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5h
comment Proving the sum of the reciprocals squared converges
$S_n \: = \: 1+... \;\;\;$
14h
comment The function $G: x \mapsto 2^{x^2}$ maps $\mathbb{R}$ onto $\{ x \in \mathbb{R} : x \geq 1 \}$
$\frac32 \: \in \: \{x\in R \: | \: x\geq 1\} \;\;\;$ but $\;\;\; \frac32 \not\in \mathbb{N}_1 \;\;\;\;\;\;\;$
15h
comment The function $G: x \mapsto 2^{x^2}$ maps $\mathbb{R}$ onto $\{ x \in \mathbb{R} : x \geq 1 \}$
Is $R$ the ring of integers? $\;$
18h
comment The function $G: x \mapsto 2^{x^2}$ maps $\mathbb{R}$ onto $\{ x \in \mathbb{R} : x \geq 1 \}$
Why is the codomain given as $\mathbb{N}_1$? $\;$
Nov
22
comment What is $\mathbb{F}_7[X]$?
The zero element of $\mathbb{Z}_7$ does not have a multiplicative inverse in $\mathbb{Z}_7$. $\;$
Nov
22
comment What is $\mathbb{F}_7[X]$?
"every element" $\: \mapsto \:$ "every non-zero element" $\;\;\;\;$
Nov
20
comment Applying Brower's Theorem for Invariance of Domain
What does that have to do with Brower's Theorem? $\;$
Nov
18
comment Is $R$ PID if every submodule of a free $R$-module is free?
What are "D.I.P."s? $\;$
Nov
17
comment What is $\mathbb{F}_7[X]$?
en.wikipedia.org/wiki/Polynomial_ring $\;$
Nov
17
revised Empty metric space, complete?
improved grammar
Nov
16
comment Uncountable reals in the theory
@aphorisme : $\;\;\;$ Do you define "X is uncountable" by $\: |\mathbb{N}| < |\hspace{.02 in}X\hspace{.03 in}| \:$ or $\: |\hspace{.02 in}X\hspace{.03 in}| \not\leq |\mathbb{N} \;$? $\;\;\;\;\;\;\;$
Nov
13
comment False homework proof?: The image of an element has the same order.
Well, your counter-example needs the domain to be non-trivial. $\;$
Nov
10
accepted In what topological abelian groups does convergence to zero imply summability?
Nov
10
comment In what topological abelian groups does convergence to zero imply summability?
Yes, and I think I can see how to modify your argument to handle the case in which $I$ is $\hspace{.81 in}$ Dedekind-finite, so I'll probably be accepting this later today. $\;$
Nov
9
comment Maximum Error Tolerances When Forecasting A Random Time Series
"Has this been done before?" $\:$ Yes. $\;\;\;\;$
Nov
9
revised Size of rankings in a round robin tournament
improved grammar
Nov
7
comment Is there a surjection of SL(2,Z) to itself with a nontrivial kernel?
Is there a similar term for groups such that every injection $\: G\to G\:$ is an isomorphism? $\;\;\;\;$
Nov
5
comment Generate product of two primes that starts with 1234
For a polynomial time algorithm, you would need polynomial time operation to suffice for the steps. $\hspace{.39 in}$ It is (not necessary and) not sufficient that polynomial time operation is required for the steps. $\hspace{.72 in}$
Nov
4
awarded  Popular Question
Nov
4
comment Generate product of two primes that starts with 1234
Although step 1 "requires polynomial time operations", it's still important how many of them it requires. $\:$ If it requires super-polynomially many of them, then the fact that the operations are polynomial time is, one might say, not particularly useful. $\;\;\;\;$