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Posts

November 24, 2014

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12:00 AM | On This Day in Mathematics - November 24
Albertus MagnusTo call in the statistician after the experiment is done may be no more than asking hm to perform a postmortem examination: he may be able to say what the experiment died of.~Fisher, Ronald AylmerThe 328th day of the year; 328 is the sum of the first fifteen primes, and is a tau-number since it is divisible by the number of divisors it has. EVENTS1639 British astronomers Jeremiah Horrocks and William Crabtree became the first observers to record a transit of Venus. Horrocks was […]

November 23, 2014

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11:34 PM | Kuperberg’s parable
Recently, longtime friend-of-the-blog Greg Kuperberg wrote a Facebook post that, with Greg’s kind permission, I’m sharing here. A parable about pseudo-skepticism in response to climate science, and science in general. Doctor: You ought to stop smoking, among other reasons because smoking causes lung cancer. Patient: Are you sure? I like to smoke. It also creates jobs. […]
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11:14 PM | an ABC experiment
  In a cross-validated forum exchange, I used the code below to illustrate the working of an ABC algorithm: Hence I used the median and the mad as my summary statistics. And the outcome is rather surprising, for two reasons: the first one is that the posterior on the mean μ is much wider than […]
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10:30 PM | Share from Repository (weekly)
Stop Hating Common Core Math | SkeptoidTags: no_tagDigital Literacy Dover: To Code or not to Code?Tags: no_tagThe Magic Roundabout: why anxiety shouldn’t stop us learning | Othmar's TromboneTags: no_tagPosted from Diigo. The rest of Read on the Web -- Repository group favorite links are here.
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10:13 PM | From Rational Canonical Form to The Kostant Section
Suppose we have a $2\times 2$ matrix $$ M = \begin{pmatrix} x_{11} & x_{12}\\ x_{21} & x_{22} \end{pmatrix} $$ with entries in a field $F$. The characteristic polynomial of this matrix is $p(t) := {\rm det}(tI_2 – M) = t^2 – (x_{11} + x_{22})t + x_{11}x_{22} – x_{21}x_{12}$. One might ask: how can we produce […]
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10:00 PM | Links for November 23
Mona Chalabi and Andrew Flowers figure out the most common name in America, using some data by Lee Hartman to correct for the fact that first name and last name are not independent, but tend to cluster based on ethnicity. … Continue reading →
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9:28 PM | A brief history of video game graphics
Part 1: Pixel PioneersPart 2: Sprite SupremePart 3: Polygon RealmPart 4: Voodoo BloomPart 5: Future Crisis
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8:58 PM | My Blog is Still under Attack
Recently I wrote that my blog is under attack by spam comments. Most of the comments were caught by my spam-filter Akismet, the best-known filter for WordPress. I was receiving about 50,000 comments a day and 200 of them were sneaking through this filter. I had to moderate those and delete them. This was an […]
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8:06 PM | Bell’s inequality 50 years later
This is a jubilee year.* In November 1964, John Bell submitted a paper to the obscure (and now defunct) journal Physics. That paper, entitled “On the Einstein Podolsky Rosen Paradox,” changed how we think about quantum physics. The paper was … Continue reading →
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8:00 PM | Frankl, My Dear : 12
It is one of the rules of my system of general harmony, that the present is big with the future, and that he who sees all sees in that which is that which shall be. Leibniz • Theodicy Re: Dick … Continue reading →
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8:00 PM | حل متراجحة جذرية -بوضع جدول اشارات دالة جذرية
حل متراجحة جذرية تمرين محلول في ما يلي شرح لطريقة حل متراجحة تحتوي على تعبير جذري وذلك بوضع جدول اشارات دالة جذرية. الحالات التي تمت دراستها في الفيديو : <!-- mathsways336-280 --> (adsbygoogle = window.adsbygoogle || []).push({}); شاهد ايضا : المعادلات من الدرجة الثانية بمجهول واحد مع التعميل […]
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6:52 PM | Jefimenko’s equation for time-dependent magnetic field
References: Griffiths, David J. (2007), Introduction to Electrodynamics, 3rd Edition; Pearson Education – Problems 10.12. Using the retarded potentials, we can find a time-dependent expression for the magnetic field to complement the equation we got earlier for the electric field. The potentials are where and The magnetic field is where we’ve used the identity We […]
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6:43 PM | كيف تحدد معادلة مستقيم انطلاقا من تمثيله المبياني
كيف تحدد معادلة مستقيم انطلاقا من تمثيله المبياني في ما يلي شرح لطريقة تحديد معادلة مستقيم انطلاقا من تمثيله المبياني مع ثلاثة امثلة تطبيقية. <!-- mathsways336-280 --> (adsbygoogle = window.adsbygoogle || []).push({}); شاهد ايضا الدالة التآلفية والدالة الخطية، ملخص الدرس وتطبيقات ثالثة […]
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6:29 PM | Taut foliations and positive forms
This week I visited Washington University in St. Louis to give a colloquium, and caught up with a couple of my old foliations friends, namely Rachel Roberts and Larry Conlon. Actually, I had caught up with Rachel (to some extent) … Continue reading →
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6:10 PM | How medieval astronomers made trig tables
