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**COMBINATORICS, TOPOLOGY AND CONVEXITY:**

THEIR MEETING POINTS

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**27 April -5 May 2003 **

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Organizer: GIL KALAI

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Hebrew University's Institute for Advanced Studies - Feldman Building,
Givat Ram, Safra campus.

Unless specified otherwise lectures will take place on Lecture Hall 130
Feldman building.
The Erdos' lecture On Thursday May 1 at 16:00 and later lectures on Thursday
and on Friday May 2 will take place in the Mathematics
building lecture hall 2.

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PROGRAM

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27 April

8:30-9:30 Registration in the Lobby of the Institute.

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Lecture Hall 130: Feldman building

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9:45 Welcome

10:00-11:10 **Francesco Brenti** - Combinatorics of Schubert varieties I

### Coffee Break

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11:30-12:40 **Eric Babson** - f-vectors I

14:30-15:40 **Yoav Segev **- Finite groups acting on acyclic
complexes I

16:00-16:55 ** Yael Karshon - **Euler-Maclaurin formula for polytopes

### Coffee Break

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17:10-18:05 Peter Csorba - Topological lower bound for Chromatic numbers

18:30 - Reception in the Lobby of the Institute.

28 April

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Lecture Hall 130: Feldman building

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9:15-10:25 **Alexander Barvinok** -
Wild convex bodies I

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### Coffee Break

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10:45-11:55 **Sergey Fomin** -
Generalized associahedra and cluster algebras
I

12:00-12:55 **Micha A. Perles**- Non-Convexity

14:30-15:25 ** ****Nati Linial** - Lifts of graphs

### Coffee Break

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16:00-16:55 **Ruth Lawrence** -
Symmetric sums and integrality of quantum 3-manifold invariants

17:00-17:55 **Roy Meshulam** - Domination numbers
and homology

29 April

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Lecture Hall 130: Feldman building

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9:15-10:25 **Yoav Segev**- Finite groups acting on acyclic
complexes II

### Coffee Break

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10:45-11:55 **Sergey Fomin** -
Generalized associahedra and cluster algebras
II

12:00-12:55 **Ron Aharoni - **
Independent systems of representatives, a survey

14:30-15:25 **Noga Alon** -
Spectral Techniques in Extremal Combinatorics

15:30-16:25 **Ron Adin** - Polytopes, face numbers,
and symmetry

### Coffee Break

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17:00-17:55 **Gil Kalai - **Topological Helly-type theorems

30 April

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Lecture Hall 130: Feldman building

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9:15-10:25 **Alexander Barvinok** - Wild convex bodies II

### Coffee Break

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10:45-11:45 Vitali Milman - How far is an arbitrary convex body
from an ellipsoid ?
a geometric question considered with a
computational-complexity type "ideology"
(joint with the HU theoretical CS seminar)

12:00-12:55 **Eli Berger**- A function dual to the Lovasz Theta Function

Afternoon: excursion

1 May

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Lecture Hall 130: Feldman building

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9:15-10:25 **Eric Babson** - f-vectors II

### Coffee Break

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10:45-11:40 **Ehud DeShalit** - Hyperplane arrangements and

Harmonic Analysis on Buildings

12:00-12:55** Alex Lubotzky **- Ramanujan complexes

14:30-15:40 **Francesco Brenti**- Combinatorics of Schubert varieties II

### Light refreshments in the Mathematics building

Lecture Hall 2: mathematics building

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16:00-17:00 Maria Chudnovsky - Erdos Lecture: The Strong Perfect Graph THEOREM

17:30-16:25 ** Emmanuel Farjoun** - The fundamental groups of
limits of simplicial complexes

2 May

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Lecture Hall 2: mathematics building

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9:15-10:10 Maria Chudnovsky - Testing for perfectness

10:20 - 11:00 Lauren K. Williams -
Some combinatorics and topology related to the totally non-negative part
of the Grassmannian.

11:25-12:20 **Eran Nevo ** - Algebraic shifting and some
basic constructions on simplicial
complexes

### coffee break

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12:30-13:25 **Gil Alon** - Realization of the Orlik-Solomon
algebra of a hyperplane arrangement on its inclusion lattice.

3 May

IAS offers an excrusion to the dead sea and Massada

4-5 May

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Back in Feldman building

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4 April

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Lecture Hall 130: Feldman building

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9:30-(?)10:40 **Shmuel Weinberger** -
Combinatorics and Homology,
Hopf conjecture in differential geometry and combinatorics
(Charney-Davies and beyond)
followed by

10:40(?)-12:45(?) Topology and combinatorics, discussion, thoughts,
open problems, coffee
Sunday afternoon - free, unformal discussions

5 April

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Lecture Hall 130: Feldman building

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Convexity and optimization
Convex bodies, mathematical programming and optimization:
10:00 - 10:40 Greg Blekherman - Volumes of wild convex sets
11:00 - 11:45 Gideon Weiss - Continuous linear programming
12:00 - 12:40 Discussion, open problems, coffee
Monday afternoon - free

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The lectures will be specially targeted for graduate and post-graduate

students.
www.as.huji.ac.il/schools.html

www.as.huji.ac.il/schools/midrasha.pdf

http://www.ma.huji.ac.il/~kalai/mathprog03.html
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Abstracts or informal descriptions
of lectures: