Kondo effect in three-dimensional Dirac and Weyl systems

Magnetic impurities in three-dimensional Dirac and Weyl systems are shown to exhibit a fascinatingly diverse range of Kondo physics, with distinctive experimental spectroscopic signatures. When the Fermi level is precisely at the Dirac point, Dirac semimetals are in fact unlikely candidates for a Kondo effect due to the pseudogapped density of states. However, the influence of a nearby quantum critical point leads to the unconventional evolution of Kondo physics for even tiny deviations in the chemical potential. Separating the degenerate Dirac nodes produces a Weyl phase: time-reversal symmetry-breaking precludes Kondo due to an effective impurity magnetic field, but different Kondo variants are accessible in time-reversal invariant Weyl systems.Comment: 4+ pages, 2 figure

Reconfiguring Household Management in Times of Discontinuity as an Open System: The Case of Agro-food Chains

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.This article is based upon a heterodox approach to economics that rejects the oversimplification made by closed economic models and the mainstream concept of ‘externality.’ This approach re-imagines economics as a holistic evaluation of resources versus human needs, which requires judgement based on understanding of the complexity generated by the dynamic relations between different systems. One re-imagining of the economic model is as a holistic and systemic evaluation of agri-food systems’ sustainability that was performed through the multi-dimensional Governance Assessment Matrix Exercise (GAME). This is based on the five capitals model of sustainability, and the translation of qualitative evaluations into quantitative scores. This is based on the triangulation of big data from a variety of sources. To represent quantitative interactions, this article proposes a provisional translation of GAME’s qualitative evaluation into a quantitative form through the identification of measurement units that can reflect the different capital dimensions. For instance, a post-normal, ecological accounting method, Emergy is proposed to evaluate the natural capital. The revised GAME re-imagines economics not as the ‘dismal science,’ but as one that has potential leverage for positive, adaptive and sustainable ecosystemic analyses and global ‘household’ management. This article proposes an explicit recognition of economics nested within the social spheres of human and social capital which are in turn nested within the ecological capital upon which all life rests and is truly the bottom line. In this article, the authors make reference to an on-line retailer of local food and drink to illustrate the methods for evaluation of the five capitals model

Real-time Planning as Decision-making Under Uncertainty

In real-time planning, an agent must select the next action to take within a fixed time bound. Many popular real-time heuristic search methods approach this by expanding nodes using time-limited A* and selecting the action leading toward the frontier node with the lowest f value. In this thesis, we reconsider real-time planning as a problem of decision-making under uncertainty. We treat heuristic values as uncertain evidence and we explore several backup methods for aggregating this evidence. We then propose a novel lookahead strategy that expands nodes to minimize risk, the expected regret in case a non-optimal action is chosen. We evaluate these methods in a simple synthetic benchmark and the sliding tile puzzle and find that they outperform previous methods. This work illustrates how uncertainty can arise even when solving deterministic planning problems, due to the inherent ignorance of time-limited search algorithms about those portions of the state space that they have not computed, and how an agent can benefit from explicitly meta-reasoning about this uncertainty

Real-space renormalization group flow in quantum impurity systems: local moment formation and the Kondo screening cloud

The existence of a length-scale $\xi_K\sim 1/T_K$ (with $T_K$ the Kondo temperature) has long been predicted in quantum impurity systems. At low temperatures $T\ll T_K$, the standard interpretation is that a spin-$\tfrac{1}{2}$ impurity is screened by a surrounding `Kondo cloud' of spatial extent $\xi_K$. We argue that renormalization group (RG) flow between any two fixed points (FPs) results in a characteristic length-scale, observed in real-space as a crossover between physical behaviour typical of each FP. In the simplest example of the Anderson impurity model, three FPs arise; and we show that `free orbital', `local moment' and `strong coupling' regions of space can be identified at zero temperature. These regions are separated by two crossover length-scales $\xi_{\text{LM}}$ and $\xi_K$, with the latter diverging as the Kondo effect is destroyed on increasing temperature through $T_K$. One implication is that moment formation occurs inside the `Kondo cloud', while the screening process itself occurs on flowing to the strong coupling FP at distances $\sim \xi_K$. Generic aspects of the real-space physics are exemplified by the two-channel Kondo model, where $\xi_K$ now separates `local moment' and `overscreening' clouds.Comment: 6 pages; 5 figure

Early CRT monitoring using time-domain optical coherence tomography does not add to visual acuity for predicting visual loss in patients with central retinal vein occlusion treated with intravitreal ranibizumab:A secondary analysis of trial data

Our primary purpose was to assess the clinical (predictive) validity of central retinal thickness (CRT) and best corrected visual acuity (BCVA) at 1 week and 1 month after starting treatment with ranibizumab for central retinal vein occlusion. The authors also assessed detectability of response to treatment

A Molecular Probe Finds Evidence of NIX Pathogen in Pacific Razor Clams (\u3cem\u3eSiliqua patula\u3c/em\u3e) in Oregon

The Pacific razor clam, Siliqua patula, is an important recreational fishery species that lives in the intertidal zone of sandy beaches from Alaska to central California. Populations have had periodic, but significant, declines over the past 30-40 years. These declines have correlated with an increase in the presences of an unidentified, intranuclear bacterial parasite known as Nuclear Inclusion X (NIX). NIX, which was first identified in 1986, has generally been screened using a histological approach. We developed a PCR-based screen to reduce both the time and cost of identifying infected clams. Use of this screen resulted in amplified sequences with a 97% match to the previously published 16S rDNA sequence for NIX. The sequence data supports placement of NIX into the gamma-proteobacteria, and suggests that it is related to isolates from diseased corals. Clams collected from the northern coast of Oregon showed ~50% infection rate using the PCR screen. This is the first report of NIX present in clams from Oregon, as all previous work had been in the state of Washington. Future work will identify the incidence rate and geographical spread of the NIX parasite throughout Oregon and Washington

Quantum phase transitions and thermodynamics of the power-law Kondo model

We revisit the physics of a Kondo impurity coupled to a fermionic host with a diverging power-law density of states near the Fermi level, $\rho(\omega) \sim |\omega|^r$, with exponent $-1<r<0$. Using the analytical understanding of several fixed points, based partially on powerful mappings between models with bath exponents $r$ and $(-r)$, combined with accurate numerical renormalization group calculations, we determine thermodynamic quantities within the stable phases, and also near the various quantum phase transitions. Antiferromagnetic Kondo coupling leads to strong screening with a negative zero-temperature impurity entropy, while ferromagnetic Kondo coupling can induce a stable fractional spin moment. We formulate the quantum field theories for all critical fixed points of the problem, which are fermionic in nature and allow for a perturbative renormalization-group treatment.Comment: 13 pages, 11 figure