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Metodiche di campionamento del protossido d'azoto nelle sale operatorie.
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Uncertainty Analysis of the Aerodynamic Performance of eVTOL Propellers via Reynolds Stress Tensor Perturbation
Full text linkGeometry of bounded critical phenomena
Full text linkThe quest for a satisfactory understanding of systems at criticality in dimensions d > 2 is a major field of research. We devise here a geometric description of bounded systems at criticality in any dimension d. This is achieved by altering the flat metric with a space dependent scale factor γ(x), x belonging to a bounded domain Ω. γ(x) is chosen in order to have a scalar curvature to be constant and matching the one of the hyperbolic space, the proper notion of curvature being-as called in the mathematics literature-the fractional Q-curvature. The equation for γ(x) is found to be the fractional Yamabe equation (to be solved in Ω) that, in absence of anomalous dimension, reduces to the usual Yamabe equation in the same domain. From the scale factor γ(x) we obtain novel predictions for the scaling form of one-point order parameter correlation functions. A (necessary) virtue of the proposed approach is that it encodes and allows to naturally retrieve the purely geometric content of two-dimensional boundary conformal field theory. From the critical magnetization profile in presence of boundaries one can extract the scaling dimension of the order parameter, Δ φ . For the 3D Ising model we find Δ φ = 0.518 142(8) which favorably compares (at the fifth decimal place) with the state-of-the-art estimate. A nontrivial prediction is the structure of two-point spin-spin correlators at criticality. They should depend on the fractional Q-hyperbolic distance calculated from the metric, in turn depending only on the shape of the bounded domain and on Δ φ . Numerical simulations of the 3D Ising model on a slab geometry are found to be in agreement with such predictions
Inverse Ising problem for one-dimensional chains with arbitrary finite-range couplings
Full text linkWe study Ising chains with arbitrary multispin finite-range couplings, providing an explicit solution of the associated inverse Ising problem, i.e. the problem of inferring the values of the coupling constants from the correlation functions. As an application, we reconstruct the couplings of chain Ising Hamiltonians having exponential or power-law two-spin plus three- or four-spin couplings. The generalization of the method to ladders and to Ising systems where a mean-field interaction is added to general finite-range couplings is also discussed
Modulational Instabilities in Lattices with Power-Law Hoppings and Interactions
No full textWe study the occurrence of modulational instabilities in lattices with nonlocal power-law hoppings and interactions. Choosing as a case study the discrete nonlinear Schrodinger equation, we consider one-dimensional chains with power-law decaying interactions (with exponent alpha) and hoppings (with exponent beta): An extensive energy is obtained for alpha,beta > 1. We show that the effect of power-law interactions is that of shifting the onset of the modulational instabilities region for alpha > 1. At a critical value of the interaction strength, the modulational stable region shrinks to zero. Similar results are found for effectively short-range nonlocal hoppings (beta > 2): At variance, for longer-ranged hoppings (1 < beta < 2) there is no longer any modulational stability. The hopping instability arises for q = 0 perturbations, thus the system is most sensitive to the perturbations of the order of the system size. We also discuss the stability regions in the presence of the interplay between competing interactions - (e. g., attractive local and repulsive nonlocal interactions). We find that noncompeting nonlocal interactions give rise to a modulational instability emerging for a perturbing wave vector q = pi while competing nonlocal interactions may induce a modulational instability for a perturbing wave vector 0 < q < pi. Since for alpha > 1 and beta > 2 the effects are similar to the effect produced on the stability phase diagram by finite range interactions and/or hoppings, we conclude that the modulational instability is "genuinely" long-ranged for 1 < beta < 2 nonlocal hoppings
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