## Monday 31 October 2016

### Publishing in SciPost: a must?

Now that I have published my first article in SciPost, let me comment on that experience.

## Wednesday 26 October 2016

### Physical Review Letters: physics' luxury journal

Have you ever wondered why this apparently interesting new paper on arXiv was only four or five pages long? Why it had this unreadable format with two columns in fine print, with formulas that sometimes straddle both columns, and with these cramped figures? Why the technical details were relegated to appendices or future work, if not omitted altogether? And why so much of the already meager text was devoted to boastful hot air?

Most physics researchers do not wonder for long, and immediately recognize a paper that is destined to be submitted to Physical Review Letters. That journal’s format is easy to recognize, as it has barely changed since 50 years ago – a time when page limits had the rationale of saving ink and paper. That rationale having now evaporated, the awful format has nevertheless survived as a signal of prestige. Because, you see, Physical Review Letters is supposed to be physics’ top journal, which means that publishing there is supposed to be good for one’s career.

Most physics researchers do not wonder for long, and immediately recognize a paper that is destined to be submitted to Physical Review Letters. That journal’s format is easy to recognize, as it has barely changed since 50 years ago – a time when page limits had the rationale of saving ink and paper. That rationale having now evaporated, the awful format has nevertheless survived as a signal of prestige. Because, you see, Physical Review Letters is supposed to be physics’ top journal, which means that publishing there is supposed to be good for one’s career.

## Friday 21 October 2016

### Finite operator product expansions in two-dimensional CFT

While the conformal bootstrap method has recently enjoyed the wide popularity that it deserves, its applications have been mostly restricted to unitary conformal field theories. (By definition, in a unitary theory, there is a positive definite scalar product on the space of states, such that the dilatation operator is self-adjoint.) Unitarity brings the technical advantage that three-point structure constants are real, so squared structure constants are positive, leading to bounds on allowed conformal dimensions. However, dealing with non-unitary theories using similar methods is surely possible, at the expense of having the signs of squared structure constants as extra discrete variables. And unitarity is sometimes assumed even in cases where it brings no discernible technical benefit, such as in studies of torus partition functions, where multiplicities are positive integers whether the theory is unitary or not.

So it is refreshing that, in their recent article, Esterlis, Fitzpatrick and Ramirez apply the conformal bootstrap method to non-unitary theories.

So it is refreshing that, in their recent article, Esterlis, Fitzpatrick and Ramirez apply the conformal bootstrap method to non-unitary theories.

## Tuesday 27 September 2016

### Abonnements aux revues scientifiques: les chiffres du CEA

En page 10 de son rapport d’activité 2015, le Service de Valorisation de l’Information du CEA publie les coûts des abonnements aux revues électroniques pour les années 2014, 2015 et 2016, avec pour 2015 l’évaluation du coût par article téléchargé. Je voudrais ici diffuser et commenter ces chiffres.

## Sunday 24 July 2016

### SciPost: the right tool for commenting arXiv articles?

ArXiv has not changed much since it started in 1991, and it is only starting to consider the obvious next steps: allowing comments on articles, followed by full-fledged open peer review. Scientists have not all been waiting idly for the sloth to make its move, and a few have tried to build systems for doing that. Here I will discuss a recent attempt, called SciPost.

#### A strong editorial college

The most distinctive feature of SciPost is its editorial college, made of well-known theoretical physicists. These people do not just lend their names to the project. Given how SciPost functions, they have a lot of work:## Saturday 28 May 2016

### Was it such a good idea to put this review article in the public domain?

Two years ago, when posting a review article on Arxiv, I did the experiment of putting it in the public domain. The idea was to allow anyone to distribute and even to modify it, in the hope of increasing the circulation and usefulness of the article, as I explained in this blog post.

Putting the text in the public domain also has potential drawbacks:

The potential loss of control is a priori more worrisome. Could my reputation be damaged if someone did something bad with my text? In order to find out, I had to wait until people actually did something with my text.

Putting the text in the public domain also has potential drawbacks:

- losing revenue,
- losing control.

The potential loss of control is a priori more worrisome. Could my reputation be damaged if someone did something bad with my text? In order to find out, I had to wait until people actually did something with my text.

