5,197 reputation
1518
bio website xavierm02.net
location France
age 21
visits member for 2 years, 11 months
seen 5 hours ago

8h
answered How to compute Lipschitz Constant for multivariate function $f(x,y)=1-xy$?
9h
comment Is there any other integral of a special function that is undetermined?
@Victor : so it "jumps" each time it encouters a prime.
9h
comment Application of computers in higher mathematics
You can also compute proofs. You just generate all proofs of a given height, check them one by one, increment the height and try again. But that's extremely slow. Some softwares such as Coq are used to verify proofs. But from what I understand they aren't that good at proving things themselves yet.
1d
comment Complex inner product aren't inner products.
It's the complex conjugate. And if you restrict $x\mapsto \overline{x}$ to the reals, you get the identity.
1d
accepted Isometry from $\ell^1$ to $\ell^\infty$
2d
comment Isometry from $\ell^1$ to $\ell^\infty$
Note: When first writing the question, I tagged is "isometry" and apparently, it created a tag with just this question in it. I assume this is not wanted but I apparently can't delete that tag.
2d
asked Isometry from $\ell^1$ to $\ell^\infty$
Apr
13
comment Alternating projections on a Hilbert space
Let's say you have a basis. Then your element is a linear combinaison of a finite number of elements of the basis. So if $P_1P_2(S)\subseteq S$ where $S$ is the subspace spanned by that finite number of elements, then we're back to the finite dimensional case. And I can't find an example where it isn't the case. Can you?
Apr
13
comment Alternating projections on a Hilbert space
I'd say it always converge: If it keeps bouncing from $S_1$ to $S_2$ and back it'll converge to $0$ because it'll have its norm reduced every time. But that's just an intuition from looking at what happens in the plane with two lines.
Apr
13
revised Evaluate determinant of an $n \times n$-Matrix
added 484 characters in body
Apr
13
answered Evaluate determinant of an $n \times n$-Matrix
Apr
13
revised Evaluate determinant of an $n \times n$-Matrix
edited body
Apr
13
revised Evaluate determinant of an $n \times n$-Matrix
added 42 characters in body
Apr
13
answered Evaluate determinant of an $n \times n$-Matrix
Apr
12
comment Finding real, distinct eigenvalues for arbitrary constants
If polynomial with real coefficients has a complex root, its conjugate is also a root of that polynomial.
Apr
7
answered Inner product over the $C^2$
Apr
5
comment What is $\Im\Big(\frac{e^{(i-t)x}}{i-t}\Big)$?
Nevermind. The thing I did didn't work because the number in the $\sin$ wasn't real.
Apr
4
answered Completeness of the real numbers
Apr
3
comment Accumulation of zeros for a $C^3$ function
@walt: It's probably possible by replacing $v(0,y)$ by $w(x,y)$ in the equality. But I can't see any obvious example.
Apr
3
answered Accumulation of zeros for a $C^3$ function