Dead and lovely

The High Frequency Instrument of Planck died the 14th of January 2012. Indeed, the cooling system of bolometers (Planck detectors of photons ranging from 100 to 857 GHz thanks to temperature differences measurements) does not do its job anymore, as expected. Now, there is one year left since the delivery of public data, which means one year to publish cosmological results…Let’s hurry !

The (ugly?) HFI logo

TransRegio Winter School

The winter (or summer) cosmology school being a necessary step in a PhD life, we decided to apply as soon as possible for the TransRegio Winter School in Passo del Tonale (Italian Alps). It took place from December 4th to 9th 2011. The school program is quite exciting : cosmology lectures, ski, meetings and parties…what else ?

About 40 PhD students were there and 5 lecturers, each one being an expert in his field :

  • Jean-Philippe Uzan (from Institut d’Astrophysique de Paris) for theoretical cosmology and inflation

  • Tamara Davis for Large Scale Structures, with a very “conceptual” lecture on the notion of horizon in cosmology 
  • Joanna Dunkley for the Cosmic Microwave Background and its observation as well as CMB anisotropies (like SZ effect, close to my field)
  • Kazuya Koyama for modified gravity theories which aims at going beyond General Relativity and could then get rid of the dark energy problem
  • Laura Covi for the particle aspect of cosmology (dark matter detection)

One of the most interesting aspects of this kind of winter school is to establish contacts, not only with the other PhD students coming from the entire world, but also with the lecturers that we met on ski tracks the afternoon and on the dance-floor later in the night !

Not to mention the skiing…

View from the hotel at Passo del Tonale

The ski resort, close to both hotel and conference room

Not much snow...

...but enough to ski !

Thanks Julian for the photos, as well as the organizers (Marco Baldi, Angela Lepidi, Valerio Marra, Valeria Pettorino, Ignacy Sawicki, Wessel Valkenburg, Georg Wolschin).

Walking drops

This week was a particularly interesting seminar given by Yves Couder from MSC (Matière et Systèmes Complexes) which dealt with a physics that I am totally not aware of and so different from my domain. This is maybe the reason why it impressed me much.

Its name was “A macroscopic situation of wave-particle duality : chaotic trajectories and probabilistic measurements”. In other words, the physical system presented here is shown as an analogy of the well-known wave-particle duality on our scale (equivalence between the quantum description of a particle as a corpuscule or as a wave : photon/light wave for example).

The system is made of a tank which contains a particularly viscous fluid which can even bounce on its own surface ! Everything is vibrating.

The effect of bouncing drops is very spectacular (see the video) and it becomes more and more incredible when you see the drops walking ! If the vibration of the tank goes beyond a certain threshold, the bouncing of the drop becomes asymmetric and the drop bounces no more in the middle of the wave it creates. Then a movement is triggered ! We have, at the end, a macroscopic system made of a “particle” (the drop) guided by the movement of the wave that it creates (due to the bouncing of the drop).

Researchers aim at reproducing the famous quantum physics experiments on these walking drops (double-slit experiment : in our case, we see where the “particle” goes on the contrary to when electrons are used !). Of course, as the system is in our scale, the analogy with quantum mechanics should not be taken too seriously and should not lead to hasty conclusions. But who knows where these walking drops will take us…