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pro vyhledávání: '"Helfer, Joseph"'
Autor:
Helfer, Joseph
We further develop Weber's notion of elementary 2-topos by proposing certain new axioms. We show that in a 2-category C satisfying these axioms, the "discrete opfibration (DOF) classifier" S is always an internal elementary 1-topos, in an appropriate
Externí odkaz:
http://arxiv.org/abs/2407.19358
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 connected and reduced, and we give an upper bound on their geometric gen
Externí odkaz:
http://arxiv.org/abs/2306.03200
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 structures on $\mathbb{R}^{2n-1}$ for all $n>2$.
Comment: Fixed gap in Pro
Comment: Fixed gap in Pro
Externí odkaz:
http://arxiv.org/abs/2111.07590
Autor:
Helfer, Joseph
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 interpretation using the framework of Grothendieck fibrations. We then use thi
Externí odkaz:
http://arxiv.org/abs/1908.08944
Autor:
Helfer, Joseph
Publikováno v:
Theory and Applications of Categories, Vol. 35, No. 35, 2020, pp. 1312-1378
We define a natural 2-categorical structure on the base category of a large class of Grothendieck fibrations. Given any model category $\mathbf{C}$, we apply this construction to a fibration whose fibers are the homotopy categories of the slice categ
Externí odkaz:
http://arxiv.org/abs/1905.10690
Autor:
Helfer, Joseph, Wise, Daniel T.
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 staggered and reducible 2-complexes.
Comment: 12 pages, 2 figure
Comment: 12 pages, 2 figure
Externí odkaz:
http://arxiv.org/abs/1410.2579
Akademický článek
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Autor:
HELFER, JOSEPH1 joj@stanford.edu
Publikováno v:
Theory & Applications of Categories. 2020, Issue 32-36, p1312-1378. 67p.
Autor:
Helfer, Joseph
Publikováno v:
Searcher (1070-4795). Jun2001, Vol. 9 Issue 6, p55. 7p. 2 Diagrams.