Colloquia/Fall18: Difference between revisions

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__NOTOC__
= Mathematics Colloquium =
= Mathematics Colloquium =


All colloquia are on Fridays at 4:00 pm in Van Vleck B239, '''unless otherwise indicated'''.
All colloquia are on Fridays at 4:00 pm in Van Vleck B239, '''unless otherwise indicated'''.


== Fall 2013 ==
== Spring 2018 ==


{| cellpadding="8"
{| cellpadding="8"
!align="left" | date
!align="left" | date  
!align="left" | speaker
!align="left" | speaker
!align="left" | title
!align="left" | title
!align="left" | host(s)
!align="left" | host(s)
|-
|-
|Sept 6
|January 30
|[http://people.math.gatech.edu/~mbaker/ Matt Baker] (Georgia Institute of Technology)
| [http://www.math.columbia.edu/~chaoli/ Li Chao] (Columbia)
|Riemann-Roch for Graphs and Applications
|[[# TBA| TBA  ]]
|Ellenberg
| Jordan Ellenberg
|-
|Sept 13
|[http://math.wisc.edu/~andrews/ Uri Andrews] (University of Wisconsin)
|
|
|-
|Sept 20
|[http://www.math.neu.edu/people/profile/valerio-toledano-laredo Valerio Toledano Laredo] (Northeastern)
|Flat connections and quantum groups
|Gurevich
|-
|'''Wed, Sept 25, 2:30PM'''
|[http://mypage.iu.edu/~alindens/ Ayelet Lindenstrauss]
|
|Meyer
|-
|'''Wed, Sept 25''' (LAA lecture)
|[http://www.cs.berkeley.edu/~demmel/ Jim Demmel] (Berkeley)
|Communication Avoiding Algorithms for Linear Algebra and Beyond
|Gurevich
|-
|'''Thurs, Sept 26''' (LAA lecture, Joint with Applied Algebra Seminar)
|[http://www.cs.berkeley.edu/~demmel/ Jim Demmel] (Berkeley)
|Implementing Communication Avoiding Algorithms
|Gurevich
|-
|Sept 27 (LAA lecture)
|[http://www.cs.berkeley.edu/~demmel/ Jim Demmel] (Berkeley)
|Communication Lower Bounds and Optimal Algorithms for Programs that Reference Arrays
|Gurevich
|-
|Oct 4
|[http://www.math.tamu.edu/~sottile/ Frank Sottile] (Texas A&M)
|
|Caldararu
|-
|Oct 11
|[http://math.uchicago.edu/~wilkinso/ Amie Wilkinson] (Chicago)
|
|WIMAW (Cladek)
|-
|'''Tues, Oct 15, 4PM''' (Distinguished Lecture)
|[http://math.mit.edu/people/profile.php?pid=1222 Alexei Borodin] (MIT)
|Integrable probability I
|Valko
|-
|'''Wed, Oct 16, 2:30PM''' (Distinguished Lecture)
|[http://math.mit.edu/people/profile.php?pid=1222 Alexei Borodin] (MIT)
|Integrable probability II
|Valko
|-
|<strike>Oct 18</strike>
|No colloquium due to the distinguished lecture
|
|
|-
|Oct 25
|[http://www.math.umn.edu/~garrett/ Paul Garrett] (Minnesota)
|
|Gurevich
|
|
|-
|Nov 1
|[http://www.cs.utexas.edu/~alewko/ Allison Lewko] (Microsoft Research New England)
|
|
|Stovall
|-
|-
|Nov 8
|February 2
|[http://www.math.cornell.edu/~riley/ Tim Riley] (Cornell)
| [https://scholar.harvard.edu/tfai/home Thomas Fai] (Harvard)
|[[# TBA|  TBA  ]]
| Spagnolie, Smith
|
|
|Dymarz
|-
|-
|Nov 15 and later
|February 9
|Reserved
| [http://www.math.cmu.edu/~wes/ Wes Pegden] (CMU)
|[[# TBA|  TBA  ]]
| Roch
|
|
|Street
|}
== Spring 2014 ==
{| cellpadding="8"
!align="left" | date
!align="left" | speaker
!align="left" | title
!align="left" | host(s)
|-
|-
|Jan 24
| March 16
|
|[https://math.dartmouth.edu/~annegelb/ Anne Gelb] (Dartmouth)
|
|[[# TBA|  TBA  ]]
| WIMAW
|
|
|-
|-
|Jan 31
|April 4 (Wednesday)
|[http://csi.usc.edu/~ubli/ubli.html Urbashi Mitra] (USC)
| [http://math.ucr.edu/home/baez/ John Baez] (UC Riverside)
|[[# TBA|  TBA  ]]
| Craciun
|
|
|Gurevich
|-
|-
|Feb 7
| April 6
|David Treumann (Boston College)
| Reserved
|[[# TBA|  TBA  ]]
| Melanie
|
|
|Street
|-
|-
|Feb 14
| April 13
|
| [https://www.math.brown.edu/~jpipher/ Jill Pipher] (Brown)
|
|[[# TBA|  TBA  ]]
| WIMAW
|
|
|-
|-
|Feb 21
| April 25 (Wednesday)
|
| Hitoshi Ishii (Waseda University) Wasow lecture
|
|[[# TBA|  TBA  ]]
| Tran
|
|
|-
|-
|Feb 28
|date
|
| person (institution)
|
|[[# TBA|  TBA  ]]
| hosting faculty
|
|
|-
|-
|March 7
|date
|
| person (institution)
|
|[[# TBA|  TBA  ]]
| hosting faculty
|
|
|-
|-
|March 14
|date
|
| person (institution)
|
|[[# TBA| TBA  ]]
|
| hosting faculty
|-
|<strike>March 21</strike>
|'''Spring Break'''
|No Colloquium
|
|
|-
|-
|March 28
|date
|[http://people.math.gatech.edu/~lacey/ Michael Lacey] (GA Tech)
| person (institution)
|The Two Weight Inequality for the Hilbert Transform
|[[# TBA| TBA  ]]
|Street
| hosting faculty
|-
|April 4
|[https://sites.google.com/site/katejuschenko/ Kate Jushchenko] (Northwestern)
|
|
|Dymarz
|-
|-
|April 11
|date
|[http://www.cs.uchicago.edu/people/risi Risi Kondor] (Chicago)
| person (institution)
|[[# TBA|  TBA  ]]
| hosting faculty
|
|
|Gurevich
|-
|-
|April 18 (Wasow Lecture)
|date
|[http://mathnt.mat.jhu.edu/sogge/ Christopher Sogge] (Johns Hopkins)
| person (institution)
|[[# TBA|  TBA  ]]
| hosting faculty
|
|
|A. Seeger
|-
|-
|April 25
|date
|[http://www.charlesdoran.net Charles Doran](University of Alberta)
| person (institution)
|[[# TBA|  TBA  ]]
| hosting faculty
|
|
|Song
|-
|-
|May 2
|date
|[http://www.stat.uchicago.edu/~lekheng/ Lek-Heng Lim] (Chicago)
| person (institution)
|[[# TBA|  TBA  ]]
| hosting faculty
|
|
|Boston
|-
|-
|May 9
|date
|[http://www.ma.utexas.edu/users/rward/ Rachel Ward] (UT Austin)
| person (institution)
|[[# TBA|  TBA  ]]
| hosting faculty
|
|
|WIMAW
|}
|}


