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U(1) charge Q. At the quantum level, Q-ball is formed due to suitable attractive interaction that binds the quanta of field into a large compact object. In some modern supersymmetric scenarios Q-balls are considered as a heavy particle-like objects, with Q being the baryon and/or lepton number. For many conceivable alternatives, Q-balls may contribute significantly to the dark matter and baryon contents of the Universe. Stable cosmological Q-balls can be searched for in existing and planned experiments. The Q-ball is a rather general physical object, which in principle can be formed in condensed matter systems.
The theoretical prediction of Q-balls in relativistic quantum fields is realized experimentally in superfluid 3He-B in collaboration with Professor Bunkov (Grenoble). The condensed-matter analogs of relativistic Q-balls are responsible for an extremely long lived signal of magnetic induction – the so-called Persistent Signal – observed in NMR at the lowest temperatures. At large Q the effect of self-localization is observed. In the language of relativistic quantum fields it is caused by interaction between the charged and neutral fields, where the neutral field provides the potential for the charged one. In the process of self-localization the charged field modifies locally the neutral field so that the potential well is formed in which the charge is condensed.
NOVEL SUPERFLUIDITY OF 3HE IN AEROGEL
Collaborator: Yuriy Bunkov (Institut Néel, CNRS, France)
Investigation of the superfluid 3He has led to connection with another area of physics – physics of disordered systems. This is the investigation of the behavior of superfluid 3He confined in aerogel. Randomly oriented silicon strands of aerogel produce the random local anisotropy for the order parameter. Superfluid 3He-A confined in aerogel provides the first example of anisotropic superfluids, which exhibits the Larkin-Imry-Ma effect: the quenched random anisotropy destroys the long-range orientational order. This is confirmed by new NMR experiments on 3He-A in aerogel.
It has been also found that a sufficiently large uniaxial deformation applied to aerogel restores the orientational order. This occurs because the deformed aerogel acquires a global anisotropy along the axis of squeezing; this regular anisotropy suppresses the Larkin-Imry-Ma effect and induces a homogeneous orientation of the order parameter in the whole sample. Thus the squeezing of the aerogel is a unique tool for obtaining a uniform orientation of the order parameter in the whole sample in both phases of He. This allowed us to study the effects that are not possible in bulk 3He, in particular new modes of coherent precession which correspond to different types of magnon BEC have been observed in the deformed aerogel, also the geometry of the deformed aerogel stabilizes the spin superfluidity in 3He-A - the Bose condensation of magnons, which never occurs in pure 3He-A.
Connection to cosmology and particle physics
Collaborator: Frans Klinkhamer (University of Karlsruhe, Germany)
Physics of superfluid 3He influences the development of many other areas of physics. There are several reasons for that. One of them is the complicated structure
Annual Report 2007