Quantum multiscale entanglement renormalization ansatz channels

Tensor network representations of many-body quantum systems can be described in terms of quantum channels. We focus on channels associated with the multiscale entanglement renormalization ansatz tensor network that has been recently introduced to efficiently describe critical systems. Our approach allows us to compute the multiscale entanglement renormalization ansatz correspondent to the thermodynamical limit of a critical system introducing a transfer matrix formalism, and to relate the system critical exponents to the convergence rates of the associated channels.     

A Fefferman-Poincaré type inequality for Carnot-Carathéodory vector fields

In this note we prove a Fefferman-Poincaré type inequality in spaces with metric induced by Carnot-Carathéodory vector fields.

     

Dynamics of fluxons in Y1−Ba2−Cu3−O7 single crystals

Summary Evidence is given that in Y₁−Ba₂−Cu₃−O₇ single crystals a critical state is developed on increasing (or decreasing) the applied fieldH ₀, only whenH ₀ is parallel to the crystalc-axis. An ?irreversibility? line in the (H, T)-plane can be drawn where the irreversibility of the second-harmonic response sets in. In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching.     

Synthesis of 2,8-disubstituted 1,2,4-triazolo[5,1-i]purines

This paper describes the preparation of 2-aryl-8-fluorobenzyl-1,2,4-triazolo[5,1-i]purines 2 , starting from 2-aryl-7,8-diamino-1,2,4-triazolo[1,5-c]pyrimidines 9 . Our synthetic procedure represents the first example of a feasible approach for the synthesis of 2,8-disubstituted triazolo[5,1-i]purines. New syntheses of 5-amino-3-arylpyrimido[5,4-e]1,2,4-triazines 12 and 8-fluorobenzyl-6-hydrazinopurines 15 are also reported.     

Moiré-fringe measurement

A simple technique and an apparatus layout, for measuring moiré-fringe spacings, used in conjunction with the moiré replica technique, are introduced. Results of measurements, using this new technique for evaluation grid spacings show an agreement of more than 99.9 percent between the actual grid spacing and those evaluated using the proposed apparatus.     

A semiclassical model of polarisation forces in atomic scattering

Low-energy elastic, differential and integral, collision cross sections for electron scattering from rare gas atoms are calculated using a simplified model treatment of the short-range polarisation forces already applied successfully to helium atoms (De Fazio et al., 1994). Static and exchange contributions to the total interaction are treated exactly, while a global semiclassical model provides a simple procedure for the short-range damping of all the long-range adiabatic terms which asymptotically lead to the polarisation forces. The results are compared with several available experimental findings for Ne and Ar atoms. The higher order terms in the perturbation expansion are found to have little effect on the cross sections and then only at low energies and in the small-angle region.Von Humboldt Stiftung Forschungspreisträger (1992)