CUNY Graduate Center Topology Seminar

General Information

The seminar meets Wednesdays 4:30-5:30 in room 4214.03 at the Graduate Center. The mathematics department lounge is room 4214.

The building is at 365 5th Avenue (34th St) in Manhattan.

Here are links for Parking lots in NY (the neighborhood is called Murray Hill).

another link for parking

For more information about the seminar, or to add a name to the seminar mailing list, contact Martin Bendersky


Schedule, Fall, 2017


·  Date Wed. Oct. 11, 4:30-5:30
Speaker: Don Davis, Lehigh University

Title: n-dimensional Klein bottles

Abstract: An n-dimensional version of the Klein bottle arose in our work in topological robotics. We discuss how it arose, and various aspects of its algebraic and differential topology.


·  Date Wed. Sept. 27, 4:30-5:30
Speaker: Michael Harrison, Lehigh University

Title: The h-principle and totally convex immersions.

Abstract: The h-principle is a powerful tool in differential topology which is used to study spaces of functions with certain distinguished properties (immersions, submersions, k-mersions, embeddings, free maps, etc.). I will discuss some examples of the h-principle and give a neat proof of a special case of the Smale-Hirsch Theorem, using the "removal of singularities" h-principle technique due to Eliashberg and Gromov. Finally, I will define and discuss totally convex immersions and discuss some h-principle statements in this context.

Restaurant: La Vie En Szechuan
14 E 33rd St.
Link to La Vie En Szechuan on Yelp


Schedule, Spring, 2017


·  Date Tuesday, January 31,  4:00 – 5:00 NOTE CHANGE OF DAY AND TIME.
Speaker: John Klein, Wayne State University

Title: Applications of higher dimensional spanning trees.

Abstract: I will introduce the notion of a spanning tree in a finite CW complex

of arbitrary dimension. We utilize this to give an analogue of Kirchhoff's

electrical and matrix-tree theorems in higher dimensions


We will also describe a new combinatorial invariant of a CW complex called the 

hypercurrent. The latter is motivated by the investigation of stochastic motion of

 cellular cycles of a given dimension.


Restaurant:  Chennai Garden 
127 East 28th Street. Between Park and Lexington
Link to Chennai Garden 





Schedule, Spring, 2016

·  Date Wed. March 9, 5:00-6:00
Speaker: Nick Kuhn, University of Virginia

Title: The topological numerical polynomial ring

Abstract: Let P be the ring of polynomials over the rationals that take integer values when evaluated on integers. This ring has long been known to appear in algebraic topology as the K-homology of infinite complex projective space. We have found P appearing in a more basic way as the homology of a nice commutative ring spectrum we are terming the topological numerical polynomial ring.

Restaurant: Restaurant: Kang Suh
1250 Broadway (near 32nd)

·  Date Wed. Feb 17, 5:00-6:00
Speaker: Joe Neisendorfer, University of Rochester


Abstract: Let p be an odd prime. We shall prove that the homotopy groups of a mod $p^r$ Moore space are annihilated by $p^{r+1}$. The method is to apply a surprising general splitting theorem and then a general "semi-splitting" theorem to the loop space of a Moore space. Although this is an old result, the proof has now been much improved and it can now be talked about.

Joe is willing to give a pre-talk if there is interest.
Abstract of Pre-talk: Let p be an odd prime. We shall prove the existence of infinite families of torsion of order p^{r+1} in the unstable homotopy groups of mod $p^r$ Moore spaces. The method is to use the Bockstein spectral sequence to study the representation of the differential graded Lie algebra of mod $p$ homotopy into the mod $p$ homology of the loop space.

Restaurant: La Vie En Szechuan
14 E 33rd St.
Link to La Vie En Szechuan on Yelp

Schedule, Fall 2015

·  Date Wed. Dec 9, 5:00-6:00
Speaker: Don Davis, Lehigh University

Title: Topological Complexity of Spaces of Polygons.

Abstract: The topological complexity of a topological space X is the number of rules required to specify how to move between any two points of X. If X is the space of all configurations of a robot, this can be interpreted as the number of rules required to program the robot to move from any configuration to any other. A polygon in the plane or in 3-space can be thought of as linked arms of a robot. We compute the topological complexity of the space of polygons of fixed side lengths. Our result is complete for polygons in 3-space, and partial for polygons in the plane.

Carbone Ristorante
331 W. 38th (between 8th and 9th)

·  Date Wed November 4, 5:00 - 6:00
Speaker: Don Larson, Penn State, Altoona,

Title: Modular forms and the beta family

Abstract: Let p be a prime greater than 3. In 2008, M. Behrens proved the existence of a 1-1 correspondence between beta elements in the p-primary Adams-Novikov spectral sequence and modular forms over Z up to certain congruence conditions depending on p. The proof used homotopical properties of a spectrum denoted Q. In this talk, I will briefly highlight some previous work on the homotopy of Q at the prime 3 (where Behrens' correspondence is not known to exist), and then I will describe work in progress at higher primes that attempts to make the correspondence explicit. The talk will be as expository as possible.

Restaurant: TBA

·  Date: Wed, Sept 30, 5:00-6:00
Speaker: Tony Bahri, Rider University

Title: On the integral cohomology rings of toric orbifolds.

