We formulate a unitary perturbation theory for quantum mechanics inspired by the Lie-Deprit formulation of canonical transformations. The original Hamiltonian is converted into a solvable one by a transformation obtained through a Magnus expansion. [...]
|
||||||
|
By using functional integral methods, we determine a computable evolution equation for the joint response-excitation probability density function of a stochastic dynamical system driven by coloured noise. This equation can be represented in terms of [...] We show that, under rather general assumptions on the form of the entropy function, the energy balance equation for a system in thermodynamic equilibrium is equivalent to a set of nonlinear equations of hydrodynamic type. This set of equations is [...] Materials having a negative Poisson’s ratio (auxetic) get fatter rather than thinner when uniaxially stretched. This phenomenon has been often explained through models that describe how particular geometric features in the micro or nanostructure of [...] We consider the influence of aerodynamic forces on the shape of a whirling filament that is held at both ends, i.e. a jump rope. At high Reynolds numbers, the rope curls out of the plane and towards the axis of rotation—a feature we demonstrate [...] A computational study of octahydridosilasequioxane, Si8O12H8, as a free molecule and when embedded in the unit cell R-3, Z=3, showed that the point group of the free molecule is indeed Oh, but that its crystal symmetry is reduced to C3i. Since the [...] Nanomaterials with chiral morphologies hold promise for a wide diversity of technologically important applications in such fields as micro/nano-electromechanical systems and medical engineering. Understanding the mechanisms underlying the formation [...] The scattering of acoustic waves by irregular structures plays an important role in a wide range of problems of scientific and technological interest. This contribution focuses on the rapid and highly accurate numerical approximation of solutions of [...] We study a model of bird migration between the summer breeding ground and the winter refuge site. The model involves time lags for the transition time between the patches, and the model parameters are periodic in time as the biological activities [...] Designs of physically large and complex (PL&C) systems, nowadays, are achieved through the use of evermore capable digital computer-based techniques. Thus, the process of such designs might be characterized as the practice of science rather than [...] |
||||||
|
|
||||||