198 reputation
10
bio website
location
age
visits member for 2 years, 5 months
seen May 28 at 13:34

Apr
13
comment How to prove and interpret $\operatorname{rank}(AB) \leq \operatorname{min}(\operatorname{rank}(A), \operatorname{rank}(B))$?
I am not familiar with the 'categorification'. How can one go from this to the rank inequality ? What functor is to be applied ?
Apr
11
comment function application order
i think you are right about the conclusion. it is the convention of most textbook, so i better suck it up. i notice that lawvere uses the natural order though !(tac.mta.ca/tac/reprints/articles/16/tr16.pdf)
Mar
21
comment If $g \circ f$ is monic, then $f$ is monic
Amazing answer.....
Mar
19
comment How to prove hom functor preserves pullbacks
@user43687 yes this is more powerful, although I quite like to have the direct proof as well.
Mar
19
comment Pullbacks of monic morphisms.
of course, by the universal mapping property on the pullback : that there is a unique $h$ making the diagram commute aka realizing $ g m'\circ h = m f\circ h$
Mar
18
comment Pullbacks of monic morphisms.
going to $f \circ h = f \circ k$ is easy, but I must be missing something as I dont see how that entails $h = k$. could you argue why ?
Mar
1
comment Show that the direct sum of a kernel of a projection and its image create the originating vector space.
sorry I know it is off-topic, but am i the only person for which mathjax does not render latex on stackexchange ?
Jan
21
comment why do we use 'non-increasing' instead of decreasing?
I think this is as good for math as the imperial system is for physics : absolutely nonsensical
Oct
26
comment Asymptotics of binomial coefficients and the entropy function
It is not by chance that taking the sum of independant bernoulli, we converge to the exponentiated entropy of such bernoulli.....
Jul
27
comment Counting the number of binary partitions of k elements
interesting equivalent perspective. I was looking for it as well. I wonder if there is not a more radically different interpretation. for instance geometrical : this is the number of separating hyperplanes in R^k
Jun
9
comment rth adjugate matrix and determinant of a sum, in Horn
interesting video on wedge stuff here. youtube.com/watch?v=uINebibjR5I
Jun
8
comment rth adjugate matrix and determinant of a sum, in Horn
i realize it might be too narrow a question, as this notion does not seem widespread.
Jun
8
comment rth adjugate matrix and determinant of a sum, in Horn
(for the compound matrix, it seems the same is used in wikipedia, which we all agree is the reference ;) ) en.wikipedia.org/wiki/Compound_matrix
Jun
8
comment rth adjugate matrix and determinant of a sum, in Horn
intesting, would you have a link for the wedge product approach ?
Dec
31
comment lower semicontinuity and closed graph
yeah, i spotted other weird stuff in the article in reference. not to be taken as a reference !
Dec
31
comment limit inferior and subsequence
Makes sense. And now that you point at it i remember thinking vaguely the subsequence def was fishy while writing it. Thanks !
Dec
26
comment Why is $\log(\sqrt{x^2+1}+x)$ odd?
that's why I love math
Oct
20
comment Does Pi contain all possible number combinations?
why would you care, really... there are so many interesting problems, why this one..
Jul
1
comment Relation between Cholesky and SVD
doesn't your first point stand as well if we assume A only semi positive definite ?
Jul
1
comment Relation between Cholesky and SVD
I guess if you already computed it somewhere, it makes a lot of sense.