Multivector Field Formulation of Hamiltonian Field Theories: Equations and Symmetries

We state the intrinsic form of the Hamiltonian equations of first-order Classical Field theories in three equivalent geometrical ways: using multivector fields, jet fields and connections. Thus, these equations are given in a form similar to that in which the Hamiltonian equations of mechanics are usually given. Then, using multivector fields, we study several aspects of these equations, such as the existence and non-uniqueness of solutions, and the integrability problem. In particular, these problems are analyzed for the case of Hamiltonian systems defined in a submanifold of the multimomentum bundle. Furthermore, the existence of first integrals of these Hamiltonian equations is considered, and the relation between {\sl Cartan-Noether symmetries} and {\sl general symmetries} of the system is discussed. Noether's theorem is also stated in this context, both the ``classical'' version and its generalization to include higher-order Cartan-Noether symmetries. Finally, the equivalence between the Lagrangian and Hamiltonian formalisms is also discussed.Comment: Some minor mistakes are corrected. Bibliography is updated. To be published in J. Phys. A: Mathematical and Genera

Systematic Review Approach to identifying key trends in adaptation governance at the supranational level

In this paper authors have analyzed peer-reviewed literature on adaptation governance focused on food security at the supranational level. A total of 281 papers were collected, of which 52 met our focus. We used 10 criteria (and 74 sub-criteria) to categorize the included papers. With research presented in these papers as our focus, we looked at key aspects of food security explored, identified types of governance measures and major challenges, and finally developed an understanding of the location of the research teams and involved countries. Overall, we found that the supranational focus in the context of adaptation governance on food security is not prevalent in current peer-reviewed literature—only approximately 16 per cent of the papers focus on this topic. In terms of the identified trends, there was a strong focus on developed countries and research led by teams from these countries; the governance systems aimed to prepare for a range of climate change impacts; and finally, there was limited interest in exploring the role of regional agencies in adaptation governance. In terms of future research needs, there is a strong need to develop processes for the integration of diverse sectors and issues when designing policies on food security in the context of climate change. It is also important to improve the skills and opportunities of research teams in the Global South to engage effectively in research on food security and governance

Mitigation of backgrounds from cosmogenic 137Xe in xenon gas experiments using 3He neutron capture

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiereThis is the Accepted Manuscript version of an article accepted for publication in Journal of Physics G: Nuclear and Particle Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at 10.1088/1361-6471/ab8915136Xe is used as the target medium for many experiments searching for 0νββ. Despite underground operation, cosmic muons that reach the laboratory can produce spallation neutrons causing activation of detector materials. A potential background that is difficult to veto using muon tagging comes in the form of 137Xe created by the capture of neutrons on 136Xe. This isotope decays via beta decay with a half-life of 3.8 min and a Q β of ∼4.16 MeV. This work proposes and explores the concept of adding a small percentage of 3He to xenon as a means to capture thermal neutrons and reduce the number of activations in the detector volume. When using this technique we find the contamination from 137Xe activation can be reduced to negligible levels in tonne and multi-tonne scale high pressure gas xenon neutrinoless double beta decay experiments running at any depth in an underground laboratoryThe work described was supported by the Department of Energy under Award numbers DE-SC0019054 and DE-SC0019223. The NEXT Collaboration acknowledges support from the following agencies and institutions: the European Research Council (ERC) under the Advanced Grant 339787-NEXT; the European Union’s Framework Program for Research and Innovation Horizon 2020 (2014–2020) under the Marie Skłodowska-Curie Grant Agreements No. 674896, 690575 and 740055; the Ministerio de Economía y Competitividad of Spain under grants FIS2014-53371-C04, the Severo Ochoa Program SEV-2014-0398 and the María de Maetzu Program MDM-2016-0692; the GVA of Spain under grants PROMETEO/2016/120 and SEJI/2017/011; the Portuguese FCT under project PTDC/FISNUC/2525/2014, under project UID/FIS/04559/2013 to fund the activities of LIBPhys, and under grants PD/BD/105921/2014, SFRH/BPD/109180/2015 and SFRH/BPD/76842/2011. Finally, we are grateful to the Laboratorio Subterráneo de Canfranc for hosting and supporting the NEXT experimen

Active commuting and the health of workers

Introduction: Research has shown that commuting is related to the health of workers, and that mode choice may have a range of effects on this relationship. We analyze the relationship between active commuting (walking and cycling) and the health status reported by US workers. Methods: We use the 2014–2016 Eating and Health (EH) Module of the American Time Use Survey (ATUS). We estimate Ordinary Least Squares models on a measure of subjective health that is the self-reported assessment of individual general health status, and on the body mass index. Results: longer commutes by bicycle are significantly related to higher levels of subjective health and to lower body mass index, while commuting by walking is only weakly related to both health measures. We test the robustness of our results to possible measurement error in commuting times, to the exclusion of compensating factors, to the estimation method, and to the inclusion of time devoted to leisure-based physical activities. Conclusions: Our results may help policy makers in evaluating the importance of infrastructures that facilitate the use of bicycles as a means of transport, boosting investment in these infrastructures, especially in larger cities

Invariant Forms and Automorphisms of Locally Homogeneous Multisymplectic Manifolds

