Américo Tavares

 Calculus and analysis

For questions about calculus, real analysis, functional analys...
Mar 23, 2018 17:53
12
Q: A series expansion for $\cot (\pi z)$

Américo TavaresHow to show the following identity holds? $$ \displaystyle\sum_{n=1}^\infty\dfrac{2z}{z^2-n^2}=\pi\cot \pi z-\dfrac{1}{z}\qquad |z|<1 $$

May 26, 2017 13:33
@BAYMAX It's not a research level question, but I will try if there is no answer in a couple of weeks.
May 26, 2017 13:07
Still unanswered.
May 26, 2017 13:03
9
Q: Convergence acceleration technique for $\zeta(4)$ (or $\eta(4)$) via creative telescoping?

Américo Tavares Question Is it already known whether the $\zeta(4):=\sum_{n=1}^{\infty}1/n^4$ accelerated convergence series $(1)$, proved for instance in [1, Corollaire 5.3], could be obtained by a similar technique to the ones explained by Alf van der Poorten in [2, section 1] for $\zeta(3)$ and $\z...

May 15, 2017 22:57
4
Q: Convergence acceleration technique for $\zeta(4)$ (or for $\eta(4)$) via creative telescoping?

Américo Tavares Question. Is it already known whether the $\zeta(4)$ accelerated convergence series $$\zeta(4)=\frac{36}{17}\sum_{1}^{\infty } \frac{1}{n^{4}\binom{2n}{n}},\tag{1}$$ proved for instance in [1, Corollaire 5.3], could be obtained by a similar technique to those described in [2, §1] for $\z...

Aug 12, 2016 10:23
To see the formulae start ChatJax as per dl.dropboxusercontent.com/u/78279253/mathjax.html
Aug 12, 2016 10:09
4
A: Sandbox for drafts of long, complex posts

anonConvergence acceleration technique of the value of the function $\zeta(s)$ at $s=4$ (or the value of $\eta(s)$ at $s=4$) using creative telescoping/Zeilberger's algorithm? Is it already kown if the $\zeta(4)$ accelerated convergence series $$\zeta(4):=\sum_{n=1}^{\infty }\frac{1}{n^{4}}=\f...

Aug 12, 2016 10:08
New revision: **Convergence acceleration technique of the value of the function $\zeta(s)$ at $s=4$ (or the value of $\eta(s)$ at $s=4$) using creative telescoping/Zeilberger's algorithm?**

