Log24

C. P. Snow on G. H. Hardy in the foreword to 
A Mathematician's Apology :

"… he had another favourite entertainment. 
'Mark that man we met last night,'
he said, and someone had to be marked
out of 100 in each of the categories
Hardy had long since invented and defined.  
STARK, BLEAK ('a stark man is not necessarily
bleak: but all bleak men without exception
want to be considered stark')…."

Related material :

Tommy Lee Jones in The New York Times  on Nov. 6th, 2014,
and Pierce Brosnan in the 2014 film "The November Man" :

“Geometry was very important to us in this movie.”

— The Missing ART   (Log24, November 7th, 2014)

Inscribed hexagon (1984)

The well-known fact that a regular hexagon
may be inscribed in a cube was the basis
in 1984 for two ways of coloring the faces
of a cube that serve to illustrate some graphic
aspects of embodied Galois geometry—

Inscribed hexagon (2013)

A redefinition of the term "symmetry plane"
also uses the well-known inscription
of a regular hexagon in the cube—

Related material

"Here is another way to present the deep question 1984  raises…."

— "The Quest for Permanent Novelty," by Michael W. Clune,
     The Chronicle of Higher Education , Feb. 11, 2013

“What we do may be small, but it has a certain character of permanence.”

— G. H. Hardy, A Mathematician’s Apology

C. P. Snow on G. H. Hardy, in Snow's foreword to A Mathematician's Apology—

"One morning early in 1913, he found, among the letters on his breakfast table, a large untidy envelope decorated with Indian stamps. When he opened it, he found sheets of paper by no means fresh, on which, in a non-English holograph, were line after line of symbols. Hardy glanced at them without enthusiasm. He was by this time, at the age of thirty-six, a world famous mathematician: and world famous mathematicians, he had already discovered, are unusually exposed to cranks. He was accustomed to receiving manuscripts from strangers, proving the prophetic wisdom of the Great Pyramid, the revelations of the Elders of Zion, or the cryptograms that Bacon has inserted in the plays of the so-called Shakespeare."

Some related material (click to enlarge)—

The author links to, but does not name, the source of the above
"line after line of symbols." It is "Visualizing GL(2,p)." See that webpage
for some less esoteric background.

See also the two Wikipedia articles Finite geometry and Hesse configuration
and an image they share—

The Hesse here is not Hermann, but Otto.

"… this notion of ‘depth’ is an elusive one
even for a mathematician who can recognize it…."

— G. H. Hardy, A Mathematician's Apology

In Geometry and the Imagination , Hilbert and Cohn-Vossen
describe the Brianchon-Pascal configuration of 9 points
and 9 lines, with 3 points on each line and 3 lines through
each point, as being "the most important configuration of all geometry."

The Brianchon-Pascal configuration is also known as the Pappus configuration—

Some background …

"The Theorem of Pappus: A Bridge Between Algebra and Geometry"
Elena Anne Marchisotto
The American Mathematical Monthly
Vol. 109, No. 6 (Jun. – Jul., 2002), pp. 497-516

From math16.com—

The story of the diamond mine continues
(see Coordinated Steps and Organizing the Mine Workers)— 

From The Search for Invariants (June 20, 2011):

The conclusion of Maja Lovrenov's 
"The Role of Invariance in Cassirer’s Interpretation of the Theory of Relativity"—

"… physical theories prove to be theories of invariants
with regard to certain groups of transformations and
it is exactly the invariance that secures the objectivity
of a physical theory."

— SYNTHESIS PHILOSOPHICA 42 (2/2006), pp. 233–241

Related material from Sunday's New York Times  travel section—

"Exhibit A is certainly Ljubljana…."

For the title, see Palm Sunday.

"There is a pleasantly discursive treatment of
Pontius Pilate's unanswered question 'What is truth?'" — H. S. M. Coxeter, 1987

From this date (April 22) last year—

Richard J. Trudeau in The Non-Euclidean Revolution , chapter on "Geometry and the Diamond Theory of Truth"– "… Plato and Kant, and most of the philosophers and scientists in the 2200-year interval between them, did share the following general presumptions: (1) Diamonds– informative, certain truths about the world– exist. (2) The theorems of Euclidean geometry are diamonds. Presumption (1) is what I referred to earlier as the 'Diamond Theory' of truth. It is far, far older than deductive geometry." Trudeau's book was published in 1987. The non-Euclidean* figures above illustrate concepts from a 1976 monograph, also called "Diamond Theory." Although non-Euclidean,* the theorems of the 1976 "Diamond Theory" are also, in Trudeau's terminology, diamonds. * "Non-Euclidean" here means merely "other than  Euclidean." No violation of Euclid's parallel postulate is implied.

Trudeau comes to reject what he calls the "Diamond Theory" of truth. The trouble with his argument is the phrase "about the world."

