35,037 research outputs found
Definitions of entanglement entropy of spin systems in the valence-bond basis
The valence-bond structure of spin-1/2 Heisenberg antiferromagnets is closely
related to quantum entanglement. We investigate measures of entanglement
entropy based on transition graphs, which characterize state overlaps in the
overcomplete valence-bond basis. The transition graphs can be generated using
projector Monte Carlo simulations of ground states of specific hamiltonians or
using importance-sampling of valence-bond configurations of amplitude-product
states. We consider definitions of entanglement entropy based on the bonds or
loops shared by two subsystems (bipartite entanglement). Results for the
bond-based definition agrees with a previously studied definition using
valence-bond wave functions (instead of the transition graphs, which involve
two states). For the one dimensional Heisenberg chain, with uniform or random
coupling constants, the prefactor of the logarithmic divergence with the size
of the smaller subsystem agrees with exact results. For the ground state of the
two-dimensional Heisenberg model (and also Neel-ordered amplitude-product
states), there is a similar multiplicative violation of the area law. In
contrast, the loop-based entropy obeys the area law in two dimensions, while
still violating it in one dimension - both behaviors in accord with
expectations for proper measures of entanglement entropy.Comment: 9 pages, 8 figures. v2: significantly expande
Nonequilibrium quench dynamics in quantum quasicrystals
We study the nonequilibrium dynamics of a quasiperiodic quantum Ising chain
after a sudden change in the strength of the transverse field at zero
temperature. In particular we consider the dynamics of the entanglement entropy
and the relaxation of the magnetization. The entanglement entropy increases
with time as a power-law, and the magnetization is found to exhibit
stretched-exponential relaxation. These behaviors are explained in terms of
anomalously diffusing quasiparticles, which are studied in a wave packet
approach. The nonequilibrium magnetization is shown to have a dynamical phase
transition.Comment: 17 pages, 15 figures; revised version; to appear in New Journal of
Physic
Construction 3D BIM-based knowledge management system: a case study
Knowledge management (KM) is the organization, creation, sharing and flow of knowledge within organizations. Knowledge can be shared and reused among involved engineers and experts to improve a construction process and reduce the time and cost of solving problems. This paper proposes a new and practical methodology to capture and represent construction project knowledge by using a Building Information Modeling (BIM) approach. Using BIM approach, users can make visual knowledge management in the 3D Computer-aided Design (CAD) environment. This study addresses the application of knowledge management in the construction phase of construction projects and proposes a Construction BIM-based Knowledge Management (CBIMKM) system for general contractors. The CBIMKM is then applied in selected case studies of a construction building project in Taiwan to verify our proposed methodology and demonstrate the effectiveness of sharing knowledge in the 3D environment. By applying the BIM approach, all participants in a project can share and reuse explicit and tacit knowledge through the 3D CAD-based knowledge map. The combined results demonstrate that the CBIMKM system can be used as a visual 3D-based knowledge management platform by utilizing the BIM approach and web technology
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