1,343 research outputs found
Self-Organized Criticality Below The Glass Transition
We obtain evidence that the dynamics of glassy systems below the glass
transition is characterized by self-organized criticality. Using molecular
dynamics simulations of a model glass-former we identify clusters of
cooperatively jumping particles. We find string-like clusters whose size is
power-law distributed not only close to T_c but for ALL temperatures below T_c,
indicating self-organized criticality which we interpret as a freezing in of
critical behavior.Comment: 4 pages, 3 figure
Critical Decay at Higher-Order Glass-Transition Singularities
Within the mode-coupling theory for the evolution of structural relaxation in
glass-forming systems, it is shown that the correlation functions for density
fluctuations for states at A_3- and A_4-glass-transition singularities can be
presented as an asymptotic series in increasing inverse powers of the logarithm
of the time t: , where
with p_n denoting some polynomial and x=ln (t/t_0). The results are
demonstrated for schematic models describing the system by solely one or two
correlators and also for a colloid model with a square-well-interaction
potential.Comment: 26 pages, 7 figures, Proceedings of "Structural Arrest Transitions in
Colloidal Systems with Short-Range Attractions", Messina, Italy, December
2003 (submitted
Vibrational origin of the fast relaxation processes in molecular glass-formers
We study the interaction of the relaxation processes with the density
fluctuations by molecular dynamics simulation of a flexible molecule model for
o-terphenyl (oTP) in the liquid and supercooled phases. We find evidence,
besides the structural relaxation, of a secondary vibrational relaxation whose
characteristic time, few ps, is slightly temperature dependent. This i)
confirms the result by Monaco et al. [Phys. Rev, E 62, 7595 (2000)] of the
vibrational nature of the fast relaxation observed in Brillouin Light
Scattering (BLS) experiments in oTP; and ii) poses a caveat on the
interpretation of the BLS spectra of molecular systems in terms of a purely
center of mass dynamics.Comment: RevTeX, 5 pages, 4 eps figure
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