Vol. 250, No. 2, 2011

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Remarks on the product of harmonic forms

Liviu Ornea and Mihaela Pilca

Vol. 250 (2011), No. 2, 353–363
Abstract

A metric is formal if all products of harmonic forms are again harmonic. The existence of a formal metric implies Sullivan formality of the manifold, and hence formal metrics can exist only in the presence of a very restricted topology. We show that a warped product metric is formal if and only if the warping function is constant and derive further topological obstructions to the existence of formal metrics. In particular, we determine the necessary and sufficient conditions for a Vaisman metric to be formal.

Keywords
formality, harmonic form, warped product, Vaisman manifold, Betti numbers
Mathematical Subject Classification 2000
Primary: 53C25
Secondary: 53C55, 58A14
Milestones
Received: 19 January 2010
Revised: 11 October 2010
Accepted: 16 November 2010
Published: 31 March 2011
Authors
Liviu Ornea
Faculty of Mathematics
University of Bucharest
Str Academiei nr 14
RO-010014 Bucharest
Romania
Institute of Mathematics “Simion Stoilow” of the Romanian Academy
Calea Grivitei nr 21
RO-010702 Bucharest
Romania
Mihaela Pilca
Fakultät für Mathematik
University of Regensburg
Universitätsstr. 31
D-93053 Regensburg
Germany
Institute of Mathematics “Simion Stoilow” of the Romanian Academy
Calea Grivitei nr 21
RO-010702 Bucharest
Romania