The New York City

Category Theory Seminar

Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
365 Fifth Avenue (at 34th Street) map
(Diagonally across from the Empire State Building)
New York, NY 10016-4309

Wednesdays 7:00 - 8:30 PM.
Room 6417 .

Contact N. Yanofsky to schedule a speaker
or to add a name to the seminar mailing list.

Spring 2017


The New York Category Theory Seminar and the New York Haskell Meetup is sponsoring a

Topos Theory Reading Group

We will be reading

Sheaves in Geometry and Logic: A First Introduction to Topos Theory

by Saunders MacLane, Ieke Moerdijk

The list for announcements and scheduling regarding this group is also at the hott-nyc google group:
https://groups.google.com/forum/#!forum/hott-nyc

We meet the first and third Wednesdays of each month from 7:00 to 8:30 PM in Room 6417. The meetings are run by Gershom Bazerman.



  • Speaker:     David Ellerman University of California at Riverside

  • Date and Time:     Wednesday January 18, 2017, 7:00 - 8:30 PM., Room 6417.

  • Title:    From Abstract Objects in Mathematics to Indefinite ''Blobs'' in Quantum Mechanics
  • Abstract:     Given an equivalence relation ~ on a set U, an abstraction operator @ takes two equivalent entities to the same abstract thing: u~u' iff @(u)=@(u'). In mathematics there two different notions of 'abstraction' at work. The #1 version is just the equivalence class, e.g., a homotopy type is just the equivalence class of homotopic spaces. The #2 version is a more abstract object that is, for example, definite on what is common to all the spaces homotopic to each other but is indefinite on where they differ.
    We show how to mathematically model the two versions starting just with a subset S of U and then focus on the less familiar #2 interpretation where S is viewed not as a set of distinct elements but as a more abstract entity 'S-ness' that is definite on what is common between the elements of S and indefinite on how they differ. The point is that the #2 case dovetails precisely with the quantum mechanics notion of a superposition of distinct eigenstates of some observable which is a state definite only on what is common to the superposed eigenstates and is objectively or onticly indefinite between them. The process in general of classifying by some attribute to make the #2 indefinite state more definite then emerges as the process of measurement in QM.




  • Speaker:     Raymond Puzio.

  • Date and Time:     Wednesday February 1, 2017, 7:00 - 8:30 PM., Room 6417.

  • Title:    Topos Theory Reading Group --- Slice Categories.







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