June 2014 at

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**Hamiltonian cycles in some easy Cayley graphs
**June 2014 at the University of Waterloo (

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(after G. A. Margulis)

May 2014 at University of Chicago

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**What is a Coxeter Group?**

October 2013 at University of Lethbridge

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**Introduction to Bruhat-Tits buildings**

October 2013 at University of Chicago

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**Arithmetic subgroups of SL( n,R)**

August 2013 in Jeonju, South Korea (

May 2013 at University of Chicago

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Strictly convex norms on
amenable groups

November 2013 at University of Utah

March 2013 at South Padre Island, Texas (*Geometric Groups on
the Gulf Coast*)

April 2012 at University of Lethbridge

March 2012 at University of Chicago

March 2012 at Indiana University

March 2012 at Purdue University

Lecture 1: *Strictly convex norms on
abstract groups* (PDF
file)

Lecture 2: *Strictly convex norms on
amenable groups* (PDF
file)

Condensed version (PDF file)

SL(n,Q) has no
volume-preserving actions on (n-1)-dimensional compact
manifolds

August 2013 at Seoul National University

May 2013 at the University of Chicago

March 2013 at Rice University

July 2012 at Oberwolfach

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file

Introduction to
vertex-transitive graphs of prime-power order

March 2013 at the University of Lethbridge

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Hamiltonian paths in
solvable Cayley digraphs

October 2012 at the University of Lethbridge

July 2011 in Regina

June 2011 in Bled (7th Slovenian International Conference on
Graph Theory)

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July 2012 at Park City Mathematics Institute

Lecture 1: Introduction (PDF file)

Lecture 2: Proof using bounded generation (PDF file)

Lecture 3: What is an amenable group? (PDF file)

Lecture 4: Introduction to bounded cohomology (PDF file)

On interactions of amenability with left orderings

February 2012 at workshop in Banff

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How to make infinitely large numbers from two-player games

December 2011 at University of Lethbridge

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Does every Cayley graph have a hamiltonian cycle?

March 2011 at University of Western Australia

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another talk on a similar subject (and others can be found below):

When do subsets of {0,1}

December 2010 in Vancouver (Canadian Mathematical Society)

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Why arithmetic groups are lattices

June 2010 at the University of Chicago

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Survey of invariant orders on arithmetic groups

September 2014 at conference on

September 2011 in AMS Sectional meeting at Cornell

June 2011 at Oberwolfach

June 2010 at the University of Chicago

October 2009 in AMS Sectional meeting at Penn State

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Introduction to Ratner's Theorems on Unipotent Flows

June 2010 at Ohio State University

March 2010 at the University of British Columbia

April 2009 at the University of Virgina

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other talks on a similar subject:

Introduction to arithmetic groups

January 2010 at KAIST in Daejeon, Korea (three 1.5-hour lectures)

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What is the Congruence Subgroup Property?

September 2009 at Carleton-Ottawa Algebra Day

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other talks on a similar subject:

The Congruence Subgroup Property and bounded generation

May 2008 at the University of Chicago

May 2008 at the University of Chicago

Lecture 1: Introduction to the Congruence Subgroup Property

Lecture 2: Proof that SL(3,Z) has the Congruence Subgroup Property

Lecture 3: Bounded generation

A lattice with no torsion-free subgroup of finite index (after P.Deligne)

June 2009 informal discussion at the University of Chicago

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Two lectures on bounded cohomology

June 2009 at the University of Chicago

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Locally symmetric subspaces of locally symmetric spaces

(joint work with Vladimir Chernousov and Lucy Lifschitz)

January 2009 at AMS meeting in Washington, DC

September 2008 at Oberwolfach

April 2008 at Indiana University

February 2008 at the University of Chicago

PDF file of slides from recent talk

PDF file of lecture notes from older talk

other talks on the same subject:

Minimal
isotropic
simple Q-groups of higher real rank

February 2008 at the University of Virginia

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February 2008 at the University of Virginia

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Using left-invariant orders to study actions on 1-manifolds

