1,037 research outputs found
Topological finiteness properties of monoids. Part 1: Foundations
We initiate the study of higher dimensional topological finiteness properties
of monoids. This is done by developing the theory of monoids acting on CW
complexes. For this we establish the foundations of -equivariant homotopy
theory where is a discrete monoid. For projective -CW complexes we prove
several fundamental results such as the homotopy extension and lifting
property, which we use to prove the -equivariant Whitehead theorems. We
define a left equivariant classifying space as a contractible projective -CW
complex. We prove that such a space is unique up to -homotopy equivalence
and give a canonical model for such a space via the nerve of the right Cayley
graph category of the monoid. The topological finiteness conditions
left- and left geometric dimension are then defined for monoids
in terms of existence of a left equivariant classifying space satisfying
appropriate finiteness properties. We also introduce the bilateral notion of
-equivariant classifying space, proving uniqueness and giving a canonical
model via the nerve of the two-sided Cayley graph category, and we define the
associated finiteness properties bi- and geometric dimension. We
explore the connections between all of the these topological finiteness
properties and several well-studied homological finiteness properties of
monoids which are important in the theory of string rewriting systems,
including , cohomological dimension, and Hochschild
cohomological dimension. We also develop the corresponding theory of
-equivariant collapsing schemes (that is, -equivariant discrete Morse
theory), and among other things apply it to give topological proofs of results
of Anick, Squier and Kobayashi that monoids which admit presentations by
complete rewriting systems are left-, right- and bi-.Comment: 59 pages, 1 figur
Logarithmic Gromov-Witten invariants
The goal of this paper is to give a general theory of logarithmic
Gromov-Witten invariants. This gives a vast generalization of the theory of
relative Gromov-Witten invariants introduced by Li-Ruan, Ionel-Parker, and Jun
Li, and completes a program first proposed by the second named author in 2002.
One considers target spaces X carrying a log structure. Domains of stable log
curves are log smooth curves. Algebraicity of the stack of such stable log maps
is proven, subject only to the hypothesis that the log structure on X is fine,
saturated, and Zariski. A notion of basic stable log map is introduced; all
stable log maps are pull-backs of basic stable log maps via base-change. With
certain additional hypotheses, the stack of basic stable log maps is proven to
be proper. Under these hypotheses and the additional hypothesis that X is log
smooth, one obtains a theory of log Gromov-Witten invariants.Comment: 58 pages, 5 figure
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