Spinning particle in an external linearized gravitational wave field

We study the interaction of a scalar and a spinning particle with a coherent linearized gravitational wave field treated as a classical spin two external field. The spin degrees of freedom of the spinning particle are described by skew-commuting variables. We derive the explicit expressions for the eigenfunctions and the Green's functions of the theory. The discussion is exact within the approximation of neglecting radiative corrections and we prove that the result is completely determined by the semiclassical contribution.Comment: 11 page

Scattering of Spinning Test Particles by Plane Gravitational and Electromagnetic Waves

The Mathisson-Papapetrou-Dixon (MPD) equations for the motion of electrically neutral massive spinning particles are analysed, in the pole-dipole approximation, in an Einstein-Maxwell plane-wave background spacetime. By exploiting the high symmetry of such spacetimes these equations are reduced to a system of tractable ordinary differential equations. Classes of exact solutions are given, corresponding to particular initial conditions for the directions of the particle spin relative to the direction of the propagating background fields. For Einstein-Maxwell pulses a scattering cross section is defined that reduces in certain limits to those associated with the scattering of scalar and Dirac particles based on classical and quantum field theoretic techniques. The relative simplicity of the MPD approach and its use of macroscopic spin distributions suggests that it may have advantages in those astrophysical situations that involve strong classical gravitational and electromagnetic environments.Comment: Submitted to Classical and Quantum Gravity. 12 page

An action principle for the quantization of parametric theories and nonlinear quantum cosmology

By parametrizing the action integral for the standard Schrodinger equation we present a derivation of the recently proposed method for quantizing a parametrized theory. The reformulation suggests a natural extension from conventional to nonlinear quantum mechanics. This generalization enables a unitary description of the quantum evolution for a broad class of constrained Hamiltonian systems with a nonlinear kinematic structure. In particular, the new theory is applicable to the quantization of cosmological models where a chosen gravitational degree of freedom acts as geometric time. This is demonstrated explicitly using three cosmological models: the Friedmann universe with a massless scalar field and Bianchi type I and IX models. Based on these investigations, the prospect of further developing the proposed quantization scheme in the context of quantum gravity is discussed.Comment: 14 page

Approaching the Problem of Time with a Combined Semiclassical-Records-Histories Scheme

I approach the Problem of Time and other foundations of Quantum Cosmology using a combined histories, timeless and semiclassical approach. This approach is along the lines pursued by Halliwell. It involves the timeless probabilities for dynamical trajectories entering regions of configuration space, which are computed within the semiclassical regime. Moreover, the objects that Halliwell uses in this approach commute with the Hamiltonian constraint, H. This approach has not hitherto been considered for models that also possess nontrivial linear constraints, Lin. This paper carries this out for some concrete relational particle models (RPM's). If there is also commutation with Lin - the Kuchar observables condition - the constructed objects are Dirac observables. Moreover, this paper shows that the problem of Kuchar observables is explicitly resolved for 1- and 2-d RPM's. Then as a first route to Halliwell's approach for nontrivial linear constraints that is also a construction of Dirac observables, I consider theories for which Kuchar observables are formally known, giving the relational triangle as an example. As a second route, I apply an indirect method that generalizes both group-averaging and Barbour's best matching. For conceptual clarity, my study involves the simpler case of Halliwell 2003 sharp-edged window function. I leave the elsewise-improved softened case of Halliwell 2009 for a subsequent Paper II. Finally, I provide comments on Halliwell's approach and how well it fares as regards the various facets of the Problem of Time and as an implementation of QM propositions.Comment: An improved version of the text, and with various further references. 25 pages, 4 figure

Towards a sustainable convention: values and practices in the French stone fruits’value chain

In this article, we first present the framework of the conventions theory (CT) and the sustainable criteria of the Alternative Food Networks (AFN). Then, we present our results chain’s actor by chain’s actor (processors, supermarkets, corner grocery stores and producers). We indicate their consideration for the local and organic food products and their values around these themes. Finally we discuss these results within the CT conceptual framework showing that the producers seems anchored in the industrial world while the other actors are in majority coordinated by the market world. Thus, we suggest that the levers will be different for the producers and for the other actors of the peach and apricot chains and yet some common values have to been found within the chain

Innovative Education for Sustainable Development in Peripheral Rural Areas

This paper aims to present the results of the Erasmus + RUR'UP project that developed educational tools for scientists, public managers, practitioners, and agricultural advisors living and working in peripheral rural areas. Based on the assessment of the educational needs and gaps for the sustainable development of the EU peripheral rural areas of Greece, Bulgaria, Romania, Croatia, Finland, Ireland and France via a participatory innovation process, we have developed: an asynchronous e-learning course and supporting educational materials. The objective was to provide educational tools that will help the professional competencies of the Higher Education (HE) institutions working with peripheral rural regions by answering to the labour market and societal needs in these regions, thereby strengthening the collaboration between higher education and regional and cross-regional employers. The project resulted in 50 students who attended the e-learning course and the development of Open-Access educational materials with pedagogically sound activities associated with them, which can be used by any actor interested in the sustainable development of peripheral rural areas, especially those with high natural values in the form of a Virtual Bank of Case studies that gathers 14 examples of case studies. © 2022 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0