Journal club
LISA technology and instrumentation
Oliver Jennrich (European Space Agency) has prepared a large review on technical aspects of LISA (space laser interferometer) mission – the project is extremely complicated for realization, many technologies are not even yet fully developed, and various prototypes will have to be launched. Yet, possible payout is so huge – even including possible detection of gravitational waves from the very early Universe – from inflationary and reheating stages (just think about it – detecting EM radiation did not really allow us to go beyond redshift 
so far, not including here CMB of course). Who is a sucker for space research as I am – please check out the paper. It does not discuss science related to the mission but contains tons of technical information about LISA you won’t find anywhere else.
Read more on LISA technology and instrumentation…
A bit about climate change
Recently, an idea that sharp terrestrial climate change might be directly correlated to spiral arm passages of the Solar system became very popular. Namely, certain correlations of times of spiral arm passage with timing of ice ages and abundance of 
in fossils were claimed to be found (in the latter case, effective abundance of grows if gets locked up in ice). The basic idea is that if Solar system goes through spiral arms of the Milky Way, the event rate of cosmic rays in the Earth’s atmosphere greatly increases (since the number of supernovae in spiral arms is clearly much larger than in between the arms) and this presumably affects formation of clouds and therefore strength of greenhouse effect. However, in reality we don’t know very well when Solar system passed between the Galactic arms to make sufficiently strong statements about presence of such correlation.
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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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Other interesting things in ArXiv (12 Jun 2009)
Wayne Hu. Acceleration from modified gravity: lessons from worked examples. The main question Wayne Hu discusses in this minireview is “How can we distinguish dark energy from modified gravity theories if the former and the latter provide the same predictions for cosmological dynamics?” He is particularly focused on DGP and 
models. His answer is the presence of anisotropic stress for modified gravity models which is coupled directly to lensing potential – if we are able to measure this effect, we will be able to discriminate between IR modified gravity and dark energy. Another idea is to study behavior of theories in non-linear regimes, for example, by means of N-body simulation, and compare it to LSS.
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Lithium problem
Apart from being a very nice review of Big Bang Nucleosynthesis (BBN), recent paper by Karsten Jedamzik and Maxim Pospelov discusses an important open problem in the physics of BBN.
In short, the lithium problem in physics of Big Bang Nucleosynthesis is seeming underproduction of 
. What do we mean by that?
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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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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Into dark ages or again about GRB090423
Back in April, I already wrote about GRB090423 – currently the most distant detected object in the Universe. Yesterday, two papers with details of mesurement have appeared in astro-ph (unfortunately, Icannot give you the links – see my comment below).
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This and that in ArXiv on Monday
Due to unbelievable overload of the last days let me simply list the recent papers in ArXiv that I found the most interesting:
1. Quantum information
T. Tilma el al., “Is entanglement a critical resource for quantum metrology?”
Read more on This and that in ArXiv on Monday…
An exoplanet near ultracool star
New record in astrometry and exoplanetology – the authors of 0906.0544 are talking about discovery of the planet in the vicinity of a very light star. The mass of the star is about 0.07 Solar masses, i.e., equivalent to 3-9 Jupiter masses – it is actually near the lower mass limit for an object to be called a star 
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How might one design a nano-machine?
Trinh Xuan Hoang is currently a postdoc at Penn State University. He is also a researcher at Institute of Physics, Vietnamese Academy of Science and Technology. Dmitry.
Significant advances in laboratory techniques in tailoring and processing materials at the atomic level have resulted in nanotechnology becoming an increasingly mature field. One of the exciting goals of nanotechnology is the design of powerful nano-machines, i.e. functional entities at the nano-scale that work like macro-world machines. A simple nano-machine would be an entity that is able to switch between two distinct conformations under some kind of external perturbation. In fact, molecular switching of various kinds has been the subject of many recent studies.
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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.
Read more on Things that go bump in the CMB polarization…
Real-time gauge/gravity duality
Balt van Rees from the U. of Amsterdam continues the discussion of non-equilibrium AdS/CFT we have started not so long time ago. Since his recent paper with Skenderis was one of the major achievements in the field, I highly recommend going through his post. Dmitry.
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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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