Fellow Craft
Susskind’s lectures on cosmology
Another amazing set of 8 lectures by Lenny Susskind – cosmology this time. Thanks for sharing this, Stanford!
P.S. If you were unable to see embedded video, here is the link to the playlist I’ve created for you.
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Notes on strongly coupled QCD in the continuum
By continuum here we mean using methods different from lattice QCD, which is currently our main instrument for quantitative understanding of QCD physics at strong coupling.
What can we actually do apart from lattice simulations to study properties of QCD in this regime? Not much really. As recent minireview paper by M. Pennington explains, one approach to the problem would be solving Schwinger-Dyson equations at strong coupling.
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Susskind’s general relativity – lecture 9
… where Leonard Susskind discusses spacetime – spacelike, timelike and lightlike directions, explains how one gets special relativity from general relativity (post-Newtonian approximation), non-relativistic limit of GR and finally … Einstein equations (hurray!)
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Susskind’s 8th lecture on general relativity
Leonard Susskind continues reading his lecture course on general relativity in U. of Stanford. Previous lectures can be found here: Lectures 1-5, Lecture 6 and Lecture 7.
Susskind continues to discuss covariant derivatives, parallel transport of vectors, Ricci and Riemann tensors. In the second part of the lecture he turns to geodesics. He is terrific lecturer but after the lecture N7 I start wondering whether it’s worth spending so much time discussing technicalities 
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Things that go bump in the CMB polarization
This post is written by Michael Mortonson, graduate student of Wayne Hu at the U. of Chicago. Michael has also asked me to thank Cora Dvorkin and Wayne Hu (U. of Chicago), and Hiranya Peiris (U. of Cambridge), who contributed to the post. Dmitry.
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Vorticity generation in cosmological perturbation theory
Adam Christopherson is a PhD student at Queen Mary, U. of London working with Karim Malik on cosmological perturbation theory. Dmitry.
In this blog post, I will summarize recent work on vorticity generation in cosmological perturbation theory, undertaken by Karim Malik, David Matravers and myself. The main result of the paper this is based on, arxiv:0904.0940, is that at second order in perturbation theory, vorticity generation is sourced by entropy gradients.
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Quantum tunneling in flux compactifications
Delia Schwartz-Perlov is a postdoc at Tufts U. working with Alex Vilenkin. Her interests include quantum field theory, string theory, general relativity and cosmology. Dmitry.
I am very happy to find myself writing a blog about a recent paper written by Jose Juan Blanco-Pillado, Alex Vilenkin and myself, and titled “Quantum tunneling in flux compactifications“. In this paper we studied bubble nucleation rates in a 6-dimensional Einstein-Maxwell theory. The two extra dimensions are compactified into a 2-sphere, and their radius is stabilized by a magnetic flux through that sphere. We picked this toy model because it is simple enough to allow a quantitative analysis, yet it also includes some of the essential features of string theory compactifications (a related paper by Sean Carroll, Matthew Johnson and Lisa Randall was posted on the same day as ours!).
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Self-improving artificial intelligence: video of the day
A lecture (colloquium, more precisely) by Steven Omohudro given at Stanford. If you don’t know about the lecturer, the guy has had quite an impressive career: he started as theoretical physicist, but switched eventually to AI and neural networks (among may other achievements on this field, he held an assistant professorship at U. of Illinois in computer science). Lecture is very interesting, although I do think that his presentation sells a certain illusion
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383. Puzzling kinetics of Bose-Enstein condensation
Just finished reading a really review “Magnon BEC and spin superfluidity” by Yu. Bunkov and G. Volovik, which left me with quite a bit of material to think about… Probably the thing that stroke me most after digesting the review is how poorly I (or in truth – it’s better to say “we”) actually understand the kinetics of Bose-Einstein condensation. But before I’ll try to explain why I think so, let me briefly describe the setup discussed by the authors.
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377. Temporal and spatial dependence of quantum entanglement
Shih-Yuin Lin is a professor at Physics Division, National Center for Theoretical Sciences, Taiwan. Dmitry.
In textbooks, quantum entanglement are often introduced to readers with the simplest case: in an isolated system with two parties or subsystems, if a quantum states can be factorized into a product of the quantum states for each subsystem,
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373. Some musings about Unruh effect
Good new long work week, science geeks! I’ve just finished reading a recent paper by Ugo Moschella and Richard Schaeffer “Quantum fields on curved space times and a new look at the Unruh effect” and wanted to share some of my thoughts with you…
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368. Inertial confinement: more on interaction of laser emission with matter
Yeah… so, where did we stop last time? I’ve just said another triviality – that laser emission strongly interacts with material of the fuel capsule. There are several mechanisms of this interaction: deflection (ablator and fuel are almost transparent but not quite), absorption and scattering.
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358. Thermonuclear reactors. Inertial confinement
I am currently keeping studying thermonuclear fusion and reactors a bit and, I should admit, I’m absolutely in love with HiPER and inertial confinement as an idea – it is so much more elegant than magnetic confinement used in Tokamaks… But before I’ll turn to the discussion of inertial confinement reactors, let me finish with generalities and trivialities (I’ll need them anyway for further reference).
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354. Vortex line representation. Clebsch variables
Let us continue our brief discussion of behavior of the vorticity field in the Eulerian flow.
(and that’s how vortex lines look like in reality… as if you wouldn’t know )
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335. What is twistor
Good Saturday evening, True Geeks!
Since everybody currently seems to be a bit crazy about twistors – see for example, the Witten’s paper “Perturbative gauge theory as a string theory in twistor space” and the buzz it started – I decided that the time has come for me to learn what it is and write minireview post about it.
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