Embeddings of SL(2,Z) into the Cremona group

Geometric and dynamic properties of embeddings of SL(2,Z) into the Cremona group are studied. Infinitely many non-conjugate embeddings which preserve the type (i.e. which send elliptic, parabolic and hyperbolic elements onto elements of the same type) are provided. The existence of infinitely many non-conjugate elliptic, parabolic and hyperbolic embeddings is also shown. In particular, a group G of automorphisms of a smooth surface S obtained by blowing-up 10 points of the complex projective plane is given. The group G is isomorphic to SL(2,Z), preserves an elliptic curve and all its elements of infinite order are hyperbolic.Comment: to appear in Transformation Group

Resistive Switching Assisted by Noise

We extend results by Stotland and Di Ventra on the phenomenon of resistive switching aided by noise. We further the analysis of the mechanism underlying the beneficial role of noise and study the EPIR (Electrical Pulse Induced Resistance) ratio dependence with noise power. In the case of internal noise we find an optimal range where the EPIR ratio is both maximized and independent of the preceding resistive state. However, when external noise is considered no beneficial effect is observed.Comment: To be published in "Theory and Applications of Nonlinear Dynamics: Model and Design of Complex Systems", Proceedings of ICAND 2012 (Springer, 2013

Nonclassical rotational inertia for a supersolid under rotation

As proposed by Leggett [4], the supersolidity of a crystal is characterized by the Non Classical Rotational Inertia (NCRI) property. Using a model of quantum crystal introduced by Josserand, Pomeau and Rica [5], we prove that NCRI occurs. This is done by analyzing the ground state of the aforementioned model, which is related to a sphere packing problem, and then deriving a theoretical formula for the inertia momentum. We infer a lower estimate for the NCRI fraction, which is a landmark of supersolidity

Land management for increased flood resilience

Natural Flood Management (NFM) (e.g. restoring watercourses, riparian tree planting, washland and wetland creation) is a core component of flood risk management strategies in Scotland. However little is known of its potential impact on the farming and land management communities, individual farm businesses, or the socioeconomic impacts and perceptions of its potential wide-spread introduction. To support policy implementation, information is required on land managers’ willingness to implement NFM, and to be able to relate willingness to generic farm characteristics (farming systems, land use types, geographical location), different types and locations of NFM measures, and to farm economics.The main objectives of the project are to undertake:1. A large scale survey of farmers’ attitudes to NFM and to the use of potential policy instruments to promote its uptake and delivery; and2. Farm-scale economic analyses of the impact of NFM measures under different scenarios

Organisations and transitions of horticultural organic producers in a periurban area of São Paulo (Brazil).

A few years after enacting the Organic Law (December 2003), Brazil is becoming a world leader in Organic Farming (OF), which covers a wide range of production and certification systems. Besides developing an export capability, there is also a growing demand for organic fresh vegetables in cities, especially in the south-eastern States. However, the ways small farmers adopt OF in ?green belts? to meet urban demands for organics have not been investigated extensively. We explored this issue in the community of Ibiúna, located in a hilly area at about 100 km from three main cities of São Paulo (São Paulo, Sorocaba and Campinas). This case study shows how small farmers were organised or organise themselves to meet urban demands and develop OF, and analyse its further implication in terms of social benefits. The approach was based on interviews with farmers, technical and political officials, organic inspectors and leaders from various organic producer associations. It then served as a basis for additional case studies in São Paulo and other States, with the extension of agro-ecological initiatives (Brandenburg, 2002)

Are Steadily Moving Crystals Unstable?

We study the dynamics of small fluctuations about the uniform state of a crystal moving through a dissipative medium, e.g. a sedimenting colloidal crystal or a moving flux lattice, using a set of continuum equations for the displacement fields, and a one-dimensional driven lattice-gas model for the coupled concentration and tilt fields. For the colloidal crystal we predict a continuous nonequilibrium phase transition to a clumped state above a critical Peclet number.Comment: 4 pages, revtex, 2 .eps figures, uses epsf.sty; To be published in Phys. Rev. Lett. This version is substantially rewritten but the essential content is the same as befor