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Hot Topics Workshop
Hot Topics: Thin Groups and Super-strong Approximation
Feb 6, 2012 to Feb 10, 2012

Organizer(s)

Emmanuel Breuillard* (Universite Paris-Sud, Orsay), Alexander Gamburd (CUNY Graduate Center), Jordan Ellenberg (University of Wisconsin - Madison), Emmanuel Kowalski (ETH Zurich), Hee Oh (Brown University)
The workshop will focus on recent developments concerning various quantitative aspects of "thin groups". These are discrete subgroups of semisimple Lie groups which are both « big » (i.e. Zariski dense) and « small » (i.e. of infinite co-volume). This dual nature leads to many intricate questions. Over the past few years, many new ideas and techniques, arising in particular from arithmetic combinatorics, have been involved in the study of such groups, leading for instance to far-reaching generalizations of the strong approximation theorem in which congruence quotients are shown to exhibit a spectral gap (super-strong approximation).


Simultaneously and sometimes surprisingly, the study of thin groups turns out to be of fundamental importance in a variety of subjects, including equidistribution of homogeneous flows and lattice points counting problems, dynamics on Teichmuller space, the Bourgain-Gamburd-Sarnak sieve in orbit, and arithmetic or geometric properties of certain types of monodromy groups and coverings. The workshop will gather a variety of experts from group theory, number theory, ergodic theory and harmonic analysis to present the accomplishments to date to a broad audience and discuss directions for further study.

Scheduled Speakers:
2-hour introductory mini-courses by:
E. Breuillard
J. Ellenberg
A. Gamburd
E. Kowalski
H. Oh

1-hour talks by:
J. Bourgain
E. Fuchs
A. Kontorovich
A. Mohammadi
C. McMullen
G. Prasad
L. Pyber
A. Rapinchuk
I. Rivin
A. Salehi-Golsefidy

Bibliography (PDF)
Notes by Peter Sarnak (PDF)

Accommodation:
A block of rooms has been reserved at the Rose Garden Inn. Reservations may be made by calling 1-800-992-9005 OR directly on their website. Click on Corporate at the bottom of the screen and when prompted enter code MATH (this code is not case sensitive). By using this code a new calendar will appear and will show MSRI rate on all room types available.

A block of rooms has been reserved at the Hotel Durant. Please mention MSRI and the workshop name when making reservations via phone, fax or e-mail. If you are making your reservations on line, please go to Hotel Durant website, choose your dates of stay and enter the "123MSRI" promo code in the box. The cut-off date for reservations is January 5, 2012. The rate is $110 per night plus tax.

MSRI has a preferred rate of $142 at the Hotel Shattuck Plaza, depending on room availability. Guests can either call the hotel's main line at 510-845-7300 and ask for the MSRI rate; or go to Hotel Shattuck Plaza and enter dates of stay at top of screen and click Book Now.  Once on the reservation page, click Preferred/Corporate Rate Accounts and input the code "MSRI11".

