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On the Kolář connection

Włodzimierz M. Mikulski (2013)

Archivum Mathematicum

Let Y M be a fibred manifold with m -dimensional base and n -dimensional fibres and E M be a vector bundle with the same base M and with n -dimensional fibres (the same n ). If m 2 and n 3 , we classify all canonical constructions of a classical linear connection A ( Γ , Λ , Φ , Δ ) on Y from a system ( Γ , Λ , Φ , Δ ) consisting of a general connection Γ on Y M , a torsion free classical linear connection Λ on M , a vertical parallelism Φ : Y × M E V Y on Y and a linear connection Δ on E M . An example of such A ( Γ , Λ , Φ , Δ ) is the connection ( Γ , Λ , Φ , Δ ) by I. Kolář.

On the L p index of spin Dirac operators on conical manifolds

André Legrand, Sergiu Moroianu (2006)

Studia Mathematica

We compute the index of the Dirac operator on a spin Riemannian manifold with conical singularities, acting from L p ( Σ ) to L q ( Σ ¯ ) with p,q > 1. When 1 + n/p - n/q > 0 we obtain the usual Atiyah-Patodi-Singer formula, but with a spectral cut at (n+1)/2 - n/q instead of 0 in the definition of the eta invariant. In particular we reprove Chou’s formula for the L² index. For 1 + n/p - n/q ≤ 0 the index formula contains an extra term related to the Calderón projector.

On the linearization theorem for proper Lie groupoids

Marius Crainic, Ivan Struchiner (2013)

Annales scientifiques de l'École Normale Supérieure

We revisit the linearization theorems for proper Lie groupoids around general orbits (statements and proofs). In the fixed point case (known as Zung’s theorem) we give a shorter and more geometric proof, based on a Moser deformation argument. The passage to general orbits (Weinstein) is given a more conceptual interpretation: as a manifestation of Morita invariance. We also clarify the precise statements of the Linearization Theorem (there has been some confusion on this, which has propagated throughout...

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