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Posts

October 21, 2014

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3:36 PM | Inflazione infinita e fine del tempo
Come saprete i dati di BICEP che sembrava dovessero confermare l'inflazione cosmica e le onde gravitazionali primordiali hanno subito una verifica negativa. Come spiegano molto bene Amedeo e Sandro, l'interpretazione dei risultati è stata completamente ribaltata dalle analisi di Planck.Uno degli aspetti che, con quell'annuncio di metà aprile, non avevo trattato ma che mi sarebbe piaciuto era la questione dell'inflazione infinita. Questa ipotesi teorica venne introdotta da Alan Guth e altri […]
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3:17 PM | Network Theory Seminar (Part 3)
  This time we use the principle of minimum power to determine what a circuit made of resistors actually does. Its ‘behavior’ is described by a functor sending circuits to linear relations between the potentials and currents at the input and output terminals. We call this the ‘black box’ functor, since it takes a circuit: […]
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3:10 PM | Martin Gardner Centennial
Martin Gardner was born on October 21, 1914, so today is his Centennial (he died on May 22, 2010, at the age of 95). We've mentioned him in the blog before:  The Life of Martin Gardner  Contribute to the Gardner Centennial  Another Post on Martin Gardner I used the anagram Tim Andrer Gran in both my review of the Lipton-Regan book (see here) and my Applications of Ramsey Theory to History paper (see here) So what can I add on his centennial? He was not the first person to […]
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11:42 AM | Rant 2: Academic "Letterhead" Requirements
I guess my first posted rant was the call for papers thing.  Here's a second.Countless times, from me to Chair/Dean xxx at Some Other University: I am happy to help with your evaluation of Professor zzz. This email will serve as my letter. [email here]...Countless times, from Chair/Dean xxx to me: Thanks very much for your thoughtful evaluation. Can you please put it on your university letterhead and re-send?Fantasy response from me to Chair/Dean xxx:Sure, no […]

October 20, 2014

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10:00 PM | Network Theory (Part 32)
Okay, today we will look at the ‘black box functor’ for circuits made of resistors. Very roughly, this takes a circuit made of resistors with some inputs and outputs: and puts a ‘black box’ around it: forgetting the internal details of the circuit and remembering only how the it behaves as viewed from outside. As […]
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5:03 PM | The CMS PhD program
At the beginning of this year I wrote an excited post announcing our new Computing and Mathematical Sciences (CMS) PhD program.  Unfortunately, the approval did not happen in time for students to apply to it last year, but everything is up and running now, so we’re looking forward to seeing the first round of applicants […]
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12:14 PM | Paradosso cosmico
The Time Machine at the End of the World, di Les Edwardsvia ahiddenworld.tumblr.comCome tutti i generi, anche la fantascienza in ultima analisi è interessata a parlare dell'essere umano. In particolare, come ricorda Isaac Asimov, parla dell'essere umano contemporaneo, nascondendo il messaggio dietro una rappresentazione meravigliosa, dietro un sense of wonder dovuto a progressi scientifici inimmaginabili.I due progressi scientifici che muovono la maggior parte della fantascienza (non sono gli […]
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6:26 AM | The Picard groups
Let be a commutative ring. From we can construct the category of -modules, which becomes a symmetric monoidal category when equipped with the tensor product of -modules. Now, whenever we have a monoidal operation (for example, the multiplication on a ring), it’s interesting to look at the invertible things with respect to that operation (for […]
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6:19 AM | Apply to join IQIM!
Editor’s Note: Dr. Chandni Usha is an IQIM postdoctoral scholar working with Prof. Eisenstein. We asked her to describe her experience as an IQIM fellow. When I look back at how I ended up here, I find myself in a … Continue reading →
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5:15 AM | Two model theory meetings
José Iovino has asked me to help advertise the following: At the 2015 Joint mathematics meetings (JMM), January 10-13, in San Antonio, TX, there will be two special sessions on model theory. The first is Beyond First Order Model Theory, a special session of the ASL and the AMS. See here for the schedule, list of […]
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4:01 AM | Sudoku Matroids and Graph Colouring Verification
As this is my first post, I feel obliged to say the obligatory Hello World!. With that aside, the problem I am going to discuss comes from the popular game Sudoku. Suppose that we are given a filled Sudoku $S$ … Continue reading →
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3:45 AM | Personification and pseudoscience
If you study the philosophy of science — and sometimes even if you just study science — then at some point you might get the urge to figure out what you mean when you say ‘science’. Can you distinguish the scientific from the non-scientific or the pseudoscientific? If you can then how? Does science have […]
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3:13 AM | 414/514 References on continuous nowhere differentiable functions
Just as the last two times I have taught 414/514, I am assigning a final project on the topic of continuous nowhere differentiable functions (see here and here for the previous times). The project requires that you choose an example of a continuous nowhere differentiable function, and to write a report describing the function, indicating who […]
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2:08 AM | hts with regressors
The hts package for R allows for forecasting hierarchical and grouped time series data. The idea is to generate forecasts for all series at all levels of aggregation without imposing the aggregation constraints, and then to reconcile the forecasts so they satisfy the aggregation constraints. (An introduction to reconciling hierarchical and grouped time series is […]

