506 reputation
821
bio website
location Paris France
age 59
visits member for 5 years, 7 months
seen 2 days ago
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.

2d
comment How much of the ATLAS of finite groups is independently checked and/or computer verified?
This hidden reliance on ATLAS is a very interesting point of "under specification" : The software does not say in some clear and well associated documentation what is presupposed. It should say so, otherwise it is useless as is any program without specification of what it does (not how it does it)..
Aug
15
comment Mathematical software wish list
Yes the_fox you right and polite: a mathematician is neither a secretary nor a typographer. Yet he has to make up with each drudgery. Knuth is precise but does not understand the functional point of view. My taxes should be used to develop latex as a tool for maths and many disciplines, instead of being given to dubious publishers asking us to pay for articles written by researchers subsided by my very taxes (from an angry programmer).
Jun
14
awarded  Notable Question
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