June 2008 at CIRM, Luminy, France

Lecture 1: Left-invariant orders and local indicability

Lecture 2: Amenability and Ghys-Burger-Monod Theorem

Lecture 3: Ghys-Burger-Monod Theorem and a theorem of Navas

Proof of the Margulis Normal Subgroups Theorem

February 2008 at the University of Chicago

Lecture 1:
Introduction to Amenable Groups (PDF file)

Lecture 2: Statement and Most of the Proof (PDF file)

Lecture 3: Proof of the 'Black Box' Result (PDF file)

Lecture 2: Statement and Most of the Proof (PDF file)

Lecture 3: Proof of the 'Black Box' Result (PDF file)

Amenable groups that act on the line

April 2008 at University of Illinois, Chicago

April 2008 at Northwestern University

April 2008 at AMS meeting in Bloomington, Indiana

February 2008 at Ohio State University

March 2007 at the University of British Columbia

November 2006 at the University of Alberta

October 2006 at the University of Karlsruhe

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a more elementary talk on the same subject:

Using recurrence to study symmetries of the real line

March 2012 at the University of Virginia

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Dani's contributions to
ergodic theory on homogeneous spaces

December 2007 at Tata Institute in Mumbai, India

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(a lecture in a course given by B.Farb and M.Kisin)

October 2007 at the University of Chicago

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Some discrete groups that cannot

at Schrodinger Institute in Vienna

Part 1: Actions of amenable
groups (PDF file)

Part 2: Actions of arithmetic groups (PDF file)

Part 3: 3 Major Theorems of Margulis (PDF file)

(Theorems in Part 3 are not part of the announced topic,

but are important and use methods similar to Part 2)

Part 2: Actions of arithmetic groups (PDF file)

Part 3: 3 Major Theorems of Margulis (PDF file)

(Theorems in Part 3 are not part of the announced topic,

but are important and use methods similar to Part 2)

**Which circulant digraphs are hamiltonian?
**June 2007 in Koper, Slovenia

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**Bounded generation of special linear groups
(after Carter, Keller, and Paige)
**April 2008 at Vanderbilt University

June 2005 at workshop in Banff

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**Actions of arithmetic groups on the circle
**April 2005 at the University of
Illinois, Chicago

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Some arithmetic groups that cannot act on the line(joint work with

Lucy Lifschitzand Vladimir Chernousov)Alternate titles:

Some arithmetic groups that cannot act on the circle,

Some arithmetic groups that cannot act on 1-manifolds,

Some arithmetic groups that cannot be right ordered

March 2012 at Purdue University

April 2010 at the University of Virginia

December 2009 at the University of Lethbridge

April 2008 at Vanderbilt University

February 2008 at the University of Virginia

January 2008 at Mississippi State University

January 2008 at the University of Texas

July 2007 at the University of Minnesota, Duluth

March 2007 at the University of British Columbia

July 2006 at Oberwolfach, Germany

March 2006 at the University of Hawaii

November 2005 at Texas A&M University

March 2005 at AMS meeting in Lubbock, Texas

March 2005 at Princeton University

March 2005 at AMS meeting in Newark, Delaware

March 2005 at Rice University

February 2005 in Auckland, New Zealand

November 2004 at the University of Alberta

November 2004 at Lorentz Dynamics Workshop in Banff

August 2004 at Alberta Topology Seminar in Banff

June 2004 at Caltech

April 2004 at the University of Regina

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Some arithmetic groups that cannot act on the circle

(alternate title:Arithmetic groups that cannot be right-ordered)

December 2001 at Tata Institute (Mumbai, India)

February 2002 at Case Western Reserve University and Virginia Tech

PDF fileSome arithmetic groups that cannot act on the circle

March 2002 at Les Diablerets, Switzerland

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SL(3,Z) cannot act continuously on the circle

October 1998 at the Ecole Normale Superieure - Lyon (France)

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Actions of semisimple Lie groups on circle bundles

(joint work withRobert J. Zimmer)

May 2000 at the Newton Institute (Cambridge, UK)

March 2000 at the University of Manchester, England

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**Cocompact Lattices
**January 2006 in
Workshop on Property RD

at the American Institute of Mathematics, Palo Alto

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**Hamiltonian checkerboards
**November 2011 at the University of Lethbridge

