of such a self-consistent resummation and show that the integral equation contains cancellations between vertex and propagator corrections.Comment: Revtex 40 pages with 29 figures, version to appear in Phys. Rev.

    Shear viscosity of hot scalar field theory in the real-time formalism

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    Within the closed time path formalism a general nonperturbative expression is derived which resums through the Bethe-Salpter equation all leading order contributions to the shear viscosity in hot scalar field theory. Using a previously derived generalized fluctuation-dissipation theorem for nonlinear response functions in the real-time formalism, it is shown that the Bethe-Salpeter equation decouples in the so-called (r,a) basis. The general result is applied to scalar field theory with pure lambda*phi**4 and mixed g*phi**3+lambda*phi**4 interactions. In both cases our calculation confirms the leading order expression for the shear viscosity previously obtained in the imaginary time formalism.Comment: Expanded introduction and conclusions. Several references and a footnote added. Fig.5 and its discussion in the text modified to avoid double counting. Signs in Eqs. (45) and (53) correcte

    Nonequilibrium perturbation theory for spin-1/2 fields

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    A partial resummation of perturbation theory is described for field theories containing spin-1/2 particles in states that may be far from thermal equilibrium. This allows the nonequilibrium state to be characterized in terms of quasiparticles that approximate its true elementary excitations. In particular, the quasiparticles have dispersion relations that differ from those of free particles, finite thermal widths and occupation numbers which, in contrast to those of standard perturbation theory evolve with the changing nonequilibrium environment. A description of this kind is essential for estimating the evolution of the system over extended periods of time. In contrast to the corresponding description of scalar particles, the structure of nonequilibrium fermion propagators exhibits features which have no counterpart in the equilibrium theory.Comment: 16 pages; no figures; submitted to Phys. Rev.

    Charge fluctuations and electric mass in a hot meson gas

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    Net-Charge fluctuations in a hadron gas are studied using an effective hadronic interaction. The emphasis of this work is to investigate the corrections of hadronic interactions to the charge fluctuations of a non-interacting resonance gas. Several methods, such as loop, density and virial expansions are employed. The calculations are also extended to SU(3) and some resummation schemes are considered. Although the various corrections are sizable individually, they cancel to a large extent. As a consequence we find that charge fluctuations are rather well described by the free resonance gas.Comment: 32 pages, 18 figure
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