Tipología y estructura de los estados antiguos de Mesoamérica.

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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

Verdaguer, un cas especial de periodisme

Verdaguer, un cas especial de periodism

La evolución del poder entre los mayas antiguos.

Sin resume