>Is it already kown if the $\zeta(4)$ accelerated convergence series
$$\zeta(4):=\sum_{n=1}^{\infty }\frac{1}{n^{4}}=\frac{36}{17}\sum_{1}^{\infty }
\frac{1}{n^{4}\binom{2n}{n}}\tag{1}$$
(proved e.g. in [1, Corollaire 5.3]) can be obtained by a similar technique to those described in [2, §1], where the defining series for $\zeta(3),\zeta(2)$ are accelerated yielding these equalities?
Aug 8, 2016 16:05
New revision of my possible question on the $\zeta(4)$ accelerated series: here meta.math.stackexchange.com/a/11745/752
Jul 30, 2016 20:50
@MartinSleziak Thanks! For the first time I've used the meta sandbox to compose a future question on the main site. I've already thought of another modification where I would try to make it shorter and stress the (possible) connection to the Zeilberger algorithm as described in the book A = B. I have no means to execute the algorithm, which if I could might answer my own question.
Jun 4, 2016 10:33
This last equality can be justified as follows:
(1) write
\begin{equation*}
X_{n,k}=\frac{(-1)^{k-1}}{k^{2}\binom{n+k}{k}\binom{n-1}{k}},\qquad D_{n,k}=\frac{(-1)^{k}}{n^{2}\binom{n+k}{k}\binom{n-1}{k}}\qquad k<n;
\end{equation*}
(2) notice that $X_{n,k}=D_{n,k-1}-D_{n,k}$, and (3) sum over $k$, $1\leq
k\leq n-1$
\begin{equation*}
\sum_{k=1}^{n-1}X_{n,k}=\sum_{k=1}^{n-1}\left( D_{n,k-1}-D_{n,k}\right)
=D_{n,0}-D_{n,n-1}.
\end{equation*}
(4) Finally, sum over $n$, $1\leq n\leq N$, because
\begin{equation*}
Jun 4, 2016 10:32
For instance the accelerated series
\begin{equation*}
\zeta (3)=\sum_{n=1}^{\infty }\frac{1}{n^{3}}=\frac{5}{2}\sum_{1}^{\infty }
\frac{(-1)^{n-1}}{n^{3}\dbinom{2n}{n}}
\end{equation*}
can be obtained by letting $N\rightarrow \infty $ in
\begin{equation*}
\sum_{n=1}^{N}\frac{1}{n^{3}}-2\sum_{n=1}^{N}\frac{\left( -1\right) ^{n-1}}{n^{3}\binom{2n}{n}}=\sum_{k=1}^{N}\frac{(-1)^{k}}{2k^{3}\binom{N+k}{k}\binom{N}{k}}-\sum_{k=1}^{N}\frac{(-1)^{k}}{2k^{3}\binom{2k}{k}}.
\end{equation*}
May 30, 2016 13:56
Does anybody know whether the $\zeta(4)$ accelerated series mencioned on section 10 of Alf van der poorten's paper A proof that Euler missed ..., transcribed at ega-math.narod.ru/Apery1.htm, can be obtain by similar techniques of those used in the same paper to derive the corresponding accelerated series for $\zeta(3),\zeta(2)$? Remark: there's a 1981 paper by Henri Cohen availble at numdam, where he used the Euler-Maclaurin summation to prove that accelerated formula for $\zeta(4)$.
May 27, 2016 14:39
The question is good enough, I think.
May 27, 2016 14:35
1
Q: Hottest and coldest points on a heated circular plate (use Lagrange multipliers)

Aya HussienA circular plate given by the relationship $x^2 + y^2 \leq 1$ is heated according to the spatial temperature function $T(x,y) = 2x^2 + y^2-y$. Find the hottest and coldest point on the plate using Lagrange multipliers. I tried to solve it but u got only one point (0,1) instead of 4 points .. ...

May 27, 2016 14:35
This question got a downvote (why?) prior to the present situation +2/-1 math.stackexchange.com/questions/1800686/…
May 22, 2016 08:15
@MartinSleziak Thanks for your informed opinion! I'll try to contribute occasionaly on Calculus and (basic) Analysis.
May 21, 2016 10:38
It's the first time I enter here. I've just known of this chatroom and liked it.
 

 Mathematics

Associated with Math.SE; for both general discussion & math qu...
May 26, 2017 14:15
@SimplyBeautifulArt Thanks! My intention was to see if there is a method for $\zeta(4)$ similar to the ones for $\zeta(2)$ and $\zeta(3)$, in order to get some idea how to obtain a similar expansion for $\zeta(5)$.
May 26, 2017 13:09
Still unanswered.
May 26, 2017 13:08
9
Q: Convergence acceleration technique for $\zeta(4)$ (or $\eta(4)$) via creative telescoping?

Américo Tavares Question Is it already known whether the $\zeta(4):=\sum_{n=1}^{\infty}1/n^4$ accelerated convergence series $(1)$, proved for instance in [1, Corollaire 5.3], could be obtained by a similar technique to the ones explained by Alf van der Poorten in [2, section 1] for $\zeta(3)$ and $\z...

May 22, 2017 22:30
Hello! Could anybody read the following question and comment here? math.stackexchange.com/q/2281000/752
May 19, 2016 10:46
Do you know whether the ...
May 19, 2016 10:39
... There's a 1981 paper by Henri Cohen availble at numdam, where he used the Euler-Maclaurin summation formula to prove the accelerated formula for $\zeta(4)$.
May 19, 2016 10:38
@robjohn Do you know wether the $\zeta(4)$ accelerated series mencioned on section 7 of Alf van der poorten's paper A proof that Euler missed ..., transcribed at ega-math.narod.ru/Apery1.htm, can be obtain by similar techniques of those used in the same paper to derive the corresponding accelerated series for $\zeta (3),\zeta(2)$?
Nov 13, 2015 08:52
@skullpetrol Thanks!
Nov 11, 2015 23:35
@skullpetrol I see, thanks!
Nov 11, 2015 23:30
@AlecTeal The question is recent.
Nov 11, 2015 23:29
@skullpetrol The question is recent.
Nov 11, 2015 23:26
@skullpetrol Could you please explain what does it mean?
Nov 11, 2015 22:28
36
Q: What is the purpose of this site?