Abstract: A criterion is described which ensures that a toric orbifold, determined by a simple polytope and a characteristic map, has torsion free cohomology concentrated in even degree. The description is shown to transform well under the simplicial wedge construction. A report of joint work with Soumen Sarkar and Jongbaek Song.

Restaurant: La Vie En Szechuan
14 E 33rd St.
Link to La Vie En Szechuan on Yelp

Schedule, Spring 2015

·  Date: Wed, April 22, 5:30-6:30
Speaker: Doug Ravenel, University of Rochester

Title: Inside the proof of the Kervaire invariant theorem or How I got bitten by the equivariant bug.


Abstract: This talk will cover one aspect of the proof of the Kervaire invariant theorem (proved with Hill and Hopkins), namely the gap theorem. It says that \pi_{-2} of a certain spectrum \Omega vanishes. It is the part of the paper that requires equivariant methods not available before 2009. It turns out that once the machinery has been set up, it follows from a surprisingly easy calculation

Restaurant: Kang Suh
1250 Broadway (near 32nd)

·  Date: Wed, February 4, 5:30-6:30
Speaker: John R. Klein, Wayne State University

Title: Unlinked Embeddings and Functor Calculus

Abstract: This talk will be about the space of codimension zero embeddings of a Poincare duality space in a disk. I will describe a tower that interpolates from the space of "Poincare immersions" to a certain space of "unlinked" Poincare embeddings. The layers of this tower are described in terms of the coefficient spectra of the identity appearing in Goodwillie's homotopy functor calculus. Time permitting, I will relate these layers to the layers of the tower that appear in the Goodwillie-Weiss manifold calculus. I will also answer a question posed by Sylvain Cappell.

Restaurant: Chennai Garden
127 East 28th Street. Between Park and Lexington
Link to Chennai Garden

Schedule, Fall 2014

Speaker: Jeremy Miller, Stanford University

·  Date: Monday, Sept 29, 4:30-5:30
Title: Representation stability for homotopy groups of configuration spaces

Abstract: In the 1970s, McDuff proved that configuration spaces of distinct unordered particles in an open manifold exhibit homological stability. That is, H_i(Conf_k(M)) is independent of k for k>>i. A natural follow up question is: Do the homotopy groups also stabilize? From explicit calculations, one can show that this is not the case. However, in joint work with Alexander Kupers, I have shown that the rational homotopy groups of configuration spaces of particles in simply connected manifolds of dimension at least 3 exhibit representation stability in the sense of Church and Farb. This follows from a more general theorem we prove relating the homotopy groups and cohomology groups of co-FI-spaces and from the work of Church on representation stability for the cohomology of ordered configuration spaces. This result on homotopy groups suggests that in situations with homological stability, one should not expect classical stability for homotopy groups. Instead, one should try to incorporate the fundamental group into the definition of stability.

Restaurant: Pippali, 129 E 27th St
Link for Yelp reviews:

·  Date: TUESDAY OCTOBER 7, 4:00-5:00

Speaker: Don Davis, Lehigh University
Title: On the topological complexity of 2-torsion lens spaces

Abstract: The topological complexity of a topological space is the minimum number of rules required to specify how to move between any two points of the space. A ``rule'' must satisfy the requirement that the path varies continuously with the choice of end points. We use connective complex K-theory to obtain new lower bounds for the topological complexity of 2-torsion lens spaces. We follow a program set up by Jesus Gonzalez, and answer a question posed by him.

Restaurant: Mandoo Bar
2 W. 32nd Street, between Broadway and 5th
Yelp review

·  Date: Wed October 15, 5:00-6:00

Speaker: Joana Cirici

Title: Topology of complex projective varieties with isolated singularities

Abstract: I will explain a homotopical treatment of intersection cohomology recently developed by Chataur-Saralegui-Tanre, which associates a "perverse homotopy type" to every singular space. In this context, there is a notion of "intersection-formality", measuring the vanishing of Massey products in intersection cohomology. The perverse homotopy type of a complex projective variety with isolated singularities can be computed from the morphism of differential graded algebras induced by the inclusion of the link of the singularity into the regular part of the variety. I will show how, in this case, mixed Hodge theory allows us prove some intersection-formality results (work in progress with David Chataur).

Restaurant: Dhaba
Link to Dhaba
108 Lexington Ave (between 27th St & 28th St) New York, NY 10016

·  Date: Wed October 22, 5:00-6:00

Speaker: John Mccleary, Vassar College

Title: Loop space homology, string homology, and closed geodesics

Abstract: The homology of free loop space of a manifold enjoys additional structure first identified by Chas and Sullivan. The string multiplication has been studied by Ralph Cohen and John Jones and together with J.~Yan, they have introduced a spectral sequence converging to string homology that is related to the Serre spectral sequence for the free loop space. Using this tool, and the work of Felix, Halperin, Lemaire and Thomas, Jones and I establish some conditions on manifolds that guarantee the existence of infinitely many closed geodesics on the manifold in any Riemannian metric.
Restaurant: Lalibela Ethiopian Restaurant 37 E 29th St (Between madison and Park)

Schedule, Spring 2014

·  Date: Wed. May 14, 5:00-6:00

Speaker: Inna Zakharevich, Institute for Advanced Study

Title: Scissors congruence and algebraic K-theory

Abstract: Hilbert's third problem asks the following question: given two polyhedra with the same volume, can we decompose them into finitely many pairwise congruence pieces? The answer, provided by Dehn in 1901 is no; there is a second invariant on polyhedra, now called the Dehn invariant. Classical scissors congruence asks this question in other dimensions and geometries. In this talk we construct an abstract framework for discussing scissors congruence problems using algebraic K-theory. By discarding much of the geometric underpinning of scissors congruence problems we are able to construct decomposition invariants in much more general settings, including Grothendieck rings of arbitrary models. As an application of this framework we construct a "derived Grothendieck ring of varieties".

