לוח שנה משולב

A colorful variety of experiments attempts to find out what all that Dark Matter in the Universe is made of, resulting in a buzzing field of research. This results in sometimes confusing and sometimes even contradicting data, which this talk attempts to shed some light on. The basic principles for the direct detection of Weakly Interacting Massive Particles (WIMPs) in laboratory-scale detectors will be presented. Various experimental techniques will then be explained together with the current status and data from running detectors, as well as prospects for the near future.

We have developed and implemented a general method to probe with high precision the thermodynamics of homogeneous quantum gases using trapped atomic samples. We have applied this technique to the two spin-component Fermi gas with short-range interactions. Using fermionic 6Li, we explored a wide parameter space by changing the interaction strength, the spin-population imbalance or the temperature of the gas. This system exhibits remarkably rich physics, such as normal/superfluid phase transitions (that can be of thermal or quantum character) or Fermi liquid-type behaviour of the normal phase.

We have extended this method to atomic bosons using 7Li close to a Feshbach resonance. We have measured the Equation of State of the Bose gas as a function of interactions at very low temperature. For the first time in atomic Bose gases, we measured quantitatively the first correction beyond mean-field of the ground state energy, the so-called Lee-Huang-Yang correction. The comparison with the LHY correction measured in a molecular Bose gas demonstrates the universality of the first beyond-mean-field correction. Finally, we have extended this study using out-of-equilibrium measurements of the Bose gas in the strongly interacting regime, which gives a first hint on properties of the hypothetical unitary Bose gas.

[1]S. Nascimbene, N. Navon, K. Jiang, F. Chevy, C. Salomon, Exploring the Thermodynamics of a Universal Fermi Gas, Nature 463, 1057 (2010).
[2] N. Navon, S. Nascimbene, F. Chevy, C. Salomon, The Equation of State of a Low-Temperature Fermi Gas with Tunable Interactions, Science 328, 729 (2010).
[3] N. Navon, S. Piatecki, K. Gunter, B. Rem, T.C. Nguyen, F. Chevy, W. Krauth, C. Salomon, Dynamics and Thermodynamics of the Low-Temperature Strongly Interacting Bose Gas, Phys. Rev. Lett 107, 135301 (2011).

The answer in general is clear: sun energy is the source of all atmospheric flows. Yet sun produces both global-scale horizontal temperature gradients and troposphere-scale vertical gradients. Which contribute the energy of weather-determining flows at the intermediate scales of hundreds of kilometers? I’ll review some recent experimental and theoretical results which shed some unexpected light on this problem.