Giovanni Jona-Lasinio

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The recent remarkable developments in quantum optics, mesoscopic and cold atom physics have given reality to wave functions. It is then interesting to explore the consequences of assuming ensembles over the wave functions simply related to the canonical density matrix. In this note we analyze a previously introduced distribution over wave functions which(More)
A major difficulty in comparing quantum and classical behavior resides in the structural differences between the corresponding mathematical languages. The Heisenberg equations of motion are operator equations only formally identical to the classical equations of motion. By taking the expectation of these equations the well known Ehrenfest theorem provides(More)
We propose a model to describe a gas of pyramidal molecules interacting via dipole-dipole interactions. The interaction modifies the tunneling properties between the classical equilibrium configurations of the single molecule and, for sufficiently high pressure, the molecules become localized in these classical configurations. We explain quantitatively,(More)
We present a simple derivation of a Feynman-Kac type formula to study fermionic systems. In this approach the real time or the imaginary time dynamics is expressed in terms of the evolution of a collection of Poisson processes. A computer implementation of this formula leads to a family of algorithms parametrized by the values of the jump rates of the(More)
Analogies have had and continue to have an important role in the development of theoretical physics. They may start from similarities of physical concepts followed by similarities in the mathematical formalization or it may be a purely mathematical aspect to suggest the development of analogous physical concepts. More often a subtle nonobvious interplay(More)
In a previous paper we proposed a model to describe a gas of pyramidal molecules interacting via dipole-dipole interactions. The interaction modifies the tunneling properties between the classical equilibrium configurations of the single molecule and, for sufficiently high pressure, the molecules become localized in these classical configurations. The model(More)
Using a sequence of Bogoliubov transformations, we obtain an exact expression for the vacuum state of a Dirac field in 2 + 1 dimensions in presence of a constant magnetic field. This expression reveals a peculiar two level pairing structure for any value of the mass m ≥ 0. This calculation clarifies the nature of the condensate in the lowest Landau level(More)
Quantum Monte Carlo methods are powerful techniques for the numerical evaluation of the properties of quantum lattice systems. In the case of fermion systems [1–4] there are special features connected with the anticommutativity of the variables involved. In a recent paper [5] progress has been made by providing an exact probabilistic representation for the(More)