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      2-step nilpotent lie groups of higher rank 

      Samiou, E. (2002)
      We construct a family of simply connected 2-step nilpotent Lie groups of higher rank such that every geodesic lies in a flat. These are as Riemannian manifolds irreducible and arise from real representations of compact Lie ...
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      The Cheeger constant of simply connected, solvable Lie groups 

      Peyerimhoff, N.; Samiou, E. (2004)
      We show that the Cheeger isoperimetric constant of a solvable simply connected Lie group G with Lie algebra script G sign is h(G) = max H ∈ script G sign, ∥H∥=1 tr(ad(H)).
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      Curvature and q-strict convexity 

      Dalla, L.; Samiou, E. (2007)
      We relate q-strict convexity of compact convex sets K ⊂ ℝd whose boundary ∂K is a differentiable manifold of class Cq to intrinsic curvature properties of ∂K. Furthermore we prove that the set of q-strictly convex sets is ...
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      Homogeneous spaces with sections 

      Kollross, A.; Samiou, E. (2005)
      We study homogeneous Riemannian manifolds all of whose geodesics can be mapped by some isometry into a fixed homogeneous, connected, totally geodesic sub-manifold, called section. We show that these spaces are locally ...
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      Integral Geometric Properties of Non-compact Harmonic Spaces 

      Peyerimhoff, N.; Samiou, E. (2013)
      On non-compact harmonic manifolds we prove that functions satisfying the mean value property for two generic radii must be harmonic. Moreover, functions with vanishing integrals over all spheres (or balls) of two generic ...
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      Manifolds with large isotropy groups 

      Kollross, A.; Samiou, E. (2011)
      We classify all simply connected Riemannian manifolds whose isotropy groups act with cohomogeneity less or equal to two. © de Gruyter 2011.
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      The Moduli Space of Six-Dimensional Two-Step Nilpotent Lie Algebras 

      Console, S.; Fino, A.; Samiou, E. (2005)
      We determine the moduli space of metric two-step nilpotent Lie algebras of dimension up to 6. This space is homeomorphic to a cone over a four-dimensional contractible simplicial complex. Moreover, we exhibit standard ...
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      The Monge-Ampère equation and warped products of higher rank 

      Bechtluft-Sachs, S.; Samiou, E. (2007)
      We show that a warped product Mf = ℝ × f ℝ has higher rank and nonpositive curvature if and only if f is a convex solution of the Monge-Ampère equation. In this case we show that M contains a Euclidean factor. © 2007 ...
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      On infinitesimally k-flat homogeneous spaces 

      Berndt, J.; Samiou, E. (2001)
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      Spherical spectral synthesis and two-radius theorems on Damek-Ricci spaces 

      Peyerimhoff, N.; Samiou, E. (2010)
      We prove that spherical spectral analysis and synthesis hold in Damek-Ricci spaces and derive two-radius theorems. © Institut Mittag-Leffler 2009.
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      The Symmetry of 2-Flat Homogeneous Spaces 

      Samiou, E. (1997)
      A Riemannian manifold M is called 2-flat homogeneous if every geodesic is contained in some 2-flat Σ, and if the group of isometries of M acts transitively on the set of pairs (p, Σ) with p ∈ Σ. By a 2-flat we mean a closed, ...