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Lie Groups are Groups that are additionally smooth manifolds such that the multiplication and the inverse maps are smooth.

1 vote
1 answer
94 views

Small deformations of maximally symmetric 3-spaces

I am looking for all 'small' deformations of the three 3-dimensional Riemannian spaces with maximal symmetry, the pseudo-sphere, Eucidean space and the sphere. By a theorem by Fubini (1903) the deform …
Thomas Schucker's user avatar
1 vote

Small deformations of maximally symmetric 3-spaces

No there are no others. Bianchi shows in ``Sugli spazi a tre dimensioni che ammettono un gruppo continuo di movimenti,'' Memorie di Matematica e di Fisica della Societa Italiana delle Scienze 11 (189 …
Thomas Schucker's user avatar
6 votes
1 answer
319 views

Deformations of the 4-sphere with 8-dimensional isometry groups

I am looking for deformations of the 4-sphere with 8-dimensional isometry group, like a 4-dimensional Berger sphere.
Thomas Schucker's user avatar
4 votes
1 answer
174 views

A pseudo-Riemannian version of a theorem by Fubini

Guido Fubini, ``Sugli spazii che ammettono un gruppo continuo di movimenti,'' Annali di Mat., ser. 3, 8 (1903) 54.: Let $M$ be a Riemannian manifold of dimension $d\ge 3$. Its isometry group cannot be …
Thomas Schucker's user avatar
1 vote

A pseudo-Riemannian version of a theorem by Fubini

I just found the answer by G. S. Hall (2003) in Class. Quantum Grav. 20 3745. Theorem 8. Let $M$ be a connected smooth paracompact manifold of dimension $n ≥ 3$ admitting a smooth metric $g$ of signat …
Thomas Schucker's user avatar
3 votes
3 answers
521 views

3-dimensional Riemannian manifolds with 4-dimensional isometry group

Is there a list of all 3-dimensional, connected Riemannian manifolds with 4-dimensional isometry group?
Thomas Schucker's user avatar
3 votes
0 answers
321 views

Maximal symmetry at the speed of light

Are there examples of 1 + 3 dimensional pseudo-Riemannian manifolds with 6 dimensional isometry group whose orbits are light-like (i.e., the metric restricted to each orbit is degenerate)? Here is a …
Thomas Schucker's user avatar