Cosmology
126. From quarks to strings. Migdal-Makeenko equation and AdS-CFT correspondence
Although Lubos wants to see my answer to the poll 
, I decided to finish my analysis of the recent Polyakov’s paper today.
Page 6. In order to justify my picture I have used intuition coming from the loop equation, while Klebanov and Maldacena appealed to the D brane picture of the gauge fielauds. Both points of view are useful but neither of them lead to the quantitative derivation of gauge/string duality.
Comment. He is talking about the Migdal-Makeenko loop equation for the expectation value of the Wilson loop 
. After Migdal’s groundbreaking proof of the fact that this equation describes a free motion of the contour 
in the large 
limit (1981, if I am not wrong (?), even before the Polyakov’s action), not much progress has been reported in this direction. The main reason is that the Migdal-Makeenko equations are formulated on the lattice, and no their continuum limit is known (it is not clear how to perform the renormalization procedure for loops).
Read more on 126. From quarks to strings. Migdal-Makeenko equation and AdS-CFT correspondence…
124. Talk in Munich. Regularizing correlators of curvature perturbation
This post is hopefully the last one in the series devoted to my seminar in Munich 
Last time I have explained why correlation functions of the scalar field on de Sitter background should be actually infrared finite. This time, using similar trick, I will argue that the correlation functions of the curvature perturbation 
(by curvature perturbation, as usual, I mean curvature of the 3-dimensional slice) should be also infrared finite due to the effects of eternal inflation.
Read more on 124. Talk in Munich. Regularizing correlators of curvature perturbation…
120. Talk in Munich. Regularizing inflaton correlation functions
Let me get again back from confinement to eternal inflation , or more precisely, to the infrared behavior of correlation functions of a self-interacting massless scalar field on de Sitter background. In what follows, I will consider the case 
(a QFT in fixed dS spacetime).
Read more on 120. Talk in Munich. Regularizing inflaton correlation functions…
118. Last two weeks of November on NEQNET
Well, those two weeks were quite productive ones! – 19 posts in overall (or 20 including this one ) This counts to 1.5 posts per day (and you should take into account that I was on leave to Munich for 4 days). I hope my writing was not too boring for you
Read more on 118. Last two weeks of November on NEQNET…
115. Talk in Munich. Leading logs
Last time I have claimed that the leading IR divergences in the loop expansion for the inflaton pair correlation function in 
theory contribute in the form of expansion
.
Let me now show how these divergences appear. First of all, let us forget about the interaction term and show that the correlation function 
for the free field 
on dS background diverges in the IR.
Read more on 115. Talk in Munich. Leading logs…
112. Talk in Munich. Other two interesting infrared scales
As Instanton figured out in comments to the previous post, the scale 
is related to the self-reproduction scale. How to show this? Well, recall that the classical displacement of the inflaton field during one efolding is
Read more on 112. Talk in Munich. Other two interesting infrared scales…
111. Talk in Munich. One interesting infrared scale in inflationary cosmology
I am back to Helsinki, was not this visit really short? :-)
For those of you how were unable to come to the Sommerfeld Center in Munich to hear my talk and for those of you who were there but did not understand it ? I decided to put the outline of my talk on the blog.
Read more on 111. Talk in Munich. One interesting infrared scale in inflationary cosmology…
110. Introducing doubt in Bayesian statistics 1
This is a guest post by my old friend Pascal Vaudrevange, who was a student of Lev Kofman when we were together in CITA, and is now a postdoc at Case Western University working with Glenn Starkman. Dmitry.
Read more on 110. Introducing doubt in Bayesian statistics 1…
99. Eternal inflation with many light scalar fields
I am going to briefly discuss one result from the recent paper by Peter Adshead, Richard Easther and Eugene Lim.
One subject of the authors’ study is the interplay between stochastic and eternal N-flation. Let us recall what is N-flation (or assisted inflation). Suppose that we have a large number 
of scalar fields with equal potentials 
and relatively large vacuum expectation values. How large? We want to have the ordinary slow roll inflation in this setup. While one needs an expectation value of the inflaton to be superplanckian in single field inflationary models in order for slow roll conditions to hold, expectation values of any one among N scalar fields can be rather small and still the inflationary slow roll regime will not be spoiled. Indeed, we have
Read more on 99. Eternal inflation with many light scalar fields…
97. Second week of November on NEQNET
Physics
* Quintessence on the string theory landscape?
I discuss the recent paper by Kaloper and Sorbo explaining how quintessence can be realized on the string theory landscape, as follows from the title. The post also contains small introduction explaining what is quintessence field and why we want so hard to find it on the landscape
Read more on 97. Second week of November on NEQNET…
96. Quintessence with w less than -1
In another very interesting recent paper on quintessence the Italian Team (Creminelli, D’Amico, Norena, Vernizzi – and warmest regards from Helsinki if you read it, Filippo ) is trying to construct an reliable example of QFT that behaves like the quintessence with ?ghost-like? effective equation of state 
.
Read more on 96. Quintessence with w less than -1…
94. Quantum scale invariance on the lattice
Arguably, the most interesting paper in archives today is the one by M. Shaposhnikov and I. Tkachev. As the authors state, they have found a scheme leading to a non-perturbative definition of lattice field theories scale invariant on the quantum level. I have so many problems understanding this paper, that I don’t even have a slightest idea where to begin… Since I know Igor personally (and he is an extraordinary guy), this probably just shows that I am pretty bad, but I shall still pose my questions – one of the most attracting blogging Powers is that you can ask dumb questions, isn’t it?
Read more on 94. Quantum scale invariance on the lattice…
92. A new theory of galaxy formation needed
It is well known that an ordinary galaxy can be described by seven physical parameters: total mass, baryon fraction, age, specific angular momentum, specific heat energy (related to random motion within the galaxy), its radius and concentration. According to the virial theorem, only six of them can be independent. This gives quite a bit of freedom for the model building and a large part of the astrophysical community is quite busy with constructing models of galaxy formation.
Read more on 92. A new theory of galaxy formation needed…
90. Unidentified extended sources of gamma ray emission
Here is another open problem in astrophysics , as far as I understand…
The H.E.S.S. system of telescopes in Namibia is among most successful instruments of its kind.
In particular, it has very large field of view allowing to discover new sources of gamma ray emission. Many of discovered sources were identified with known objects such as SN remnants, pulsars, star clusters etc. Sometimes a gamma-ray emission source discovered by H.E.S.S. was in one-to-one correspondence with some object from the class of potential gamma-ray emitters, sometimes – not.
Read more on 90. Unidentified extended sources of gamma ray emission…
89. First week of November on NEQNET
Below is the list of what I wrote on this blog during the first week of November… not bad actually, it looks like with Agata’s birth I have become more productive, not less… Surprising
Read more on 89. First week of November on NEQNET…
Loading ...