Transport Properties of the Infinite Dimensional Hubbard Model

Results for the optical conductivity and resistivity of the Hubbard model in infinite spatial dimensions are presented. At half filling we observe a gradual crossover from a normal Fermi-liquid with a Drude peak at $\omega=0$ in the optical conductivity to an insulator as a function of $U$ for temperatures above the antiferromagnetic phase transition. When doped, the ``insulator'' becomes a Fermi-liquid with a corresponding temperature dependence of the optical conductivity and resistivity. We find a $T^2$-coefficient in the low temperature resistivity which suggests that the carriers in the system acquire a considerable mass-enhancement due to the strong local correlations. At high temperatures, a crossover into a semi-metallic regime takes place.Comment: 14 page

A new approach for perovskites in large dimensions

Using the Hubbard Hamiltonian for transition metal-3d and oxygen-2p states with perovskite geometry, we propose a new scaling procedure for a nontrivial extension of these systems to large spatial dimensions $D$. The scaling procedure is based on a selective treatment of different hopping processes for large $D$ and can not be generated by a unique scaling of the hopping element. The model is solved in the limit $D \rightarrow \infty$ by the iterated perturbation theory and using an extended non-crossing approximation. We discuss the evolution of quasi particles at the Fermi-level upon doping, leading to interesting insight into the dynamical character of the charge carriers near the metal insulator instability of transition metal oxide systems, three dimensional perovskites and other strongly correlated transition metal oxides.Comment: 5 pages (TeX) with 2 figures (Postscript

Clients’ Perspectives of Meaningful Healthcare Relationships

The aim of this study was to increase understanding of how clients view meaningful relationships within the healthcare context and how clients respond to differences in approaches or expectations for a meaningful relationship

Capitol Records v. Vimeo: The Peculiar Case of Pre-1972 Sound Recordings and Federal Copyright Law

In Capitol Records, L.L.C. v. Vimeo, L.L.C., the U.S. Court of Appeals for the Second Circuit held that the “safe harbor” provisions of Section 512 of the federal Copyright Act covered state law claims against an online service provider for infringement of pre-1972 sound recordings. The evidentiary basis for this conclusion was slender. At the heart of the decision was the court’s surmise that Congress must have intended to cover state law “copyright,” because a contrary interpretation would undermine the policy objectives of the Digital Millennium Copyright Act (DMCA). In reaching its decision, the court apparently misread the Copyright Act and misunderstood both the nature of state law protection for pre-1972 sound recordings and the trade-offs that underlay the DMCA. We submit that this holding of Vimeo should not be followed by courts in other circuits, however sympathetic its policy underpinnings may be. It is doubtful that Congress considered state law “copyright” claims in passing the DMCA, or that it meant to include them under § 512. As a policy matter, it probably should have done so. But had it done so, Congress almost certainly would have said so explicitly, and would have altered other provisions of the DMCA to achieve a fairer result for owners of rights in pre-1972 sound recordings than the Second Circuit did. Congress could, for example, have protected pre-1972 sound recordings under § 1201 et seq., or otherwise provided those recordings with greater protection under the Copyright Act. The court’s focus on only one policy objective of the DMCA led it to interpret the Copyright Act in an implausible manner that benefits online service providers (OSPs), at the expense of owners of pre-1972 sound recordings, and the unique position of those recordings under copyright law. The central issues in this case that concern pre-1972 sound recordings are more appropriately under Congressional purview, as the Second Circuit should have recognized. And indeed, Congress should act to resolve these issues, particularly now, in view of the conflicting treatment of state law claims between Vimeo (concerning the safe harbor in § 512 of the Copyright Act) and the Ninth Circuit’s sweeping conclusion in Perfect 10, Inc. v. CCBill, L.L.C. that state law intellectual property claims are barred by § 230 of the Communications Decency Act (CDA). Accordingly, we recommend legislation to address this issue and to resolve other problems and inconsistencies that have arisen due to the peculiar situation of pre-1972 sound recordings and federal copyright law, as discussed below. In Part I, we discuss the legal status of pre-1972 sound recordings as necessary background to evaluating the Second Circuit’s decision in Vimeo. Part II discusses that decision in greater detail, and Part III explains the flaws in the court’s rationale. In Part IV, we address the Second and Ninth Circuits’ contradictory views concerning the treatment of state law claims against OSPs under § 512 of the Copyright Act and § 230 of the CDA. In Part V, we explain that it is up to Congress to change the role of pre-1972 sound recordings in the federal copyright scheme, and argue that the time is ripe for Congress to exercise that power. We conclude in Part VI

