Efficient simulation of quantum evolution using dynamical coarse-graining

A novel scheme to simulate the evolution of a restricted set of observables of a quantum system is proposed. The set comprises the spectrum-generating algebra of the Hamiltonian. The idea is to consider a certain open-system evolution, which can be interpreted as a process of weak measurement of the distinguished observables performed on the evolving system of interest. Given that the observables are "classical" and the Hamiltonian is moderately nonlinear, the open system dynamics displays a large time-scales separation between the dephasing of the observables and the decoherence of the evolving state in the basis of the generalized coherent states (GCS), associated with the spectrum-generating algebra. The time scale separation allows the unitary dynamics of the observables to be efficiently simulated by the open-system dynamics on the intermediate time-scale.The simulation employs unraveling of the corresponding master equations into pure state evolutions, governed by the stochastic nonlinear Schroedinger equantion (sNLSE). It is proved that GCS are globally stable solutions of the sNLSE, if the Hamilonian is linear in the algebra elements.Comment: The version submitted to Phys. Rev. A, 28 pages, 3 figures, comments are very welcom

The Milky Way and the Local Group

The beauty and the charm of the Milky May (MW) have been celebrated by countless poets and writers of many Countries along the centuries (see e.g. the beautiful anthology of Piero Boitani 2012 ). The stellar nature of the MW was firstly observed by Galileo. In 1610 in the Sidereus Nuncius ( Galilei 1993 ) Galileo wrote that the MW is “nient’altro che una congerie di innumerevoli Stelle, disseminate a mucchi; chè in qualunque regione di essa si diriga il cannocchiale, subito una ingente folla di Stelle si presenta alla vista, delle quali parecchi si vedono abbastanza grandi e molto distinte; ma la moltitudine delle piccole è del tutto inesplorabile”. In the same paragraph, Galileo remarked that observations with his telescope, for the first time, wipe out centuries of philosophical discussions about the nature of the MW. Three more centuries have been necessary to complete a second radical Copernican Revolution that displaces the solar system from being roughly at the center of the MW and project this latter in the vast Universe populated by billions of similar spiral galaxies (see Chap. 1)

New Eyes for Galaxies Investigation

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