Event-based simulation of neutron experiments: interference, entanglement and uncertainty relations

We discuss a discrete-event simulation approach, which has been shown to give a unified cause-and-effect description of many quantum optics and single-neutron interferometry experiments. The event-based simulation algorithm does not require the knowledge of the solution of a wave equation of the whole system, yet reproduces the corresponding statistical distributions by generating detection events one-by-one. It is showm that single-particle interference and entanglement, two important quantum phenomena, emerge via information exchange between individual particles and devices such as beam splitters, polarizers and detectors. We demonstrate this by reproducing the results of several single-neutron interferometry experiments, including one that demonstrates interference and one that demonstrates the violation of a Bell-type inequality. We also present event-based simulation results of a single neutron experiment designed to test the validity of Ozawa's universally valid error-disturbance relation, an uncertainty relation derived using the theory of general quantum measurements.Comment: Invited paper presented at the EmQM13 Workshop on Emergent Quantum Mechanics, Austrian Academy of Sciences (October 3-6, 2013, Vienna

Internet-based 'social sharing' as a new form of global production: The case of SETI@home

Benkler ('Sharing Nicely', Yale Law Journal, 2004, Vol. 114, pp. 273-358) has argued that 'social sharing' via Internet-based distributed computing is a new, so far under-appreciated modality of economic production. This paper presents results from an empirical study of SETI@home (the Search for Extraterrestrial Intelligence), which is the classic example of such a computing project. The aim is to explain SETI@home participation and its intensity in a cross-country setting. The data are for a sample of 172 developed and developing countries for the years 2002-2004. The results indicate that SETI@home participation and its intensity can be explained largely by the degree of ICT access (proxied by the International Telecommunication Union's 'Digital Access Index'), as well as GDP per capita and dummy variables for major country groups. Some other variables, such as the Human Development Index, perform less well. Although SETI@home is a global phenomenon, it is never-the-less mostly concentrated in rich countries. However, there are indications of a slowly narrowing global SETI@home digital divide

"The Social Capital of Regional Dynamics: A Policy Perspective"

This paper deals with social capital as an extra-market externality, and its role for innovations and growth. It analyses the changes of innovation activity over time, from early industrialism to the global knowledge economy, how the relations between the actors of today's innovation systems have developed and the role of social networks for innovations. The different kinds of networks built by the three constructers of social networks: the individual, the organizations and the (public and civic) society are discussed. The role of public policy in building social capital for innovations and growth is analyzed.

Quasi-Lagrangian Systems of Newton Equations

Systems of Newton equations of the form $\ddot{q}=-{1/2}A^{-1}(q)\nabla k$ with an integral of motion quadratic in velocities are studied. These equations generalize the potential case (when A=I, the identity matrix) and they admit a curious quasi-Lagrangian formulation which differs from the standard Lagrange equations by the plus sign between terms. A theory of such quasi-Lagrangian Newton (qLN) systems having two functionally independent integrals of motion is developed with focus on two-dimensional systems. Such systems admit a bi-Hamiltonian formulation and are proved to be completely integrable by embedding into five-dimensional integrable systems. They are characterized by a linear, second-order PDE which we call the fundamental equation. Fundamental equations are classified through linear pencils of matrices associated with qLN systems. The theory is illustrated by two classes of systems: separable potential systems and driven systems. New separation variables for driven systems are found. These variables are based on sets of non-confocal conics. An effective criterion for existence of a qLN formulation of a given system is formulated and applied to dynamical systems of the Henon-Heiles type.Comment: 50 pages including 9 figures. Uses epsfig package. To appear in J. Math. Phy

Unverzeihlicher Antikonformismus: Die Schriften Hans Paasches in der Ära des deutschen Kolonialismus

In an entry of his 1916 journal, Hans Paasche (1881-1920) wrote a long reflection on metánoia, a concept indicating a radical shift in thinking. In fact, the whole life of Hans Paasche itself could be read as such a radical conversion. He was all that follows: officer in the repression of the Maji-Maji riots in the German colonies of Ostafrika, skilled hunter, volunteer in the Great War, and then vigorous pacifist, relentless opponent of alcohol abuse and fervent vegetarian, ironic writer and passionate political reformer. In a context in which attempts at change were seen as traitorous, his life shows that self-acknowledgement may lead to marginalisation and to murder. The absence of forgiveness and understanding in his case still continues and his work and thought have been almost totally removed from any public and literary discourse in Germany. This paper intends to analyze his thought through his works, mainly "Die Forschungsreise des Afrikaners Lukanga Mukara ins innerste Deutschland", highlighting how, in his later years, Paasche felt the need to communicate his traumatic experiences with the intent of avoiding their repetition

Semiclassical Nonconcentration near Hyperbolic Orbits

For a large class of semiclassical pseudodifferential operators, including Schr\"odinger operators, $P (h) = -h^2 \Delta_g + V (x)$, on compact Riemannian manifolds, we give logarithmic lower bounds on the mass of eigenfunctions outside neighbourhoods of generic closed hyperbolic orbits. More precisely we show that if $A$ is a pseudodifferential operator which is microlocally equal to the identity near the hyperbolic orbit and microlocally zero away from the orbit, then $$\| u \| \leq C (\sqrt{\log(1/h)}/ h) \| P (h)u \| + C \sqrt {\log(1/h)} \| (I - A) u \| .$$ This generalizes earlier estimates of Colin de Verdi\`ere-Parisse \cite{CVP} obtained for a special case, and of Burq-Zworski \cite{BZ} for real hyperbolic orbits.Comment: 45 pages, 5 figure

Resolvent estimates with mild trapping

We discuss recent progress in understanding the effects of certain trapping geometries on cut-off resolvent estimates, and thus on the qualititative behavior of linear evolution equations. We focus on trapping that is unstable, so that strong resolvent estimates hold on the real axis, and large resonance-free regions can be shown to exist beyond it.Comment: 15 pages. For Journ\'ees EDP 2012 conference proceeding