title: Gradient marker: a universal wave pattern in an inhomogeneous continuum.
abstract: Wave transport in a media with a slow spatial gradient of its characteristics is found to exhibit a universal wave pattern ("gradient marker") in a vicinity of the maxima or minima of the gradient. The pattern is common for optics, quantum mechanics, and any other propagation governed by the same wave equation. Derived analytically, it has an elegantly simple yet nontrivial profile found in perfect agreement with numerical simulations for specific examples. We also find resonant states in continuum in the case of quantum wells, and formulated criteria for their existence.
authors.affiliation: Electrical and Computer Engineering Department, The Johns Hopkins University, Baltimore, Maryland 21218, USA. alexander.kaplan@jhu.edu
authors.forename: A E
authors.initials: AE
authors.lastname: Kaplan