36 research outputs found
On the static length of relaxation and the origin of dynamic heterogeneity in fragile glass-forming liquids
The most puzzling aspect of the glass transition observed in laboratory is an
apparent decoupling of dynamics from structure. In this paper we recount the
implication of various theories of glass transition for the static correlation
length in an attempt to reconcile the dynamic and static lengths associate with
the glass problem. We argue that a more recent characterization of the static
relaxation length based on the bond ordering scenario, as the typical length
over which the energy fluctuations are correlated, is more consistent with, and
indeed in perfect agreement with the typical linear size of the dynamically
heterogeneous domains observed in deeply supercooled liquids. The correlated
relaxation of bonds in terms of energy is therefore identified as the physical
origin of the observed dynamic heterogeneity.Comment: 6 pages, 1 figur
Cognition-Enhancing Drugs: Can We Say No?
Normative analysis of cognition-enhancing drugs frequently weighs the liberty interests of drug users against egalitarian commitments to a level playing field. Yet those who would refuse to engage in neuroenhancement may well find their liberty to do so limited in a society where such drugs are widespread. To the extent that unvarnished emotional responses are world-disclosive, neurocosmetic practices also threaten to provide a form of faulty data to their users. This essay examines underappreciated liberty-based and epistemic rationales for regulating cognition-enhancing drugs
A Study of Activated Processes in Soft Sphere Glass
On the basis of long simulations of a binary mixture of soft spheres just
below the glass transition, we make an exploratory study of the activated
processes that contribute to the dynamics. We concentrate on statistical
measures of the size of the activated processes.Comment: 17 pages, 9 postscript figures with epsf, uses harvmac.te
Langevin dynamics of the Lebowitz-Percus model
We revisit the hard-spheres lattice gas model in the spherical approximation
proposed by Lebowitz and Percus (J. L. Lebowitz, J. K. Percus, Phys. Rev.{\
144} (1966) 251). Although no disorder is present in the model, we find that
the short-range dynamical restrictions in the model induce glassy behavior. We
examine the off-equilibrium Langevin dynamics of this model and study the
relaxation of the density as well as the correlation, response and overlap
two-time functions. We find that the relaxation proceeds in two steps as well
as absence of anomaly in the response function. By studying the violation of
the fluctuation-dissipation ratio we conclude that the glassy scenario of this
model corresponds to the dynamics of domain growth in phase ordering kinetics.Comment: 21 pages, RevTeX, 14 PS figure