October 19, 2014

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9:48 PM | Fresh brain with no thoughts, yet
I just like his picture obtained with chemlambda because it gives many ideas, among them the following: if multiplication (reproduction) is Nature’s way to do a fanout and if a brain (and actually the whole organism) grows from a small seed then it must be that we may think about a brain as having one […]
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7:31 PM | Alan Guth, eternal inflation and the multiverse
http://t.co/CnvvOY0mAI about #AlanGuth #multiverse #CosmicInflation #icep2014 At the beggining of October, Alan Guth was at the workshop Fine-Tuning, Anthropics and the String Landscape at Madrid, and he concluded his talk with the following slide: The complete talk, without question time, follows:He presented the same talk also at ICEP 2014:
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6:01 PM | Maples
No summary available for this post.
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5:56 PM | Pippo e l'arte moderna
da Topolino e il ladro di quadri, dall'edizione uscita per il Tascabilone #8
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2:09 PM | Online bipartite matching in offline time
In 1973 Hopcroft and Karp gave a very nice time algorithm computing a maximum matching in unweighted bipartite graphs. This algorithm turned out to be the milestone that is hard to beat. The bipartite maximum matching problem has been studied … Continue reading →
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3:30 AM | PhilStat/Law: Nathan Schachtman: Acknowledging Multiple Comparisons in Statistical Analysis: Courts Can and Must
The following is from Nathan Schachtman’s legal blog, with various comments and added emphases (by me). He will try to reply to comments/queries. “Courts Can and Must Acknowledge Multiple Comparisons in Statistical Analyses” Nathan Schachtman, Esq., PC * October 14th, 2014 In excluding the proffered testimony of Dr. Anick Bérard, a Canadian perinatal epidemiologist in the […]

October 18, 2014

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9:32 PM | Hideout
Ad attirarmi sono stati innanzitutto i disegni: precisi e dettagliati, giocano moltissimo con i bianchi e i neri. Sono infatti opportunamente luminosi nelle scene cittadine, le più tranquille, e sono pesantemente bui nelle scene ambientate nel bosco o nella prigione sotterranea dove si trovano i protagonisti della vicenda, una coppia di giovani in crisi coniugale alla ricerca, apparentemente, di una soluzione ai loro problemi.In un fumetto dell'orrore, ad ogni modo, la parte grafica ha […]
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6:54 PM | FINAL CFP and *EXTENDED DEADLINE*: SoTFoM II 'Competing Foundations?', 12-13 January 2015, London.
The focus of this conference is on different approaches to the foundations of mathematics. The interaction between set-theoretic and category-theoretic foundations has had significant philosophical impact, and represents a shift in attitudes towards the philosophy of mathematics. This conference will bring together leading scholars in these areas to showcase contemporary philosophical research on different approaches to the foundations of mathematics. To accomplish this, the conference has […]
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2:36 PM | Dirichlet’s Theorem Revisited
Number theory: An Approach Through History from Hammurapi to Legendre选择Legendre作为征程的句点,自然有其理由:在阅读Disquisitiones Arithmeticae时找到灵感进而提出Weil猜想的人,比谁都深刻地认识到“还不到总结Gauss的时候”。在Weil去世的16年之后,我们积累了更多证据支持这一判断,例如新科Fields奖得主Bhargava同样是在阅读Disquisitiones […]
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11:47 AM | FOCS 2014 is starting
Hope everyone has a great FOCS! In the previous post we mentioned the two workshops on different aspects of the Fourier transforms occurring today. I also wanted to mention the Tutorial on obfuscation today with talks by  Amit Sahai, Allison Lewko and Dan Boneh. The new constructions of obfuscation and their applications form one of the most exciting and […]

October 17, 2014

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9:09 PM | I macachi del giappone
Vi parlerò di due isole, Kojima, la più grande, e Torishima, per metà nascosta dietro l'altra. Entrambe ospitano branchi di macachi selvatici. Ci fu un tempo in cui l'intera isola di Kyushu pullulava di queste scimmie, tuttavia in seguito all'invasione dell'uomo ne sono rimasti solo pochi gruppi sporadici, perlopiù su isolette remote come queste. Le scimmie locali sono le meno influenzate dall'uomo e, in quanto tali, oggetto di studi approfonditi da parte dei ricercatori.Qualche anno fa, le […]
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2:16 PM | Dirichlet’s Theorem Revisited
Number theory: An Approach Through History from Hammurapi to Legendre选择Legendre作为征程的句点,自然有其理由:在阅读Disquisitiones Arithmeticae时找到灵感进而提出Weil猜想的人,比谁都深刻地认识到“还不到总结Gauss的时候”。在Weil去世的16年之后,我们积累了更多证据支持这一判断,例如新科Fields奖得主Bhargava同样是在阅读Disquisitiones […]
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11:07 AM | Binary intersection property, and not fixing what isn’t broken
A metric space has the binary intersection property if every collection of closed balls has nonempty intersection unless there is a trivial obstruction: the distance between centers of two balls exceeds the sum of their radii. In other words, for every family of points and numbers such that for all there exists such that for […]
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1:17 AM | Solution: Kaplansky’s Commutative Rings 4.3.2
Let $R$ be a ring and $M$ an $R$-module with a finite free resolution (an “FFR module”). That is, there exists an exact sequence $0\to F_n\to F_{n-1}\to \cdots\to F_0\to M\to 0$ with each $F_i$ a finitely generated free $R$-module. If we denote by $r_i$ the rank of $F_i$, then the Euler characteristic of $M$ is […]

October 16, 2014

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8:59 PM | Network Theory Seminar (Part 2)
  This time I explain more about how ‘cospans’ represent gadgets with two ends, an input end and an output end: I describe how to glue such gadgets together by composing cospans. We compose cospans using a category-theoretic construction called a ‘pushout’, so I also explain pushouts. At the end, I explain how this gives […]
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7:28 PM | Optimal proof systems — a survey (slides by Olaf Beyersdorff)
Olaf Beyersdorff surveys Optimal Proof Systems in the attached slides presented at the October 12-17, 2014 Dagstuhl Seminar on Optimal algorithms and proofs.
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