Introduction to stochastic error correction methods

We propose a method for eliminating the truncation error associated with any subspace diagonalization calculation. The new method, called stochastic error correction, uses Monte Carlo sampling to compute the contribution of the remaining basis vectors not included in the initial diagonalization. The method is part of a new approach to computational quantum physics which combines both diagonalization and Monte Carlo techniques.Comment: 11 pages, 1 figur

Material condition assessment with eddy current sensors

Eddy current sensors and sensor arrays are used for process quality and material condition assessment of conducting materials. In an embodiment, changes in spatially registered high resolution images taken before and after cold work processing reflect the quality of the process, such as intensity and coverage. These images also permit the suppression or removal of local outlier variations. Anisotropy in a material property, such as magnetic permeability or electrical conductivity, can be intentionally introduced and used to assess material condition resulting from an operation, such as a cold work or heat treatment. The anisotropy is determined by sensors that provide directional property measurements. The sensor directionality arises from constructs that use a linear conducting drive segment to impose the magnetic field in a test material. Maintaining the orientation of this drive segment, and associated sense elements, relative to a material edge provides enhanced sensitivity for crack detection at edges

A nonperturbative study of three-dimensional quartic scalar field theory using modal field methods

The method of modal field theory is a new development in the field of nonperturbative quantum field theory. This approach reduces a quantum field theory to a finite-dimensional quantum mechanical system by expanding field configurations in terms of free-wave modes. In this dissertation we apply this method to three-dimensional &phis;4 theory using two kinds of modal field approaches: a spherical partial wave expansion and a periodic-box mode expansion. The resulting modal-field quantum-mechanical systems are analyzed with the use of the diffusion Monte Carlo method and by calculating the spectrum and eigenstates of the Hamiltonian directly. In the latter approach we employ the recently introduced quasi-sparse eigenvector method which is designed to diagonalize infinite-dimensional yet very sparse matrices. We study the phase structure of three-dimensional &phis;4 theory, computing the critical coupling and the critical exponents ν and β. We also investigate the spectrum of low-lying energy eigenstates and find evidence of a nonperturbative state in the broken-symmetry phase of the theory