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# Posts

### April 25, 2015

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Another powerful procedure of SAS, my favorite one, that I would like to share is the PROC IML (Interactive Matrix Language). This procedure treats all objects as a matrix, and is very useful for doing scientific computations involving vectors and matrices. To get started, we are going to demonstrate and discuss the following: Creating and Shaping Matrices;Matrix Query;Subscripts;Descriptive Statistics;Set Operations;Probability Functions and Subroutine;Linear Algebra;Reading and Creating […]

### April 24, 2015

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Filed under: Books, Kids, pictures Tagged: atheism, ontological argument, xkcd
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I’ve been busy with other things, but after taking a look today at various new things related to quantum gravity, I was struck by how much things have changed sociologically in that subject over the last few years. Back in … Continue reading →
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I have given the first two lectures: lecture 1 (categories of dynamical systems, basics of entropy, exercises) lecture 2 (Lyapunov exponents, Oseledets theorem, applications)
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the colors-to-corners assignment here is nonstandard… i.e., inconsistent with the one i’ve been using as my “base case” in earlier blog entries. so for heck sake don’t memorize ’em this way. the “algebraic” aspect here… whereby certain “vertex triples” are assigned “dual vectors” according to the scheme [1] = [0:0:1] —> {010, 100, 110} [2] […]
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Just a few minutes ago I conceived a definition of generalized Fréchet filters with definition for every poset on which filters are considered (however, I have not yet calculated the class of posets for which generalized Fréchet filter is defined; it should be easy but I am busy with other business). Generalized Fréchet filter on […]
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“It is no good just finding particular instances where peer review has failed because I can point you to specific instances where peer review has been very successful,” she said. She feared that abandoning peer review would make scientific literature no more reliable than the blogosphere, consisting of an unnavigable mass of articles, most of … Continue reading A second opinion on “Slay peer review” article →
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yet another sketch from the “lectures without words” run of MEdZ. here improved with colored inks (and spoiled by flouting the “without words” rule). “binary arithmetic” is here exploited to assign *number values* to the corners; the symbol “xyz” chosen from 000, 001, 010, 011, 100, 101, 110, 111 corresponds on this model to 4x […]
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Today I wanted to mention a theorem of Chenever about components of the Eigencurve. Let denote weight space (which is basically a union of discs), and let be the Coleman-Mazur eigencurve together with its natural map to It will do … Continue reading →
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4 + 2 - 4 = √|(1 - 5|) Also: (4 * 2) - 4 = |1 - 5| Also: 4 = 24 / (1 + 5)
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Filed under: pictures, Running, Travel Tagged: Amsterdam, canals, chain, Holland, Markov chain, sunrise
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A colori uguali corrispondono oggetti uguali. Dunque un angolo maggiore di un angolo retto è congruente a un angolo retto. Ehm.
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I’ve just been to an excellent seminar on Double Field Theory by its co-creator, Chris Hull. You may know that string theory exhibits a meta-symmetry called T-duality. More precisely, it’s equivalent to put strings on circles of radius and . This is the simplest version of T-duality, when spacetime has no background fields. Now suppose … Continue reading T-duality and Isometries of Spacetime →
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Did I detect just a small amount of provocation at NBSAN when Vicky Gould (from York) said to Rick Thomas (from Leicester), “You got our king”? Of course, this refers to Richard III, whose bones (as you most likely know) … Continue reading →
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During the graduate workshop on moduli of curves (organized by Samuel Grushevsky, Robert Lazarsfeld, and Eduard Looijenga last July 2014), Alex Wright gave a minicourse on the -orbits on moduli spaces of translation surfaces (the videos of the lectures and the corresponding lecture notes are available here and here). These lectures by Alex Wright made […]
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An introduction to homotopy type theory for philosophers
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My last post was about “Cheryl’s birthday puzzle”, which recently became an internet sensation.  I mentioned several additional puzzles in that post and promised solutions; here they are. Let me begin, though, with a “cryptography” variant of the Cheryl puzzle which was sent to me by my friend and puzzle guru Pete Winkler: Cheryl’s birthday […]
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It has been a year since UBC announced its very first …“president of colour”. And as of yesterday, UBC has its very first woman provost. On the surface, these look like de-facto corollaries of a post-racial, post-sexist era, at a … Continue reading →

### April 23, 2015

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here one has labeled the vertices of a cube with (“euclidean”) 3-space co-ordinates. the “origin”… we can think of it as our “point of view”… is at 000. [the “point” in 3-space usually denoted (x, y, z) is here written as “xyz”; we restrict our attention to the values in {0, 1} for these variables […]
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Kate Lee pointed me to a rather surprising inefficiency in matlab, exploited in Sylvia Früwirth-Schnatter’s bayesf package: running a gamma simulation by rgamma(n,a,b) takes longer and sometimes much longer than rgamma(n,a,1)/b, the latter taking advantage of the scale nature of b. I wanted to check on my own whether or not R faced the same […]
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This week, during a spell of lovely spring weather and new blossom, the 20th meeting of the North British Semigroups and Applications Network was held in St Andrews, organised by Markus Pfeiffer. It was good to see old friends such … Continue reading →
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On approche les dernières médailles ;-)...
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The purpose is to understand clearly what is this story about. The most simple stuff, OK? in order to feel it in familiar situations. Proceed. Chemlambda is a collection of rules about rewritings done on pieces of files in a certain format. Without an algorithm which tells which rewrite to use, where and when,  chemlambda … Continue reading A comparison of two models of computation: chemlambda and Turing machines →
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Hier in Korea, auch im demokratischen Süden, liest man öfter mal erbauliche Sprüche an den Wänden. Ich habe schon länger die Absicht mal ein paar Kuriositäten zu sammeln und hier im Blog vorzustellen. Heute will ich aber nur einen Spruch weitergeben, den wohl jeder Mathematiker ohne Zögern wird bestätigen können (und bei dem man sich…
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4 - 2 = |(3 * 1) - 5| Also: |4 - (2 * 3)| = √|(1 - 5)| Also: (4 * 2) - 3 = 1 * 5
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Filed under: Travel Tagged: elections, UK Elections 2015, United Kingdom, vote, voters apathy

### April 22, 2015

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A silly LaTeX error took me a few minutes too many to solve: I defined which got me the error message that I understood as a recursive definition. So I instead pre-defined the new θ as which did not work either… After google-ing the issue, I found this on-line LaTeX Wikibook that provided me with […]
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I’ve done several posts explaining why I think roguelikes are a great genre of game to play. It is probable that the most important feature of a roguelike for me is permadeath. For example, see this post for reasons why. … Continue reading →
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one has already learned the 7-cycle sunday-monday-tuesday-wednesday-thursday- -friday-saturday-(sunday-…) as part of one’s cultural heritage as an english speaker. and it’s high time i *used* that fact in studying “fano’s rainbow” (aka “the seven-point [projective] space”). and so to each of the *positions* in the well-known “three corners, three midpoints, one center” representation of fano space, […]
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Here is a question I asked myself yesterday: Suppose that X is an algebraic space which has degree 2 finite etale covering X_2 —> X and a degree 3 finite etale covering X_3 —> X such that both X_2 and … Continue reading →