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bio website gilkalai.wordpress.com
location Jerusalem
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visits member for 5 years, 2 months
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Professor of Mathematics at the Hebrew University of Jerusalem and at Yale University

Nov
23
comment Examples for Decomposition Theorem
To what extent does Lusztig's work rely on the decomposition theorem?
Nov
23
comment Fundamental Examples
Here is a link for ADE classification: en.wikipedia.org/wiki/ADE_classification and here are links for the A-B-C-D-E-F-G root systems and finite Coxeter groups via Dynkin diagrams en.wikipedia.org/wiki/Root_system en.wikipedia.org/wiki/Coxeter%E2%80%93Dynkin_diagram
Nov
23
comment Fundamental Examples
here is a link: en.wikipedia.org/wiki/Penrose_tiling
Nov
23
comment Fundamental Examples
This answer is by Euclid mathoverflow.net/users/2033/euclid I just added the link and picture.
Nov
23
revised Fundamental Examples
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Nov
23
revised The Sylvester Gallai Theorem and Sections of Varieties with “Simple Topology”.
added 1 characters in body
Nov
23
answered Generalizations of Boolean posets/lattices
Nov
22
awarded  Nice Answer
Nov
22
revised Fundamental Examples
added the words - or few
Nov
22
comment Fundamental Examples
How does it touches the Quaternions?
Nov
22
answered Fundamental Examples
Nov
22
awarded  Nice Question
Nov
22
comment Combinatorics of the Stasheff polytopes
Many thanks, Greg!
Nov
22
revised The Sylvester Gallai Theorem and Sections of Varieties with “Simple Topology”.
added 1138 characters in body; edited tags; edited tags
Nov
22
revised A “round” lattice with low kissing number?
typos corrected, link added
Nov
22
revised A “round” lattice with low kissing number?
update
Nov
22
comment Definition of “simplicial complex”
There are many interesting notions of complexes (and more general structures on spaces) from the point of view of combinatorics. A natural condition (which is satisfied even by regular CW complexes) is that the combinatorics of the cells determones the topology of the space described by the complex. (But some combinatorics can be done even if this condition is violated.) Simplicial complexes in the second definition has also the advantage that they can be embedded linearly (not just PW linearly) to Euclidean spaces. Also cubical complexes are interesting in combinatorics and topology.
Nov
22
comment Combinatorics of the Stasheff polytopes
Greg, is this the original paper where the Hatcher-Thurston objects defined? A. Hatcher, On triangulations of surfaces, Topology Appl. 40 (1991), 189–194. Also can you describe the construction in a little more detail?
Nov
22
comment Theorems for nothing (and the proofs for free)
Indeed this is a wonderful theorem. Why is it intuitive correct? From all the first year algebra theorems it was the one where I had no intuition whatsoever.
Nov
22
revised The Sylvester Gallai Theorem and Sections of Varieties with “Simple Topology”.
added 184 characters in body