Once while visiting Fra Angelico’s cell at the Convent of San Marco, Florence, I was struck by the comparison of his cloister to offices in research institutes such as the IHES, where I am visiting now. Fra Angelico’s cloister was housed in a garden behind a high wall, and inside the monks went about their daily business, in his case producing his exquisite paintings. The IHES is in a woods behind a stone wall and big iron gate, with a central building with cells for about 40. When you arrive at the IHES you are given an empty office and the freedom to work without the usual external pressures. We filter in during the morning and the halls are remarkably quiet. At 1:00 we all go in unison for a communal lunch. After coffee it is back in the cell until tea at 5:00 – and then some more work until heading home. I am sure that for the permanent professors, and above all the Director, this is “the real world”, with pressures on fund raising, careers, politics, personalities etc. However, for the visitors, it is a remarkable opportunity for pure contemplation.

Mohamed and I have a new paper out on the emergence of a common speed of light in theories where different particles have different limiting speeds (the speed of the particle at very high energy). The motivation of this is that if a universal Lorentz invariance is not imposed, the wave equations of different particles will in general contain different velocities in the relation between time derivatives and space derivatives. Mohamed and I show that if the different particles are interacting, then the interactions yield a scale dependence to this limiting velocity, and the velocities approach each other at low energy. This can be a mechanism for the emergence of a universal speed of light and Lorentz invariance at low energy. There is more to the story, and it is not clear if this mechanism can be effective enough to satisfy the experimental constraints, and this is discussed in the paper.