@article {2011,
	title = {On the Space of Symmetric Operators with Multiple Ground States},
	journal = {Functional Analysis and its Applications, Volume 45, Issue 4, December 2011, Pages 241-251},
	number = {arXiv:1107.3010;},
	year = {2011},
	publisher = {SISSA},
	abstract = {We study homological structure of the filtrations of the spaces of
self-adjoint operators by the multiplicity of the ground state. We consider
only operators acting in a finite dimensional complex or real Hilbert space but
infinite dimensional generalizations are easily guessed.},
	keywords = {Multiple eigenvalue},
	doi = {DOI: 10.1007/s10688-011-0026-5},
	url = {http://hdl.handle.net/1963/7069},
	author = {Andrei A. Agrachev}
}
