256 research outputs found
Dynamics on the Way to Forming Glass: Bubbles in Space-time
We review a theoretical perspective of the dynamics of glass forming liquids
and the glass transition. It is a perspective we have developed with our
collaborators during this decade. It is based upon the structure of trajectory
space. This structure emerges from spatial correlations of dynamics that appear
in disordered systems as they approach non-ergodic or jammed states. It is
characterized in terms of dynamical heterogeneity, facilitation and excitation
lines. These features are associated with a newly discovered class of
non-equilibrium phase transitions. Equilibrium properties have little if
anything to do with it. The broken symmetries of these transitions are obscure
or absent in spatial structures, but they are vivid in space-time (i.e.,
trajectory space). In our view, the glass transition is an example of this
class of transitions. The basic ideas and principles we review were originally
developed through the analysis of idealized and abstract models. Nevertheless,
the central ideas are easily illustrated with reference to molecular dynamics
of more realistic atomistic models, and we use that illustrative approach here.Comment: 21 pages, 8 figures. Submitted to Annu. Rev. Phys. Che
Active glasses
Active glassy matter has recently emerged as a novel class of non-equilibrium
soft matter, combining energy-driven, active particle movement with dense and
disordered glass-like behavior. Here we review the state-of-the-art in this
field from an experimental, numerical, and theoretical perspective. We consider
both non-living and living active glassy systems, and discuss how several
hallmarks of glassy dynamics (dynamical slowdown, fragility, dynamical
heterogeneity, violation of the Stokes-Einstein relation, and aging) are
manifested in such materials. We start by reviewing the recent experimental
evidence in this area of research, followed by an overview of the main
numerical simulation studies and physical theories of active glassy matter. We
conclude by outlining several open questions and possible directions for future
work.Comment: Invited review for J. Phys. Condens. Matte
Anti-fragile ICT Systems
This book introduces a novel approach to the design and operation of large ICT systems. It views the technical solutions and their stakeholders as complex adaptive systems and argues that traditional risk analyses cannot predict all future incidents with major impacts. To avoid unacceptable events, it is necessary to establish and operate anti-fragile ICT systems that limit the impact of all incidents, and which learn from small-impact incidents how to function increasingly well in changing environments. The book applies four design principles and one operational principle to achieve anti-fragility for different classes of incidents. It discusses how systems can achieve high availability, prevent malware epidemics, and detect anomalies. Analyses of Netflix’s media streaming solution, Norwegian telecom infrastructures, e-government platforms, and Numenta’s anomaly detection software show that cloud computing is essential to achieving anti-fragility for classes of events with negative impacts
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