18,982 research outputs found
12th International Workshop on Termination (WST 2012) : WST 2012, February 19–23, 2012, Obergurgl, Austria / ed. by Georg Moser
This volume contains the proceedings of the 12th International Workshop on Termination (WST 2012), to be held February 19–23, 2012 in Obergurgl, Austria. The goal of the Workshop on Termination is to be a venue for presentation and discussion of all topics in and around termination. In this way, the workshop tries to bridge the gaps between different communities interested and active in research in and around termination. The 12th International Workshop on Termination in Obergurgl continues the successful workshops held in St. Andrews (1993), La Bresse (1995), Ede (1997), Dagstuhl (1999), Utrecht (2001), Valencia (2003), Aachen (2004), Seattle (2006), Paris (2007), Leipzig (2009), and Edinburgh (2010). The 12th International Workshop on Termination did welcome contributions on all aspects of termination and complexity analysis. Contributions from the imperative, constraint, functional, and logic programming communities, and papers investigating applications of complexity or termination (for example in program transformation or theorem proving) were particularly welcome. We did receive 18 submissions which all were accepted. Each paper was assigned two reviewers. In addition to these 18 contributed talks, WST 2012, hosts three invited talks by Alexander Krauss, Martin Hofmann, and Fausto Spoto
Quantum Computing and Hidden Variables I: Mapping Unitary to Stochastic Matrices
This paper initiates the study of hidden variables from the discrete,
abstract perspective of quantum computing. For us, a hidden-variable theory is
simply a way to convert a unitary matrix that maps one quantum state to
another, into a stochastic matrix that maps the initial probability
distribution to the final one in some fixed basis. We list seven axioms that we
might want such a theory to satisfy, and then investigate which of the axioms
can be satisfied simultaneously. Toward this end, we construct a new
hidden-variable theory that is both robust to small perturbations and
indifferent to the identity operation, by exploiting an unexpected connection
between unitary matrices and network flows. We also analyze previous
hidden-variable theories of Dieks and Schrodinger in terms of our axioms. In a
companion paper, we will show that actually sampling the history of a hidden
variable under reasonable axioms is at least as hard as solving the Graph
Isomorphism problem; and indeed is probably intractable even for quantum
computers.Comment: 19 pages, 1 figure. Together with a companion paper to appear,
subsumes the earlier paper "Quantum Computing and Dynamical Quantum Models"
(quant-ph/0205059
Quantifying Changes in the Spatial Structure of Trabecular Bone
We apply recently introduced measures of complexity for the structural
quantfication of distal tibial bone. For the first time, we are able to
investigate the temporal structural alteration of trabecular bone. Based on
four patients, we show how bone may alter due to temporal immobilisation
Invariance: A Tale of Intellectual Migration
The plotline of the standard story told about the development of intellectual history at the end of the 19th/turn of the 20th century follows the move from absolutism to perspectivalism. The narrative takes us, on the one hand, from the scientism of late Enlightenment writers like Voltaire, Mill, D’Alebert, and Comte and the historical determinism of Hegel, all of which were based upon a universal picture of rationality, to, on the other hand, the relativistic physics of Einstein, the perspectival art of Picasso, and the individualism of Nietzsche and Kierkegaard leading to the phenomenology of Husserl and Heidegger to and on through the deconstructivist work of Derrida in which universal proclamations were deemed meaningless. In their place, was relative dependent upon subjective, political, and social factors, influences, and interpretations. Like all sketches, of course, the story is more complicated than that.
There is another trend in the intellectual air of the early 20th century that gets left out of this oversimplified picture, one that threads a middle path between absolutism and perspectivalism, a path that considers both frame-dependent or covariant truths and frame-independent or invariant truths and examines the relations between them. Indeed, the notions of covariance and invariance play important roles in the development of the fields of mathematics, physics, philosophy, and psychology in the decades after the turn of the 20th century.
The migration of the concepts of invariance and covariance illustrates not only the interconnectedness of the working communities of intellectuals, but also displays ways in which the personal, social, and political overlaps between groups of disciplinary thinkers are essential conduits for the conceptual cross-fertilization that aids in the health of our modern fields of study. [excerpt
Foundations of Quantum Gravity : The Role of Principles Grounded in Empirical Reality
When attempting to assess the strengths and weaknesses of various principles
in their potential role of guiding the formulation of a theory of quantum
gravity, it is crucial to distinguish between principles which are strongly
supported by empirical data - either directly or indirectly - and principles
which instead (merely) rely heavily on theoretical arguments for their
justification. These remarks are illustrated in terms of the current standard
models of cosmology and particle physics, as well as their respective
underlying theories, viz. general relativity and quantum (field) theory. It is
argued that if history is to be of any guidance, the best chance to obtain the
key structural features of a putative quantum gravity theory is by deducing
them, in some form, from the appropriate empirical principles (analogous to the
manner in which, say, the idea that gravitation is a curved spacetime
phenomenon is arguably implied by the equivalence principle). It is
subsequently argued that the appropriate empirical principles for quantum
gravity should at least include (i) quantum nonlocality, (ii) irreducible
indeterminacy, (iii) the thermodynamic arrow of time, (iv) homogeneity and
isotropy of the observable universe on the largest scales. In each case, it is
explained - when appropriate - how the principle in question could be
implemented mathematically in a theory of quantum gravity, why it is considered
to be of fundamental significance and also why contemporary accounts of it are
insufficient.Comment: 21 pages. Some (mostly minor) corrections. Final published versio
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