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seen Nov 20 at 18:48

Oct
20
comment “Isomorphy” in mathematical texts
I have added an explanation.
Oct
20
comment “Isomorphy” in mathematical texts
I there is common agreement on that, can feel free to migrate it.
Oct
7
comment Term of partially ordered set with “levels”
Not necessarily, although in the application I have in mind, the sets $X_i$ are antichains. Thanks for making me aware of that.
Oct
2
comment Basis of vector space invariant under group action (of symmetric group)
What is $c_2$? However, indeed, such a basis might not exist, but how can this be shown?
Sep
10
comment Approximate root of $\alpha x - \beta y$ over $\mathbb Z$ except origin
@RobertIsrael Can you give more hints? I have no clue where to start with this.
Sep
10
comment Approximate root of $\alpha x - \beta y$ over $\mathbb Z$ except origin
Assuming $\beta > 0$, I see the equivalences. But what does it tell?
Sep
10
comment Approximate root of $\alpha x - \beta y$ over $\mathbb Z$ except origin
Has been a late night. Of course, the origin is excluded.
Jul
18
comment Canonical term for $\overline X / X$ where $X$ is a normed space.
This appears in the theory of Hilbert complexes, as quotient of the closure of the boundaries by the boundaries. More, generally, for Banach complexes see: link.springer.com/article/10.1007%2FBF02922133?LI=true
Sep
9
comment Formula for surface measure of spherical cap on $S^n$.
In the section 'hyperspherical cap', the wikipedia article gives a formula for the surface in terms of regularized incomplete beta functions. I wonder whether a single integral formula like for the volume, at the beginning of the same section, does exist.
Sep
8
comment Formula for surface measure of spherical cap on $S^n$.
I am specifically looking for formulas nicer than there.
Apr
5
comment Boundedness of a Solution Operator
@user17904: You need to show that for Sobolev space $H$ of sufficient regularity the trace from $H$ to $L^2(\partial\Omega)$ has closed range. Than a bounded right-inverse exists by functional analysis. Typically, you can prove surjectivity, say, by partition of unity, smoothing and an explicit construction.
Mar
7
comment pseudoinverse under change of norm
I have completely rewritten the question.
Mar
4
comment An variation of “Lk” in simplicial complexes
@StefanH.: Yes, thanks.
Feb
13
comment How can not-equals be expressed as an inequality for a linear programming model
It is intutive it does not work, because polyhedrons are convex and closed, while not-equals correspond to non-convex open regions.
Jan
29
comment Approaches to integrate $\int_0^1 \frac{x}{\sqrt{a+bx+cx^2}} dx$
Thanks, that got me on the right track.
Jan
27
comment If A $\subset S^n$ has spherical diameter < $\pi$, then $S^n - A$ contains a closed semisphere.
The original statement was blatantly wrong. I have editted the question into what I actually meant.
Dec
19
comment Distinction between 'adjoint' and 'formal adjoint'
These lines on Wikipedia only describe the construction for a differential operator. I have been concerned about general operators and their formal adjoints.
Nov
2
comment Solid angle between vectors in n-dimensional space
Your second formula is quite awkward, because you apply arctan against a vector.
Jul
18
comment Proof by Induction $n^2+n$ is even
You know you don't need induction, do you?
Apr
7
comment Antisymmetric functions in higher dimensions
Okay, maybe a nice definition of signed permuation of coordinates is a permuation matrix times a ${-1,1}$-diagonal matrix, and the signum is the determinant of that transform.