Obstructions to Lagrangian concordance

Obstructions to special Lagrangian desingularizations and the Lagrangian prescribed boundary problem

We also use soft methods from symplectic geometry (the relative version of the h–principle for Lagrangian immersions) and tools from algebraic topology to prove (both positive and negative) results about Lagrangian desingularizations of Lagrangian submanifolds with isolated singularities; we view the (Maslov-zero) Lagrangian desingularization problem as the natural soft analogue of the special ...

Obstructions to the Existence of Exact Lagrangian Embeddings into Cotangent Bundles

We give topological obstructions to the existence of a closed exact Lagrangian submanifold L →֒ T M , where M is the total space of a fibration over the circle. For instance, we show that π1(L) cannot be the direct product of two non-trivial groups and that the difference between the number of generators and the number of relations in a finite presentation of π1(L) is less than two. Mathematics ...

Obstructions to Shiftedness

In this paper we show results on the combinatorial properties of shifted simplicial complexes. We prove two intrinsic characterization theorems for this class. The first theorem is in terms of a generalized vicinal preorder. It is shown that a complex is shifted if and only if the preorder is total. Building on this we characterize obstructions to shiftedness and prove there are finitely many i...

Obstructions to Homotopy Invariance

Obstructions to Shellability

We consider a simplicial complex generaliztion of a result of Billera and Meyers that every nonshellable poset contains the smallest nonshellable poset as an induced subposet. We prove that every nonshellable 2-dimensional simplicial complex contains a nonshellable induced subcomplex with less than 8 vertices. We also establish CL-shellability of interval orders and as a consequence obtain a fo...