Mathblogging.orgRecent Postshttp://www.mathblogging.org/scripts/feed.php2014-04-24T14:39:45-04:00No copyright asserted over individual posts; see original posts for copyright and/or licensing.Mathblogging.org Atom serializerBirth and death of zipper combinators (II)http://www.mathblogging.org/post/858702014-04-24T07:38:10-04:00chorasimilarityContinues from Birth and death of zipper combinators (I). In the following is presented another mechanism of birth/death of zipper combinators, which is not using a garbage collecting arrow and termination node. For any zipper combinator there is a number and a succession o f CLICK, ZIP and LOC PRUNING moves such that   So this […]Truthiness From Yablohttp://www.mathblogging.org/post/858662014-04-24T07:15:00-04:00"Shecky Riemann"<br />This isn't everyone's cup-o-tea, but I've mentioned Yablo's Paradox before, and, since I love it, will do so again! As Sam Alexander states, Yablo's Paradox is "a cute version of the Liar’s Paradox" that manages "to achieve paradox without any direct self-reference." The simply-stated paradox involves a countably infinite number of sentences, each of which refer only to sentences that come after it:<br />Sentence 1: Sentence n is false for every n > 1Sentence 2: Sentence n is false
[…]I burned my eyes reading the Wall Street Journal this morninghttp://www.mathblogging.org/post/858672014-04-24T07:10:59-04:00Cathy O'Neil, mathbabeIf you want to do yourself a favor, don’t read this editorial from the Wall Street Journal like I did. It’s an unsigned “Review & Outlook” piece which I’m guessing was written by Rupert Murdoch himself. Entitled Telling Students to Earn Less: Obama now calls for reforming his bleeding college loan program, it’s a rant against […]April 24, 2014http://www.mathblogging.org/post/858592014-04-24T07:00:00-04:00Mathematical Association of America<br /><br /><br /><br /><br /><br /><br />Solution at the bottom of this page.Like this problem? Try our Contest Problem Book series!<br /><br /><br /><br />April is Mathematics Awareness Month! <br />From magic squares and Möbius bands to magical card tricks and illusions, mysterious phenomena with elegant “Aha!” explanations have permeated mathematics for centuries. Such brain-teasing challenges promote creative and rational thinking, attract a wide range of people to the subject, and often inspire serious mathematical research. <br /> The
[…]Where People Bike and Run, Worldwidehttp://www.mathblogging.org/post/858612014-04-24T05:52:02-04:00Nathan YauRemember those running maps I made with limited data from RunKeeper? Strava, which also provides an app to track your …Elsevier journals — some factshttp://www.mathblogging.org/post/858572014-04-24T05:40:36-04:00gowersA little over two years ago, the Cost of Knowledge boycott of Elsevier journals began. Initially, it seemed to be highly successful, with the number of signatories rapidly reaching 10,000 and including some very high-profile researchers, and Elsevier making a number of concessions, such as dropping support for the Research Works Act and making papers […]The #1 Thing I Won't Teach Next Year: Integer Operationshttp://www.mathblogging.org/post/858582014-04-24T05:30:00-04:00Sarah HaganI realize it's still April. Our last day of school is May 14th. But, I'm already thinking about next year. In fact, I'm thinking a lot about next year. Things I want to do. Things I don't want to do. Things I need to do. Things I should think about doing. <br /><br />Here's the deal. Oklahoma is changing standards next year. Originally, we were a PARCC state. Next year is supposed to be our first year of full implementation of Common Core. […]Navigare con la matematica – Maddmaths!http://www.mathblogging.org/post/858562014-04-24T03:55:07-04:00Angelo StellaNavigare con la matematica leggi articolo completo
Announcement: TikZ workshophttp://www.mathblogging.org/post/858552014-04-24T03:29:42-04:00pbelmansI should’ve made this announcement sooner, but today I am giving an introductory workshop to TikZ (and friends). It is organised by my friends of PRIME and takes place today (Thursday, April 24) at 17h30 in room Turing, of building S9 on the Sterre campus of Ghent University. Everyone can attend, but it will be […]Still learning - Diagrams and conceptual understandinghttp://www.mathblogging.org/post/858502014-04-24T02:29:00-04:00Unknown5535http://www.mathblogging.org/post/858492014-04-24T02:00:00-04:00Mathematical Association of America5535 = 3 x 3 x 3 x 5 x 41.<br /><br />Every digit of 5535 is a prime factor of 5535 (A062239).<br /><br />5535 and the square of 5535 use only the digits 0, 2, 3, 5, and 6 (A136888).<br /><br />5535 is a number n such that n3 - 4 and n3 + 4 are prime (A161589).<br /><br />5535 is a number n such that (n3 + 2 and n3 + 4) is a twin prime pair (A178337).<br /><br />5535 divides 7312 - 1.<br /><br />5535 is a number that cannot be written as a sum of three squares.<br /><br /><br />Source: OEISAnche le scimmie sanno la matematica, e contano (almeno) da 0 a 25 – Greenreporthttp://www.mathblogging.org/post/858512014-04-24T01:58:36-04:00Angelo StellaAnche le scimmie sanno la matematica leggi articolo completo
Publishing an R package in the Journal of Statistical Softwarehttp://www.mathblogging.org/post/858482014-04-24T01:41:29-04:00Rob J HyndmanI’ve been an editor of JSS for the last few years, and as a result I tend to get email from people asking me about publishing papers describing R packages in JSS. So for all those wondering, here are some general comments. JSS prefers to publish papers about packages where the package is on CRAN and has been there long enough to have matured (i.e., obvious bugs ironed out and a few active users). This is partly because we have so many submissions that it helps to filter some out and this […]IXL Maths: matematica pratica dalla scuola dell’infanzia alla secondaria di II gradohttp://www.mathblogging.org/post/858522014-04-24T01:33:32-04:00Angelo StellaRisorse di matematica dalle scuole elementari fino alle scuole superiori leggi articolo completo
NASA Space Crewshttp://www.mathblogging.org/post/858632014-04-24T01:32:03-04:00Neil SpellingsIn the Apollo missions many of the crew were experienced, but some were
not. So I drew a diagram - see what patterns you see.Software Checklisthttp://www.mathblogging.org/post/858622014-04-24T01:32:02-04:00Neil SpellingsDuring the second World War, fighter pilots would scramble to take off.