#### Enters Amazon

My review article is now available for sale on Amazon, in the Kindle format, at the price of about $9. I had nothing to do with that edition, I guess it was done by an Amazon robot.## Monday 18 April 2016

### Building a website for physics courses with Drupal

I have been involved in building a new website for the theoretical physics courses at IPhT, using the content management framework Drupal. This post is the story of this experience, written for researchers who are considering embarking in similar projects.

Riccardo Guida and I have been organizing the IPhT courses for years (

Riccardo Guida and I have been organizing the IPhT courses for years (

*many*years in Riccardo's case), and one year ago we finally decided to escape the IPhT website and set up a dedicated website for the courses. The problem with the IPhT website was that it did not know what a course was. A course was a collection of various objects: a number of "seminars", a "publication" where lecture notes could be stored, a few lines in a list of courses on a static webpage, etc. These objects did not talk to one another, and the same information had to be copy-pasted several times.## Tuesday 12 April 2016

### The light asymptotic limit of $W$ algebra conformal blocks

\(W\) algebras are natural extensions of the Virasoro algebra, the symmetry algebra of local conformal field theories in two dimensions. Conformal field theories with \(W\) algebra symmetry include \(W\) minimal models and conformal Toda theories, which are generalizations of Virasoro minimal models and Liouville theory respectively. In particular, \(sl_N\) conformal Toda theory is based on the \(W_N\) algebra, which has \(N-1\) generators with spins \(2,3,\dots, N\), and reduces to the Virasoro algebra in the case \(N=2\).

#### The problem of solving conformal Toda theory

#### Solving \(sl_{N\geq 3}\) conformal Toda theory is an outstanding problem. One may think that this is due to the complexity of the \(W_N\) algebra, with its quadratic commutators. I would argue that this is rather due to the complexity of the fusion ring of \(W_{N}\) representations, with its infinite fusion multiplicities. Due to these fusion multiplicities, solving \(sl_N\) conformal Toda theory does not boil down to computing three-point function of primary fields: rather, one should also compute three-point functions of infinitely many descendent fields.

## Saturday 2 April 2016

### Perverse bibliometrics: the case of patents

Bibliometrics, the counting of publications and citations, is being used for evaluating researchers, research institutions, and academic journals. But simple bibliometric indicators can be gamed, and complex indicators lack transparency. No known indicator avoids these two problems, while some indicators (such as the journal impact factor) manage to have both. As a result, the misuse of bibliometrics has been widely denounced.

In spite of these problems with bibliometrics, someone had the idea to do bibliometrics with patents, in order to rank research institutions. The result is Reuters' list of the world's most innovative research institutions, which is topped by the Alternative Energies and Atomic Energy Commission (CEA). The methodology for establishing the list is not known in detail, but we do know that it is involves 10 different criterions, and is mainly based on the numbers of patents and citations thereof.

In spite of these problems with bibliometrics, someone had the idea to do bibliometrics with patents, in order to rank research institutions. The result is Reuters' list of the world's most innovative research institutions, which is topped by the Alternative Energies and Atomic Energy Commission (CEA). The methodology for establishing the list is not known in detail, but we do know that it is involves 10 different criterions, and is mainly based on the numbers of patents and citations thereof.

## Wednesday 16 March 2016

### Free bosons and Virasoro null vectors

In a recent article, Manabe and Sulkowski have proposed a method for deriving Virasoro null vectors, starting with certain deformed matrix integrals. In this blog post I will look for a conformal field theory interpretation of this method.

\[|\chi_{r,s}\rangle = L_{r,s} |\Delta_{r,s}\rangle\] where \(|\Delta_{r,s}\rangle\) is the primary state of our Verma module, and \(L_{r,s}\) is a level \(rs\) creation operator.

#### Quick reminders on Virasoro null vectors.

#### A null vector of the Virasoro algebra is labelled by two integers \(r,s\geq 1\), whose product is the level of the null vector. This null vector occurs in the Verma module with a specific conformal dimension \(\Delta_{r,s}\), and it can be written as

\[|\chi_{r,s}\rangle = L_{r,s} |\Delta_{r,s}\rangle\] where \(|\Delta_{r,s}\rangle\) is the primary state of our Verma module, and \(L_{r,s}\) is a level \(rs\) creation operator.

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