1 citations · 1 across the 9 of their papers we have counts for
9 papers
Set-theoretic universes and paradoxes in 2-topoi
Joseph Helfer
This paper continues the development of (elementary) 2-topos theory, a foundational theory based on an axiomatization of the 2-category of categories. We prove that any 2-topos con…
Y is a least fixed point combinator
Joseph Helfer
The theory of recursive functions is related in a well-known way to the notion of *least fixed points*, by endowing a set of partial functions with an ordering in terms of their do…
The integral chow ring of
Joseph Helfer, Eric Jovinelly, Eric Larson +2
This paper computes the integral Chow ring of the moduli space of stable genus 2 curves of compact type. This is done by excising boundary strata from one-by-…
Internal 1-topoi in 2-topoi
Joseph Helfer
We further develop the notion of elementary 2-topos, introduced by Weber, by proposing certain new axioms. We show that in a 2-category C satisfying these axioms, the "discrete opf…
Severi curves of rational elliptic surfaces
François Greer, Joseph Helfer, John Sheridan
We study Severi curves parametrizing rational bisections of elliptic fibrations associated to general pencils of plane cubics. Our main results show that these Severi curves are co…
Exotic tight contact structures on
François-Simon Fauteux-Chapleau, Joseph Helfer
We introduce a variant of contact homology for convex open contact manifolds. As an application, we prove the existence of (in fact, infinitely many) exotic tight contact structure…
First-order homotopical logic
Joseph Helfer
We introduce a homotopy-theoretic interpretation of intuitionistic first-order logic based on ideas from Homotopy Type Theory. We provide a categorical formulation of this interpre…
Homotopies in Grothendieck fibrations
Joseph Helfer
We define a natural 2-categorical structure on the base category of a large class of Grothendieck fibrations. Given any model category , we apply this construction to a…
Counting cycles in labeled graphs: The nonpositive immersion property for one-relator groups
Joseph Helfer, Daniel T. Wise
We prove a rank 1 version of the Hanna Neumann Theorem. This shows that every one-relator 2-complex without torsion has the nonpositive immersion property. The proof generalizes to…