Following Jones and Williams (2000), we assume that R&D is simultaneously subject to positive and to negative external effects (e.g., the non rival nature of technology conflicts with congestion externalities). This observation allows to conceive an economy where two R&D sectors evolve without...

Technological progress produces both positive and negative economy wide externalities. Although positive spillovers seem to prevail most of the times, there is evidence and logical arguments revealing that investment in R&D can exceed the corresponding socially optimal level. Taking on board the...

The standard new Keynesian monetary policy problem is, in its original presentation, a linear model. As a result, only three possibilities are admissible in terms of long term dynamics: the equilibrium may be a stable node, an unstable node or a saddle point. Fixed point stability (a stable...

The new Keynesian monetary policy model studies the response of the inflation – output gap trade-off to policy decisions taken by the Central Bank, concerning the nominal interest rate time trajectory. Under an optimal setup, this model displays a saddle-path stable equilibrium and, if the...

Economic phenomena are interrelated. From a growth perspective, time analysis concerning the choices of present and future consumption and the choices between the allocation of scientific resources should be combined with a space analysis regarding the dissemination of economic activity through...