Restaurant: La Vie En Szechuan
14 E 33rd St.
Link to La Vie En Szechuan

·  Date: Wed May 7, 5:00-6:00

Speaker: Rob Thompson, Hunter College/ CUNY Grad Center

Title: An unstable Morava change of rings theorem for Lubin-Tate homology

Abstract: The Morava Change of rings theorem is a central result in stable homotopy theory. For certain spectra it allows one to compute the E_2-term of the Adams-Novikov Spectral Sequence (i.e. the Adams spectral based on complex cobordism) in terms of the E_2-term of the Adams spectral based on various periodic homology theories like Johnson-Wilson theory (a generalization of topological K-theory), Morava K-theory ( a generalization of mod p K-theory), and Lubin-Tate theory (a homology theory based on the theory of lifts of the Honda formal group law to complete local rings whose residue fields are F_p algebras). A number of results along these lines in the unstable realm have been obtained. In this talk I will focus on the case mentioned in the title.

Restaurant: Restaurant: Kokum, 106 Lexinton Ave, between 27th and 28th
A south Indian vegitarian restaurant. Here is the link.

·  Date: Wed Apr. 30, 5:00-6:00

Speaker: Rita Jimenez Rollan, Northeastern University

Title: The cohomology of M_{g,n} and other representation stability phenomena

Abstract: Let M_{g,n} be the moduli space of genus g Riemann surfaces with n marked points. Given a non negative integer i, we want to understand how the i-th rational cohomology group of M_{g,n} changes as the parameter n increases. It turns out that the symmetric group S_n acts on it and the sequence of S_n-representations ``stabilizes'' in a certain sense once n is large enough.
In this talk I will explain the behavior of this and other examples via the language of representation stability. Moreover, I will introduce the notion of a finitely generated FI-module and show our sequence of interest has this underlying structure which explains the stability phenomena mentioned above. As a consequence we obtain that, for n large enough with respect to i, the i-th Betti number of M_{g,n} is a polynomial in n of degree at most 2i.

Restaurant: Hunan Manor.
339 Lexington Ave (at 39th St.)
Link to NY Times review.


·  Date: Wed. April 30: 3:00-4:00 pm. Room 7395

Speaker: Speaker: Sander Kupers, Stanford University

Title: E_n-cell attachments and a local to global homological stability theorem.

Abstract: We define degreewise bounded generation for framed E_n-algebras in chain complexes and prove that this property is equivalent to homological stability. Using this we prove a local-to-global principle for homological stability, in the sense that if a framed E_n-algebra A has homological stability (or equivalently the topological chiral homology of R^n with coefficients in A has homology stability), then so has the topological chiral homology of any open oriented connected manifold M with coefficients in A.

·  Date: Wed. Apr 2, 5:00-6:00

Speaker: Mohamed Abouzaid, Columbia University

Title: Title: Lagrangian immersions and the Floer homotopy type

Abstract: A conjecture of Arnold would imply that every exact Lagrangian in a cotangent bundle is isotopic to the zero section through Lagrangian embeddings. We now know that every such Lagrangian is homotopy equivalent to the zero section. I will explain how, combining the h-principle with the spectrum-valued invariants introduced by T. Kragh, one can hope to show that such Lagrangians are in fact isotopic to the zero section through Lagrangian immersions. I will discuss partial results obtained with Kragh, constraining the Lagrangian isotopy class of Lagrangians embeddings.

Restaurant: Kokum, 106 Lexinton Ave, between 27th and 28th
A south Indian vegitarian restaurant.
Here is the link.

·  Date: Wed March 26, 5:00-6:00

Speaker: Kate Poirier/ CUNY City Tech

Title: On the higher topological Hochschild homology of F_p and commutative F_p-group algebras

Abstract: The construction of the classical Hochschild homology of an algebra uses a simplicial model for the circle. Higher Hochschild homology uses higher-dimensional spheres. The constructions of topological Hochschild and higher topological Hochschild homology model the algebraic constructions and replace algebras by spectra. In his thesis, Torleif Veen calculated higher Hochschild and higher topological Hochshild homology for finite fields F_p, assuming certain bounds. In this talk, we review the definitions and Veen's results and show how his bounds may be pushed and his calculations generalized.