How would you create a table of trig functions without calculators or calculus? It’s not too hard to create a table of sines at multiples of 3°. You can use the sum-angle formula for sines sin(α+β) = sin α cos β + sin β cos α. to bootstrap your way from known values to other […]
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6:10 PM | Journey of Imagination
Journey of Imagination   by Roovodi   http://im-possible.info/english/art/computer/roovodi.html   Author - http://roovodi.deviantart.com/
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6:07 PM | Jefimenko’s equation for time-dependent electric field
References: Griffiths, David J. (2007), Introduction to Electrodynamics, 3rd Edition; Pearson Education – Problem 10.11. Using the retarded potentials, we can find a time-dependent expression for the electric field . The potentials are where and The expression for is given by The derivatives are complicated by the fact that the integrands in 1 and 2 […]
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5:14 PM | Happy Fibonacci Day (11/23)!
Happy Fibonacci Day (11/23)!
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5:13 PM | What’s the most-used textbook on statistical mechanics?
I was interested in working through a textbook on statistical mechanics, but as I’m no longer active in a physics department at a university, I was wondering what textbooks are commonly used these days. I have the book Fundamentals of Statistical and Thermal Physics by F. Reif, but this was published in 1965 and doesn’t seem […]
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4:10 PM | Elternbrechtag
Habe ich das neulich richtig gelesen? Jan schrieb ungefähr: “Elternsprechtage sind ja immer ganz nett.” Nein, sind sie nicht. Das heißt jetzt nicht, dass ich sie schlecht finde, denn gut sind sie eigentlich schon, aber nett? Bei uns läuft vormittags Unterricht bis 13.10 Uhr und dann Elternsprechtag von 14 bis … Continue reading →
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3:44 PM | Undergrad Math Tuition: Maxima and Minima (Multivariable Calculus)
At the undergraduate level, sometimes functions are of two variables (x,y). How do we find the maximum or minimum points of such a function? Read the following PDF to find out! Recommended Book: Multivariable Calculus, 7th Edition This is a … Continue reading →
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3:11 PM | Adding an equation to the table of contents
Next week I’ll be giving a lecture on spectral sequences in algebraic geometry, and in the notes I’m preparing I wanted to put the spectral sequence below the title of the corresponding section in the table of contents. The \addcontentsline command was known to me, but \addtocontents wasn’t, and there is one caveat in using […]
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2:57 PM | Math is a flat Circle
There are few things that bruise your professional ego more than no one showing up to an event you painstakingly and excitedly planned. In my case, it all came crashing down in early October. I had been planning to start … Continue reading →
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2:00 PM | The Math Geek Holiday Gift Guide
Looking for a gift that says, “Hey, I know you like math”? Look no further. There is an embarrassment of riches when it comes to wonderful mathematical things to give to people, but here are some of... -- Read more on ScientificAmerican.com
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1:40 PM | Exploring Fractions
Fourth grade students started to explore fraction computation last week. Since the beginning of the year they’ve been periodically reviewing how to add and subtract simple fractions. About a month ago this same group of students used fraction pieces of a pie to show a visual model of adding/subtracting different fraction less than one. Last […]
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1:31 PM | WEB LIVE Futura al lancio: Inizia L'avventura Di Samantha Nello Spazio
La Mission Futura è al lancio. Inizia, oggi 23 novembre 2014, l'avventura dell'astronauta italiana Samantha Cristoforetti nello spazio. Il decollo della navicella russa Soyouz è previsto per le 22.01 (ore italiane).Potete seguire, in web live, la partenza della Spedizione 42, con a bordo la prima astronauta donna italiana:► dalla sede Asi di Tor Vergata oppure ► dal sito dell'ESASul sito Esa di avamposto 42, si può leggere:Continua a leggere...»
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1:30 PM | 11/23/14
1 + 1 = 2 = 3 - 1 = √4 Also: (1 + 1) / 2 = (3 + 1) / 4 Also: 1 + 1 + 2 - 3 = 1^4
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1:23 PM | Terry Tao’s MoMath lecture part 3: The speed of light and paralax
[sorry if this doesn't read too well.  woke up sick today and am getting sicker.  boo :( Didn't have the energy for too much editing. ] In the last few weeks I’ve been writing about Terry Tao’s incredible public lecture … Continue reading →
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1:16 PM | Christmas Presents for Herrrr…
I believe that after my last post about ideas for Christmas gifts, you would expect this post immediately. With no further introduction, here are some of my favorite gift ideas for HeRRrrr: 1. Jewelry - I personally always like a good … Continue reading →
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12:53 PM | Uniqueness of Factorization
A few days ago I came across a proof of the Fundamental Theorem of Arithmetic (aka Unique Factorization) in Courant and Robbin’s What is Mathematics that I hadn’t seen it before. I liked it enough to learn it. Then another surprise … Continue reading →
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