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Dec
11
asked What does the theory of the empty set look like?
Nov
22
comment Proving that the diagram commutes
In case you aren’t already on it, fixing it: You have a math processing error in your upper latex code.
Nov
21
comment Why is the union of two closed sets again closed in the Scott topology?
So it turns out that it’s easier to think of it as the intersection of open sets being open. Okay.
Nov
21
accepted Why is the union of two closed sets again closed in the Scott topology?
Nov
21
comment Why is the union of two closed sets again closed in the Scott topology?
(Sorry for all the edits. I’m in a state of utter confusion right now.)
Nov
21
revised Why is the union of two closed sets again closed in the Scott topology?
added 63 characters in body
Nov
21
revised Why is the union of two closed sets again closed in the Scott topology?
added 63 characters in body
Nov
21
asked Why is the union of two closed sets again closed in the Scott topology?
Nov
19
comment At what point is the phrase “couldn't go slower” true.
It’s another thing if you’re actually asking about the slowest possible speed using a car. Then you would probably have to specify the car, including engine, gears and whatnot, the road, including slope, ground, the possibly weather. I dunno. But you most certainly would have to ask a physicist or an engineer or maybe both, but not a mathematician.
Nov
19
comment At what point is the phrase “couldn't go slower” true.
This is rather a physics question. If you talk about idealised motion, then you can always go a little slower without stopping. Take your favorite unit of measurement for speed. Take your favorite candidate for “the slowest speed” (such that you can’t go slower without stopping). Measure that speed. Take half of what you got. Move that fast. There you go, a little bit slower than before.
Nov
17
answered Prove that a Linear-Map is surjective.
Nov
17
comment Prove that a Linear-Map is surjective.
Write “Let $V = \{p ∈ ℝ[X];~\deg p ≤ 2\}$” in the beginning and change $g$’s signature to “$V → ℝ^3$”. (You mean “less or equal to”, by the way.)
Nov
17
comment Prove that a Linear-Map is surjective.
What is $R2[X]$? Did you mean to write $ℝ[X]$?
Nov
17
comment Is the following union connected
Are $U_ω;~ω ∈ J$ open sets?
Nov
13
comment Linear Algebra Help (Kernel, Linear Transformations)
Please tell us on which questions you are stuck. Have you already thoughts on some of them? Do you know and understand all the used definitions?
Nov
13
revised Linear Algebra Help (Kernel, Linear Transformations)
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Nov
10
comment Holomorphic in a unit disk based on Identity Theorem
If $f_1\lvert_D = f_2\lvert_D$ and $1/2 ∈ D$, …
Nov
10
comment Is there a name for a monoid with a distinguished absorbing element?
I think I might just call it “steroid” …
Nov
9
comment Is there some sort of trick to show naturality?
@QiaochuYuan Ok, well. It’s good that you can see it, but it’s a shame you can’t describe what’s going on. If you ever find a good phrase or some sort of intuition you can convey, I would be extremely interested! It might also help for the likes of me if you could pinpoint to what sort of experience enabled you to see naturality (if there was one). (Thanks in any case.)
Nov
9
comment Is there a name for a monoid with a distinguished absorbing element?
@rschwieb Yes, exactly. A little background for this question: Valuations on fields $F$ are morphisms $F → M$ of such structures (with an additional requirement of some subaddivity of “$+$” and “$∨$”), where $M$ is an ordered group with an adjoint absorbing element at the bottom. Then, $M^×$ would be called the valuation group.