Today I Learned

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June 2021

June 1st

Today I learned about the Mahler measure, from here . (continue reading...)

June 2nd

Today I learned a proof that $e^q$ is irrational for any $q\in\QQ\setminus\{0\},$ following Hermite. (continue reading...)

June 3rd

Today I learned an example of spectral graph theory doing something of number-theoretic interest, from THE BOOK. (continue reading...)

June 5th

Today I learned about the difficulty generalizing the result from yesterday to arbitrary dimensions. (continue reading...)

June 6th

Today I learned that a number of geometric concepts can be defined purely formally from an arbitrary distance metric, from the ARML Power Round. (continue reading...)

June 6th

Today I learned the classification of primes in polynomial rings over principal ideal domains, from Undergraduate Commutative Algebra. (continue reading...)

June 7th

Today I learned a truly clever proof to the Spectal theorem, from THE BOOK of course. (continue reading...)

June 8th

Today I learned about the semi-failure of function extensionality for polynomials. (continue reading...)

June 9th

Today I learned a little about group homology and chain complexes, from Napkin . (continue reading...)

June 10th

Today I learned a proof to Sperner's theorem, from THE BOOK. (continue reading...)

June 11th

Today I learned about the P\'olya-Vinogradov inequality, from Joni and Tao . (continue reading...)

June 12th

Today I learned about representing numbers as sums of distinct squares, from a bunch of places. (continue reading...)

June 13th

Today I learned a few ways to evaluate $\zeta$ at even integers, from THE BOOK, and some consequences. (continue reading...)

June 14th

Today I learned more formally about the association between points in $k^n$ and maximal ideals of $k[x_1,\ldots,x_n],$ from Undergraduate Commutative Algebra. (continue reading...)

June 15th

Today I learned the start of some group cohomology. (continue reading...)

June 16th

Today I learned finish to the proof that any $G$-module can be embedded into an injective $G$-module. (continue reading...)

June 17th

Today I learned that group cohomology is well-defined. (continue reading...)

June 18th

Today I learned an algebraic proof of the Cayley-Hamilton theorem. (continue reading...)

June 19th

Today I learned a more thorough version of the Snake Lemma to set up for the long exact sequence of cohomology. (continue reading...)

June 20th

Today I learned some stuff around the Cauchy-Schwartz inequality, from THE BOOK. (continue reading...)

June 21st

Today I learned a proof of Nakayama's lemma as a corollary of the determinant trick. (continue reading...)

June 22nd

Today I learned some stuff about short exact sequences. (continue reading...)

June 23rd

Today I learned (and reviewed) some proofs of the Sylow theorems that I like. (continue reading...)

June 24th

Today I learned about the Wronskian. (continue reading...)

June 25th

Today I learned a little more about polynomial statistics over finite fields. (continue reading...)

June 26th

Today I learned a proof of the Hilbert basis theorem. (continue reading...)

June 27th

Today I learned about Artinian rings. (continue reading...)

June 28th

Today I learned a toy model for schemes, as more or less the opposite category of commutative algebras. (continue reading...)

June 29th

Today I learned more about the Zariski topology. (continue reading...)

June 30th

Today I learned more formally about integral elements and closures. (continue reading...)