Charge Screening in the Finite Temperature Schwinger Model

We compute the effective action and correlators of the Polyakov loop operator in the Schwinger model at finite temperature and discuss the realization of the discrete symmetries that occur there. We show that, due to nonlocal effects of massless fermions in two spacetime dimensions, the discrete symmetry which governs the screening of charges is spontaneously broken even in an effective one-dimensional model, when the volume is infinite. In this limit, the thermal state of the Schwinger model screens an arbitrary external charge; consequently the model is in the deconfined phase, with the charge of the deconfined fermions completely screened. In a finite volume we show that the Schwinger model is always confining.Comment: 27 pages, latex, no figures. References addded and some misprints correcte

Firms’ perceptions of barriers to innovation and resilience: the Italian region of Friuli Venezia Giulia during the crisis

This paper connects the literature on obstacles to innovation to the concept of regional economic resilience by empirically assessing the relationship between the intensity of firms’ engagement in innovative activities and self-reported obstacles to innovation during the unfolding of the latest economic and financial downturn. The analysis is grounded on a unique dataset on firm-level accounting data (CAD) and on information from two waves (2008-10 and 2010-12) of the Community Innovation Survey (CIS) for a representative sample of firms in the Italian region of Friuli Venezia Giulia. The main results support the existence of severe deterring barriers in the region, suggesting that during the economic and financial crisis after 2008 firms’ uncertainty about the market demand became dominant

Superconducting Topological Fluids in Josephson Junction Arrays

We argue that the frustrated Josephson junction arrays may support a topologically ordered superconducting ground state, characterized by a non-trivial ground state degeneracy on the torus. This superconducting quantum fluid provides an explicit example of a system in which superconductivity arises from a topological mechanism rather than from the usual Landau-Ginzburg mechanism.Comment: 4 page