2,012 research outputs found
Capturing Topology in Graph Pattern Matching
Graph pattern matching is often defined in terms of subgraph isomorphism, an
NP-complete problem. To lower its complexity, various extensions of graph
simulation have been considered instead. These extensions allow pattern
matching to be conducted in cubic-time. However, they fall short of capturing
the topology of data graphs, i.e., graphs may have a structure drastically
different from pattern graphs they match, and the matches found are often too
large to understand and analyze. To rectify these problems, this paper proposes
a notion of strong simulation, a revision of graph simulation, for graph
pattern matching. (1) We identify a set of criteria for preserving the topology
of graphs matched. We show that strong simulation preserves the topology of
data graphs and finds a bounded number of matches. (2) We show that strong
simulation retains the same complexity as earlier extensions of simulation, by
providing a cubic-time algorithm for computing strong simulation. (3) We
present the locality property of strong simulation, which allows us to
effectively conduct pattern matching on distributed graphs. (4) We
experimentally verify the effectiveness and efficiency of these algorithms,
using real-life data and synthetic data.Comment: VLDB201
Superconductivity and local-moment magnetism in Eu(FeCo)As
We report the measurements of resistivity and magnetization under magnetic
fields parallel and perpendicular to the basal plane, respectively, on a
cobalt-doped Eu(FeCo)As single crystal. We
observed a resistivity drop at 21 K, which shifts toward lower
temperatures under external fields, suggesting a superconducting transition.
The upper critical fields near show large anisotropy, in contrast with
those of other '122' FeAs-based superconductors. Low-field magnetic
susceptibility data also show evidence of superconductivity below 21 K. Instead
of expected zero-resistance below , however, a resistivity reentrance
appears at 17 K under zero field, coincident with the magnetic ordering of
Eu moments. Based on the temperature and field dependences of
anisotropic magnetization, a helical magnetic structure for the Eu spins
is proposed. External magnetic fields easily changes the helimagnetism into a
ferromagnetism with fully polarized Eu spins, accompanying by
disappearance of the resistivity reentrance. Therefore, superconductivity
coexists with ferromagnetic state of Eu spins under relatively low
magnetic field. The magnetic and superconducting phase diagrams are finally
summarized for both and .Comment: 8 pages, 10 figure
Counterfactual explanation at will, with zero privacy leakage
While counterfactuals have been extensively studied as an intuitive explanation of model predictions, they still have limited adoption in practice due to two obstacles: (a) They rely on excessive access to the model for explanation that the model owner may not provide; and (b) counterfactuals carry information that adversarial users can exploit to launch model extraction attacks. To address the challenges, we propose CPC, a data-driven approach to counterfactual. CPC works at the client side and gives full control and right-to-explain to model users, even when model owners opt not to. Moreover, CPC warrants that adversarial users cannot exploit counterfactuals to extract models. We formulate properties and fundamental problems underlying CPC, study their complexity and develop effective algorithms. Using real-world datasets and user study, we verify that CPC does prevent adversaries from exploiting counterfactuals for model extraction attacks, and is orders of magnitude faster than existing explainers, while maintaining comparable and often higher quality
Spin-1/2 XYZ model revisit: general solutions via off-diagonal Bethe ansatz
The spin-1/2 XYZ model with both periodic and anti-periodic boundary
conditions is studied via the off-diagonal Bethe ansatz method. The exact
spectra of the Hamiltonians and the Bethe ansatz equations are derived by
constructing the inhomogeneous T-Q relations, which allow us to treat both the
even N (the number of lattice sites) and odd N cases simultaneously in an
unified approach.Comment: 20 pages, 3 tables, published version, numerical check is adde
- …