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8h
answered Is $\ell^1$ an inner product space?
9h
comment What happens when you drop “étale” from the construction of étale fundamental groups
"It seems like the answer you get, if there is one, won't be morally the same as in the etale case." Well, yes. For instance, I strongly doubt the thing you'd get would be a group -- I imagine the things corresponding to ramified covers aren't invertible.
19h
answered Subspace not open of a differentiable manifold
19h
comment Can the zero vector be an eigenvector for a matrix?
Regardless, Wolfram|Alpha shouldn't be reporting $(0,0,0)$ as an eigenvector. Show us your input so we can see what's going on.
19h
comment Can the zero vector be an eigenvector for a matrix?
The simple example is the matrix $\begin{pmatrix} 0 & 1 \\ 0 & 0 \end{pmatrix}$. The only eigenvalue is zero, with multiplicity two. It has a one-dimensional space of zero-eigenvectors, spanned by $(1,0)$. $(0,1)$ is not a zero-eigenvector, but it is a generalized zero-eigenvector: if we hit it with the matrix it goes to $(1,0)$, which then goes to $(0 0)$ if we hit it again.
19h
comment Can the zero vector be an eigenvector for a matrix?
An eigenvalue always has at least a one-dimensional space of eigenvectors. If it has multiplicity $n$, it might still just have a one-dimensional space of eigenvectors, but it definitely has an $n$-dimensional space of generalized eigenvectors.
20h
answered Quick question: Chern classes of Sym, Wedge, Hom, and Tensor
20h
comment Perimeter of an ellipse intuition help
"For now lets view the cone as a trapezoid." Huh?
20h
answered Can a $3\times3$ matrix have more than $3$ linear independent eigenvectors?
1d
comment incorrect notation in math?
Like so: ${}^{{}^c} {}^b a$
1d
comment How to check if a set of coordinates creates a polygon?
What do you mean "if it creates one polygon"? You seem just to have an ordered sequence of points in the plane. Given enough points, you could draw any number of polygons through them.
1d
answered Compute $\lim_{x\to0^{+}}\left(\frac{1}{x}-\frac{1}{\sin x}\right)$
1d
comment Nursing Home Question
This appears to be a question about accounting, not about math. Moreover, there's something wrong with it; an operating margin is a percentage, not a dollar amount.
1d
revised Nursing Home Question
edited tags
1d
answered What is the difference between a local maximum and an unconstrained local maximum?
1d
comment Intersection of Segre variety with linear spaces
If $k$ is large enough that the intersection is empty, then yes. Are there some constraints here?
1d
asked What happens when you drop “étale” from the construction of étale fundamental groups
2d
answered Fulton 8.17 ¿$\Gamma(X) = k$?
Oct
22
asked Something like the Weierstrass preparation theorem?
Oct
21
comment A holomorphic function with non-vanishing derivative
Oh, so the point is that they're proving a bigger result and are just observing that this falls out of the proof at the beginning?