Master Postdoc
Other interesting things in ArXiv (11 Jun 2009)
Basically, there were so many interesting and useful papers (or at least they were useful for me) – lecture notes, reviews – that it will give me hard time posting reviews of all of them here – since I am lazy, I’ll just try to list some of them.
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Workshop on tests of gravity in Case Western – day 2: aether and modified gravity
Let me finally briefly review the reminder of the second day of the workshop.
Justin Khoury (whom I knew from Perimeter years and who is in Penn now) gave the first talk afternoon – titled “observational hints of IR modified gravity”. His talk followed Nima’s, and the latter almost completely blew me away, so I was somewhat unfocused during Justin’s presentation. Yet, I was able to capture that as such observational hints he wanted to present local bulk flow of matter within 50 
MPc scale, excess power in Lyman 
(about 30%) and small scale CMB anomalies (which I would hardly call anomalies due to lack of statistics there). According to him, all this shows that gravity should be stronger at larger scales – and that’s exactly what many models of modified gravity predict.
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Correlator of Wilson and t’Hooft loops at strong coupling in N=4 SYM theory
Andrew Zayakin works at LMU, Munich and ITEP, Moscow. His interests include non-perturbative physics of QCD, string theory and AdS/CFT correspondence. Dmitry.
This post is about my recent paper with Alexander Gorsky and Alexander Monin about a correlator of a Wilson and a ‘t Hooft loop. Before I proceed, I should explain what these objects are and why they are important to be studied. QCD possesses a consistent description in terms of “dual variables” – charges and monopoles. Reader familiar with the systematics of particle-like solutions in different theories would stop me at this very moment by pointing out there are no monopoles in QCD. True, there are no monopoles in the sense of e.g. Georgi-Glashow model. However, effectively there is such a thing as monopole, which is widely observed on lattice as a non-zero Abelian flux through a closed lattice surface. A lot is known on “thermodynamics” and “phenomenology” of these quasiparticles. They do not exist in the sense of theory spectrum. Still, they are an important tool of describing QCD. The QCD phase transition, which is an element of common lore, can easily be understood in terms of monopoles (Fig.1).
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String theory and the diffusion equation
Gianluca Calcagni is a postdoc at Penn State working in the group of Martin Bojowald. His interests include string theory, string field theory and cosmology. Dmitry.
This post is based on arXiv:0904.3744, in collaboration with Giuseppe Nardelli. Check the links for references and introductory reviews on the subject.
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(In)visible Z’ and dark matter
Alberto Romagnoni is a postdoc at LPT, Orsay. Dmitry.
In this post I discuss my recent work “(In)visible Z’ and dark matter”, done in collaboration with E. Dudas, Y. Mambrini and S. Pokorski. I think there are two main messages I should stress to summarize our paper. The first one is more interesting for its phenomenological consequences and a possible striking signature for dark matter. The second one is more important from a theoretical point of view, and concerns the so-called “decoupling” theorem.
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More on IR divergences and decoherence in inflationary universe
I happened recently to dig through a couple of interesting papers by Yuko Urakawa and Takahiro Tanaka about IR divergences that cosmological perturbation theory in quasi-dS space features, namely “No influence on observation from IR divergence during inflation — Single field inflation –” and “Influence on observation from IR divergence during inflation — Multi field inflation –“.
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366. Some interesting recent papers in Arxiv
Just wanted to acknowledge their existence, although I’ll not be really able to review them due to the lack of time…
1. Quantum field theory
1.1. “Non-Abelian Duality and Confinement in N=2 Supersymmetric QCD” by Michail Shifman and Alesha Yung. The authors study transitions from weak to strong coupling in N = 2 SQCD that happen when you change parameters of the theory – that is, the coefficient 
in front of Fayet?Iliopoulos term and quark mass differences. Here the authors are interested in the case 
and study phases of the theory at different values of .
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330. Some properties of the Burgers dynamics with Brownian or white-noise initial velocity
Patrick Valageas is a permanent researcher at the IPhT (Theoretical Physics department) of CEA, Saclay. His interests include turbulence, observational cosmology (LSS formation in particular) and astrophysics. Dmitry.
I would like to thank Dmitry for giving me the opportunity to present two recent papers of mine (arXiv:0810.4332 and arXiv:0903.0956), on the Burgers equation, from the point of view of a cosmologist. They consider the one-dimensional Burgers dynamics for Brownian and white-noise initial velocity, and expand some previous results on the probability distributions of velocity and Lagrangian increments, as well as on the distribution of the density and the shock mass function.
321. Holographic hydrodynamics
Miguel Paulos is a PhD student at DAMTP, U. of Cambridge working on non-equilibrium AdS/CFT. Dmitry.
In this post I will describe recent work done by myself, Robert Myers, and Aninda Sinha to understand strongly coupled plasmas with a finite chemical potential. For more details and full references see 0903.2834.
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302. Dynamical black holes & expanding plasmas
Pau Figueras, research associate at the Department of Mathematical Sciences in Durham University, works on black hole solutions (and their relatives) in string theory. Dmitry.
The AdS/CFT correspondence has over the years played an invaluable role in providing insight into the dynamics of strongly coupled gauge theories. An important application of the correspondence has been to understand the holographic description of hydrodynamic properties of field theories. This can be used to understand qualitative features of the Quark-Gluon plasma (QGP) produced in heavy ion collisions. Current theoretical understanding of this system is that subsequent to rapid thermalization, the system evolves as an almost ideal fluid, expanding rapidly away from the central collision region. The evolution in this regime has been well described by the so called Bjorken flow [1].
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297. Exact gravity dual of a gapless superconductor
This is a guest post by George Koutsoumbas from the National Technical University of Athens. Dmitry.
I would like to thank Dmitry for the invitation to write a blog entry on my recent work with E.Papantonopoulos and G. Siopsis entitled “Exact Gravity Dual of a Gapless Superconductor”, arXiv:0902.0733 [hep-th].
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295. Weak lensing signal in Unified Dark Matter models
This is a guest post by Stefano Camera (INFN and U. of Torino) about the work he has done in collaboration with D. Bertacca, A. Diaferio, N. Bartolo and S. Matarrese. Dmitry.
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294. The leptonic Higgs as a messenger of dark matter
This is a guest post by Piyush Kumar from U. of California, Berkeley. Dmitry.
I would like to thank Dmitry for inviting me to post a guest blog on my recent paper “The leptonic Higgs as a messenger of dark matter” with Lawrence Hall and Hock-seng Goh on Dark Matter (DM).
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292. Universal properties of the U(1) current at deconfined quantum critical points
This is a guest post by Flavio Nogueira from the U. of Berlin. Dmitry.
Before I start talking my recent preprint [http://arxiv.org/abs/0902.0364], let me thank Dmitry for inviting me to write this contribution in his blog.
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291. Chiral symmetry breaking in soft wall AdS/QCD model
This is a guest post by Tom Kelley from the U. of Minnesota who works on AdS/QCD with Tony Gherghetta. Dmitry.
I would like to thank Dmitry for inviting me to talk a little about chiral symmetry breaking in the soft-wall AdS/QCD model, a topic in my recent work “Chiral Symmetry Breaking in Soft-Wall AdS/QCD” (arXiv:hep-ph/0902.1998). In this post, I’d like to paint, in broad strokes, the picture of how AdS/QCD incorporates chiral symmetry breaking.
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