Geometry, a part of pure mathematics, is not  about the world. See G. H. Hardy, A Mathematician's Apology .

Rigor

“317 is a prime, not because we think so,
or because our minds are shaped in one way
rather than another, but because it is so,
because mathematical reality is built that way.”

 – G. H. Hardy,
A Mathematician’s Apology

The above photo is taken from
a post in this journal dated
March 10, 2010.

This was, as the Pope might say,
the dies natalis  of a master gameplayer–

New York Times, March 16, 2010– Tim Holland, Backgammon Master, Dies at 79 By DENNIS HEVESI Tim Holland, who was widely considered the world’s greatest backgammon player during that ancient board game’s modern heyday, in the 1960s and ’70s, died on March 10 at his home in West Palm Beach, Fla. He was 79. <<more>>

In Holland's honor, a post
from Columbus Day, 2004—

Tuesday October 12, 2004 11:11 PM  Time and Chance Today’s winning lottery numbers in Pennsylvania (State of Grace): Midday: 373 Evening: 816.

A quote from Holland on backgammon–

"It’s the luck factor that seduces everyone
into believing that they are good,
that they can actually win,
but that’s just wishful thinking."

For those who are, like G.H. Hardy,
suspicious of wishful thinking,
here is a quote and a picture from
Holland's ordinary  birthday, March 3—

"The die is cast." — Caesar

Today's previous entry quoted a review by Edward Rothstein of Jung's The Red Book. The entry you are now reading quotes a review by Jim Holt of a notable book by Rothstein:

The Golden Book—

Cover illustration— Arithmetic and Music,
Borgia Apartments, The Vatican

Jim Holt reviewing Edward Rothstein's Emblems of Mind: The Inner Life of Music and Mathematics in The New Yorker of June 5, 1995:

Advent

"The fugues of Bach, the symphonies of Haydn, the sonatas of Mozart: these were explorations of ideal form, unprofaned by extramusical associations. Such 'absolute music,' as it came to be called, had sloughed off its motley cultural trappings. It had got in touch with its essence. Which is why, as Walter Pater famously put it, 'all art constantly aspires towards the condition of music.'

The only art that can rival music for sheer etheriality is mathematics. A century or so after the advent of absolute music, mathematics also succeeded in detaching itself from the world. The decisive event was the invention of strange, non-Euclidean geometries, which put paid to the notion that the mathematician was exclusively, or even primarily, concerned with the scientific universe. 'Pure' mathematics came to be seen by those who practiced it as a free invention of the imagination, gloriously indifferent to practical affairs– a quest for beauty as well as truth."

Related material: Hardy's Apology, Non-Euclidean Blocks, and The Story Theory of Truth.

See also Holt on music and emotion:

"Music does model… our emotional life… although
  the methods by which it does so are 'puzzling.'"

Also puzzling: 2010 AMS Notices.

DENNIS OVERBYE

"From the grave, Albert Einstein poured gasoline on the culture wars between science and religion this week.

A letter the physicist wrote in 1954 to the philosopher Eric Gutkind, in which he described the Bible as 'pretty childish' and scoffed at the notion that the Jews could be a 'chosen people,' sold for $404,000 at an auction in London. That was 25 times the presale estimate."

Einstein did not, at least in the place alleged, call the Bible "childish." Proof:

The image of the letter is
from the Sept./Oct. 2008
Search Magazine.

By the way, today is
the birthday of G. H. Hardy.

Here is an excerpt from his
thoughts on childish things:

"What 'purely aesthetic' qualities can we distinguish in such theorems as Euclid's or Pythagoras's?…. In both theorems (and in the theorems, of course, I include the proofs) there is a very high degree of unexpectedness, combined with inevitability and economy. The arguments take so odd and surprising a form; the weapons used seem so childishly simple when compared with the far-reaching results; but there is no escape from the conclusions."

"Space: what you
damn well have to see."

— James Joyce, Ulysses  

The Diamond Theorem
 

 

“I don’t think the ‘diamond theorem’ is anything serious, so I started with blitzing that.”

— Charles Matthews at Wikipedia, Oct. 2, 2006

“The ‘seriousness’ of a mathematical theorem lies, not in its practical consequences, which are usually negligible, but in the significance of the mathematical ideas which it connects. We may say, roughly, that a mathematical idea is ‘significant’ if it can be connected, in a natural and illuminating way, with a large complex of other mathematical ideas.”

— G. H. Hardy, A Mathematician’s Apology

Proof 101

From a course description:

“This module aims to introduce the student to rigorous university level mathematics….
    Syllabus: The idea of and need for mathematical statements and proofs…. proof by contradiction… proof by induction…. the infinite number of primes….”

