5,302 research outputs found
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 , of the gap function and
of the effective pairing interaction. Thus we find that becomes maximal
for doping. In {\it overdoped} systems 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 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 Poisson-Nijenhuis Lie algebroids
The modular vector field of a Poisson-Nijenhuis Lie algebroid is defined
and we prove that, in case of non-degeneracy, this vector field defines a
hierarchy of bi-Hamiltonian -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
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
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
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
Thermodyamic bounds on Drude weights in terms of almost-conserved quantities
We consider one-dimensional translationally invariant quantum spin (or
fermionic) lattices and prove a Mazur-type inequality bounding the
time-averaged thermodynamic limit of a finite-temperature expectation of a
spatio-temporal autocorrelation function of a local observable in terms of
quasi-local conservation laws with open boundary conditions. Namely, the
commutator between the Hamiltonian and the conservation law of a finite chain
may result in boundary terms only. No reference to techniques used in Suzuki's
proof of Mazur bound is made (which strictly applies only to finite-size
systems with exact conservation laws), but Lieb-Robinson bounds and exponential
clustering theorems of quasi-local C^* quantum spin algebras are invoked
instead. Our result has an important application in the transport theory of
quantum spin chains, in particular it provides rigorous non-trivial examples of
positive finite-temperature spin Drude weight in the anisotropic Heisenberg XXZ
spin 1/2 chain [Phys. Rev. Lett. 106, 217206 (2011)].Comment: version as accepted by Communications in Mathematical Physics (22
pages with 2 pdf-figures
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