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J.-E. Pin
  • Member for 8 years, 10 months
  • Last seen this week
  • Paris
73 votes

What's the point in being a "skeptical" learner

46 votes

Why is Lebesgue so often spelled "Lebesque"?

40 votes

I get a wrong determinant - why?

30 votes

Why does intersection always preserve "closed" structures?

21 votes
Accepted

subset of binary space countable?

14 votes
Accepted

Math Symbol for "Where"

12 votes

Why can ALL quadratic equations be solved by the quadratic formula?

11 votes
Accepted

Is there such a thing as backwards sigma?

11 votes

How many rings are there for a given order?

10 votes

example of a set that is closed and bounded but not compact

10 votes

What will mathematicians do when they run out of letters in the Greek and English alphabets?

9 votes
Accepted

Sequence vs Progression

8 votes

Are there two non-regular languages whose concatenation is regular?

8 votes
Accepted

How to determine the scope of a proof?

8 votes

Why doesn't this hold for $p=2$?

8 votes
Accepted

Is there a name for a monoid with a distinguished absorbing element?

8 votes
Accepted

Complexity of Thue-Morse Sequence

8 votes

Semigroup analogue to the classification of finite simple groups?

7 votes

If $L$ is regular, prove that $\sqrt{L}=\left\{ w : ww\in L\right\}$ is regular

7 votes
Accepted

Is there another name for this "power of two" sequence?

7 votes
Accepted

Do these very VERY weak axioms guarantee a group? (Every element has left identity $e_L$ or right identity $e_R$, with same-sided inverse)

7 votes
Accepted

Proving that all equivalent regular expressions are reachable via algebraic laws

7 votes
Accepted

How can you use Green's relations to learn about a monoid?

7 votes

Monoids where $\operatorname{Hom}(M,M) \cong M$

7 votes

Total ordering on the free group

6 votes

What can we learn about a group by studying its monoid of subsets?

6 votes
Accepted

Eilenberg's rational hierarchy of nonrational automata & languages

6 votes
Accepted

Distributor? Distributive analog of commutator and associator?

6 votes
Accepted

Free idempotent semigroup with 3 generators

6 votes
Accepted

Terminology for a "subgroup" that has a different identity element.

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