According to J. Feldman and C. Moore’s wellknown theorem on Cartan subalgebras, a variant of the group measure space construction gives an equivalence of categories between twisted countable standard measured equivalence relations and Cartan pairs, i.e., a von Neumann algebra (on a separable Hilbert space) together with a Cartan subalgebra. A. Kumjian gave a C∗-algebraic analogue of this theore...

A BRST perturbative analysis of SU(N) Yang-Mills theory in a class of maximal Abelian gauges is presented. We point out the existence of a new nonintegrated renormalizable Ward identity which allows to control the dependence of the theory from the diagonal ghosts. This identity, called the diagonal ghost equation, plays a crucial role for the stability of the model under radiative corrections i...

We present a new approach to the covariant canonical formulation of EinsteinCartan gravity that preserves the full Lorentz group as the local gauge group. The method exploits lessons learned from gravity in 2+1 dimensions regarding the relation between gravity and a general gauge theory. The dynamical variables are simply the frame field and the spin-connection pulled-back to the hypersurface, ...

The following four statements have been proven decades ago already, but they continue to induce a strange feeling: All curvature invariants of a gravitational wave vanish inspite of the fact that it represents a nonflat spacetime. The eigennullframe components of the curvature tensor (the Cartan ”scalars”) do not represent curvature scalars. The Euclidean topology in the Minkowski spacetime doe...

We prove that any simply connected and complete Riemannian manifold, on which a Randers metric of positive constant flag curvature exists, must be diffeomorphic to an odd-dimensional sphere, provided a certain 1-form vanishes on it. 1. Introduction. The geometry of Finsler manifolds of constant flag curvature is one of the fundamental subjects in Finsler geometry. Akbar-Zadeh [1] proved that, u...

According to J. Feldman and C. Moore's well-known theorem on Cartan subalgebras, a variant of the group measure space construction gives an equivalence of categories between twisted countable standard measured equivalence relations and Cartan pairs, i.e. a von Neumann algebra (on a separable Hilbert space) together with a Cartan subalgebra. A. Kumjian gave a C *-algebraic analogue of this theor...

We study local automorphisms of holomorphic Cartan geometries. This leads to classification results for compact complex manifolds admitting holomorphic Cartan geometries. We prove that a compact Kähler Calabi-Yau manifold bearing a holomorphic Cartan geometry of algebraic type admits a finite unramified cover which is a complex

It is safe to say that the theory of modular representations of finite groups is not a part of the average mathematician's toolkit. Matrix representations of finite groups over the complex field, and the resulting characters (traces of matrices), occur rather widely in both pure and applied mathematics. But replacing complex numbers by elements of a finite or other field of prime characteristic...

Abstract The covariant canonical gauge theory of gravity (CCGG) is a field formulation which priori includes non-metricity and torsion. It extends the Lagrangian Einstein’s general relativity by terms at least quadratic in Riemann–Cartan tensor. This paper investigates implications metric compatible CCGG on cosmological scales. For totally anti-symmetric torsion tensor we derive resulting equat...

Cartan matrices are of fundamental importance in representation theory. For algebras defined by quivers (i.e. directed graphs) with relations the computation of the entries of the Cartan matrix amounts to counting nonzero paths in the quivers, leading naturally to a combinatorial setting. In this paper we study a refined version, so-called q-Cartan matrices, where each nonzero path is weighted ...