Author Archives: apgoucher

MODA: Geometry bashing

A tried and tested technique for attacking geometry problems is ‘bashing’ them with an algebraic approach. We’ve already seen how projective geometry can be based around a coordinate system (giving rise to areal and projective Cartesian coordinates as special cases). Two-dimensional Cartesian coordinates … Continue reading

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Combinatorial game theory

Dating the discovery of the integers is difficult indeed. Positive integers have been used since time immemorial for counting, and positive rationals were later used by the Ancient Greeks to express lengths. However, this was not sufficient, as the Pythagorean … Continue reading

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A slice of π

If I were more diligent and could actually be bothered to tag and categorise my blog posts, this one would belong in the esoteric realm of ‘probabilistic geometry’. Suppose we have three variables, X, Y and Z, which are independent and random, determined … Continue reading

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MODA: Projective geometry

(This is a pre-recorded message scheduled to automatically publish on the 1st October. If you’re reading this, I’m in Cambridge, probably either very busy with work, or very inebriated, or both. Here’s an emoticon which is also valid punctuation in this … Continue reading

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Hiatus interruptus

I shall be rather busy during the next couple of months, so there may be a noticeable drop in the frequency of posts on Complex Projective 4-Space. Nevertheless, I shall endeavour to maintain a steady stream of interesting articles, assuming I … Continue reading

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Good fibrations

We’ll begin by considering Hamiltonian quaternions, a four-dimensional extension to the complex numbers. A particularly interesting bunch of quaternions is the multiplicative group of 120 ‘icosians’. These can be thought of as the vertices of a 600-cell or, by duality, the … Continue reading

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Cipher 2: Labyrinth

The Labyrinth usually refers to a particular maze in Knossos on the Greek island of Crete, designed by Daedalus to contain the Minotaur: a ravenous bull-human hybrid, which found human sacrifices particularly appetising. Theseus navigated these tortuous underground passageways by means of … Continue reading

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MODA: Inequalities

I imagine you’re all eagerly anticipating Cipher Tuesday, which is only a couple of days away now! Meanwhile, the sixth chapter of MODA, namely ‘Inequalities’, is available for download. Preface Combinatorics I (enumerative and geometrical combinatorics) Linear algebra Combinatorics II (graph theory) Polynomials Sequences Inequalities Projective geometry … Continue reading

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163

There is a reasonably popular card game entitled 24, where players attempt to derive 24 by applying basic arithmetic operations to a set of four positive integers. For example, the provided integers may be {3, 3, 8, 8}. A solution must … Continue reading

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Antikythera mechanism

Near the beginning of the 20th century, a shipwreck was discovered. It contained a horde of treasure en route from Greece to Rome, including a life-size bronze head of a philosopher. The most valuable treasure, however, was a 2000-year-old analogue … Continue reading

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