## Archive for john Conway

## lost mathematicians of 2020

Posted in Books, Kids, Statistics, University life with tags 2020, Annals of Inquiry, Freeman Dyson, john Conway, Ronald Graham, The New Yorker on January 17, 2021 by xi'an## “a rare blend of monster raving egomania and utter batshit insanity”

Posted in Books, pictures, University life with tags Bill Gates, book exchange, book review, Carnegie Mellon University, cellular automata, Cosma Shalizi, game of life, john Conway, Mathematica, Mathematical Reviews, Pittsburgh, Stephen Wolfram, xkcd on November 12, 2020 by xi'an

“I don’t object to speculation or radical proposals, even to radical, grandiose speculative proposals; I just want there to be arguments to back them up, reasons to take them seriously. I don’t object to scientists displaying personality in their work, or staking out positions in vigorous opposition to much of the opinion in their field, and engaging in heated debate; I do object to ignoring criticism and claiming credit for commonplaces, especially before popular audiences who won’t pick up on it.”

**A** recent post by Andrew on Stephen Wolfram’s (mega) egomania led to a much older post by Cosma Shalizi reviewing the perfectly insane 5.57 pounds of a New Kind of Science. An exhilarating review, trashing the pretentious self-celebration of a void paradigm shift advanced by Wolfram and its abyssal lack of academic rigour, showing anew that a book recommended by Bill Gates is not necessarily a great book. (Note that A New Kind of Science is available for free on-line.)

*“Let me try to sum up. On the one hand, we have a large number of true but commonplace ideas, especially about how simple rules can lead to complex outcomes, and about the virtues of toy models. On the other hand, we have a large mass of dubious speculations (many of them also unoriginal). We have, finally, a single new result of mathematical importance, which is not actually the author’s. Everything is presented as the inspired fruit of a lonely genius, delivering startling insights in isolation from a blinkered and philistine scientific community.”*

When I bought this monstrous book (eons before I started the ‘Og!), I did not get much further into it than the first series of cellular automata screen copies that fill page after page. And quickly if carefully dropped it by my office door in the corridor. Where it stayed for a few days until one of my colleagues most politely asked me if he could borrow it. (This happens all the time: once I have read or given up on a book I do not imagine reopening again, I put it in the coffee room or, for the least recommended books, on the floor by my door and almost invariably whoever is interested will first ask me for permission. Which is very considerate and leads to pleasant discussions on the said books. Only recently did the library set shelves outside its doors for dropping books free for the taking, but even there I sometimes get colleagues wondering [rightly] if I was the one abandoning there a particular book.)

*“I am going to keep my copy of A New Kind of Science, sitting on the same shelf as Atlantis in Wisconsin, The Cosmic Forces of Mu, Of Grammatology, and the people who think the golden ratio explains the universe.” *

In case the review is not enough to lighten up your day, in these gloomy times, there is a wide collection of them from the 2000’s, although most of the links have turned obsolete. (The Maths Reviews review has not.) As presumably this very post about a eighteen-years-old non-event…

## Covid’s game-of-life

Posted in Books, pictures, Travel, University life with tags COVID-19, game of life, game theory, john Conway, Le Monde, lockdown, quarantine, Vietnam on May 7, 2020 by xi'an**A** colleague from Paris Dauphine, Miquel Oliu-Barton made a proposal in Le Monde for an easing of quarantine that sounds somehow like Conway’s game of life. The notion is to define a partition of the country into geographical zones with green versus red labels, representing the absence versus presence of contagious individuals. With weekly updates depending on the observed cases or the absence thereof. While this is a nice construct that can be processed as a game theory problem, I am not so sure that it fits the specific dynamics of the coronavirus, which is not immediately detected while active, hence inducing a loss of efficiency in returning quickly enough to a red status. Not mentioning the unreliability and unavailability of tests at this scale. Or an open society (as opposed to China or Vietnam) where (a) people will resent local lockdown more than they do with global lockdown and (b) mostly operate outside the box for work or family interactions.

## more games of life

Posted in Books, Kids, R with tags brute-force solution, john Conway, numbers, R, The Guardian on May 5, 2020 by xi'an**A**nother puzzle in memoriam of John Conway in The Guardian:

*Find the ten digit number, abcdefghij. Each of the digits is different, and*

*a is divisible by 1**ab is divisible by 2**abc is divisible by 3**abcd is divisible by 4**abcde is divisible by 5**abcdef is divisible by 6**abcdefg is divisible by 7**abcdefgh is divisible by 8**abcdefghi is divisible by 9**abcdefghij is divisible by 10*

Which brute force R coding by checking over random permutations of (1,2,…,9) [since j=0] solves within seconds:

while(0<1) if (prod(!(x<-sum(10^{0:8}*sample(1:9)))%/%10^{7:0}%%2:9))break()

into x=3816547290. And slightly less brute force R coding even faster:

while(0<1){ e=sample(c(2,6,8))#even o=sample(c(1,3,7,9))#odd if((!(o[1]+e[1]+o[2])%%3)& (!(10*o[2]+e[2])%%4)& (!(o[1]+e[1]+o[2]+e[2]+5+4)%%3)& (!sum(10^{6:0}*c(o[1],e[1],o[2],e[2],5,4,o[3]))%%7)& (!(10*o[3]+e[3])%%8)& (!(sum(o)+sum(e))%%9)){ print(sum(10^{9:0}*c(o[1],e[1],o[2],e[2],4,5,o[3],e[3],o[4],0)));break()}}

## Le Monde puzzle [#1141]

Posted in Kids, pictures, R, University life with tags brute-force solution, chess, code golf, coronavirus epidemics, game of life, john Conway, Le Monde, mathematical puzzle, R on May 4, 2020 by xi'an**T**he weekly puzzle from Le Monde is in honour of John Conway, who just passed away, ending up his own game of life:

On an 8×8 checker-board, Alice picks n squares as “infected”. She then propagates the disease by having each square with least two infected neighbours to become infected as well. What is the minimal value of n for the entire board to become infected? What if three infected neighbours are required?

A plain brute force R random search for proper starting points led to n=8 (with a un-code-golfed fairly ugly rendering of the neighbourhood relation, I am afraid!) with the following initial position

With three neighbours, an similar simulation failed to return anything below n=35 as for instance:

oops, n=34 when running a little longer:

which makes sense since an upper bound is found by filling one square out of two (32) and adding both empty corners (2). But this upper bound is only considering one step ahead, so is presumably way too large. (And indeed the minimal value is 28, showing that brute force does not always work! Or it may be that forcing the number of live cells to grow at each step is a coding mistake…)