Their heart would stop when the engine mis-fired. Was the fuel mix too
rich, or too lean? Turn the control wrong way and they could die ...Equazione di II grado parametrica | Prof. Albertihttp://www.mathblogging.org/post/858532014-04-24T01:28:47-04:00Angelo StellaEquazione parametrica di secondo grado vedi video
Invariant subspaces and Deddens algebrashttp://www.mathblogging.org/post/858462014-04-24T01:26:03-04:00Miguel LacruzMy paper entitled `Invariant subspaces and Deddens algebras’ has been accepted for publication in Expositiones Mathematicae. Here is the abstract It is shown that if the Deddens algebra associated with a quasinilpotent operator on a complex Banach space is closed … Sigue leyendo →Sistemi simmetrici | Prof. Albertihttp://www.mathblogging.org/post/858432014-04-24T01:25:16-04:00Angelo StellaSistemi simmetrici vedi video
Blind Image Deblurring by Spectral Properties of Convolution Operators - implementation -http://www.mathblogging.org/post/858452014-04-24T01:00:00-04:00IgorHere is a somewhat 'older' blind deconvolution algorithm (compared to this one)<br />Blind Image Deblurring by Spectral Properties of Convolution Operators by Guangcan Liu, Yi Ma<br /><br />In this paper, we study the problem of recovering a sharp version of a given blurry image when the blur kernel is unknown. Previous methods often introduce an image-independent regularizer (such as Gaussian or sparse priors) on the desired blur kernel. For the first time, this paper shows that the blurry image
[…]Peirce’s 1870 “Logic Of Relatives” • Comment 10.10http://www.mathblogging.org/post/858422014-04-24T00:00:18-04:00Jon AwbreyThe last of the three examples involving the composition of triadic relatives with dyadic relatives is shown again in Figure 25. (25) The hypergraph picture of the abstract composition is given in Figure 26. (26) This example illustrates the way that Peirce … Continue reading →[NCTMNOLA Processing Session 5] Networks and Siloshttp://www.mathblogging.org/post/858472014-04-23T23:59:44-04:00GeoffThis will be the fifth and final NCTMNOLA Processing Session. It’ll be short too, just a quick debrief. I vacillate between the poles of “math is different” and “math is just like other subjects.” Sometimes I wonder if math teachers … Continue reading →[NCTMNOLA Processing Session 4] I may have missed my callinghttp://www.mathblogging.org/post/858382014-04-23T23:25:38-04:00GeoffThose most mathematical fun I had at NCTMNOLA was in sessions focused on Elementary School level math. Either by accident or by impulse I found myself drifting into sessions that one would associate with K-5. Well, if that’s the case, … Continue reading →The Math of Rock Climbinghttp://www.mathblogging.org/post/858412014-04-23T21:57:00-04:00UnknownWhat's it like to fall 40 feet down a sheer cliff face, while dangling from a rope hundreds of feet from the ground? Emory mathematician Skip Garibaldi describes his rock climbing experiences on El Capitan in Yosemite National Park. He also explains some basic climbing math, such as the fall factor, used to reduce the risk of injury during a rope climb.[NCTMNOLA Processing Session 3] Summer School is Dead, Long Live Summer Schoolhttp://www.mathblogging.org/post/858392014-04-23T21:55:36-04:00GeoffIn between the instant they opened the door to Jo Boaler’s talk on “Promoting Equity Through Teaching for a Growth Mindset” and when she began speaking, I, Eleanor, and a few others in my row banded together as Jo Boaler … Continue reading →American Pihttp://www.mathblogging.org/post/858372014-04-23T21:44:28-04:00MaiuITU 100 GHz Frequency Grid Mathhttp://www.mathblogging.org/post/858342014-04-23T21:42:13-04:00mathscinotesIntroduction A physicist in my group and I were having a discussion about how the wavelengths (i.e. colors) for lasers are specified by an international standard and I thought this discussion would provide a nice example of a differential approximation. … Continue reading →backwardinduction:
In mathematics, an algebraic set is the set...http://www.mathblogging.org/post/858362014-04-23T21:08:31-04:00Unknownbackwardinduction:
In mathematics, an algebraic set is the set of solutions of a system of polynomial equations. Algebraic sets are sometimes also called algebraic varieties, but normally an algebraic variety is an irreducible algebraic set, i.e. one which is not the union of two other algebraic sets. Algebraic sets and algebraic varieties are the central objects of study in algebraic geometry. The word “variety” is employed in the sense which is similar to that of manifold;
[…]Believe it or not, we've been talking about the nice Krugman -- some perspective on the 538 debatehttp://www.mathblogging.org/post/858352014-04-23T21:01:00-04:00Mark[You may have trouble getting past the NYT firewall on these. If so, the easiest way around this is either to Google name and author or do what I did and go here for a complete set.]<br /><br />One of the side questions in the ongoing 538 debate is whether or not Nate Silver and his writers are being excessively criticized. There is certainly some truth to the charge (for reasons I'll get into later), but it's also important to remember that, to a remarkable extent, Silver walked into a bar fight, a number […]Lecturer in Pure Mathematicshttp://www.mathblogging.org/post/858542014-04-23T20:09:55-04:00Unknown