501 reputation
721
bio website
location Paris France
age 59
visits member for 5 years, 3 months
seen Apr 21 at 23:11
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.

Mar
3
comment A weaker concept of graph homomorphism
ATTENTION: Your nice drawing is misleading: you forgot four arrows. In fact apart from $C_3$ the three others are homeomorphic and each have an Hom towards $C_3$.
Feb
18
comment Are there other nice math books close to the style of Tristan Needham?
It certainly catches the eye and made me discover this great book ,thank you!
Dec
10
comment Lens spaces and generalized Petersen graphs
@DavidEppstein : Definition seems correct else both wickipedia and Wolfram are wrong.
Dec
9
comment Generalizations of the Four-Color theorem
One basic source is: "The Four-color Problem: Assaults and Conquest" by Saaty and Kainen. It contains so many nice reformulations (over 120!). Could be useful to "parallel" a generalization.
Sep
24
awarded  Autobiographer
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 groups are not the automorphism group of some rooted finite tree?
Thank you very much , there is still an aspect of "density". Do we loose kind of "half" when restricting to (FTAG) FiniteTree-Automorphism -Groups ?