== Abstracts ==
===Sep 6: Matt Baker (GA Tech) ===
''Riemann-Roch for Graphs and Applications''


We will begin by formulating the Riemann-Roch theorem for graphs due to the speaker and Norine. We will then describe some refinements and applications. Refinements include a Riemann-Roch theorem for tropical curves, proved by Gathmann-Kerber and Mikhalkin-Zharkov, and a Riemann-Roch theorem for metrized complexes of curves, proved by Amini and the speaker. Applications include a new proof of the Brill-Noether theorem in algebraic geometry (work of by Cools-Draisma-Payne-Robeva), a "volume-theoretic proof" of Kirchhoff's Matrix-Tree Theorem (work of An, Kuperberg, Shokrieh, and the speaker), and a new Chabauty-Coleman style bound for the number of rational points on an algebraic curve over the rationals (work of Katz and Zureick-Brown).
== Spring Abstracts ==


===Sep 25: Jim Demmel (Berkeley) ===
<DATE>: <PERSON> (INSTITUTION)
''Communication Avoiding Algorithms for Linear Algebra and Beyond''
Title: <TITLE>


Algorithm have two costs: arithmetic and communication, i.e. moving data between levels of a memory hierarchy or processors over a network. Communication costs (measured in time or energy per operation) already greatly exceed arithmetic costs, and the gap is growing over time following technological trends. Thus our goal is to design algorithms that minimize communication. We present algorithms that attain provable lower bounds on communication, and show large speedups compared to their conventional counterparts. These algorithms are for direct and iterative linear algebra, for dense and sparse matrices, as well as direct n-body simulations. Several of these algorithms exhibit perfect strong scaling, in both time and energy: run time (resp. energy) for a fixed problem size drops proportionally to the number of processors p (resp. is independent of p). Finally, we describe extensions to algorithms involving arbitrary loop nests and array accesses, assuming only that array subscripts are affine functions of the loop indices.
Abstract: <ABSTRACT>


===Sep 26: Jim Demmel (Berkeley) ===
== Past Colloquia ==
''Implementing Communication Avoiding Algorithms''


Designing algorithms that avoiding communication, attaining
[[Colloquia/Blank|Blank Colloquia]]
lower bounds if possible, is critical for algorithms to minimize runtime and
energy on current and future architectures. These new algorithms can have
new numerical stability properties, new ways to encode answers, and new data
structures, not just depend on loop transformations (we need those too!).
We will illustrate with a variety of examples including direct linear algebra
(eg new ways to perform pivoting, new deterministic and randomized
eigenvalue algorithms), iterative linear algebra (eg new ways to reorganize
Krylov subspace methods) and direct n-body algorithms, on architectures
ranging from multicore to distributed memory to heterogeneous.
The theory describing communication avoiding algorithms can give us a large
design space of possible implementations, so we use autotuning to find
the fastest one automatically. Finally, on parallel architectures one can
frequently not expect to get bitwise identical results from multiple runs,
because of dynamic scheduling and floating point nonassociativity;
this can be a problem for reasons from debugging to correctness.
We discuss some techniques to get reproducible results at modest cost.


