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Algebra Seminar

New Mexico State University

Mondays 12:30 - 1:30 in Science Hall 235

Here is a google calendar for the Algebra Seminar.

Spring 2019

February 1: Cameron Calk, Université de Lyon

Title: Time-reversal and directed homotopy

Abstract: Directed topology was introduced as a model of concurrent programs, where

the flow of time is described by distinguishing certain ”directed” paths in the topological

space representing such a program. Algebraic invariants which respect this directedness have

been introduced to classify directed spaces. We will discuss the properties of such invariants

with respect to the reversal of the flow of time in directed spaces. A known invariant, natural

homotopy, has been shown to be unchanged under time-reversal. We will see that it can

be equipped with additional algebraic structure witnessing this reversal; when applied to a

directed space and to its reversal, the refined invariant yields dual objects.

Fall 2018

November 5: Andreas Reinhart, University of Graz

Title: Arithmetic invariants of monoids of ideals of quadratic orders

October 29: Janet Vassilev, University of New Mexico

Title: Tight interiors of parameter ideals.

Abstract: The tight interior of a module is a dual notion to the tight closure of a module.

In this talk we will focus on the tight interior of an ideal and in particular the tight interior

of a parameter ideal and methods to compute tight interiors. We will introduce some ideals

related to an ideal through its tight interior, that we call ∗-extentions and the ∗-hull. We will discuss conditions on the ring where the *-hull of an ideal is its tight closure and the

∗-core of an ideal is its tight interior.

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https://www.google.com/calendar/embed?src=i3fnbi69jpmha50ua0l2p8qhag@group.calendar.google.com&ctz=America/Chicago&gsessionid=OK

October 15, 22: Luca Carai, NMSU

Title:Characterization of metrizable Esakia spaces via some forbidden configurations

Abstract: Priestley duality provides a dual equivalence between the category of bounded

distributive lattices and the category of Priestley spaces; and Esakia duality provides a dual

equivalence between the category of Heyting algebras and the category of Esakia spaces. A

Priestley space is a compact topological space X with a partial order ≤ such that x 6≤ y implies the existence of a clopen upset U with x ∈ U and y /∈ U . Esakia spaces are those Priestley spaces that satisfy the additional condition that the downset of each clopen is

clopen.

After a review of these dualities, we show that in the metrizable case Esakia spaces can

be singled out by forbidding three simple configurations. Metrizability of a Priestley space

yields that the corresponding lattice, given by the collection of all clopen upsets, is countable.

Therefore this provides a characterization of countable Heyting algebras. We show that this

characterization no longer holds in the uncountable case. This result easily generalizes to

the setting of p-algebras, i.e. pseudocomplemented distributive lattices.

October 1, 8: Pat Morandi, NMSU

Title: Specker algebras: a survey

Abstract: In these talks we describe some of the historical motivation for our study of

Specker algebras over a commutative ring. The origins of this study is in the work of Baer,

Specker, Nöbeling, and Conrad on groups and lattice-ordered groups.

September 17, 24: Jonathan Montaño, NMSU

Title: Asymptotic behavior of symbolic powers

Abstract: The symbolic powers of an ideal is a filtration that encodes important al-

gebraic and geometric information of the ideal and the variety it defines. In this talk we

will discuss recent advances on the asymptotic behavior of the number of generators and

regularity of symbolic powers.

September 10: Richard Epstein

Title: Two new ways to take account of time in formal logic will be presented.

Abstract: In the first, true propositions are seen as picking out times that can be ordered

by relating them with propositional connectives like ”before”, as in ”Spot barked before Dick

yelled”. New true propositions can be added by relating them to others in the before-after

ordering. The ordering need not be linear, for we might not be able to determine whether,

for example, ”Spot barked” describes a time before, the same as, or after the time that ”Tom

called Suzy” picks out. The method should be easy to implement in artificial intelligence

and is clearer and more flexible than what has been used before in taking account of time.

In the second, we allow talk of times as things and quantify over them. All we assume

about times is that there is a before and after (not necessarily linear) and that one time can

be within another. This is a new way of talking about time that leads to new mathematical

structures and many new questions about how we understand the relation of time and truth.

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The talk will be accessible to undergraduates. It should be of interest to people working

in mathematics, philosophy, and computer science.

Fall 2017

November 17: Susan Morey, Texas State University

Title: Depth and Cohen-Macaulay Properties of Monomial Ideals through Combinatorial

Representations

Abstract: There is a natural one-to-one correspondence between square-free monomial

ideals generated in degree two and graphs. Such ideals are called edge ideals of the associated

graphs. This correspondence can be extended naturally in multiple ways, including using

simple hypergraphs (also called clutters), paths or substructures within graphs, or by starting

with directed graphs and using monomial ideals that are not square-free. The goal of this

talk will be to use a combination of algebraic and combinatorial techniques to determine

information about depth properties of these ideals, with a particular interest in when the

ideals have the maximum depth possible, that is, when they are Cohen-Macaulay.

October 30, November 6, 13: Bruce Olberding, NMSU

Title: Complete intersections over zero dimensional rings

October 23: Elóısa Grifo, University of Virginia

Title: Symbolic powers and differential operators

Abstract: Given an ideal I in a polynomial ring, its n-th symbolic power consists of the

functions that vanish up to order n at each point in the variety defined by I, which can be

described via differential operators. However, this description fails in mixed characteristic.

In this talk, we will introduce symbolic powers, discuss the classical Zariski-Nagata theorem,

and explain why the usual differential powers are not enough to describe symbolic powers–

and how to fix that. This is joint work with Alessandro De Stefani and Jack Jeffries.

October 9, 16: Yongjian Xie, NMSU.

Title: Pasting of lattice-ordered effect algebras

September 25, October 2: Angel Zaldivar, NMSU

Title: The point-free content of module categories

Abstract: Usually to study a ring, one can look the category of left modules over the

ring and and observe the categorical properties of certain classes of module to get information

of the ring, One of those techniques is localization of the category, as in the commutative

case, this is useful. In this series of lectures we will review this technique and eventually this

will lead us to the construction of a frame associated to the category modules, the frame of

localizations.

September 11, 18: Pat Morandi, NMSU

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Title: Canonical extensions of bounded archimedean vector lattices, continued.

August 28: Guram Bezhanishvili, NMSU

Title: Canonical extensions of bounded archimedean vector lattices

Spring 2017

February 20, 27, March 6, 13: Francisco Ávila, NMSU

Title: The Frame of Qp

January 30, February 6: Louiza Fouli, NMSU

Title: On Chudnovsky’s Conjecture

Abstract: Given a finite set of points in the projective space, it is natural to ask what

is the least degree of a hypersurface passing through all the points with a given multiplicity.

Establishing such a degree is in general very difficult. Chudnovksy in 1981 stated a conjecture

concerning a lower bound for this degree. He established his conjecture in the case of

the projective plane. In recent years, there has been a renewed interest in this conjecture

and various authors have established the conjecture in certain special cases. However, the

conjecture is still open in full generality. We will discuss known results and some further

progress towards this conjecture. This is joint work with Paolo Mantero and Yu Xie.

Fall 2016

September 16: Anna Romanowska, Warsaw Institute of Technology

Title: Dyadic intervals and dyadic triangles

Spring 2016

April 20, May 4: Bruce Olberding, NMSU

Title: Compactness and holomorphy rings in the space of valuations of a field

April 13: Zahi Fawaz, NMSU

Title: Bounded Archimedean f-Rings

March 30: Luca Spada, University of Salerno

Title: The ind- and pro-completion of an algebraic category.

Abstract: Given a category C one can form its ind- or pro-completion by