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吉野 元@阪大サイバー
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2016年10月28日(金) 13:30 - 大阪大学豊中キャンパス サイバーメディアセンター7F会議室
http://www.cp.cmc.osaka-u.ac.jp
Vortex networks in thermal equilibrium and quench dynamics of
U(1)-symmetry broken systems:
an analysis of the stochastic partial differential equations
小林 未知数 氏 (京都大学大学院理学研究科物理学宇宙物理学専攻)
Michikazu Kobayashi (Department of Physics, Kyoto. Univ.)
U(1)-symmetry breaking occurs in various systems such as relativistic
bosons with the finite chemical potential, type-II superconductors,
Bose-Einstein condensates, XY-magnets, and a simple model of cosmology.
Following to the symmetry breaking, vortices can appear in 3-dimensional
systems as topological line defects. In this work, we consider the
geometrical property of thermally generated vortex loops in equilibrium
and their decay in thermal quench dynamics by using the U(1)-invariant
stochastic partial differential equation with a relativistic complex
field which describes the stochastic Goldstone model, the stochastic
Gross-Piteavskii model and so on in various limits. We have found that
vortex lines in equilibrium increase with the temperature and shows the
line percolation over the whole volume at a line-tension point which is
different from and lower than the thermodynamic critical point of the
2nd ordered phase transition. At the line-tension point, vortex network
shows the fractal structure classified by the self-seeking random work
with the fractal dimension of about 2.56. In thermal quench dynamics
starting from the system at high temperatures, the system spontaneously
entering a slowly ordering critical state with many vortices, which has
been discussed as the Kibble-Zurek mechanism. We have also found that
the generated critical state after the quench can be characterized by
the system in equilibrium at the line-tension point rather than that at
the thermodynamic critical point because the slow ordering process in
the critical state is dominated by vortices. In the seminar, starting
from a brief introduction of U(1)-symmetry broken systems, I will talk
about details of our works.
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Hajime Yoshino
Associate Professor
Cybermedia Center, Osaka University
1-32 Machikaneyama, Toyonaka
560-0043 Japan
Tel: +81-(0)6-6850-6841
FAX: +81-(0)6-6850-6842
E-mail: yoshino@cmc.osaka-u.ac.jp
http://www.cp.cmc.osaka-u.ac.jp/~yoshino/