Energy diffusion in strongly driven quantum chaotic systems

The energy evolution of a quantum chaotic system under the perturbation that harmonically depends on time is studied for the case of large perturbation, in which the rate of transition calculated from the Fermi golden rule exceeds the frequency of perturbation. It is shown that the energy evolution retains its diffusive character, with the diffusion coefficient that is asymptotically proportional to the magnitude of perturbation and to the square root of the density of states. The results are supported by numerical calculation. They imply the absence of the quantum-classical correspondence for the energy diffusion and the energy absorption in the classical limit $\hbar \to 0$.Comment: 12 pages, 3 figures, RevTe

Compensación de grandes redes geodésicas

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Computational form-finding methods for fabric structures

Form-finding is a process that determines the surface configuration of a fabric structure under prestress. This process can be carried out using a variety of numerical methods, of which the most common are (a) transient stiffness, (b) force density, and (c) dynamic relaxation. The paper describes the three methods, discusses their advantages and limitations, and provides insights into their applicability as numerical tools for the design of fabric structures. Further, it describes various approaches to surface discretisation, and discusses consequences of using ‘mesh control’ and elastic effects in the design of form-found surfaces. A brief discussion of the general recommendations given in the European design guide for tensile surfaces structures concludes the paper