In the December Notices of the American Mathematical Society, Brian (E. B.) Davies, a professor of mathematics at King’s College London, questions the consistency of Peano Arithmetic (PA), which has the following axioms:

From BookRags.com—

Axiom 1. 0 is a number.

Axiom 2. The successor of any number is a number.

Axiom 3. If a and b are numbers and if their successors are equal, then a and b are equal.

Axiom 4. 0 is not the successor of any number.

Axiom 5. If S is a set of numbers containing 0 and if the successor of any number in S is also in S, then S contains all the numbers.

It should be noted that the word “number” as used in the Peano axioms means “non-negative integer.”  The fifth axiom deserves special comment.  It is the first formal statement of what we now call the “induction axiom” or “the principle of mathematical induction.”

Peano’s fifth axiom particularly troubles Davies, who writes elsewhere:

I contend that our understanding of number should be placed in an historical context, and that the number system is a human invention.  Elementary arithmetic enables one to determine the number of primes less than twenty as certainly as anything we know.  On the other hand Peano arithmetic is a formal system, and its internal consistency is not provable, except within set-theoretic contexts which essentially already assume it, in which case their consistency is also not provable.  The proof that there exists an infinite number of primes does not depend upon counting, but upon the law of induction, which is an abstraction from our everyday experience…. 
… Geometry was a well developed mathematical discipline based upon explicit axioms over one and a half millennia before the law of induction was first formulated.  Even today many university students who have been taught the principle of induction prefer to avoid its use, because they do not feel that it is as natural or as certain as a purely algebraic or geometric proof, if they can find one.  The feelings of university students may not settle questions about what is truly fundamental, but they do give some insight into our native intuitions.

— E. B. Davies in
   “Counting in the real world,”
    March 2003 (word format),
    To appear in revised form in
    Brit. J. Phil. Sci. as
   “Some remarks on
    the foundations
    of quantum mechanics”

Exercise:

Discuss Davies’s claim that

The proof that there exists an infinite number of primes does not depend upon counting, but upon the law of induction.

Cite the following passage in your discussion.

It will be clear by now that, if we are to have any chance of making progress, I must produce examples of “real” mathematical theorems, theorems which every mathematician will admit to be first-rate. 

… I can hardly do better than go back to the Greeks.  I will state and prove two of the famous theorems of Greek mathematics.  They are “simple” theorems, simple both in idea and in execution, but there is no doubt at all about their being theorems of the highest class.  Each is as fresh and significant as when it was discovered– two thousand years have not written a wrinkle on either of them.  Finally, both the statements and the proofs can be mastered in an hour by any intelligent reader, however slender his mathematical equipment.

I. The first is Euclid’s proof of the existence of an infinity of prime numbers.

The prime numbers or primes are the numbers

   (A)   2, 3, 5, 7, 11, 13, 17, 19, 23, 29, … 

which cannot be resolved into smaller factors.  Thus 37 and 317 are prime.  The primes are the material out of which all numbers are built up by multiplication: thus

    666 = 2 ^. 3 ^. 3 ^. 37. 

Every number which is not prime itself is divisible by at least one prime (usually, of course, by several).   We have to prove that there are infinitely many primes, i.e. that the series (A) never comes to an end.

Let us suppose that it does, and that

   2, 3, 5, . . . , P
 
is the complete series (so that P is the largest prime); and let us, on this hypothesis, consider the number

   Q = (2 ^. 3 ^. 5 ^{. . . . .} P) + 1.

It is plain that Q is not divisible by any of

   2, 3, 5, …, P;

for it leaves the remainder 1 when divided by any one of these numbers.  But, if not itself prime, it is divisible by some prime, and therefore there is a prime (which may be Q itself) greater than any of them.   This contradicts our hypothesis, that there is no prime greater than P; and therefore this hypothesis is false.

The proof is by reductio ad absurdum, and reductio ad absurdum, which Euclid loved so much, is one of a mathematician’s finest weapons.  It is a far finer gambit than any chess gambit: a chess player may offer the sacrifice of a pawn or even a piece, but a mathematician offers the game.

— G. H. Hardy,
   A Mathematician’s Apology,
   quoted in the online guide for
   Clear and Simple as the Truth:
   Writing Classic Prose, by
   Francis-Noël Thomas
   and Mark Turner,
   Princeton University Press

In discussing Davies’s claim that the above proof is by induction, you may want to refer to Davies’s statement that

Geometry was a well developed mathematical discipline based upon explicit axioms over one and a half millennia before the law of induction was first formulated

and to Hardy’s statement that the above proof is due to Euclid.

Permanence

“What we do may be small, but it has a certain character of permanence.”

— G. H. Hardy, A Mathematician’s Apology

For further details, see
Geometry of the 4×4 Square.

“There is no permanent place in the world for ugly mathematics.”

— Hardy, op. cit.

For further details, see
Four-colour proof claim.