It is shown that the geometry of locally homogeneous multisymplectic manifolds (that is, smooth manifolds equipped with a closed nondegenerate form of degree > 1, which is locally homogeneous of degree k with respect to a local Euler field) is characterized by their automorphisms. Thus, locally homogeneous multisymplectic manifolds extend the family of classical geometries possessing a similar property: symplectic, volume and contact. The proof of the first result relies on the characterization of invariant differential forms with respect to the graded Lie algebra of infinitesimal automorphisms, and on the study of the local properties of Hamiltonian vector fields on locally multisymplectic manifolds. In particular it is proved that the group of multisymplectic diffeomorphisms acts (strongly locally) transitively on the manifold. It is also shown that the graded Lie algebra of infinitesimal automorphisms of a locally homogeneous multisymplectic manifold characterizes their multisymplectic diffeomorphisms.Comment: 25 p.; LaTeX file. The paper has been partially rewritten. Some terminology has been changed. The proof of some theorems and lemmas have been revised. The title and the abstract are slightly modified. An appendix is added. The bibliography is update

On the k-Symplectic, k-Cosymplectic and Multisymplectic Formalisms of Classical Field Theories

The objective of this work is twofold: First, we analyze the relation between the k-cosymplectic and the k-symplectic Hamiltonian and Lagrangian formalisms in classical field theories. In particular, we prove the equivalence between k-symplectic field theories and the so-called autonomous k-cosymplectic field theories, extending in this way the description of the symplectic formalism of autonomous systems as a particular case of the cosymplectic formalism in non-autonomous mechanics. Furthermore, we clarify some aspects of the geometric character of the solutions to the Hamilton-de Donder-Weyl and the Euler-Lagrange equations in these formalisms. Second, we study the equivalence between k-cosymplectic and a particular kind of multisymplectic Hamiltonian and Lagrangian field theories (those where the configuration bundle of the theory is trivial).Comment: 25 page

Non-standard connections in classical mechanics

In the jet-bundle description of first-order classical field theories there are some elements, such as the lagrangian energy and the construction of the hamiltonian formalism, which require the prior choice of a connection. Bearing these facts in mind, we analyze the situation in the jet-bundle description of time-dependent classical mechanics. So we prove that this connection-dependence also occurs in this case, although it is usually hidden by the use of the ``natural'' connection given by the trivial bundle structure of the phase spaces in consideration. However, we also prove that this dependence is dynamically irrelevant, except where the dynamical variation of the energy is concerned. In addition, the relationship between first integrals and connections is shown for a large enough class of lagrangians.Comment: 17 pages, Latex fil

Higher-order Mechanics: Variational Principles and other topics

After reviewing the Lagrangian-Hamiltonian unified formalism (i.e, the Skinner-Rusk formalism) for higher-order (non-autonomous) dynamical systems, we state a unified geometrical version of the Variational Principles which allows us to derive the Lagrangian and Hamiltonian equations for these kinds of systems. Then, the standard Lagrangian and Hamiltonian formulations of these principles and the corresponding dynamical equations are recovered from this unified framework.Comment: New version of the paper "Variational principles for higher-order dynamical systems", which was presented in the "III Iberoamerican Meeting on Geometry, Mechanics and Control" (Salamanca, 2012). The title is changed. A detailed review is added. Sections containing results about variational principles are enlarged with additional comments, diagrams and summarizing results. Bibliography is update

¿Existe un sesgo en la participación y visibilidad de las mujeres en ecología? Una comparación entre los congresos ibérico y suizo

Women are still under-represented in science and technology because there is a bias in the different evaluation processes from the admission of oral communications at conferences to the access to more qualified positions. In this study, we compared the participation and visibility of female ecologists in the IV Iberian Ecological Conference (CIE4) with the Annual Swiss Conference on Ecology, Evolution, Systematics, Biogeography and Conservation (Biology16) where a method of blind evaluation was applied. In both conferences, and after active selection by conference committees, male delegates presented proportionately more regular oral contributions than female ones, although these differences were marginally significant. In the Biology16, this bias was due to lower female applicants for oral contributions, and in the CIE4, to a lower selection rate of female oral contributions. In the CIE4, the higher male presence in oral contributions was consistent with male greater visibility, whereas female visibility was higher in the Biology16. This different visibility was caused by contrasting selection for invited speakers; being male researches preferentially invited at the CIE4, but female ones at the Biology16. Implementing a blind review system of contributions and active policies to promote the participation of women as invited speakers may reduce the differences in visibility and could contribute in the medium term to eliminate the bias against women in the selection of oral contributions at the Iberian conferences

Quantum Conductance Steps in Solutions of Multiwalled Carbon Nanotubes

We have prepared solutions of multiwalled carbon nanotubes in Aroclor 1254, a mixture of polychlorinated biphenyls. The solutions are stable at room temperature. Transport measurements were performed using a scanning--tunneling probe on a sample prepared by spin--coating of the solution on gold substrates. Conductance steps were clearly seen. An histogram of a high number of traces shows maximum peaks at integer values of the conductance quantum $G_0 = 2e^2/h$, demonstrating ballistic transport at room temperature along the carbon nanotube over distances longer than $1.4\mu m$.Comment: 4 pages and 2 figure