Theory of incommensurate magnetic correlations across the insulator-superconductor transition in underdoped La_{2-x}Sr_xCuO_4

The main feature in the elastic neutron scattering of La_{2-x}Sr_xCuO_4 is the existence of incommensurate peaks with positions that jump from 45 to 0 degrees at 5% doping. We show that the spiral state of the t-t'-t''-J model with realistic parameters describes this data perfectly. We explain why in the insulator the peak is at 45 degrees while it switches to 0 degrees precisely at the insulator-metal transition. The calculated positions of the peaks are in agreement with the data in both phases.Comment: 5 pages, 1 figure; minor change

Theory of Anisotropic Hopping Transport due to Spiral Correlations in the Spin-Glass Phase of Underdoped Cuprates

We study the in-plane resistivity anisotropy in the spin-glass phase of the high-$T_{c}$ cuprates, on the basis of holes moving in a spiral spin background. This picture follows from analysis of the extended $t-J$ model with Coulomb impurities. In the variable-range hopping regime the resistivity anisotropy is found to have a maximum value of around 90%, and it decreases with temperature, in excellent agreement with experiments in La$_{2-x}$Sr$_x$CuO$_4$. In our approach the transport anisotropy is due to the non-collinearity of the spiral spin state, rather than an intrinsic tendency of the charges to self-organize.Comment: 5 pages, 4 figures; expanded versio

AC Hopping Magnetotransport Across the Spin Flop Transition in Lightly Doped La_2CuO_4

The weak ferromagnetism present in insulating La_{2}CuO_4 at low doping leads to a spin flop transition, and to transverse (interplane) hopping of holes in a strong external magnetic field. This results in a dimensional crossover 2D $\to$ 3D for the in-plane transport, which in turn leads to an increase of the hole's localization length and increased conduction. We demonstrate theoretically that as a consequence of this mechanism, a frequency-dependent jump of the in-plane ac hopping conductivity occurs at the spin flop transition. We predict the value and the frequency dependence of the jump. Experimental studies of this effect would provide important confirmation of the emerging understanding of lightly doped insulating La_{2-x}Sr_xCuO_4.Comment: 4 pages, 1 figur

Reliability of T-WSI to evaluate neighborhoods walkability and its changes over time

More walkable neighborhoods are linked to increased physical activity. The Walking Suitability Index of the territory (T-WSI) is an easy method to evaluate walkability on the basis of direct observation. T-WSI provides 12 indicators divided into 4 categories (practicability, safety, urbanity, pleasantness); the weighted analysis of these indicators gives an overall score of the actual usability of the neighborhood. The aim of the study is to evaluate the ability of T-WSI’ indicators to measure, in a reliable way, any street’s walkability variations occurred over time. The investigation was performed in 2018 in nine urban neighborhoods of Rieti city. Cronbach’s α is used to evaluate internal consistency of T-WSI; Intraclass Correlation Coefficient (ICC) is used to evaluate the reproducibility of measurements (or ratings) made by different investigators. Cronbach’s α is 0.89 (± 0.02); ICC is also good (ICC = 0.89; 95% CI: 0.84–0.92). The results of the 2018 investigation are also compared with those collected in 2016 in the same districts. The results show that T-WSI is a reliable and easy to use tool, useful to measure the effectiveness of the interventions already realized at local level, but it could also contribute to making decisions to develop regeneration projects