d-wave Superconductivity in the Hubbard Model

The superconducting instabilities of the doped repulsive 2D Hubbard model are studied in the intermediate to strong coupling regime with help of the Dynamical Cluster Approximation (DCA). To solve the effective cluster problem we employ an extended Non Crossing Approximation (NCA), which allows for a transition to the broken symmetry state. At sufficiently low temperatures we find stable d-wave solutions with off-diagonal long range order. The maximal $T_c\approx 150K$ occurs for a doping $\delta\approx 20$ and the doping dependence of the transition temperatures agrees well with the generic high-$T_c$ phase diagram.Comment: 5 pages, 5 figure

Anomalous Normal-State Properties of High-Tc_c Superconductors -- Intrinsic Properties of Strongly Correlated Electron Systems?

A systematic study of optical and transport properties of the Hubbard model, based on Metzner and Vollhardt's dynamical mean-field approximation, is reviewed. This model shows interesting anomalous properties that are, in our opinion, ubiquitous to single-band strongly correlated systems (for all spatial dimensions greater than one), and also compare qualitatively with many anomalous transport features of the high-T$_c$ cuprates. This anomalous behavior of the normal-state properties is traced to a ``collective single-band Kondo effect,'' in which a quasiparticle resonance forms at the Fermi level as the temperature is lowered, ultimately yielding a strongly renormalized Fermi liquid at zero temperature.Comment: 27 pages, latex, 13 figures, Invited for publication in Advances in Physic

Kinks in the electronic dispersion of the Hubbard model away from half filling

We study kinks in the electronic dispersion of a generic strongly correlated system by dynamic mean-field theory (DMFT). The focus is on doped systems away from particle-hole symmetry where valence fluctuations matter potentially. Three different algorithms are compared to asses their strengths and weaknesses, as well as to clearly distinguish physical features from algorithmic artifacts. Our findings extend a view previously established for half-filled systems where kinks reflect the coupling of the fermionic quasiparticles to emergent collective modes, which are identified here as spin fluctuations. Kinks are observed when strong spin fluctuations are present and, additionally, a separation of energy scales for spin and charge excitations exists. Both criteria are met by strongly correlated systems close to a Mott-insulator transition. The energies of the kinks and their doping dependence fit well to the kinks in the cuprates, which is surprising in view of the spatial correlations neglected by DMFT.Comment: 13 pages, 15 figure

Heavy-Fermions in a Transition-Metal Compound: LiV2O4LiV_2O_4

The recent discovery of heavy-Fermion properties in Lithium Vanadate and the enormous difference in its properties from the properties of Lithium Titanate as well as of the manganite compounds raise some puzzling questions about strongly correlated Fermions. These are disscussed as well as a solution to the puzzles provided.Comment: late

A comparison of cost and quality of three methods for estimating density for wild pig (\u3ci\u3eSus scrofa\u3c/i\u3e)

A critical element in effective wildlife management is monitoring the status of wildlife populations; however, resources to monitor wildlife populations are typically limited. We compared cost effectiveness of three common population estimation methods (i.e. non-invasive DNA sampling, camera sampling, and sampling from trapping) by applying them to wild pigs (Sus scrofa) across three habitats in South Carolina, U.S.A where they are invasive. We used mark-recapture analyses for fecal DNA sampling data, spatially-explicit capture-recapture analyses for camera sampling data, and a removal analysis for removal sampling from trap data. Density estimates were similar across methods. Camera sampling was the least expensive, but had large variances. Fecal DNA sampling was the most expensive, although this technique generally performed well. We examined how reductions in effort by method related to increases in relative bias or imprecision. For removal sampling, the largest cost savings while maintaining unbiased density estimates was from reducing the number of traps. For fecal DNA sampling, a reduction in effort only minimally reduced costs due to the need for increased lab replicates while maintaining high quality estimates. For camera sampling, effort could only be marginally reduced before inducing bias. We provide a decision tree for researchers to help make monitoring decisions