Paper by T. Karpiuk, P. Deuar, P. Bienias, E. Witkowska, K. Pawłowski,
M. Gajda, K. Rzążewski i M. Brewczyk,
"Spontaneous Solitons in the Thermal Equilibrium of a Quasi-1D Bose Gas",
published in Phys. Rev. Lett., 109, 205302 (2012)

More

Solitons, or non-destructible local disturbances, are important features of many one-dimensional nonlinear wave phenomena. In a Bose-Einstein condensate confined to a cigar shaped trap they were observed already a decade ago. In all these experiments Solitons in the condensate were created by external perturbation. In the Letter published in Physical Review Letters (Phys. Rev. Lett., 109, 205302 (2012)) we have shown that such an external influence is not necessary. As it turns out, at thermal equilibrium, in nonzero temperature the solitons are generated spontaneously. To show this we used the, so called, classical fields approximation, developed earlier by our group. We argue that thermal solitons are just manifestations of the type II excitations discovered in 1963 by E. Lieb and W. Liniger.

http://old.cft.edu.pl/...aktualnosci_en.html#123