Reputation
1,590
Next privilege 2,000 Rep.
Edit questions and answers
Badges
6 18
Newest
 Custodian
Impact
~52k people reached

1d
comment Discrete Laplace operator and its eigenvalues
Problem is, Chung's book is solely devoted to the so-called normalized Laplacian, whose spectral properties have very little in common with those of the discrete Laplacian. Mohar's survey are probably a better start.
Feb
5
comment Can you hear the shape of a drum by choosing where to drum it?
@EmilioPisanty A good starting point, with a survey of earlier results and more numerical experiments than proofs is journals.cambridge.org/action/…
Feb
5
comment Can you hear the shape of a drum by choosing where to drum it?
Very nice question and I wonder whether there is any connection to the theory of spectral maximal partitions.
Feb
5
reviewed No Action Needed Formalizations of category theory in proof assistants
Feb
5
awarded  Custodian
Feb
5
reviewed Reviewed Dieudonne modules and Cartier-Dieudonne module of a formal group
Feb
5
revised What are some useful invariants for distinguishing between random graph models?
fixes the spelling in the names of Erdős, Rényi, Albert.
Feb
5
suggested approved edit on What are some useful invariants for distinguishing between random graph models?
Feb
4
answered Laplacian spectrum for product graphs
Feb
4
accepted Hard maths on viXra?
Feb
4
comment Hard maths on viXra?
@StanleyYaoXiao Of course you're right, but I was not looking for a site to trust in the first place: I was wondering whether for any reason any pieces of decent mathematical ever made it to viXra, for whatever reason. It also struck me that the authors very seldom mention a way to contact them, just in case - not an affiliation, of course, not an address, not even an e-mail address.
Feb
4
revised Hard maths on viXra?
add a conclusion about the closure of this question
Feb
3
asked Hard maths on viXra?
Jan
21
comment Interpreting the Famous Five equation
@BoPeng Well, it is not so bizarre, and in fact this is how many (european) textbooks proceed. You introduce $\cos$ and $\sin$ starting from the complex exponential, and $\pi$ as twice the first zero of $\cos$ (which is essentially equivalent to QiaochuYuan's proposed definition). True, the geometrical interpretation has still to be provided, but this definition of $\pi$ is obviously much more comfortable when it comes to calculus.
Jan
17
accepted Airy's equation on $\mathbb R_-$
Jan
17
awarded  Necromancer
Jan
14
awarded  Inquisitive
Jan
13
revised Airy's equation on $\mathbb R_-$
added 6 characters in body
Jan
13
comment Airy's equation on $\mathbb R_-$
@ChristianRemling Indeed! There are several works suggesting that two b.c. have to be imposed on the right and one on the left endpoints; but in these works I can never find a "clean" well-posedness theorem in a "nice" function space (ideally, a Sobolev or Lebesgue space, but I'd be happy even with one space from Triebel's zoo; ideally, by means of a unitary $C_0$-group). Remarkably, the equation on $\mathbb R$ is governed by a propagator that is just the convolution of an integral kernel based on Airy's function and the Fourier transform of the initial data, so a group might exist after all.
Jan
13
revised Airy's equation on $\mathbb R_-$
added 1 character in body