Restaurant: :Lalibela Ethiopian Restaurant 37 E 29th St (Between madison and Park)

·  Date: Wed. Feb 26, 5:00-6:00

Speaker: Mahmoud Zeinalian

Title: A concise construction of differential K-theory

One knows a generalized cohomology theory h tensor the reals is canonically isomorphic to ordinary cohomology with coefficients in h[point] tensor the reals. Representing the latter by deRham forms and the former by classes of objects like maps into a universal space one can form triples consisting of a pair of these objects and an equivalence between their real images represent elements in a formal fibre product as in homotopy theory. Equivalence classes of these triples define a functor that combines differential forms and the cohomology theory h called differential cohomology with flavor h.The first one appeared in the 70s [the foliation decade] and was a natural receptacle for the chern simons invariant and other secondary invariants related to bundles with connections or to foliations. There has been interest recently in axiomatizing differential cohomology in general and to give more geometric models for particular theories. There are two axioms that hold for and characterize many specific examples. They involve a diagram building on the fibre product idea [introduced in the chern simons example] and an integration along the fibres of the product bundle with fibre the circle introduced more recently. The second axiom replaces the suspension axiom of usual cohomology theories. For differential theories with flavor complex Ktheory the situation of geometric models and axioms that characterize is known and satisfactory in the even degree but heretofore unknown in the odd degree. In this lecture we will build a new geometric model of differential K theory in both degrees, eliminating one part of the triple and introducing a geometric spectrum, and verify both the diagram and the the integration along circle fibres axiom. Thus it will follow from known work that any differential theory with flavor complex K-theory satisfying the diagram and the integration along the circle fibres axiom will be naturally isomorphic to our constructed theory.
Restaurant: TBA

Schedule, Fall 2013

·  Date: Wed. Dec 4, 5:00-6:00

Speaker: Luis Diogo, Columbia University

Title: Symplectic homology from Gromov-Witten theory

Symplectic homology is a very useful tool in the study of symplectic manifolds. I will review the construction of this invariant and its deep relations with string topology. Despite its usefulness, symplectic homology can be very hard to compute explicitly. I will talk about joint work with Sam Lisi, on a procedure to compute this invariant for a class of symplectic manifolds. This method uses information about holomorphic spheres on symplectic manifolds, which can sometimes be obtained using tools from algebraic geometry.
Restaurant: Hunan Manor.
339 Lexington Ave (at 39th St.)
Link to NY Times review.

·  Date: Wed. October 23, 5:00-6:00

Speaker: Sander Kupers, Stanford University

Title: Topological chiral homology and homological stability for completions

An interesting phenomenon is that the configuration space of particles on an open manifold has homology independent of the number of particles in an increasing range. Such configuration spaces are one of the simplest examples of topological chiral homology, which is a homology theory for n-dimensional manifolds taking values in spaces and taking E_n-algebras as coefficients. I will explain how many previous results on homological stability, including that for configuration spaces, fit into the framework of topological chiral homology and are a consequence of a general result by myself and Jeremy Miller.

Restaurant: Dhaba
Link to Dhaba
108 Lexington Ave (between 27th St & 28th St) New York, NY 10016

·  Date: Wed, October 9, 5:00-6:00
Speaker: Joana Cirici

Title. Rational homotopy of singular complex varieties

Abstract. The rational homotopy type of a singular complex variety can be read from the first term of a spectral sequence encoding cohomology groups of smooth projective varieties. This result is based on Deligne's theory of mixed Hodge structures, and generalizes the Formality Theorem of compact Kahler manifolds. I will show how to compute this spectral sequence in simple examples and provide some applications to the topology of singular complex varieties.

Restaurant: La Vie En Szechuan
14 E 33rd St.
Link to La Vie En Szechuan

·  Date: Wed October 2, 5:00-6:00
Speaker: Pavle Blagojevic, Freie University, Berlin/Mathematical Institute SASA, Belgrade

Title: "On k-regular maps"

Abstract: The question about the existence of a continuous k-regular map from a topological space X to an N-dimensional Euclidean space R^N, which would map any k distinct points in X to linearly independent vectors in R^N, was first considered by Borsuk in 1957. In this talk we present a proof of the following theorem, which extends results by Cohen--Handel 1978 (for d=2) and Chisholm 1979 (for d power of 2): For integers k and d greater then zero, there is no k-regular map R^d -> R^N for N < d(k-a(k))+a(k), where a(k) is the number of ones in the dyadic expansion of k. Joint work with G. M. Ziegler and W. Luck.

Restaurant: TBA

Schedule, Spring 2013

·  Date Wed May 8 , 5:45- 6:45
Speaker: Joey Hirsh/ CUNY, MIT

Title: Derived Noncommutative Deformation Theory

Abstract: We will explain the basic principles behind deformation theory, how deformation theory fits into homotopy theory, and how noncommutative deformation theory generalizes the classical commutative theory.

Restaurant: La Vie En Szechuan
14 E 33rd St.
Link to La Vie En Szechuan

NY Times review
Noodles about $10, chicken about $15.
We liked it so much we are going again.

·  Date Wed April 10 , 5:45- 6:45
Speaker: Jose La Luz. Hostos CC.


