17,325 research outputs found
Conserved charges of black holes in Weyl and Einstein-Gauss-Bonnet gravities
An off-shell generalization of the Abbott-Deser-Tekin (ADT) conserved charge
was recently proposed by Kim et al. They achieved this by introducing off-shell
Noether currents and potentials. In this paper, we construct the crucial
off-shell Noether current by the variation of the Bianchi identity for the
expression of motion equation, with the help of the property of Killing vector.
Our Noether current, which contains an additional term that is just one half of
the Lie derivative of a surface term with respect to the Killing vector, takes
a different form in comparison with the one in their work. Then we employ the
generalized formulation to calculate the quasi-local conserved charges for the
most general charged spherically symmetric and the dyonic rotating black holes
with AdS asymptotics in four-dimensional conformal Weyl gravity, as well as the
charged spherically symmetric black holes in arbitrary dimensional
Einstein-Gauss-Bonnet gravity coupled to Maxwell or nonlinear electrodynamics
in AdS spacetime. Our results confirm those through other methods in the
literature.Comment: 21 Pages, no figures, references adde
Off-shell Noether current and conserved charge in Horndeski theory
We derive the off-shell Noether current and potential in the context of
Horndeski theory, which is the most general scalar-tensor theory with a
Lagrangian containing derivatives up to second order while yielding at most to
second-order equations of motion in four dimensions. Then the formulation of
conserved charges is proposed on basis of the off-shell Noether potential and
the surface term got from the variation of the Lagrangian. As an application,
we calculate the conserved charges of black holes in a scalar-tensor theory
with non-minimal coupling between derivatives of the scalar field and the
Einstein tensor.Comment: 19 pages, no figures, to appear in PL
Practical Fine-grained Privilege Separation in Multithreaded Applications
An inherent security limitation with the classic multithreaded programming
model is that all the threads share the same address space and, therefore, are
implicitly assumed to be mutually trusted. This assumption, however, does not
take into consideration of many modern multithreaded applications that involve
multiple principals which do not fully trust each other. It remains challenging
to retrofit the classic multithreaded programming model so that the security
and privilege separation in multi-principal applications can be resolved.
This paper proposes ARBITER, a run-time system and a set of security
primitives, aimed at fine-grained and data-centric privilege separation in
multithreaded applications. While enforcing effective isolation among
principals, ARBITER still allows flexible sharing and communication between
threads so that the multithreaded programming paradigm can be preserved. To
realize controlled sharing in a fine-grained manner, we created a novel
abstraction named ARBITER Secure Memory Segment (ASMS) and corresponding OS
support. Programmers express security policies by labeling data and principals
via ARBITER's API following a unified model. We ported a widely-used, in-memory
database application (memcached) to ARBITER system, changing only around 100
LOC. Experiments indicate that only an average runtime overhead of 5.6% is
induced to this security enhanced version of application
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