Martin Sleziak What is (and what should be) the purpose of math.SE? As far as I can say, various users have different views on this question. Some users view it as a repository of knowledge. Some users approach it as teaching opportunity. Similar to previous, but slightly different: It could be understoo...

Nov 9, 2015 15:23
24
Q: What is the purpose of this site?

Martin Sleziak What is (and what should be) the purpose of math.SE? As far as I can say, various users have different views on this question. Some users view it as a repository of knowledge. Some users approach it as teaching opportunity. Similar to previous, but slightly different: It could be understoo...

Nov 8, 2015 18:50
15
Q: What is the purpose of this site?

Martin Sleziak What is (and what should be) the purpose of math.SE? As far as I can say, various users have different views on this question. Some users view it as a repository of knowledge. Some users approach it as teaching opportunity. Similar to previous, but slightly different: It could be understoo...

Nov 8, 2015 12:36
0
A: What is the purpose of this site?

Américo TavaresI see this site mainly as an opportunity to help other users clarifying their mathematical doubts, and being helped by others in my own doubts, in an exchanging process. Normally, as a non-mathematician and a non-native English speaker, I only answer low-level questions. By reading questions and...

Jul 28, 2015 20:23
The Portuguese Language at Stack Exchange is in Public Beta.
Jul 22, 2015 12:51
arXiv vs MathOverflow - popularity of disciplines meta.mathoverflow.net/q/2363/9479 i.sstatic.net/p5UQI.png
Jul 20, 2015 21:47
The Portuguese Language SE is now in private beta. area51.stackexchange.com/proposals/64172/portuguese-language . Visit the site! portuguese.stackexchange.com
 
Jul 14, 2016 10:18
@JorgeB. Acho que sim. É pena não haver mais utilizadores com reputação acima de 200 e, especialmente, não se terem atraído (mais) professores e linguistas, como pressupõe a descrição geral deste site, que se destinará a "linguists, teachers, and learners wanting to discuss the finer points of the Portuguese language".
Jul 13, 2016 21:18
Jul 13, 2016 20:34
Estatísticas de hoje (365
dias em beta): https://i.sstatic.net/sGd4L.png
Nov 11, 2015 12:58
5
Q: Vírgulas obrigatórias e facultativas em orações subordinadas causais, finais e temporais

Américo TavaresEm frases com orações subordinadas causais, finais e temporais, lendo este post sobre Pontuação do blogue Livro de Estilo, as vírgulas utilizam-se conforme a posição dessas orações na frase. Se for no início ou no meio, levam obrigatoriamente vírgula; no fim, não. Penso, porém, que neste último c...

Jul 23, 2015 11:23
@GitGud De nada.
Jul 23, 2015 10:40
São homógrafas (=mesma grafia), como "este", pronome, e "este", ponto cardeal.
Jul 23, 2015 10:39
@GitGud São homogra
Jul 21, 2015 19:44
6
Q: Quantos dias ficaremos em beta privado?

Guilherme NascimentoHow many days we would in private beta? How many days will be? Or I wonder if is it something that will be determined by a superior decision (SE team, for example, will decide whether the private beta was successful)? Quantos dias ficaremos em beta privado? Tem dias determinados ou é algo que ...

Jul 20, 2015 17:56
@BlasSoriano Obrigado pela sua informação.
 

 CURED

For feedback/discussion/requests of Close/Undelete/Reopen/Edit...
Jul 30, 2015 20:37
... common in elementary Algebra ...
Jul 30, 2015 20:34
@ArthurFischer I agree that it's specialised, but because it is or was very common in polynomials root finding, I think it's a useful information.
Jul 30, 2015 12:24