153,654 research outputs found
Counting Complexity for Reasoning in Abstract Argumentation
In this paper, we consider counting and projected model counting of
extensions in abstract argumentation for various semantics. When asking for
projected counts we are interested in counting the number of extensions of a
given argumentation framework while multiple extensions that are identical when
restricted to the projected arguments count as only one projected extension. We
establish classical complexity results and parameterized complexity results
when the problems are parameterized by treewidth of the undirected
argumentation graph. To obtain upper bounds for counting projected extensions,
we introduce novel algorithms that exploit small treewidth of the undirected
argumentation graph of the input instance by dynamic programming (DP). Our
algorithms run in time double or triple exponential in the treewidth depending
on the considered semantics. Finally, we take the exponential time hypothesis
(ETH) into account and establish lower bounds of bounded treewidth algorithms
for counting extensions and projected extension.Comment: Extended version of a paper published at AAAI-1
The counterSharp Model Counting Benchmark
We present the counterSharp benchmark consisting of 123 projected model counting instances. The instances originate from work on the reliability quantification of programs written in C. We briefly introduce the application field and describe the benchmark selection process
Is the largest aqueous gold cluster a superatom complex? Electronic structure & optical response of the structurally determined Au146(pMBA)57
The new water-soluble gold cluster Au146(pMBA)57, the structure of which has
been recently determined at sub-atomic resolution by Vergara et al. [1], is the
largest aqueous gold cluster ever structurally determined and likewise the
smallest cluster with a stacking fault. The core presents a twinned truncated
octahedron, while additional peripheral gold atoms follow a C2 rotational
symmetry. According to the usual counting rules of the superatom complex (SAC)
model, the compound attains a number of 92 SAC electrons if the overall net
charge is 3- (three additional electrons). As this is the number of electrons
required for a major shell closing, the question arises if Au146(pMBA)57 should
be regarded as a superatom complex. Starting from the experimental coordinates
we have analyzed the structure using density-functional theory. The optimized
(relaxed) structure retains all the connectivity of the experimental
coordinates, while removing much of its irregularities in interatomic
distances, thereby enhancing the C2-symmetry feature. Analyzing the
angular-momentum projected states, we show that, despite a small gap, the
electronic structure does not exhibit SAC model character. In addition, optical
absorption spectra are found to be relatively smooth compared to the example of
the Au144(SR)60 cluster. The Au146(SR)57 cluster does not derive its stability
from SAC character; it cannot be considered a superatom complex
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