Abstract: Quasitoric manifolds sit at the crossroads of topology and combinatorics. The clasification of these manifolds has been the focus of intense research among many researchers. The homotopy groups of quasitoric manifolds and other related toric spaces is an area of active research utilizing techniques across many discplined. The author will present results in a program to calculate the homotopy groups of these manifolds using machinery from homotopy theory, combinatorics and commutative algebra. The material to be presented generalizes previous results about the derived functors of coalgebras. In addition, another application regarding necessay conditions for ridigity of quasitoric manifolds will be discussed.

Restaurant: La Vie En Szechuan
14 E 33rd St.
Link to La Vie En Szechuan

NY Times review
Noodles about $10, chicken about $15.

·  Date: Wed March 20, 5:45- 6:45
Speaker: Jeremy Miller/ CUNY Graduate Center
Title: Localization and homological stability of configuration spaces

Abstract: Tom Church used representation stability to prove that the space of configurations of distinct unordered points in a closed manifold exhibit rational homological stability. In join work with Martin Bendersky, we give another proof using localization and rational homotopy theory. Our methods also yield new information about stability for torsion in the homology of configuration spaces of points in a closed manifold. For example, we prove that the 2 torsion in the group homology of spherical braid groups on an even number of strands stabilize while the 2 torsion in the group homology of torus braid groups on an odd number of strands stabilize.

Restaurant: Restaurant: \itemCopper Chimney
126 28th (between Lexington and Park Ave).
Indian Restaurant. Main courses between between $12 and $20.
Link to Copper Chimney

·  Date: Tuesday March 5, 6:45-7:45
NOTE CHANGE OF DAY AND TIME. Speaker Michael Barr/ McGill university

Title : Is every separated uniform space a limit of metric spaces.

Abstract. The answer is no. Following a conjecture of James Cooper, we have characterized limits of metric in terms of a weak completeness property. This characterization can be used to show that Omega, the first uncountable ordinal, with the uniform structure that it inherits from the compact space Omega+1, is not in the limit of metric spaces. This is a variation of the original example (epsilon_0) suggested by Cooper. This is joint work with John Kennison and Robert Raphael.

Restaurant: Bamiyan
358 3rd Ave
Between 26th and 27th
Afghan Restaurant.
Link to Bamiyan

·  Date: Wed February 6. 5:45 - 6:45
Speaker: John Klein/ Wayne State University
Title: Algebraic Topology as Applied to a Problem in Statistical Mechanics

Abstract: An area of interest in statistical mechanics is the study of statistical distributions of stochastic currents generated in graphs. It turns out that this problem amounts to the study of loops of probability distributions on the state space that evolve according to a certain "master equation." This master equation is a first order linear differential equation that is associated with a loop of Markov processes. Physicists have observed that, for almost every generated current, quantization occurs in the "adiabatic" and "low temperature" limits. My main goal in this talk will be to explain how this story can be understood using the standard tools of algebraic topology.

Restaurant: Franchia - a Vegan, asian restaurant.
Link to Franchia

Schedule, Fall 2012

·  Date: Wed, Dec. 12th. 5:30-6:30
Speaker: Sholom Rosen/ Retired!!
Title: Families of submodules of the mod 2 Steenrod Algebra and their realizations.
Link to Szechuan Gourmet web page

·  Date: Wed Dec. 5, 5:30-6:30
Speaker: Jeremy Miller/ CUNY Grad Center
Title: The topology of the space of J-holomorphic maps to CP^2
Abstract: In the 1970's, Graeme Segal proved that the space of holomorphic maps from a Riemann surface to a complex projective space is homology equivalent to the corresponding continuous mapping space through a range of dimensions increasing with degree. I will address if a similar result holds when other almost complex structures are put on projective space. For CP^2, I prove that the inclusion map from the space of J-holomorphic maps to the space of continuous maps induces a homology surjection through a range of dimension tending to infinity with degree. The proof involves comparing the scanning map of topological chiral homology (Salvatore, Lurie, Andrade) with gluing of J-holomorphic curves (Floer, McDuff-Salamon, Sikorav).
Restaurant: TBA

·  Date: Tuesday, Nov. 20th, 5:15PM - 6:15PM
ROOM 3310 A
Speaker: Tony Bahri/ Rider University
Title: On the topology of weighted projective spaces.

Abstract: As singular toric varieties, weighted projective spaces have an action of a real torus. The equivariant cohomology with respect to this action is isomorphic to the ring of piecewise polynomials on the defining fan. Choosing a particularly nice presentation of this ring allows the theory is to be seen as paralleling that for smooth toric varieties. The survey will include also a report on the complete topological classification of weighted projective spaces obtained in collaboration with Mattias Franz, Dietrich Notbohm and Nigel Ray.

Restaurant: TBA

·  Date: Wed Nov. 14, 5:30-6:30
Speaker: Tatyana Khodorovskiy/Hunter College
Title: Embeddings of Rational Homology Balls
Abstract: We will begin with a description of the rational homology balls appearing in Fintushel and Stern's rational blow-down procedure for smooth 4-manifolds, a generalization of the standard blow-down operation. We will then discuss various smooth and symplectic embedding results of these rational homology balls, as well as a description of a symplectic rational blow-up operation.