===Sep 27: Jim Demmel (Berkeley) ===
[[Colloquia/Fall2017|Fall 2017]]
''Communication Lower Bounds and Optimal Algorithms for Programs that Reference Arrays''


Our goal is to minimize communication, i.e. moving data, since it increasingly
[[Colloquia/Spring2017|Spring 2017]]
dominates the cost of arithmetic in algorithms. Motivated by this, attainable
communication lower bounds have been established by many authors for a
variety of algorithms including matrix computations.


The lower bound approach used initially by Irony, Tiskin and Toledo
[[Archived Fall 2016 Colloquia|Fall 2016]]
for O(n^3)  matrix multiplication, and later by Ballard et al
for many other linear algebra algorithms, depends on a geometric result by
Loomis and Whitney: this result bounds the volume of a 3D set
(representing multiply-adds done in the inner loop of the algorithm)
using the product of the areas of certain 2D projections of this set
(representing the matrix entries available locally, i.e., without communication).


Using a recent generalization of Loomis' and Whitney's result, we generalize
[[Colloquia/Spring2016|Spring 2016]]
this lower bound approach to a much larger class of algorithms,
that may have arbitrary numbers of loops and arrays with arbitrary dimensions,
as long as the index expressions are affine combinations of loop variables.
In other words, the algorithm can do arbitrary operations on any number of
variables like A(i1,i2,i2-2*i1,3-4*i3+7*i_4,…).
Moreover, the result applies to recursive programs, irregular iteration spaces,
sparse matrices,  and other data structures as long as the computation can be
logically mapped to loops and indexed data structure accesses.


We also discuss when optimal algorithms exist that attain the lower bounds;
[[Colloquia/Fall2015|Fall 2015]]
this leads to new asymptotically faster algorithms for several problems.


[[Colloquia/Spring2014|Spring 2015]]


[[Colloquia/Fall2014|Fall 2014]]


===March 28: Michael Lacey (GA Tech) ===
[[Colloquia/Spring2014|Spring 2014]]
''The Two Weight Inequality for the Hilbert Transform ''


The individual two weight inequality for the Hilbert transform
[[Colloquia/Fall2013|Fall 2013]]
asks for a real variable characterization of those pairs of weights
(u,v) for which the Hilbert transform H maps L^2(u) to L^2(v).
This question arises naturally in different settings, most famously
in work of Sarason. Answering in the positive a deep
conjecture of Nazarov-Treil-Volberg, the mapping property
of the Hilbert transform is characterized by a triple of conditions,
the first being a two-weight Poisson A2 on the pair of weights,
with a pair of so-called testing inequalities, uniform over all
intervals.  This is the first result of this type for a singular
integral operator.  (Joint work with Sawyer, C.-Y. Shen and Uriate-Tuero)


== Past talks ==
[[Colloquia 2012-2013|Spring 2013]]


Last year's schedule: [[Colloquia 2012-2013]]
[[Colloquia 2012-2013#Fall 2012|Fall 2012]]

Revision as of 23:59, 20 January 2018

Mathematics Colloquium

All colloquia are on Fridays at 4:00 pm in Van Vleck B239, unless otherwise indicated.

Spring 2018

date speaker title host(s)
January 30 Li Chao (Columbia) TBA Jordan Ellenberg
February 2 Thomas Fai (Harvard) TBA Spagnolie, Smith
February 9 Wes Pegden (CMU) TBA Roch
March 16 Anne Gelb (Dartmouth) TBA WIMAW
April 4 (Wednesday) John Baez (UC Riverside) TBA Craciun
April 6 Reserved TBA Melanie
April 13 Jill Pipher (Brown) TBA WIMAW
April 25 (Wednesday) Hitoshi Ishii (Waseda University) Wasow lecture TBA Tran
date person (institution) TBA hosting faculty
date person (institution) TBA hosting faculty
date person (institution) TBA hosting faculty
date person (institution) TBA hosting faculty
date person (institution) TBA hosting faculty
date person (institution) TBA hosting faculty
date person (institution) TBA hosting faculty
date person (institution) TBA hosting faculty
date person (institution) TBA hosting faculty


Spring Abstracts

<DATE>: <PERSON> (INSTITUTION) Title: <TITLE>

Abstract: <ABSTRACT>

Past Colloquia

Blank Colloquia

Fall 2017

Spring 2017

Fall 2016

Spring 2016

Fall 2015

Spring 2015

Fall 2014

Spring 2014

Fall 2013

Spring 2013

Fall 2012