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Generalized transformation design: Metrics, speeds, and diffusion

Research output: Contribution to journalJournal article

<mark>Journal publication date</mark>03/2018
<mark>Journal</mark>Wave Motion
Number of pages16
Pages (from-to)91-106
Early online date11/11/17
<mark>Original language</mark>English


We show that a unified and maximally generalized approach to spatial transformation design is possible, one that encompasses all second order waves, rays, and diffusion processes in anisotropic media. Until the final step, it is unnecessary to specify the physical process for which a specific transformation design is to be implemented. The principal approximation is the neglect of wave impedance, an attribute that plays no role in ray propagation, and is therefore irrelevant for pure ray devices; another constraint is that for waves the spatial variation in material parameters needs to be sufficiently small compared with the wavelength. The key link between our general formulation and a specific implementation is how the spatial metric relates to the speed of disturbance in a given medium, whether it is electromagnetic, acoustic, or diffusive. Notably, we show that our generalised ray theory, in allowing for anisotropic indexes (speeds), generates the same predictions as does a wave theory, and the results are closely related to those for diffusion processes.

Bibliographic note

This is the author’s version of a work that was accepted for publication in Wave Motion. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Wave Motion, 77, 2017 DOI: 10.1016/j.wavemoti.2017.11.002