·  Date: Wed Oct.24, 5:30-6:30
Speaker: Don Davis/Lehigh University
Title: Combinatorial number theory arising from algebraic topology.
Abstract: We will show how studying v1-periodic homotopy groups of SU(n) led to the following question. Let f(n) denote the sum of the reciprocals of the binomial coefficients (n choose i). For which p-adic integers x does the sequence f(x_n) approach a p-adic limit? Here x_n are the partial sums for x. The answer when p is odd is quite simple, but when p=2 is complicated and not completely understood.

Restaurant : Kang Suh. 1250 Broadway (32nd st).

·  Date: Wed Oct. 3, 5:30-6:30
Speaker: Rob Thompson/ CUNY Hunter College, Graduate Center

Title: Homotopy theory from the point of view of cohomology of profinite groups.
Restaurant: TBA

·  Date: Wed Sept. 19, 5:30-6:30
Speaker: Scott Wilson/ CUNY Queens College, Graduate Center
Title: Refined information in smooth compact families of unitary matrices

Abstract: This is joint work with T. Tradler and M. Zeinalian towards giving an elementary construction of (the odd part of) differential K-theory. The idea is to put an equivalence relation, finer than homotopy equivalence, on the set of maps of a manifold into the unitary group. We'll show that we obtain a group that fits nicely into commutative diagrams and exact sequences involving K-theory and differential forms.

Restaurant: \item Chimney
126 28th (between Lexington and Park Ave).

Indian Restaurant. Main courses between between $12 and $20.

Schedule, Spring 2011

·  Date: Wed April 27 5:30-6:30
Speaker: Steven Simon / NYU
Title: Equivariant and Orthogonal Ham Sandwich Theorems
This talk will present two generalizations of the Ham Sandwich Theorem, which states that under very broad conditions, any n finite measures on R^n can be bisected by a single hyperplane. Giving the theorem a S^0 interpretation, we provide equivariant analogues for the finite subgroups of the spheres S^1 and S^3. Secondly, we ask for the maximum number of pairwise orthogonal hyperplanes which can bisect a generic set of m measures on R^n, m
Restaurant: TBA

·  Wed April 13 5:30-6:30
Speaker; Tilman Bauer/Vrije Universiteit- Amsterdam
Title: Formal plethories
The natural transformations between generalized multiplicative cohomology theories (on spaces) form the set of unstable operations for these cohomology theories. This set has a lot of structure: one can pointwise add and multiply operations, the diagonal gives a comultiplication, and one can compose operations. In my talk I will discuss an algebro-geometric setup for studying this kind of structure which is an extension of the concept of a formal group.
Restaurant: Ben's Kosher Deli - 209 W 38th Street

·  Wed. Wed March 2 5:30-6:30
SPEAKER: Matt Miller/ Vassar
TITLE: A brief history of k-equal arrangements
ABSTRACT : Since their appearance in the 1992 paper of Bjorner, Lovazs, and Yao on computational complexity theory, k-equal arrangements have been studied extensively, both for their combinatorial and topological properties. In this talk we describe the original motivation for studying k-equal arrangements and their continued role in the study of subspace arrangements. We focus on their relationship to the combinatorics of the partition lattice, some recursive formulas for the cohomology of their complements, and our recent results about Massey products and formality.
Restaurant: TBA

Schedule, Fall 2010

·  Wed. Dec 15 5:30-6:30
SPEAKER: Mark Hovey/ Wesleyan University
TITLE: : Ideals in ring spectra
ABSTRACT: We present a rethinking of Jeff Smith's theory of ideals in ring spectra. The key point is that subobjects make no sense in homotopy theory, because every map is homotopic to an inclusion. So an ideal must be thought of as a map f rather than an object. This suggests study of the category of maps. This category turns out to have two different symmetric monoidal structures; in one such structure, a monoid is a homomorphism of ring spectra, but in the other, a monoid is precisely the definition Smith gave of an ideal of ring spectra. This work is still preliminary; in particular, calculations are sorely needed.
Restaurant: One of the vegetarian Indian restaurants on Lexington

·  Wed Dec. 8 5:30-6:30
SPEAKER: Shaun Ault/ Fordham University
TITLE: Elements Partially Annihilated by the Steenrod Algebra
ABSTRACT: We examine the dual of the so-called "hit problem", the latter being the problem of determining a minimal generating set for the cohomology of products of infinite projective spaces as module over the Steenrod Algebra (at the prime 2). The dual problem is to determine the set of $\mathcal {A}$-annihilated elements in homology. This set is easily shown to be a free associative algebra. Our current work shows that the set of elements that are annihilated by $Sq^i$ for each $i$ up to a fixed $2^k$ also forms a free associative algebra. Such a result could pave the way toward inductively determining all A-annihilateds.

·  Wed December 1 5:30-6:30
SPEAKER: Mark Behrens/MIT
TITLE: The homotopy groups of the K(2) local sphere at p > 3, revisited.
ABSTRACT: The stable homotopy groups of spheres admit a filtration called the chromatic filtration. The first layer of this filtration is completely understood. I will describe the structure of the second layer of this filtration, at primes > 3, building off of work of Shimomura and Yabe. Restaurant: TBA

·  Wed Oct 20. 5:30-6:30
ROOM 4214.03
SPEAKER: Don Davis/ Lehigh University
TITLE: Vector fields on the product of two real projective spaces.
ABSTRACT: The span of a manifold is the maximal number of linearly independent vector fields on it. Let P^n denote real projective space. We present current work on the question of whether span(P^m x P^n) exceeds span(P^m) + span (P^n).

