### Andrej Bauer

Shared publicly -I hereby challenge the comic authors of the world to produce a comic that explains bound and free variables (as in logic).

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Aren't we all secretly mathematicians? :)

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Andrej Bauer

Works at University of Ljubljana

Attended United World College of the Adriatic

Lives in Ljubljana, Slovenia

670 followers|63,221 views

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I hereby challenge the comic authors of the world to produce a comic that explains bound and free variables (as in logic).

9

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7 comments

Aren't we all secretly mathematicians? :)

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While doing koho tento undos, I remembered an old problem which is perfect for all you G+ mathematicians. And I am posting this on FB as well, so consider it a competition between FB and G+ (if you are on both you will have to choose sides).

Queen Cersei rules a land which is a perfect square 100 kilometers to the side. Her castle is at the center of the land and her knights are posted throughout the land, with a standing order not to move. Every knight knows the position of every other knight (but once a knight starts moving, the others don't know anymore where he is). One day the Queen summons all her knights to the castle. She relays the order to Lord Commander, the first of Queen's knights. Knights travel at 20 km/h and only relay queen's orders personally to each other. How quickly can the knights gather at the castle?

The answer should be a constant which does not depend on the positions or the number of the knights.

Queen Cersei rules a land which is a perfect square 100 kilometers to the side. Her castle is at the center of the land and her knights are posted throughout the land, with a standing order not to move. Every knight knows the position of every other knight (but once a knight starts moving, the others don't know anymore where he is). One day the Queen summons all her knights to the castle. She relays the order to Lord Commander, the first of Queen's knights. Knights travel at 20 km/h and only relay queen's orders personally to each other. How quickly can the knights gather at the castle?

The answer should be a constant which does not depend on the positions or the number of the knights.

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+Aleš Časar I was thinking in the same direction but found one problem I couldn't solve - what if you don't have any spare knights on the surrounding triangle to go to the N+1th?

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For the first time in 20 years I wrote a program in C. It computed the Mandelbrot set. I was amazed at the speed, computers really have gotten faster! And I was also impressed at how fast C was. But then I got the bright idea of writing the same program in OCaml. And you know what? **OCaml is just as fast as C!** I really do not have to go back to C, ever.

Feel free to make your own experiments:

https://gist.github.com/andrejbauer/7919569

https://gist.github.com/andrejbauer/8165198

#ocaml

Feel free to make your own experiments:

https://gist.github.com/andrejbauer/7919569

https://gist.github.com/andrejbauer/8165198

#ocaml

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+Anthony Cowley Agreed, and the new phone/tablet GPUs that will come out this year are looking very attractive.

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Henceforth I shall be known as google.com/+AndrejBauer

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+Andrej Bauer - how did you get it?

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Is there such a thing as **non-symmetric** closed monoidal category, and if so, are there two internal hom-set operators (left and right)?

#mathematics

#mathematics

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+Neelakantan Krishnaswami is right. This is the standard setting for categorial grammar.

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I give to the world the normals to Costa's minimal surface. Boy, this was a pain to get right, I had to review my differential geometry. Also, if anyone can compute the normals using pencil and paper, I would like to know about it. I relied very heavily on Mathematica, which produced complicated expressions. I wonder if those can be simplified. Weierstraß could probably do it over a breakfast coffee.

#mathematica #geometry #povray

#mathematica #geometry #povray

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The pair of functions ℘ and ℘' give a way to parametrise elliptic curves so there's an algebraic relationship between them. If (x,y)=(℘(z), y=℘'(z)) then y^2=4x^3-g_2x-g_3. I'm not sure about how to pick the right branch of the square root. If I wasn't in the middle of another small project I'd give this some thought.

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Job announcement:

Faculty of Mathematics and Physics, University of Ljubljana, has a vacancy for a full-time university professor in computer science or a closely related area. The teaching load is 6 to 8 hours of lectures per week, which amounts to approximately 3 courses per semester. The candidate would teach primarily our computer science courses: programming, algorithms and data structures, introduction to databases, etc. Research activity is expected as well. The candidate must be prepared to learn Slovene (within reasonable time frame).

All inqueries and questions can be directed at me. The official announcement is at http://www.uni-lj.si/news/job_vacancies/2013120208251147/, the deadline for applications is January 16th, 2014.

#jobs #computerscience

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William Uther

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If you like that, I highly recommend: http://www.jsfuck.com/

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Where could I look up things about universal arrows, adjunctions, etc., for (ordinary non-symmetric) multicategories on Set?

#categorytheory +Michael Shulman

#categorytheory +Michael Shulman

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That's a good question! I'm not sure. If the monad is commutative, then they are the constraints of a monoidal structure on the monad T, and commutative monads are equivalent to monoidal monads, so maybe that's "canonical" somehow. But if they're not equal, then I don't know of any universal or canonical characterization of them. How could you characterize both of them?

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Work

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- University of LjubljanaProfessor, present

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Ljubljana, Slovenia

Previously

Pittsburgh, USA - Duino, Italy

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- Random art (current)
- Mathematics and computation (current)
- Videos of lectures and talks (current)
- andrej.com (current)

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Education

- United World College of the Adriatic1988 - 1990
- Univerza v Ljubljanimathematics, 1990 - 1994
- Carnegie Mellon Universitylogic, 1994 - 2000

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Male