380 reputation
112
bio website wamath.sinaapp.com
location china
age 27
visits member for 3 years
seen Oct 20 at 23:27

I am a postgraduate student in Southwest University, Chongqing, China, majored in elementary mathematics and interested fields include Riemannian Geometry and Elliptic Differential Equation. I always confused about the textbooks, so I would like have a discussion with anybody on the net.


Oct
18
comment Existence of normal orthogonal frame on sphere such that it is normal at every point in a neighbourhood?
I mean orthogonal but not normal ftame and the relation can be allowed with a comformal factor?
Oct
18
comment Existence of normal orthogonal frame on sphere such that it is normal at every point in a neighbourhood?
yeah, after a while, I also kown that. But since the sphere is comformally flat, maybe I can expect this can be improved to be a more valuable answer?
Oct
18
revised Existence of normal orthogonal frame on sphere such that it is normal at every point in a neighbourhood?
Change the coordinates into frame
Oct
18
comment Existence of normal orthogonal frame on sphere such that it is normal at every point in a neighbourhood?
I think I'd better replace the coordinates by frame.
Oct
18
comment Existence of normal orthogonal frame on sphere such that it is normal at every point in a neighbourhood?
It should be note that the second equation just means the local frame is just parallel on $R^n$, and I don't know how to proof that in this case it will impliy that $S^{n-1}$ is flat. So maybe your can explain it in the answer.
Oct
17
revised Existence of normal orthogonal frame on sphere such that it is normal at every point in a neighbourhood?
edited title
Oct
17
asked Existence of normal orthogonal frame on sphere such that it is normal at every point in a neighbourhood?
Jul
8
comment Monotonically approximate $L^p$ function by step function
That's it! I just forgot what I have learned in my mind.
Jul
8
accepted Monotonically approximate $L^p$ function by step function
Jul
8
comment Monotonically approximate $L^p$ function by step function
By the way, Can you give some exactly reference or raise an answer here, of your second TRUE? I believe it will be useful to me, although the step function is replaced by simple function.
Jul
8
comment Monotonically approximate $L^p$ function by step function
@PhoemueX The step function usually means simple function on Cubes( intervals in $R^1$ case).
Jul
8
comment Monotonically approximate $L^p$ function by step function
I think you have some misunderstanding about the approximate, I think we should allow $g\leq f$ holds in the a.e. sense. In that case, we can take $f_k\equiv 1$ on $[0,1]$ as step function in your counterexample on $[0,1]$.
Jul
8
comment Monotonically approximate $L^p$ function by step function
I googled and get no results. And my knowledge of proof of the classical fact can not modify easily to get a proof of my requirement.
Jul
8
asked Monotonically approximate $L^p$ function by step function
Jul
2
awarded  Curious
Jul
2
accepted A problem concern about the relationship between homotopy groups.
Jul
2
comment A problem concern about the relationship between homotopy groups.
Thanks a lot! It really helps me, I mean as a beginner to algebra topology.
Jun
18
comment A problem concern about the relationship between homotopy groups.
@QiaochuYuan I try to work with your hint, but still can't get it, so would you please post an answer?
Jun
17
comment A problem concern about the relationship between homotopy groups.
@SanathDevalapurkar sorry, already corrected.
Jun
17
asked A problem concern about the relationship between homotopy groups.