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2013 May 29

Recent Discoveries, part II

This is intended to be a follow-up to my earlier post on cp4space (mentioning Mike Playle's new reflector). The content of this post is slightly too niche for cp4space, so I've included it here instead.

Mike Playle's new reflector has prompted a new surge in activity, with several derivative patterns being constructed. Firstly, Dave Greene has utilised the 'Snark' to reduce the area of the period-59 gun (Goucher and Summers) by two orders of magnitude.

Dave Greene's period-59 gun.

Secondly, a contributor on Nathaniel Johnston's forum has found a way to synthesise the reflector using 50 gliders. There has been much interest about the constructibility and destructibility of reflectors, with Paul Chapman writing a program entitled Seeds of Destruction to search for efficient self-destruction circuits. This is part of an ongoing project by Chapman and Greene to produce a smaller replicator than Andrew Wade's Gemini. A preliminary edition of Seeds of Destruction can be downloaded from here.

Screenshot of the Seeds of Destruction puzzle game.

Another recent discovery is a true period-20 glider gun, making it the most rapid glider gun known. This was discovered after a large period-40 gun was built by Adam P. Goucher and optimised by Matthias Merzenich, and (since 40 is a multiple of 20) can be trivially modified to yield a more compact p40 gun.

Matthias' period-20 glider gun.

Mike Playle has used his search program (Bellman) to find further discoveries, including a completion of the elusive period-94 AK47 glider gun and an elegant stabilisation of a known period-33 oscillator. There has been speculation about whether the latter could be coaxed into releasing gliders.

Mike Playle's period-94 gun and a new period-33 oscillator stabilisation.