20 research outputs found
On the Toral Rank Conjecture and Variants of Equivariant Formality
We investigate the topological consequences of actions of compact connected Lie groups. Our focus lies on the \emph{Toral Rank Conjecture}, which states that a suitable space with an almost free -action has to satisfy . We investigate various refinements of formality in an equivariant setting and show that they imply the TRC in several cases. Furthermore, we study the properties of the newly developed terminology with regards to possible implications, inheritance under elementary topological constructions, and characterizations in terms of higher operations on the equivariant cohomology. We also attack the problem of finding bounds for in the spirit of the TRC outside of the formal context. Different lower bounds are constructed and applied in particular to the case of cohomologically symplectic spaces
GKM manifolds are not rigid
We construct effective GKM -actions with connected stabilizers on the
total spaces of the two -bundles over with identical GKM graphs.
This shows that the GKM graph of a simply-connected integer GKM manifold with
connected stabilizers does not determine its homotopy type. We complement this
by a discussion of the minimality of this example: the homotopy type of integer
GKM manifolds with connected stabilizers is indeed encoded in the GKM graph for
smaller dimensions, lower complexity, or lower number of fixed points.
Regarding geometric structures on the new example, we find an almost complex
structure which is invariant under the action of a subtorus. In addition to the
minimal example, we provide an analogous example where the torus actions are
Hamiltonian, which disproves symplectic cohomological rigidity for Hamiltonian
integer GKM manifolds.Comment: v2: simplified construction of the minimal example. Comments are
welcome
Poincar\'e dualization and formal domination
We consider the question of whether formality of the domain of a non-zero
degree map of closed manifolds implies formality of the target. Though there
are various situations where this is indeed the case, we show the answer is
negative in general, with a counterexample given by a non-zero degree map from
a formal manifold to one that carries a non-vanishing quadruple Massey product.
This violates a general heuristic that the domain of a non-zero degree map
should be more complicated than its target. For the construction of the
counterexample we introduce a method to turn a cdga into one that satisfies
Poincar\'e duality, which is natural in certain situations.Comment: 15 pages, comments very welcom