Hot Spots and Pseudogaps for Hole- and Electron-Doped High-Temperature Superconductors

Using cluster perturbation theory, it is shown that the spectral weight and pseudogap observed at the Fermi energy in recent Angle Resolved Photoemission Spectroscopy (ARPES) of both electron and hole-doped high-temperature superconductors find their natural explanation within the t-t'-t''-U Hubbard model in two dimensions. The value of the interaction U needed to explain the experiments for electron-doped systems at optimal doping is in the weak to intermediate coupling regime where the t-J model is inappropriate. At strong coupling, short-range correlations suffice to create a pseudogap but at weak coupling long correlation lengths associated with the antiferromagnetic wave vector are necessary.Comment: RevTeX 4, 4 pages, 5 figures (2 in color

Strong-Coupling Perturbation Theory of the Hubbard Model

The strong-coupling perturbation theory of the Hubbard model is presented and carried out to order (t/U)^5 for the one-particle Green function in arbitrary dimension. The spectral weight A(k,omega) is expressed as a Jacobi continued fraction and compared with new Monte-Carlo data of the one-dimensional, half-filled Hubbard model. Different regimes (insulator, conductor and short-range antiferromagnet) are identified in the temperature--hopping integral (T,t) plane. This work completes a first paper on the subject (Phys. Rev. Lett. 80, 5389 (1998)) by providing details on diagrammatic rules and higher-order results. In addition, the non half-filled case, infinite resummations of diagrams and the double occupancy are discussed. Various tests of the method are also presented.Comment: 28 pages, 19 figure

Symmetry properties of Penrose type tilings

The Penrose tiling is directly related to the atomic structure of certain decagonal quasicrystals and, despite its aperiodicity, is highly symmetric. It is known that the numbers 1, $-\tau$, $(-\tau)^2$, $(-\tau)^3$, ..., where $\tau =(1+\sqrt{5})/2$, are scaling factors of the Penrose tiling. We show that the set of scaling factors is much larger, and for most of them the number of the corresponding inflation centers is infinite.Comment: Paper submitted to Phil. Mag. (for Proceedings of Quasicrystals: The Silver Jubilee, Tel Aviv, 14-19 October, 2007

Greenhouse Gas Emissions and Fire Behavior Impacts Following California Fuel Treatments

Fuel treatments are being increasingly applied across California landscapes as communities struggle to recover from wildfire disasters nationwide. Increased funding for treatments stems from grants under CARB’s Greenhouse Gas Reduction Fund and funding requires reports accounting the yielded benefits from these fuel treatments. Using data from real-world local scale fuel treatments, I used the forest simulation model FVSFEE and fire behavior software IFTDSS to quantify GHG emission benefits and fire behavior impacts 70 years after treatment. Results suggest that fuel treatments do not yield significant GHG benefits, and fire behavior impacts (conditional flame length) are minimal but overall show slight reductions in the impact area’s burn severity. However, treatment outcomes may vary on the localized landscapes, size of treatment, and unique parameters applied to each treatment simulation

Topological Equivalence between the Fibonacci Quasicrystal and the Harper Model

One-dimensional quasiperiodic systems, such as the Harper model and the Fibonacci quasicrystal, have long been the focus of extensive theoretical and experimental research. Recently, the Harper model was found to be topologically nontrivial. Here, we derive a general model that embodies a continuous deformation between these seemingly unrelated models. We show that this deformation does not close any bulk gaps, and thus prove that these models are in fact topologically equivalent. Remarkably, they are equivalent regardless of whether the quasiperiodicity appears as an on-site or hopping modulation. This proves that these different models share the same boundary phenomena and explains past measurements. We generalize this equivalence to any Fibonacci-like quasicrystal, i.e., a cut and project in any irrational angle.Comment: 7 pages, 2 figures, minor change

Interacting two helical edge modes in quantum spin Hall systems

We study theoretically the two interacting one-dimensional helical modes at the edges of the quantum spin Hall systems. A new type of inter-edge correlated liquid (IECL) without the spin gap is found. This liquid shows the diverging density wave (DW) and superconductivity (SC) correlations much stronger than those of the spinfull electrons. Possible experimental observations are also discussed

Integrable lattices and their sublattices II. From the B-quadrilateral lattice to the self-adjoint schemes on the triangular and the honeycomb lattices

An integrable self-adjoint 7-point scheme on the triangular lattice and an integrable self-adjoint scheme on the honeycomb lattice are studied using the sublattice approach. The star-triangle relation between these systems is introduced, and the Darboux transformations for both linear problems from the Moutard transformation of the B-(Moutard) quadrilateral lattice are obtained. A geometric interpretation of the Laplace transformations of the self-adjoint 7-point scheme is given and the corresponding novel integrable discrete 3D system is constructed.Comment: 15 pages, 6 figures; references added, some typos correcte

BIOREFINERIES USING AGRICULTURAL RESIDUE FEEDSTOCK IN THE GREAT PLAINS

Rising prices and uncertain supplies of petroleum, together with environmental concerns regarding fossil fuel combustion, has enhanced interest in biobased products and fuels. The work reported here analyzes the feasibility of a multi-product biorefinery using wheat straw as feedstock that produces ethanol, electricity, and cellulose nanofibers. The nanofibers (nanowhiskers) would be used as reinforcements in a biobased nanocomposite material that could substitute for fiberglass in many applications. The analysis indicates that, at 2005 prices and costs, the biorefinery would be marginally profitable. Anticipated advances in bioprocessing technology would enhance profitability. The facility would also make a substantial contribution to the biorefinery site area economy, as a high percentage of operating expenses would be payments to local entities. The growth of a biobased industry could have major economic development implications for the Great Plains/Midwest region.biomass, biomaterials, ethanol, wheat straw, cellulose nanowhiskers (CNW), economic development, Resource /Energy Economics and Policy,

Use of Agricultural Residue Feedstock In North Dakota Biorefineries

Rising prices and uncertain supplies of petroleum, together with environmental concerns regarding fossil fuel combustion, have enhanced interest in biobased products and fuels. This study analyzes the feasibility of a multi-product biorefinery that uses wheat straw as feedstock to produce ethanol, electricity, and cellulose nanofibers. Nanofibers (nanowhiskers) would be used as reinforcements in a biobased nanocomposite material that could substitute for fiberglass in many applications. The growth of a biobased industry could have major economic development implications for the Great Plains/Midwest region.biomass, biomaterials, cellulose nanofibers (CNFs), economic development, ethanol, wheat straw, Agribusiness, Resource /Energy Economics and Policy,