426 reputation
720
bio website
location Paris France
age 58
visits member for 4 years, 7 months
seen Aug 14 at 22:48
Subjects : finite maths , combinatorics, graphs , categories. I am problem oriented and of the geometric type. I believe the linguistic-literary side of maths should be put forward in particular as a means to fill the gap between mathematics and general culture.

Jul
21
comment Theorems true but wrong.
@djechlin : Not at all : I am saying that saying $P_1$ and $P_2 \RightArrow C_1 and C_2$ is wrong when actually each $A_i$ implies $C_i$. Also asserting " $a+b$ is less than $a'+b'$" is wrong when in fact $a$ (resp. $b$) is less than $a'$ ( resp. $b'$).
Jul
2
awarded  Curious
Feb
22
comment Less general edge reconstruction problem for simple graphs
It couls very wel be the only example...
Feb
8
awarded  Nice Answer
Feb
4
awarded  Revival
Jan
24
awarded  Nice Answer
Dec
24
comment A weaker concept of graph homomorphism
I have a problem with statement 2 .If you are calling the rigid definition that for homomorphism of graphs which is classical . Then you can contract any tree to K_2 (the complete graph with 2 vertices).
Oct
29
awarded  Quorum
Mar
30
comment Enumerating 0-1 finite boxes without null rays.
@Casteels : OK you are right there was a typo the 4 and the 6 where exchanged in front of the powers ^p.
Mar
30
revised Enumerating 0-1 finite boxes without null rays.
Exchange coeffs. 6 and 4 inf front of 7^p and 3^p
Mar
29
asked Enumerating 0-1 finite boxes without null rays.
Mar
3
revised Difficult examples for Frankl's union-closed conjecture
minor
Mar
2
revised Difficult examples for Frankl's union-closed conjecture
Added a third point C)
Mar
1
answered Difficult examples for Frankl's union-closed conjecture
Feb
8
comment Which finite group is not the automorphism group of some rooted finite trees
Thank you very much , there is still an aspect of "density". Do we loose kind of "half" when restricting to (FTAG) FiniteTree-Automorphism -Groups ?
Feb
8
comment Which finite group is not the automorphism group of some rooted finite trees
How funny that my context is in fact graph isomorphism and Brendan is the first to answer this. Mysterious or funny ?
Feb
8
comment Why is Set, and not Rel, so ubiquitous in mathematics?
Too short and too partial for an answer: I think that functions are on the technical side whereas relation are on the conceptual side. A function (partial) "is" a partition whereas a relation thought as a bipartite graph is much more complicated. A related (no pun) question is that partial functions should be used instead of function.
Feb
8
asked Which finite group is not the automorphism group of some rooted finite trees
Jan
24
comment Galois connections
@jim It is a detail : in galois.pdf the property is symetric (not reflexive as given).
Dec
25
comment What would you want to see at the Museum of Mathematics?
@Todd : I have seen a very nice documentary about professional dancers at the Opéra de Paris ( from Reichenbach ? ) . You see them talk and act (dance) for training and interpreting, yet the "truth" they reach through successive corrections is felt but not understood (unless you are semi professional). So the idea is that people may understand the general aim and the kind of logic used by mathematicians without a proper grasp.