RT Book, Section T1 Algèbres de Lie rigides A1 Goze, Michel A1 Ancochea Bermúdez, José María A2 Khakimdjanov, Yusupdjan A2 Goze, Michel A2 Ayupov, Shavkat A. AB Let Ln Kn3 be the affine variety of all n-dimensional Lie algebras over an algebraically closed field of characteristic zero. An element g 2 Ln can be identified with the bilinear mapping μ defining the multiplication in g. If f is an element of the general linear group GL(n,K) then f−1μ(f, f) defines a Lie algebra in Ln. In this way GL(n,K) operates on Ln. μ 2 Ln is called rigid iff the orbit O(μ) is Zariski-open in Ln. The vanishing of the second cohomology group H2(μ, μ) implies rigidity of the Lie algebra μ. Hence semisimple Lie algebras are rigid.The classification of rigid Lie algebras is somewhat more accessible than the general case. The authors classify all rigid solvable Lie algebras up to dimension eight. A nilpotent Lie algebra n of dimension n is called filamentous iff its characteristic sequence is (n − 1, 1). The rank of a filamentous Lie algebra is at most two. A rigid Lie algebra with filamentous nilradical is necessarily solvable. The authors answer the question as to when a filamentous Lie algebra occurs as the nilradical of a rigid Lie algebra: This is always the case if the rank of the filamentous Lie algebra n is two (Theorem 3), and in the case of rank one it depends on the existence of diagonalizable derivations of n with certain integral eigenvalues (Theorem 4). PB Kluwer Academic SN 0-7923-5094-4 YR 1998 FD 1998 LK https://hdl.handle.net/20.500.14352/60670 UL https://hdl.handle.net/20.500.14352/60670 NO Proceedings of the 2nd French-Uzbek Colloquium held in Tashkent, September 29–October 5, 1997. DS Docta Complutense RD 4 may 2024