11,488 research outputs found

### Synthesizing framework models for symbolic execution

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

AMoRE (Advanced Mo-based Rare process Experiment) is an experiment to search
a neutrinoless double-beta decay of $^{100}$Mo in molybdate crystals. The
neutron and muon-induced backgrounds are crucial to obtain the zero-background
level (<$10^{-5}$ counts/(keV$\cdot$kg$\cdot$yr)) 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

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
$\mathcal{N} = 4$ 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

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 $\Lambda/K^-$ 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

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

### Measures of Charge Fluctuations in Nuclear Collisions

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 $\phi^4$ theory from an extended ladder resummation

We study shear viscosity in weakly coupled hot $\phi^4$ 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

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

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

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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