8,794 research outputs found
Book review: accelerating democracy: transforming governance through technology
John O. McGinnis demonstrates how new technologies combine to address a problem as old as democracy itself: how to help citizens better evaluate the consequences of their political choices. Ana Polo Alonso thinks we can support or dismiss McGinnis’s proposals, but we cannot deny that the author makes a major effort to bring forth ingenious measures to really ‘accelerate democracy.’ Accelerating Democracy: Transforming Governance through Technology. John O. McGinnis. Princeton University Press. December 2012
Book review: The violent image: insurgent propaganda and the new revolutionaries
"The Violent Image: Insurgent Propaganda and the New Revolutionaries." Neville Bolt. Hurst. May 2012. --- Fast-moving, self-propelled ‘violent images’ have radically changed the nature of insurgency in the modern world. The global media has revolutionised the way ideas, messages and images are disseminated, and the speed with which they travel. Neville Bolt investigates how today’s revolutionaries have rejuvenated the nineteenth century ‘propaganda of the deed’ so that terrorism no longer simply goads states into overreacting, thereby losing legitimacy. Ana Polo Alonso finds an elegantly-written and well-researched read, suitable for students of media studies and terrorism
Multi-partite analysis of average-subsystem entropies
So-called average subsystem entropies are defined by first taking partial
traces over some pure state to define density matrices, then calculating the
subsystem entropies, and finally averaging over the pure states to define the
average subsystem entropies. These quantities are standard tools in quantum
information theory, most typically applied in bipartite systems. We shall first
present some extensions to the usual bipartite analysis, (including a
calculation of the average tangle, and a bound on the average concurrence),
follow this with some useful results for tripartite systems, and finally extend
the discussion to arbitrary multi-partite systems. A particularly nice feature
of tri-partite and multi-partite analyses is that this framework allows one to
introduce an "environment" for small subsystems to couple to.Comment: Minor changes. 1 reference added. Published versio
Entropy budget for Hawking evaporation
Blackbody radiation, emitted from a furnace and described by a Planck
spectrum, contains (on average) an entropy of bits per photon.
Since normal physical burning is a unitary process, this amount of entropy is
compensated by the same amount of "hidden information" in correlations between
the photons. The importance of this result lies in the posterior extension of
this argument to the Hawking radiation from black holes, demonstrating that the
assumption of unitarity leads to a perfectly reasonable entropy/information
budget for the evaporation process. In order to carry out this calculation we
adopt a variant of the "average subsystem" approach, but consider a tripartite
pure system that includes the influence of the rest of the universe, and which
allows "young" black holes to still have a non-zero entropy; which we identify
with the standard Bekenstein entropy.Comment: Proceedings of the conference "VARCOSMOFUN'16" in Szczecin, Poland,
12-17 September, 2016. Accepted for publication in "Universe", belonging to
the Special Issue "Varying Constants and Fundamental Cosmology
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