Schedule, Fall 2008

·  Wed Nov 12 5:00-6:00
Room: 4214
Speaker: Santiago Lopez de Medrano
Title: Moment-angle manifolds and intersection of quadrics

·  Thursday Nov 20 (Note change of date)
TIME 3:30-4:30
Room; TBA
Alex Suciu, Northeastern University
Title: Geometry and topology of cohomology jumping loci
Abstract: The cohomology jumping loci of a space X come in two basic flavors: the characteristic varieties (the support loci for homology with coefficients in rank 1 local systems), and the resonance varieties (the support loci for the homology of the cochain complexes arising from multiplication by degree 1 classes in the cohomology ring of X). I will discuss various ways in which the geometry of these varieties is related to the formality, (quasi-) projectivity, and homological finiteness properties of the fundamental group of X.

·  Wed Dec 10; 5:00-6:00
ROOM: 4214.03
Don Davis: Lehigh University
Title Immersions of real projective spaces.
Abstract: We review several recent results on the problem of finding the smallest Euclidean space in which RP^n can be immersed.
Restaurant: TBA

·  Wed, Oct. 29
SPEAKER: Constance Leidy (Wesleyan University)
TITLE: The complexity of the structure of the knot concordance group

ABSTRACT: In 1997, T. Cochran, K. Orr, and P. Teichner defined a filtration of the classical knot concordance group. The filtration is defined in terms of gropes or Whitney towers and is connected to the classification of topological 4-manifolds. We will discuss some joint work with Tim Cochran and Shelly Harvey that establishes explicit families of knots that generate infinite rank subgroups of each filtration quotient.
Restaurant: Kung Shu

Schedule, Spring 2008

·  THURSDAY Apr. 10 5-6 PM (Note change of day).
Room: 4214-03 (Note change of room)
Tony Bahri/Rider University
Title: Piecewise Polynomials and the Equivariant Cohomology of Weighted Projective Spaces
Abstract: A report of joint work with Matthias Franz and Nigel Ray. Weighted projective spaces are the easiest examples of singular toric varieties. Unlike the case of smooth varieties, the integral equivariant cohomology ring depends on more than just the combinatorics of the underlying fan. We describe the ring structure in terms of piecewise polynomial functions on the fan. Unlike the ordinary integral cohomology, this ring distinguishes among weighted projective spaces.
Restaurant: TBA

·  April 2 Laurentiu Maxim/Lehman college

TITLE: Atiyah-Meyer formulae for Hodge-type invariants of algebraic varieties.
ABSTRACT: I will report on recent progress on the study of genera and characteristic classes of algebraic varieties. I will describe Hodge-theoretic analogues of the Atiyah-Meyer signature formula, and discuss possible extensions of these results to the singular setting. This is joint work with S. Cappell, A. Libgober and J. Shaneson.
Restaurant: : Kang Suh. 1250 Broadway (32nd st).

·  March 26 Nancy Hingston/College of New Jersey

Title: Loop products and closed geodesics
Abstract: The critical points of the energy function on the free loop space L(M) of a compact Riemannian manifold M are the closed geodesics on M. Filtration by the length function gives a link between the geometry of closed geodesics and the algebraic structure given by the Chas-Sullivan product on the homology of L(M). Geometry reveals the existence of a related product on the cohomology of L(M). For manifolds such as spheres and projective spaces for which there is a metric with all geodesics closed, the resulting homology and cohomology rings are nontrivial, and closely linked to the geometry. I will not assume any knowledge of the Chas-Sullivan product. Joint work with Mark Goresky.
Restaurant: TBA

·  March 12 Joe Neisendorfer/University of Rochester

Restaurant: 2nd Avenue Deli
Title: Samelson products over loops on H-spaces

·  Nov. 14 Bill Singer/Fordham University

Room: 6417
Restuarant: Kang Suh. 1250 Broadway (32nd st).
Title: "Rings of Symmetric Functions as Modules over the Steenrod Algebra".

Schedule, Fall 2007

·  Dec. 5 Don Davis/Lehigh University

Room: 6417
Restuarant: TBA
Title: From invariant theory to homotopy groups.
We determine the v1-periodic homotopy groups of all irreducible p-compact groups (BX,X). In the most difficult, modular, cases, we follow a direct path from their associated invariant polynomials to these homotopy groups. We show that, if p is odd, every irreducible p-compact group has X of the homotopy type of a product of explicit spaces related to p-completed Lie groups.

·  Friday October 19, 10:00-11:00 am John Klein/ Wayne state University

Title: Bundle structures and Algebraic K-theory

This talk will describe algebraic K-theoretic obstructions to lifting fibrations to fiber bundles having compact smooth/topological manifold fibers. The surprise will be that a lift can often be found in the topological case. Examples will be given realizing the obstructions.

·  Oct. 3 Jesus Gonzalez/ Centro de Investigacion, Mexico City

Title: Topological complexity of lens spaces
The topological complexity of lens spaces can be used to approach the immersion problem for odd dimensional projective spaces. Following work of Fadell-Husseini (1992) and Farber-Grant (2007), I will describe how to compute the initial stages in such an approach.

