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José Carlos Santos

Porto, Portugal

http://www.fc.up.pt/mp/jcsantos/

I am a mathematician who works at the University of Porto (Portugal). My PhD, on Representation Theory, was obtained at the Université Paris — Denis Diderot, in 1996.

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Top Questions
169 votes

Why was “An Update to our Community and an Apology” deleted?

discussion meta deleted-questions stack-exchange-team censor asked Dec 24 '19 at 12:16
meta.stackexchange.com

105 votes

Unexpected examples of natural logarithm

soft-question logarithms big-list asked Jul 3 '17 at 13:07
math.stackexchange.com

47 votes

Why were the Allies so much better cryptanalysts?

world-war-two espionage cryptology secrecy asked Nov 22 '20 at 9:03
history.stackexchange.com

46 votes

Proving $\left(1-\frac13+\frac15-\frac17+\cdots\right)^2=\frac38\left(\frac1{1^2}+\frac1{2^2}+\frac1{3^2}+\frac1{4^2}+\cdots\right)$

real-analysis sequences-and-series summation asked Oct 2 '17 at 10:17
math.stackexchange.com

33 votes

In what way were Renaissance battles like chess matches?

middle-ages warfare renaissance reference asked Oct 29 '19 at 17:55
history.stackexchange.com

30 votes

Could a German insult Hitler without being arrested?

nazi-germany hitler asked Dec 15 '19 at 10:02
history.stackexchange.com

26 votes

Is every matrix conjugate to its transpose in a continuous way?

linear-algebra matrices continuity transpose similar-matrices asked Dec 14 '18 at 10:03
math.stackexchange.com

19 votes

Did Emanuel Lasker write a book declaring that Germany had to win World War I if civilization were to be saved?

world-war-one germany book biography asked Sep 12 '18 at 9:48
history.stackexchange.com

17 votes

Was the insanity of kings used as an argument against monarchy?

monarchy republic illness asked Apr 9 '19 at 10:09
history.stackexchange.com

16 votes

Must a continuous, non-constant, and periodic functions have a smallest period?

real-analysis continuity periodic-functions asked Oct 16 '19 at 7:58
math.stackexchange.com

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Top Answers
129
Why not include as a requirement that all functions must be continuous to be differentiable?
math.stackexchange.com

86
How can a “proper” function have a vertical slope?
math.stackexchange.com

84
Can a binary operation have an identity element when it is not associative and commutative?
math.stackexchange.com

82
Does an increasing sequence of reals converge if the difference of consecutive terms approaches zero?
math.stackexchange.com

73
Unsolved Problems due to Lack of Computational Power
math.stackexchange.com

62
False proof that $ρe^{iθ} = ρ$ and so complex numbers do not exist?
math.stackexchange.com

58
Why a $20$ digit number starting with eleven $1$'s cannot be a perfect square?
math.stackexchange.com

53
What is an example of a sequence which “thins out” and is finite?
math.stackexchange.com

48
How many times do you have to use L'Hôpital's rule?
math.stackexchange.com

46
How are the known digits of $\pi$ guaranteed?
math.stackexchange.com

45
Why is the notion of analytic function so important?
math.stackexchange.com

45
Can we use symmetry rules in improper integrals?
math.stackexchange.com

43
How to determine if a set of five $2\times2$ matrices is independent
math.stackexchange.com

42
If derivative of $f$ is continuous, then $f$ is continuous.
math.stackexchange.com

41
Problem with estimating a sequence with intuition
math.stackexchange.com

39
Non abelian group which contains no abelian subgroup
math.stackexchange.com

38
Can the product of three complex numbers ever be real?
math.stackexchange.com

38
Understandable questions which are hard for non-mathematicians but easy for mathematicians
math.stackexchange.com

36
Simple Calculus view on Fermat's Last Theorem
math.stackexchange.com

35
How could $\varnothing$ be unique if it could be vacuously false?
math.stackexchange.com

35
Integration of secant
math.stackexchange.com

35
Cross product in higher dimensions
math.stackexchange.com

35
Finding the 10th root of a matrix
math.stackexchange.com

34
Sets that are both Sum-free and Product-free
math.stackexchange.com

34
Are these square matrices always diagonalisable?
math.stackexchange.com

33
If I don't have a computer at hand (or an app), how can I know that $1637$ is prime?
math.stackexchange.com

32
What is the context for Napoleon's quote “[the Austrians] did not know the value of five minutes”?
history.stackexchange.com

32
Why does Zorn's Lemma fail to produce a largest group?
math.stackexchange.com

32
General request for a book on mathematical history, for a VERY advanced reader.
math.stackexchange.com

31
How to compute the determinant of this Toeplitz matrix?
math.stackexchange.com

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