## Seventh Linkfest

I’m extremely happy to present the seventh Linkfest for your pleasure, fun and profit. Thousands of men meditated for thousands of years to generate the pure knowledge and wisdom contained in these links. I hope they will revolutionize your life. I hope thirty years from now you will gaze down from the heights of power and success and remember the Seventh Linkfest which gave you the tools to conquer the world.

The previous linkfest was Linkfest 6.

## Technical

Scott Aaronson: Projects aplenty (a huge list of project suggestions for grad students in computer science), Tools for the modern complexity theorist

Ngô Quốc Anh: Norm of traceless Ricci tensor, Variations of the determinant, The entropy logarithmic energy inequality

John Armstrong: Integral curves and local flows, The Maximal Flow of a Vector Field, Vector fields on compact manifolds are complete, Maps Intertwining Vector Fields, The Lie algebra of a Lie group, General linear groups are Lie groups, The Lie algebra of a general linear group

Jeremy Avigad, Edward Dean, and Jason Rute: Algorithmic randomness, reverse mathematics, and the dominated convergence theorem (arXiv)

John Baez: Christopher Walker on Hall Algebras

Andrej Bauer: Stone duality for skew boolean algebras with intersections

Ken Baker: Rational Tangle Fibration

Alexandre Borovik quoting Jeff Sarnat: More on abstract thinking and computer science

James Freitag: Indecomposability for differential algebraic groups, Completeness in Partial Differential Fields (both arXiv)

William Gasarch: RaTLoCC (or: on a conference about Ramsey theory)

Hilbertthm90: Multiplication is repeated addition

Jesse Johnson: A funny thing about circular thin position

Tanya Khovanova: Freedom and Diamonds

Carlos Matheus: Billiards, Flat Surfaces and Dynamics on Moduli Spaces at Oberwolfach 2011, Non-uniformly hyperbolic horseshoes have Hausdorff dimension < 2

Akhil Mathew: The nPOV, sheathes, and derived categories, Verdier duality, Soft sheaves

Arnold Miller: Uniquely Universal Sets (arXiv)

Antonio Montalban: A fixed point for the jump operator on structures (arXiv)

Kenneth Regan: How powerful are random strings?, Types of Math Papers

Dan Piponi: Simulating visual artifacts with Fourier optics

Gordon Royle: An elusive conjecture (that a finite projective plane with a point-transitive automorphism group must be Desarguesian)

Hans Schoutens: O-minimalism (arXiv)

Shreevatsa: How does Tupper’s self-referential formula work?

Terence Tao: The Cotlar-Stein Lemma, Locally compact groups with faithful finite-dimensional representations, van Dantzig’s Theorem, The Furstenberg multiple recurrence theorem and finite extensions

Peter Woit: Math and Physics, Summer 2011 (specifically: about a conference thereon)

Qiaochu Yuan: Euler characteristic as homotopy cardinality

## Non-Technical

Avoision: Finding Time to Write

Michel Bauwens: The Shanzai electric car revolution in China, Software + data as business models, The amazing bike-sharing program in Hangzhou, China

Matthew Belinkie: Clichemaggedon 3D: The Winners

Alexandre Borovik: An “average word problem” in the Khan Academy, Is the world mathematical?, Assessment by linear ordering, More on Raspberry Pi, First appearance of algebraic notation

Peter Casazza: A Mathematician’s Survival Guide (PDF)

Sonic Charmer: Buster Posey (or: why baseball shouldn’t be a contact sport)

Diana Davis: Submitting a (math) paper online

Cory Doctorow: Google’s YouTube policy for Android users is copyright extremism

Lance Fortnow: 75 years of computer science

Simon Grey: A decent half-measure (or: on a copyright law proposal), Good news from YouTube (specifically, availability of more Creative Commons content for developers to use)

Nathan Eady: Firefox: Why I Refuse to Upgrade

Henrir: How the next generation (of video game consoles) should shape up, E3 Impressions: The WiiU, Asymmetric Multiplayer

JSE: What experimental math taught me about my intuition

Brian Katz: Technology Supporting Innovative Pedagogy

Tanya Khovanova: A nerd’s way to walk up the stairs, Recent Geeky Jokes

Izabella Laba: PIMS collaborative research groups (and why Izabella doesn’t like them)

Mark Lee: The Prestige Factor for Actors

Michael Lugo: The most well-read cities in the United States

Matt Novak: A Trip through Space for Boys and Girls (1954)

Christopher Olah: Alien Mathematics, Numbers, and Polynomial Centric Societies

Orchid64: Will miss #327: Cat cafes

Alex Papadimoulis: Divide by Zero (or: a terrible implementation thereof in PHP)

The Physicist: Is it possible to destroy a black hole?, Q: How close is Jupiter to being a star? What would happen to us if it were?

Remy Porter: Design for the Future, Twenty-Four Bits per Intern

Derek Sivers: Any Questions? (or: on learning and on conscious vs. unconscious competence), I moved to Singapore

Derek Smith: The Bore Method, or Challenging Students

Moor Xu: Dreams (or: when math enters your dreams)

## Pictures and Photography

Avoision: Tiny signs in Logan Square

Ruben Berenguel: Road Trip Through Iceland: Day 9 – Goðafoss and Hólar

Izabella Laba: Spring Photos

Loco: Best Shots of the Week

Telefunker: Filature EDP (abandoned spinning mill in Belgium)