Tidal activity in the meteor zone over Budrio, Italy

A brief survey is presented of the variations with time and height of atmospheric tides observed at Budrio (45 deg N, 12 deg E) in the wind field between 80 and 110 km altitude during the 1978 to 1982 year period. Variations of amplitude maxima mainly of the semidiurnal tide in the winter data of 1979 and 1980 show periodicities of a few days throughout the observing period. Upward propagation of tidal energy during a stratospheric warming in January 1982 is proposed to be inhibited because of instabilities in atmospheric conditions

Analysis of the buildup of spatiotemporal correlations and their bounds outside of the light cone

In non-relativistic quantum theories the Lieb-Robinson bound defines an effective light cone with exponentially small tails outside of it. In this work we use it to derive a bound for the time evolution of the correlation function of two local disjoint observables if the initial state has a power-law decay. We show that the exponent of the power-law of the bound is identical to the initial (equilibrium) decay. We explicitly verify this result by studying the full dynamics of the susceptibilities and correlations in the exactly solvable Luttinger model after a sudden quench from the non-interacting to the interacting model

Protected quasi-locality in quantum systems with long-range interactions

We study the out-of-equilibrium dynamics of quantum systems with long-range interactions. Two different models describing, respectively, interacting lattice bosons and spins are considered. Our study relies on a combined approach based on accurate many-body numerical calculations as well as on a quasiparticle microscopic theory. For sufficiently fast decaying long-range potentials, we find that the quantum speed limit set by the long-range Lieb-Robinson bounds is never attained and a purely ballistic behavior is found. For slowly decaying potentials, a radically different scenario is observed. In the bosonic case, a remarkable local spreading of correlations is still observed, despite the existence of infinitely fast traveling excitations in the system. This is in marked contrast to the spin case, where locality is broken. We finally provide a microscopic justification of the different regimes observed and of the origin of the protected locality in the bosonic model

Giochi dei beni pubblici: il problema dei beni pubblici nella prospettiva della teoria dei giochi

The provision of public goods is an important problem in economics and the social sciences. It is often claimed that this problem has the structure of the well-known Prisoner’s Dilemma so that rational and self-interested individuals would not be able to provide any public good by spontaneous cooperation. In this paper, we argue that this pessimistic view of the possibility spontaneous cooperation is largely unjustified, since the game theoretic analysis of public goods shows how their voluntary provision is indeed feasible in a number of circumstances. We conclude by considering the implications of the game theoretic approach to the problem of public goods for political philosophy and, in particular, for the possibility of "ordered anarchy" as defended in the works of Anthony de Jasay