# A Two-Dimensional “Flea on the Elephant” Phenomenon and its Numerical Visualization

Bianchini, R., Gosse, L., Zuazua, E. , Multiscale Model. Simul., Vol. 17, No. 1 (2019), pp. 137–166, DOI: 10.1137/18M1179985.

Abstract: Localization phenomena (sometimes called “flea on the elephant”) for the operator $L ε = −ε 2 ∆u + p(x)u, p(x)$ being an unbounded potential, are studied both analytically and numerically, mostly in two space dimensions and within a perturbative framework. Starting from the classical harmonic potential, the effects of various perturbations is retrieved, especially in the case of two asymmetric potential wells. These findings are illustrated numerically by means of an original algorithm, which relies on a discrete approximation of the Steklov-Poincaré operator for L ε , and for which error estimates are established. Such a two-dimensional discretization produces less mesh-imprinting than more standard finite-differences and captures correctly sharp layers.

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