May 2010 at the University of Manitoba

(Prairie Discrete Mathematics Conference)

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other talks on related subjects:

**Hamiltonian cycles in Cayley graphs
**August 2005 at the University of Winnipeg

(Prairie Discrete Mathematics Conference)

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**Open problems on hamiltonian cycles in Cayley graphs
**June 2006 in Minisymposium in SIAM conference

at University of Victoria

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**Hamiltonian cycles in circulant graphs and digraphs
**May 2004 at the University of Lethbridge

(Combinatorics Day)

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May 2003 at Simon Fraser University

(conference for Brian Alspach's 65th birthday)

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**Which flows are
sums of hamiltonian cycles in abelian Cayley graphs?
**(joint work with

May 2003 in Koper, Slovenia (

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(joint work with

March 2002 at Southeastern Combinatorics Conference in Boca Raton, Florida

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**Hamiltonian paths in cartesian
powers of directed cycles**

(joint work with **David Austin** and **Heather Gavlas**)

November 2002 at the University of Lethbridge

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March 2008 at the University of Michigan

April 2002 at the University of Lethbridge, Canada

November 2001 at Oklahoma State University

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**Geometric interpretation of the Q-rank of a locally
symmetric space
**May 2004 at AMS/SMM Meeting in Houston

(joint work with Pralay Chatterjee)

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another talk on a related subject:

**Orbits of Cartan
subgroups on homogeneous spaces
(after George Tomanov and Barak Weiss)
**December 2001 at Tata Institute
(Mumbai, India)

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**Real representations of sp(n) have Q-forms
**April 2003 at the University of North Carolina

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another talk on a related subject:

Q-forms of real representations of compact semisimple Lie groups

(after Raghunathan and Eberlein)

October 2001 at OSU

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**Gromov and Piatestski-Shapiro's Nonarithmetic****
Lattices in **SO(1,n)

September 2002 at Oklahoma State University

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**Some ideas in the proof of Ratner's Theorem**

(alternate title: **An Introduction to Unipotent
Flows**)

September 2007 at Pennsylvania State University

January 2007 at University of Calgary

July 2002 at ETH, Zurich

June 2002 at the University of Chicago

February 2000 at the Newton Institute (Cambridge,
UK)

previously at a few other universities

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**Ergodic actions of semisimple Lie groups on
compact principal bundles**

(joint work with **Robert J. Zimmer**)

April 2001 at the University of Illinois, Chicago

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**Rigidity of some characteristic-p nillattices**

(joint work with **Lucy Lifschitz**)

June 2000 at the Newton Institute (Cambridge, UK)

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**What is a superrigid
subgroup?**

(alternate title: **Superrigid subgroups of solvable Lie groups**)

November 2013 at U
of Utah and Idaho State U

April 2002 at the University of Regina, Canada

February 2002 at Virgina Tech

May 2000 at the University of Birmingham, England

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Other talks on the same subject:

More elementary: What is a superrigid
subgroup? (August 1997 at the MAA Mathfest, Atlanta)

More advanced: Superrigid subgroups of
solvable Lie groups (April 1999 at the U of Chicago)

**Tessellations of homogeneous spaces of SU(2,n)**

(joint work with **Alessandra Iozzi** and **Hee
Oh** )

March 2000 at the Newton Institute (Cambridge, UK)

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**Cartan-decomposition subgroups**

(joint work with **Hee Oh** and **Alessandra
Iozzi** )

September 1999 at the University of Michigan

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**Transitive permutation groups of prime-squared
degree**

(joint work with **Edward Dobson**)

May 1999 Group Theory Junior Seminar at the
University of Chicago

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**Foliation-preserving maps between
solvmanifolds**

(joint work with **Holly Bernstein**)

March 1998 at Kansas State University AMS meeting

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**Simple groups of real rank at least two have
Kazhdan's property T**

January 28, 1998 Lie Groups Seminar at Oklahoma
State University

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**Introduction to Kazhdan's property T**

January 21, 1998 Lie Groups Seminar at Oklahoma
State University

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L