July 15 2013

18.07.2013 Talk of Giovanni Manfredi in the Kolloquium

Giovanni Manfredi (Université de Strasbourg) will give a talk with the titel "Antimatter under extreme conditions: electronpositron clusters and positronium condensates" in the physikalisches Kolloquium in C6.3 HS II at 16 ct.

Recent years have witnessed a renewed spur of interest in the physics of
antimatter. For instance, the international collaboration GBAR [1], to which our
Strasbourg group contributes, aims at determining the gravitational acceleration of
anti-hydrogen atoms falling in the gravitational field of the Earth. These
investigations require the production of significant amounts of positrons, followed by
the formation of cold electron-positron plasmas and positronium gases. The
availability of such systems will open the possibility to perform experiments on
antimatter under extreme conditions of temperature and density.
In this talk, I will focus on two such systems: electron-positron clusters and Bose-
Einstein condensates of positronium atoms.
Previous research [2] suggested that electron-positron systems at sufficiently high
densities can display “metallic” properties very similar to those of ordinary metal
clusters (shell structure, magic numbers, etc…). Here, I will show results of a study
of electron-positron clusters using a quantum hydrodynamic model that includes
Coulomb and exchange interactions [3]. A variational method is used to determine
their stationary and dynamical properties, including the nonlinear response regime.
Secondly, I will discuss the possibility to produce a Bose-Einstein condensate of
positronium atoms in a porous silica material containing nanometric cavities [4].
Numerical simulations reveal that the condensation process takes place in around
ten nanoseconds and is thus compatible with the lifetime of ortho-positronium [5].
[1] P. Debu for the GBAR collaboration, Hyperfine Interact. 212, 51 (2012).
[2] A.V. Solov’yov, V.K. Ivanov, and R.G. Polozkov, Eur. Phys. J. D 40, 313 (2006).
[3] G. Manfredi, P.-A. Hervieux, and F. Haas, New J. Phys. 14 (2012) 075012.
[4] D. B. Cassidy, V. E. Meligne and A. P. Mills, Phys. Rev. Lett. 104, 173401 (2010).
[5] O. Morandi, P.-A. Hervieux, G. Manfredi, submitted to PRL.

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