Marra

Brazil

Jun
17
awarded Nice Question
Mar
17
awarded Yearling
Mar
17
awarded Yearling
Jan
27
reviewed Approve suggested edit on Combinatorial approach to calculate determinant
Jan
21
awarded Supporter
Jan
21
accepted Holomorphic function is zero on an analytic set then $df=0$.
Jan
20
comment Holomorphic function is zero on an analytic set then $df=0$.
Also. It might bot be entirely clear that $d$ refers to the exterior differentiation. That is, $df$ is an 1-form
Jan
20
comment Holomorphic function is zero on an analytic set then $df=0$.
Can you give me a counterexample? Things are a lot different in the holomorphic world
Jan
20
comment Holomorphic function is zero on an analytic set then $df=0$.
You may think of an analytic set as it's defined in here en.m.wikipedia.org/wiki/Analytic_variety . Also, $df=0$ implying $f$ constant would be true only if $V$ is open, which is not
Jan
20
comment Holomorphic function is zero on an analytic set then $df=0$.
I really meant $f$ restricted to $V$… sorry. Already edited.
Jan
20
revised Holomorphic function is zero on an analytic set then $df=0$.
edited body
Jan
20
asked Holomorphic function is zero on an analytic set then $df=0$.
Jan
15
comment Installing WinUSB on Ubuntu 14.04
Error 404: not found :(
Dec
19
awarded Popular Question
Dec
10
awarded Excavator
Dec
2
comment Isometries of a Connected Surface
Is this exercise on Do Carmo's? I think I remember seeing it there. Might need to use the exponential map.
Dec
2
comment Does every differentiable function has an infliction point between a local maximum and minimum?
Limiting the interval does not makes the result true. Just take $(-3,3)\subset\mathbb{R}$ on the example of the answer below.
Dec
2
comment Does every differentiable function has an infliction point between a local maximum and minimum?
Now this is a very good answer. As I've seen on Calculus, an inflection point is where the concavity of the graphic changes. There is none to be found on this one despite the existence of points where the second derivative is zero (this happens on an interval however).
Dec
2
comment Does every differentiable function has an infliction point between a local maximum and minimum?
Also, assume that $f$ is not constant.
Dec
2
comment Does every differentiable function has an infliction point between a local maximum and minimum?
If $X$ is a closed subset on the line, you can have $f$ linear which has maximum and minimum on the lateral limits of $X$. You might want to assume that $X$ is open and connected (this last one just to simplify things).
1 2 3 4 5