The natural pseudo-distance is a similarity measure conceived for the purpose of comparing shapes. In this paper we revisit this pseudo-distance from the point of view of quotients. In particular, we show that the natural pseudo-distance coincides with the quotient pseudo-metric on the space of continuous functions on a compact manifold, endowed with the uniform convergence metric, modulo self-...

This is the third in a series of papers aimed at generalizing Siebenmann’s famous PhD thesis [13] so that the results apply to manifolds with nonstable fundamental groups at infinity. Siebenmann’s work provides necessary and sufficient conditions for an open manifold of dimension ≥ 6 to contain an open collar neighborhood of infinity, ie, a manifold neighborhood of infinity N such that N ≈ ∂N ×...

In pseudo-Riemannian geometry the spaces of space-like and timelike geodesics on a pseudo-Riemannian manifold have natural symplectic structures (just like in the Riemannian case), while the space of light-like geodesics has a natural contact structure. Furthermore, the space of all geodesics has a structure of a Jacobi manifold. We describe the geometry of these structures and their generaliza...

This article discusses the existence problem of a compact quotient of a symmetric space by a properly discontinuous group with emphasis on the non-Riemannian case. Discontinuous groups are not always abundant in a homogeneous space G/H if H is non-compact. The first half of the article elucidates general machinery to study discontinuous groups for G/H , followed by the most update and complete ...

This article discusses the existence problem of a compact quotient of a symmetric space by a properly discontinuous group with emphasis on the non-Riemannian case. Discontinuous groups are not always abundant in a homogeneous space G/H if H is non-compact. The first half of the article elucidates general machinery to study discontinuous groups for G/H, followed by the most update and complete l...

We consider a nearly hyperbolic Sasakian manifold endowed with a quarter symmetric non-metric connection and study CRsubmanifolds of nearly hyperbolic Sasakian manifold endowed with a quarter symmetric nonmetric connection. We also obtain parallel distributions and discuss inerrability conditions of distributions on CR-submanifolds of nearly hyperbolic Sasakian manifold with quarter symmetric n...

There are various statements in the physics literature about stratification of quantum states, for example into orbits a unitary group, and generalized differentiable structures on it. Our aim is to clarify make precise some these statements. For A an arbitrary finite-dimensional C*-algebra U(A) group elements A, we observe that partition state space S(A) not decomposition orbit types (its piec...

This is a survey of recent contributions to the area of special Kähler geometry. It is based on lectures given at the 21st Winter School on Geometry and Physics held in Srni in January 2001. 1 Remarkable features of special Kähler manifolds A (pseudo-) Kähler manifold (M,J, g) is a differentiable manifold endowed with a complex structure J and a (pseudo-) Riemannian metric g such that (i) J is ...

We consider the unit tangent sphere bundle of Riemannian manifold ( M, g ) with g-natural metric G̃ and we equip it to an almost contact B-metric structure. Considering this structure, we show that there is a direct correlation between the Riemannian curvature tensor of ( M, g ) and local symmetry property of G̃. More precisely, we prove that the flatness of metric g is necessary and sufficien...