Marra

Brazil

2d
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 sequence uniformly convergent on a compact set
What have you tried?
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).
Dec
2
comment $\mathbb R$ ~ $[0,1) \cap (\mathbb R\ $\ $\mathbb Q)$
What do you mean by "~"?
Dec
2
comment $\mathbb R$ ~ $[0,1) \cap (\mathbb R\ $\ $\mathbb Q)$
Note that $[0,1)\cap (\mathbb{R}$\ $ \mathbb{Q}) = (0,1)\cap (\mathbb{R} $\ $ \mathbb{Q})$
Nov
4
asked Virtual Euler Characteristic of a Curve in Brunella's paper
Oct
26
comment Computing these multiplicities
I meant $y\rightarrow x^3$, sorry for that. I'll start another question after I work a little more on this one, thanks :)
Oct
26
comment Computing these multiplicities
It actually could, the result would be the same...
Oct
26
comment Computing these multiplicities
I just don't see why you are choosing this particular ring isomorphism (did you mean surjective ring morphism?). Is it because of the first ideal $(y-x^2)$? Then could it be, and would it work, if the morphism were $x\rightarrow x^3$?
Oct
26
comment Computing these multiplicities
That's probably the reason why I'll never get it.
Oct
26
comment Computing these multiplicities
Why is $(\mathbb C[x,y]/(y-x^2,y-x^3))_{(x,y)}=( \mathbb C[x]/(x^2-x^3))_{(x)}$? I'm guessing that the ideals $(y-x ^2,y-x^3)$ and $(y,x^2-x^3)$ are equal?
Oct
26
accepted Computing these multiplicities
Oct
26
revised Computing these multiplicities
added 75 characters in body
Oct
26
comment Computing these multiplicities
Damn, that's right, I was thinking about something else. Lemme correct that.
Oct
26
asked Computing these multiplicities
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