Theory for Superconducting Properties of the Cuprates: Doping Dependence of the Electronic Excitations and Shadow States

The superconducting phase of the 2D one-band Hubbard model is studied within the FLEX approximation and by using an Eliashberg theory. We investigate the doping dependence of $T_c$, of the gap function $\Delta ({\bf k},\omega)$ and of the effective pairing interaction. Thus we find that $T_c$ becomes maximal for $13 \; \%$ doping. In {\it overdoped} systems $T_c$ decreases due to the weakening of the antiferromagnetic correlations, while in the {\it underdoped} systems due to the decreasing quasi particle lifetimes. Furthermore, we find {\it shadow states} below $T_c$ which affect the electronic excitation spectrum and lead to fine structure in photoemission experiments.Comment: 10 pages (REVTeX) with 5 figures (Postscript

Laminar flows in porous elastic channels

Laminar flows of viscous fluids in porous elastic channel

Modular classes of skew algebroid relations

Skew algebroid is a natural generalization of the concept of Lie algebroid. In this paper, for a skew algebroid E, its modular class mod(E) is defined in the classical as well as in the supergeometric formulation. It is proved that there is a homogeneous nowhere-vanishing 1-density on E* which is invariant with respect to all Hamiltonian vector fields if and only if E is modular, i.e. mod(E)=0. Further, relative modular class of a subalgebroid is introduced and studied together with its application to holonomy, as well as modular class of a skew algebroid relation. These notions provide, in particular, a unified approach to the concepts of a modular class of a Lie algebroid morphism and that of a Poisson map.Comment: 20 page

Modular classes of Poisson-Nijenhuis Lie algebroids

The modular vector field of a Poisson-Nijenhuis Lie algebroid $A$ is defined and we prove that, in case of non-degeneracy, this vector field defines a hierarchy of bi-Hamiltonian $A$-vector fields. This hierarchy covers an integrable hierarchy on the base manifold, which may not have a Poisson-Nijenhuis structure.Comment: To appear in Letters in Mathematical Physic

Participatory planning for eco-trekking on a potential World Heritage site: The communities of the Kokoda Track

Participatory Rural Appraisal (PRA) is an approach to data collection in participatory research. In this approach, the researcher is required to acknowledge and appreciate that research participants have the necessary knowledge and skills to be partners in the research process. PRA techniques were used to collect data on the Kokoda Track, Papua New Guinea, illuminating the communities' perceptions of eco-trekking and how they could better benefit from it. This case study is an example of the implementation of community-based eco-tourism development and of understanding the multiplicity of forces that support or undermine it. © The Australian National University

Electronic Theory for Bilayer-Effects in High-T_c Superconductors

The normal and the superconducting state of two coupled CuO_2 layers in the High-T_c superconductors are investigated by using the bilayer Hubbard model, the FLEX approximation on the real frequency axis and the Eliashberg theory. We find that the planes are antiferromagnetically correlated which leads to a strongly enhanced shadow band formation. Furthermore, the inter-layer hopping is renormalized which causes a blocking of the quasi particle inter-plane transfer for low doping concentrations. Finally, the superconducting order parameter is found to have a d_{x^2-y^2} symmetry with significant additional inter-layer contributions.Comment: 5 pages, Revtex, 4 postscript figure