23 January 2015

Is modern science a by-product of Reformation?

There is a strong connection between Reformation and the birth of modern science, not only in time but also with respect to the number of notable Protestant scientists1. Several explanations were proposed:

20 January 2015

Dielectric sphere in a static field

I'll try to give the simplest solution I can think of to the classical problem of a dielectric sphere in a constant external field, see for instance  Landau & Lifshitz, vol. 8, chapter II, §8.

The sphere radius is \(R\) and its dielectric constant is \(\epsilon_i\), while that of the surrounding medium is \(\epsilon_e\). The electric field at infinity is along the \(z\) axis: \(\mathbf{E}_0 = E_0\, \hat{z}\). Considering the symmetry of the object we will work in spherical coordinates \((r,\theta,\phi)\). Before writing down any equations, let us note the following points:
  1. The system has rotational symmetry about the \(z\) axis. Thus, the field has no component along \(\hat{\phi}\).
  2. The problem is antisymmetric with respect to \(z\) (changing \(E_0\) to \(-E_0\) reverses the sign of the field everywhere).
  3. The field scales by \(E_0\) (doubling the applied field doubles the field at any point in the system).
  4. The only length parameter is the sphere radius \(R\).

18 January 2015

Missing the point on Charlie Hebdo

 A few days ago in the New York Times, David Brooks announced his position very clearly: I am not Charlie Hebdo. I'm responding to his Op-Ed because:
  • similar positions are quite common in the wake of the Paris attack, but at least here
  • the argument is reasoned, carefully presented and respectful of the victims and
  • it is published in a very respected, mainstream journal.
Still, I believe it manages to get the "I am Charlie" response completely wrong.

7 January 2015

Mr K

Yet another story about Khodorkovsky (a little more critical of the man and his past than the usual articles). We learn that he thinks about returning to Russia and that even the even the perspective of replacing Putin is not completely out of the question.

Khodorkovsky's fall does resemble something out of Kafka. All the elements are there: the oppressive state, the lack of a real crime, down to the hero's initial.
However, it also reminds me of an older story: Faust makes a pact with the devil, reaps the benefits, and then complains about the stench of brimstone.
The place does stink, and the publicity for a high-profile victim may be very effective in raising the international awareness, but I cannot bring myself to empathize with Mr K. Not because he is still alive and rich, but because for a long time he has been a part of the problem he now decries. In fact, the only reason he became a cause célèbre is his former belonging to an international elite, and the only reason of this elevated status was the favor of the regime.

Massacre in Paris. We are all Charlie !

27 December 2014

On my 2015 wishlist...

...is an e-print server where I can submit my pdf preprint and have it archived as-is, without making me jump through hoops just because someone somewhere thought it would be a good idea to force the authors to provide their publication in some particular format.

Case in point: I've tried storing the preprint of a recent paper (published online in September 2014).

20 December 2014

"Universal" Casimir forces

What is remarkable about the quantum Casimir force between perfect conductors is its very simple formula, which depends only on the geometry and on universal constants. Would this force be the same in the presence of different interactions?

11 December 2014


Great illustration of normal modes in acoustics!

3 December 2014

What science is

I am not satisfied with most definitions of science I've seen so far, either essentialist or enumerative. I think the "social" definition below is much better:

1. Science is what scientists do [1].

It may not be very satisfying, but neither is it as glib as it first appears. Still, I believe it needs some precisions: obviously, not everything scientists do is science. This applies in private life (some scientists are atheists and others are deeply religious) but also to public attitudes: Johannes Stark was an authentic Nazi, but this does not prevent us from studying the Stark effect. Conversely, his scientific achievements do not render Nazism respectable. Then:

2 December 2014

CNRS positions - the 2015 campaign

[Updated with 2015 data]
The 2015 campaign for permanent research positions at the CNRS (Centre national de la recherche scientifique) is officially open. The submission deadline is January 6th 2015. There are 212 open positions at the CR2 level (same as in 2014), 77 CR1 (+11), 253 DR2 (-26) and 2 DR1 (+2).