2,694 research outputs found
XOR-Sampling for Network Design with Correlated Stochastic Events
Many network optimization problems can be formulated as stochastic network
design problems in which edges are present or absent stochastically.
Furthermore, protective actions can guarantee that edges will remain present.
We consider the problem of finding the optimal protection strategy under a
budget limit in order to maximize some connectivity measurements of the
network. Previous approaches rely on the assumption that edges are independent.
In this paper, we consider a more realistic setting where multiple edges are
not independent due to natural disasters or regional events that make the
states of multiple edges stochastically correlated. We use Markov Random Fields
to model the correlation and define a new stochastic network design framework.
We provide a novel algorithm based on Sample Average Approximation (SAA)
coupled with a Gibbs or XOR sampler. The experimental results on real road
network data show that the policies produced by SAA with the XOR sampler have
higher quality and lower variance compared to SAA with Gibbs sampler.Comment: In Proceedings of the Twenty-sixth International Joint Conference on
Artificial Intelligence (IJCAI-17). The first two authors contribute equall
Dynamical Condensation in a Holographic Superconductor Model with Anisotropy
We study dynamical condensation process in a holographic superconductor model
with anisotropy. The time-dependent numerical solution is constructed for the
Einstein-Maxwell-dilaton theory with complex scalar in asymptotic AdS
spacetime. The introduction of dilaton field generates the anisotropy in
boundary spatial directions. In analogy of isotropic case, we have two black
hole solutions below certain critical temperature , the anisotropic
charged black hole with and without scalar hair, corresponding respectively to
the supercooled normal phase and superconducting phase in the boundary theory.
We observe a nonlinear evolution from a supercooled anisotropic black hole
without scalar hair to a anisotropic hairy black hole. Via AdS/CFT
correspondence, we extract time evolution of the condensate operator, which
shows an exponential growth and subsequent saturation, similar to the isotropic
case. Furthermore, we obtain a nontrivial time evolution of the boundary
pressure, while in isotropic case it remains a constant. We also generalize
quasinormal modes calculation to anisotropic black holes and shows scalar
quasinormal modes match with relaxation time scale of the condensate operator.
In addition, we present the final temperature and anisotropic pressure as
functions of initial temperature and background anisotropy.Comment: 18 pages, 12 figures. v2: minor revision and references adde
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