
Recent Posts
Subscribe to Complex Projective 4Space
Archives
 July 2022
 June 2022
 May 2022
 January 2022
 December 2021
 September 2021
 July 2021
 June 2021
 May 2021
 February 2021
 January 2021
 December 2020
 November 2020
 October 2020
 September 2020
 August 2020
 July 2020
 June 2020
 May 2020
 June 2019
 May 2019
 March 2019
 November 2018
 September 2018
 July 2018
 June 2018
 May 2018
 April 2018
 March 2018
 February 2018
 November 2017
 October 2017
 November 2016
 May 2016
 March 2016
 February 2016
 December 2015
 September 2015
 March 2015
 February 2015
 January 2015
 December 2014
 November 2014
 October 2014
 September 2014
 August 2014
 July 2014
 June 2014
 May 2014
 April 2014
 March 2014
 February 2014
 January 2014
 December 2013
 November 2013
 October 2013
 September 2013
 August 2013
 July 2013
 June 2013
 May 2013
 April 2013
 March 2013
 February 2013
 January 2013
 December 2012
 November 2012
 October 2012
 September 2012
 August 2012
Recent Comments
 tomtom2357 on The inadequacy of SCLT
 apgoucher on The neural network of the Stockfish chess engine
 El número TREE(3) no es infinito, pero es tan grande que ni siquiera cabe en el universo  La Fragua on TREE(3) and impartial games
 El número TREE(3) no es infinito, pero es tan grande que ni siquiera cabe en el universo – Radio Región on TREE(3) and impartial games
 El número TREE(3) no es infinito, pero es tan grande que ni siquiera cabe en el universo – Radio Centro F.M. 97.1 Pcia. De Buenos Aires on TREE(3) and impartial games
Monthly Archives: October 2013
Cipher 50: Nontrivial evasion
You may have wondered why the last few ciphers have been erratic. The answer is so that the 50th cipher will land exactly on Professor Imre Leader‘s 50th birthday, which was celebrated 14 hours ago. One of the main components … Continue reading
Posted in Activities, Ciphers, Uncategorized
Leave a comment
Curves of constant width
The 50pence and 20pence coins are regular curvilinear heptagons, where each edge is a circular arc centred on the opposite vertex. One may ask why the coins have such an unusual shape. One possible answer is that it is impossible … Continue reading
Posted in Uncategorized
Leave a comment
Enumerating the rationals
It is a wellknown fact, attributed to Cantor, that the set of rationals is countably infinite or, equivalently, we can find a bijection between the rationals and integers. These are easy to construct, but typically quite ugly. If you want … Continue reading
Posted in Uncategorized
Leave a comment
Cipher 49: Feline cartograph
This one is entirely graphical: Thanks go to James Aaronson for the design.
Posted in Ciphers
Leave a comment
Punting in clearings of arbitrarily small Lebesgue measure
Breaking news: A £500 prize for the most elegant solution in the British Mathematical Olympiad has been founded in the memory of Christopher Bradley, whose contributions to the United Kingdom Mathematics Trust were both plentiful and invaluable. Amongst his portfolio is the bestselling … Continue reading
Posted in Uncategorized
Leave a comment
Mathematical innuendo
Here are some primarily mathematical doubleentendres conceived by members of the Trinity Mathematicians’ Alcoholic Society. Some of them are biological or particlephysical, but never mind. Also, some names are censored for legal reasons. Disclaimer: I accept no responsibility for any offence caused … Continue reading
Posted in Uncategorized
Leave a comment
Mathieu groupoid
You have probably encountered the 15puzzle, where all but one of the squares of a 4 × 4 grid are occupied by counters. The only acceptable moves are to move a counter into an adjacent unoccupied square. Sam Loyd challenged … Continue reading
Posted in Uncategorized
Leave a comment
MOG results released
MOG results released The results for the aforementioned Mathematical Olympiad for Girls have now been released on Joseph Myers’ website. There are impressively many excellent scores, as compared with previous years, including some names previously unknown to us. Hence, the … Continue reading
Posted in Uncategorized
Leave a comment
What should this group be called?
Consider the Riemann sphere, obtained by adjoining a ‘point at infinity’ to the complex plane. The conformal maps from the Riemann sphere to itself form a group, the Möbius group, which is abstractly isomorphic to (and also the proper orthochronous … Continue reading
Posted in Uncategorized
Leave a comment
Cipher 48: Endoplasmic reticulum
After an important and immersive conversation lasting no fewer than four hours, I had very little time to compile this particular cipher. Its appearance reminded me of the endoplasmic reticulum surrounding the nuclei of biological cells, hence the name. I would … Continue reading
Posted in Ciphers
Leave a comment