Puzzlebomb is a monthly puzzle compendium. Issue 53 of Puzzlebomb, for May 2016, can be found here:
Puzzlebomb – Issue 53 – May 2016
The solutions to Issue 53 will be posted at the same time as Issue 52.
Previous issues of Puzzlebomb, and their solutions, can be found at Puzzlebomb.co.uk.
From Mark C. Wilson of the University of Auckland, a little public service announcement for anyone who’s ever been involved with a mathematical journal.
There is much dissatisfaction with the current state of research
publication, but little information on community attitudes and priorities.
I have started a survey which I hope you will fill in (I estimate 10-15
minutes, and it is completely anonymous). The results will be made publicly
available later this year. I hope that it will help to focus our efforts as
a community by allowing us to work toward broadly agreed goals. I want to
get as representative and as large a sample of the world mathematical
community as possible. Please forward to your local colleagues.
Please answer this survey if and only if you have been involved with a
mathematical journal as editor, reviewer/referee, author or reader in the
last 3 years. By “mathematical” we also mean to include theoretical
computer science and mathematical statistics journals, and disciplinary
journals used by applied mathematicians. Essentially, any journal covered
by Mathematical Reviews qualifies.
Answer the survey
Here’s something fun you might want to spend some money on: a poster of the Mandelbrot set, in the style of an old-fashioned navigation chart.
The Kickstarter has already racked up many multiples of the original funding goal with three weeks still to go, so it’s at the “effectively a pre-order” stage. The posters start at \$26.
Kickstarter: Mandelmap poster by Bill Tavis.
Conjecture Every planar graph without 4-cycles and 5-cycles is 3-colourable.
In a paper just uploaded to the arXiv, Vincent Cohen-Addad, Michael Hebdige, Daniel Kral, Zhentao Li and Esteban Salgado show the construction of a graph with no cycles of length 4 or 5 which isn’t 3-colourable: it isn’t possible to assign colours to its vertices so that no pair of adjacent vertices have the same colour, using only three different colours. This is a counterexample to a conjecture of Richard Steinberg from 1976.
The problem was listed in the Open Problem Garden as of “outstanding” importance.
Read the paper: Steinberg’s conjecture is false
via Parcly Taxel on Twitter
Warning: you could make a very strong argument I’ve thought far too much about something inconsequential. If that makes your stomach turn, look away now.
This morning in the shower, I had an idle thought about my towel. It was, as always, folded neatly on the toilet seat. A problem that’s been bugging me for a few days is how to pick up the towel by a section of the long edge, so when it unfolds it’s the right way round.
The problem is that the short edge and the long edge look the same, and once I’ve folded the towel over a couple of times and had a shower only a madman* would remember which is which. But my towel isn’t square, so it occurred to me that either the longer or the shorter edge, after folding, could be the edge I want. Since I never make a diagonal fold, the long edge is only ever folded on top of the long edge, and likewise for the short edge. I fold the towel until it fits comfortably on top of the toilet seat, and by the time I’ve finished my shower I can’t be relied upon to remember which sequence of folds I did.
Which got me thinking about the ratio between the width and height of my towel: if I know this ratio then, by looking at the towel and counting the number of folds, I can work out which folds I’ve done, and hence which of the sides will unfold to be the long edge.
The next issue of the Carnival of Mathematics, rounding up blog posts from the month of March, and compiled by Matthew, is now online at Chalkdust Magazine.
The Carnival rounds up maths blog posts from all over the internet, including some from our own Aperiodical. See our Carnival of Mathematics page for more information.
In this series of posts, Katie will be going on about some of her favourite board games and card games, and some of the interesting mathematics to be found there. If you’d like the chance to play a mathematical board game, why not find or start a Maths Arcade at university, or join your local MathsJam.
6 Nimmt! (German: Take 6!) is a card-based game which involves a hand of numbered cards, each also containing a number of cow heads. The cards are played in rounds, and during each round everyone chooses a card to play, they’re played in order, and you may find yourself having to take cards. The aim of the game is to end with the fewest cow heads.