Schedule
Monday, February 06, 2012
9:00AM - 9:45AM MSRI, Simons Auditorium Welcome and Registration
9:45AM - 10:00AM MSRI, Simons Auditorium Introduction by the MSRI director and staff
10:00AM - 11:00AM MSRI, Simons Auditorium Alexander Gamburd Mini-course 1: Expander Graphs, Thin Groups, and Super-strong Approximation [Video available]
11:00AM - 11:30AM MSRI, Atrium Tea
11:30AM - 12:30PM MSRI, Simons Auditorium Jean Bourgain On Zaremba\'s conjecture [Video available]
12:30PM - 2:10PM MSRI, Atrium Lunch
2:10PM - 3:10PM MSRI, Simons Auditorium Hee Oh Mini-course 2: Effective circle count for Apollonian circle packings, via spectral methods ( Abstract ) [Video available]
3:10PM - 3:40PM MSRI, Atrium Tea
3:40PM - 4:40PM MSRI, Simons Auditorium Alex Kontorovich On the Strong Density Conjecture for Apollonian Circle Packings ( Abstract ) [Video available]
Tuesday, February 07, 2012
9:00AM - 10:00AM MSRI, Simons Auditorium Alexander Gamburd Mini-course 1: Expander Graphs, Thin Groups, and Super-strong Approximation [Video available]
10:00AM - 10:30AM MSRI, Atrium Tea
10:30AM - 11:30AM MSRI, Simons Auditorium Andrei Rapinchuk On the strong approximation in algebraic groups ( Abstract ) [Video available]
11:35AM - 12:35PM MSRI, Simons Auditorium Emmanuel Kowalski Mini-course 3: Sieve in discrete groups, Part I ( Abstract ) [Video available]
12:35PM - 2:10PM MSRI, Atrium Lunch
2:10PM - 3:10PM MSRI, Simons Auditorium Hee Oh Mini-course 2: Counting for orbits of thin groups, via ergodic methods ( Abstract ) [Video available]
3:10PM - 3:40PM MSRI, Atrium Tea
3:40PM - 4:40PM MSRI, Simons Auditorium Emmanuel Breuillard Mini-course 4: Approximate groups, Part I ( Abstract   Notes ) [Video available]
4:40PM - 6:15PM MSRI, Atrium Reception
Wednesday, February 08, 2012
9:00AM - 10:00AM MSRI, Simons Auditorium Jordan Ellenberg Mini-course 5: Thin groups as monodromy groups, Part I ( Abstract ) [Video available]
10:00AM - 10:30AM MSRI, Atrium Tea
10:30AM - 11:30AM MSRI, Simons Auditorium Alireza Salehi Golsefidy Affine sieve and expanders ( Abstract ) [Video available]
11:35AM - 12:35PM MSRI, Simons Auditorium Curtis McMullen Dynamics of units and packing constants of ideals ( Abstract ) [Video available]
Thursday, February 09, 2012
9:00AM - 10:00AM MSRI, Simons Auditorium Emmanuel Kowalski Mini-course 3: Sieve in discrete groups, Part II ( Abstract ) [Video available]
10:00AM - 10:30AM MSRI, Atrium Tea
10:30AM - 11:30AM MSRI, Simons Auditorium Alan Reid 3-Manifold groups, surface groups and thin subgroups of SL(3,Z) [Video available]
11:35AM - 12:35PM MSRI, Simons Auditorium Jordan Ellenberg Mini-course 5: Thin groups as monodromy groups, Part II ( Abstract ) [Video available]
12:35PM - 2:10PM MSRI, Atrium Lunch
2:10PM - 3:10PM MSRI, Simons Auditorium Laci Pyber Growth in linear groups ( Abstract ) [Video available]
3:10PM - 3:40PM MSRI, Atrium Tea
3:40PM - 4:40PM MSRI, Simons Auditorium Informal and Optional Problem Session
Friday, February 10, 2012
9:00AM - 10:00AM MSRI, Simons Auditorium Elena Fuchs How generic are thin groups? ( Abstract ) [Video available]
10:00AM - 10:30AM MSRI, Atrium Tea
10:30AM - 11:30AM MSRI, Simons Auditorium Emmanuel Breuillard Mini-course 4: Approximate groups, Part II ( Abstract ) [Video available]
11:35AM - 12:35PM MSRI, Simons Auditorium Gopal Prasad Weakly-commensurable Zariski-dense subgroups and isospectral arithmetic compact locally symmetric spaces ( Abstract ) [Video available]
12:35PM - 2:10PM MSRI, Atrium Lunch
2:10PM - 3:10PM MSRI, Simons Auditorium Igor Rivin Asymptotic properties of obscure groups ( Abstract ) [Video available]
3:10PM - 3:40PM MSRI, Atrium Tea


Questions about this workshop should be sent either by email to
or by regular mail to:
Hot Topics: Thin Groups and Super-strong Approximation
Mathematical Sciences Research Institute
17 Gauss Way, Berkeley, CA
94720-5070.
USA

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