We investigate the effect of sampling on linearization for continuous time systems. It is shown that the discretized system is linearizable by state coordinate change for an open set of sampling times if and only if the continuous time system is linearizable by state coordinate change. Also, it is shown that linearizability via digital feedback imposes highly nongeneric constraints on the struc...

This paper is concerned with state-space realizations of the adjoints of the variationals of Hamiltonian control systems. It will be shown that the variational systems of a class of Hamiltonian systems have self-adjoint state-space realizations, that is, the variational system and its adjoint have the same state-space realizations. This implies that the inputoutput mapping of the adjoint of the...

The numerical approximation to a parabolic control problem with control and state constraints is studied in this paper. We use standard piecewise linear and continuous finite elements for the space discretization of the state, while the backward Euler method is used for time discretization. A priori error estimates for control and state are obtained by an improved maximum error estimate for cor...

Lüscher’s local bosonic algorithm for Monte Carlo simulations of quantum field theories with fermions is applied to the simulation of a possibly supersymmetric Yang-Mills theory with a Majorana fermion in the adjoint representation. Combined with a correction step in a two-step polynomial approximation scheme, the obtained algorithm seems to be promising and could be competitive with more conve...

Waveform inversion is a velocity-model-building technique based on full waveforms as the input and seismic wavefields as the information carrier. Conventional waveform inversion is implemented in the data domain. However, similar techniques referred to as image-domain wavefield tomography can be formulated in the image domain and use a seismic image as the input and seismic wavefields as the in...

The magnetohydrodynamics (MHD) equations are used to model the flow of electrically conducting fluids in such applications as liquid metals and plasmas. This system of nonself-adjoint, nonlinear PDEs couples the Navier–Stokes equations for fluids and Maxwell’s equations for electromagnetics. There has been recent interest in fully coupled solvers for the MHD system because they allow for fast s...

The magnetohydrodynamics (MHD) equations are used to model the flow of electrically conducting fluids in such applications as liquid metals and plasmas. This system of non-self adjoint, nonlinear PDEs couples the Navier-Stokes equations for fluids and Maxwell’s equations for electromagnetics. There has been recent interest in fully coupled solvers for the MHD system because they allow for fast ...

Let A ⊆ B(H) be a C∗-algebra of operators and let P1 ≤ P2 ≤ . . . be an increasing sequence of finite dimensional projections in B(H). In a previous paper [3] we developed methods for computing the spectrum of self adjoint operators T ∈ A in terms of the spectra of the associated sequence of finite dimensional compressions PnTPn. In a suitable context, we showed that this is possible when Pn in...

S U M M A R Y We propose a level-set adjoint-state method for crosswell traveltime tomography using both first-arrival transmission and reflection traveltime data. Since our entire formulation is based on solving eikonal and advection equations on finite-difference meshes, our traveltime tomography strategy is carried out without computing rays explicitly. We incorporate reflection traveltime d...