It is proved that one can choose a control function on an arbitrarilly small open subset of the boundary of an obstacle so that the total radiation from this obstacle for a fixed direction of the incident plane wave and for a fixed wave number will be as small as one wishes. The obstacle is called "invisible" in this case.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-ap90-2-4,
author = {A. G. Ramm},
title = {Invisible obstacles},
journal = {Annales Polonici Mathematici},
volume = {92},
year = {2007},
pages = {145-148},
zbl = {1134.35032},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-ap90-2-4}
}
A. G. Ramm. Invisible obstacles. Annales Polonici Mathematici, Tome 92 (2007) pp. 145-148. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-ap90-2-4/