Quantum field theory
155. Witten explains how to quantize gauge theory
Long time (almost 6 months?) ago Peter Woit wrote about Yau Birthday Conference and briefly mentioned the talk Edward Witten gave there. I was wondering is there preprint going to appear some day with outline of this talk, and it has finally appeared yesterday in ArXiv.
Read more on 155. Witten explains how to quantize gauge theory…
152. Volume of the Universe after inflation
Back to work after a way too short Xmas break 
Since we were recently a bit into black hole complementarity and information loss paradox, maybe it is also worth discussing a bit the physics of de Sitter space.
Read more on 152. Volume of the Universe after inflation…
150. Susskind’s lectures on quantum entanglement
Discussing black holes and information loss paradox with Lubos, I decided to return back to basics. Here comes the nicest basic introduction into quantum entanglement – Susskind’s lectures on the subject in Stanford U. given back in 2006. Be prepared for almost 15 hours of fun
Read more on 150. Susskind’s lectures on quantum entanglement…
149. Towers of vacua in SUSY field theories
Reading the previous post about dynamical RG treatment of the fractal surface growth problem some of you may have recalled that several months ago we (me, Niko Jokela and Jaydeep Majumder) have used dynamical RG methods to describe behavior of eternal inflation on a nearly continuous landscape. Later, I have also applied these methods to study eternal stochastic inflation in a random potential.
Read more on 149. Towers of vacua in SUSY field theories…
145. Quantum and thermal decay in de Sitter space
Yesterday there was an interesting talk at Perimeter Institute – Adam Brown from Columbia University has discussed vacuum decay in de Sitter space. The title in the announcement immediately caught me, since I expected that Adam was actually going to discuss instability of de Sitter space, the subject I am currently working on. Then I have realized that Adam probably is to talk about his recent paper with Eric Weinberg, well, not decay of de Sitter space but still – very interesting.
Read more on 145. Quantum and thermal decay in de Sitter space…
143. The structure of correlation functions in single-field inflation
This is a guest post by Sarah Shandera from the University of Columbia. Dmitry.
Dmitry has asked me to write a post about my recent paper, arXiv:0812.0818, about correlation functions in single field inflation. The motivation behind this work is the potential of very near-future data (from the Planck satellite and large scale structure surveys) to more significantly test the Gaussianity of primordial fluctuations. In standard single-field slow-roll models, the flatness (and smoothness) of the potential guarantees that the primordial fluctuations are Gaussian to a part in 
. Current observational bounds only require the primordial fluctuations to be Gaussian to a part in 
or 
– still pretty Gaussian, but leaving a surprising amount of room for some interesting physics. Measurements of non-Gaussianity would be a very useful tool for understanding the fundamental picture of inflation, because they probe interactions of the inflaton, and because observations can distinguish between wide classes of models. There are many different statistics that can be used to test Gaussianity. Clearly the 
-point functions are one class of possibilities, but there are also measures like Minkowski functionals or galaxy cluster number counts that depend on an integrated contribution from a series of correlation functions. Often, this series can be simply truncated to depend on a few lower-order moments (for example, when the non-Gaussianity comes from the non-linear gravitational evolution), and this truncation looks suggestively like a perturbative series for the fundamental interactions.
Read more on 143. The structure of correlation functions in single-field inflation…
142. Chaotic inflation on the landscape?
By a chance, do you remember the paper by Nemanja Kaloper and Lorenzo Sorbo that we have recently discussed? There, the authors were modeling quintessence by axion-like fields that dynamically mix with 4-form fields. The mixing introduced mass terms for the axions approximately preserving the shift symmetry. (By the way, I was surprised to see how many people are looking for “Caloper Sorbo quintessence” in Google – it seems that the topic is going to become hot soon.)
Read more on 142. Chaotic inflation on the landscape?…
141. On information loss paradox, statistical and quantum mechanics
Recently, I got into the discussion of information loss paradox in spacetimes with timelike and spacelike horizons (that is, black holes, de Sitter and staff like them). Let me remind you what is the issue (see for example Susskind’s recent book for details).
Read more on 141. On information loss paradox, statistical and quantum mechanics…
140. First two weeks of December at NEQNET
Dear friends
Before I proceed to the (becoming usual already) list of posts published at NEQNET during the last two weeks, let me say a couple of words about the blog itself, which is currently the source of my pride 
Read more on 140. First two weeks of December at NEQNET…
134. Cosmic strings – simple and nice introduction into the topic
After my recent post on textures I have been asked what could a newcomer to the field read about topological defects in cosmology apart from the canonical book by Vilenkin and Shellard that I’ve recommended?
Read more on 134. Cosmic strings – simple and nice introduction into the topic…
133. Multi-Field Inflation on the Landscape
This is the guest blog post by my friend Thorsten Battefeld from Princeton. Dmitry.
Dmitry asked me to write a guest post about a recent paper written by Diana and myself on “Multi-field Inflation on the Landscape” (a followup to “Staggered Multi-Field Inflation”) where we ask a simple question: assuming that inflaton is driven by many (say of the order of 
) scalar fields, what are the observable consequences of fields decaying or stabilizing one after the other during inflation?
Read more on 133. Multi-Field Inflation on the Landscape…
131. Non-gaussianities from postinflationary universe
Mark Trodden and Alessandra Silvestri have recently released a paper about signatures of non-gaussianity from the post-inflationary early Universe.
The title of the paper is speaking for itself: one can immediately recall that CMB fluctuations can be generated from cosmic strings and other topological defects, i.e., they may be partially sourced by various phase transitions in the very early Universe. This is indeed what Mark and Alessandra consider – in particular, they focus on effects of textures.
Read more on 131. Non-gaussianities from postinflationary universe…
127. Ashtekar at Perimeter Institute
Abhay Ashtekar has recently visited the Perimeter Institute and gave a couple of talks – about loop quantum gravity of course, since he is one of the major players in the LQG field (considered to be its inventor). I think, both of the talks are worth watching (or at least scanning through his transparencies available as PDF file at PIRSA) for a person who wants to understand what LQG is about. If you do not have an intention to watch them , I shall explain you what both of them are about.
Read more on 127. Ashtekar at Perimeter Institute…
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…
125. From quarks to strings. On Liouville mode, instantons and confinement in abelian theories
Alexander Polyakov have released this week a preprint about history of string theory, which is also so full of non-trivial physical ideas that I decided to list some of them in this post as well as to include my comments (or rather my ramblings )
Loading ...