Schedule, Fall 2006

·  Oct. 25 Tony Bahri/ Rider University

Title: "Stable decompositions of complements of complex coordinate subspace arrangements and generalized moment angle complexes"

Abstract: A report of joint work with Martin Bendersky, Fred Cohen and Sam Gitler. We investigate a splitting, after one suspension, of a generalized moment angle complex into pieces related directly to the underlying simplicial complex defining it. In the particular case of the complements of complex coordinate subspace arrangements, our result implies a well known homology result of Goresky and MacPherson.
Restaurant: TBA

Schedule, Spring 2006

·  March 8 Joel Zablow

Title:On the relations and homology in the Dehn twist quandle of a surface

Schedule, Fall 2005

·  Nov 9, 1:30-2:30, Rm 8405Dennis Sullivan -Cuny Grad. Center

Title: Are the operations in the free loop space of a closed manifold invariants of homotopy type?

·  Oct. 26 Hayden Harker,Vasser College

Title: Derived functors of the locally finite functor
Abstract: Define the functor G from A-modules to A-modules to be the locally finite functor where G(M) = {m in M | Am is finitely generated as a vector space}. We describe our interest in this functor and discuss the specific case when A is an exterior algebra over Z_2 with a countably infinite number of generators.


·  Oct. 12Don Davis, Lehigh University

Title "Homotopy exponents of SU(n)."
Abstract: We use methods of combinatorial number theory to prove that some homotopy group of SU(n) has an element of order p^{n-1+[n/p^2]+[n/p^3]+...}
Restaurant: Ben's Deli 209 W 38th St. near 7th ave.

Schedule, Spring 2005

·  March 23 Selman Akbulut, IAS/MSU

Title: Topology and Geometry of G_2 manifolds.
Restaurant: TBA

·  Feb. 16 Rob Schneiderman, NYU

Title: Whitney towers and low dimensional topology.
Restaurant: TBA

Schedule, Fall 2004

·  Dec. 1 Martin Bendersky, CUNY Hunter College/Graduate Center

Title: A spectral sequence approach to normal forms.
Restaurant: Ben's Deli

·  Nov. 17Craig Westerland, IAS

Title:Function Spaces from Surfaces and stable decompositions.
Abstract: We discuss the function spaces Map(X,M) of continuous maps from a surface, X, to a manifold M,,studying some multiplicative properties and giving a new stable splitting when M is a sphere.
Restaurant: TBA

·  Oct. 27 Nancy Hingston, The College of New Jersey

Title: Subharmonic Solutions of Hamiltonian Equations on Tori
Restaurant: TBA

Schedule, Spring 2004

·  March 17 Cindy Curtis, The College of New Jersey

Title: On the SL(2,C)-Casson Invariant.
Restaurant: Kang Suh (1250 Broadway)

·  April 21 Stefan Bauer, IAS

Title: Refined Seiberg Witten Invariant
Restaurant: TBA

·  April 28 John McCleary, Vassar College

Title: Contribution of Hinz Hopf
Restaurant: TBA

Schedule, Fall 2003

·  Oct. 15 Lee Mosher, Rutgers University, Newark

Title: Parageometric Automorphisms of Free Groups.

Restaurant:Kang Suh (1250 broadway)

·  Oct. 29 Katarzyna Potocka, Lehigh University

Title: The number of summands in the v_1 periodic homotopy of SU(n)
Restaurant: Ben's Deli (38th St. and 7th Ave.)

·  November 19Martin Bendersky, CUNY Hunter College/Grad Center

Title: Stable Geometric Dimension of Vector Bundles over RP^n
Restaurant: Crestanello (475 5th Ave. Between 40 and 41st)

Schedul, Fall 2002

·  Oct. 2 John Klein, Wayne State University

Title:Poincare Duality and Brave New Rings

Schedule, Fall 2001

Title: The K-Theory Bousfield Kan Spectral Sequence. Applications and Generalizations
Restaurant: TBA


Schedule, Spring 2001

Title: Cellular vs. Acyclic
Restaurant: Brew's, 34th st between lexigton and 3rd Ave. Very good burgers!

Title: Atiyah's real K-theory and algebraic K-theory of real varieties
Restaurant: Da Ciro (239 Lexinton Ave near 33rd St.)

Title: Homology decompositions and constructions of group actions.
Restaurant: Da Ciro

Title: Hopf invariants and periodic orbits of Hamiltonian flows
Restaurant: TBA

Title: Holomorphic disks and invariants for 3-manifolds and smooth 4-manifolds
Abstract: We will introduce and study topological invariants for closed 3 manifolds and smooth 4-manifolds. The 3-manifold constructions uses Heegaard diagrams and a version of Langrangian FLoer homology. The 4-manifold invariant uses the previous construction, a pairing on FLoer-homology and a handle decomposition of the 4 manifold. We will also present some applications in three and 4-manifold topology. This is a joint result with Peter Ozsvath.
Restaurant: TBA

Title: A model category for algebraic 2-theories
Restaurant: TBA

Schedule, Fall 2000


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