Massimo Giovannini

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This paper studies the role of endogenous producer entry and product creation for monetary policy analysis and business cycle dynamics in a general equilibrium model with imperfect price adjustment. Optimal monetary policy stabilizes producer prices, but lets the consumer price index vary to accommodate changes in the number of available products. The free(More)
Previously circulated under the title " Business Cycles and Firm Dynamics " and …rst presented in the summer of 2004. For helpful comments, we thank Robert Shimer, two anonymous referees, and participants in many conferences and seminars. We are grateful to and Banque de France for …nancial support through the Chaire Banque de France at the Paris School of(More)
Cosmology, high-energy physics and astrophysics are converging on the study of large-scale magnetic fields. While the experimental evidence for the existence of large-scale magnetization in galaxies, clusters and superclusters is rather compelling, the origin of the phenomenon remains puzzling especially in light of the most recent observations. The purpose(More)
A large class of string-cosmology backgrounds leads to a spectrum of relic stochastic grav-itational waves, strongly tilted towards high frequencies, and characterized by two basic parameters of the cosmological model. We estimate the required sensitivity for detection of the predicted gravitational radiation and show that a region of our parameter space is(More)
We compute the spectrum of scalar and tensor metric perturbations generated, as amplified vacuum fluctuations, during an epoch of dilaton-driven inflation of the type occurring naturally in string cosmology. In the tensor case the computation is straightforward while, in the scalar case, it is made delicate by the appearance of a growing mode in the(More)
In the innationary scenarios suggested by string theory, the vacuum uctuations of the electromagnetic eld can be ampliied by the time-evolution of the dilaton background, and can grow large enough to explain both the origin of the cosmic magnetic elds and of the observed CMB anisotropy. The normalization of the perturbation spectrum is xed, and implies a(More)
We present a comprehensive study of the cosmological solutions of 6D braneworld models with azimuthal symmetry in the extra dimensions, moduli stabilization by flux or a bulk scalar field, and which contain at least one 3-brane that could be identified with our world. We emphasize an unusual property of these models: their expansion rate depends on the(More)