Small departures from rationality magnify fluctuations

This note shows that introducing into the economy a few number of agents who do not support sunspots theories magnifies endogenous business cycles fluctuations when the current state of the economic system is sensitive enough to traders' forecasts, or equivalently, in presence of indeterminacy.

Growth and labor supply in the presence of habit formation in consumption

This paper examines a model with habit formation in consumption. The model leads to higher equilibrium values in consumption, output, capital accumulation and labor supply than the neoclassical growth model with elastic labor supply. Comparative static analysis shows that an increase in the importance of consumption in the recent past in habit formation is associated with a decrease in growth and labor supply. On the other hand, an increase of the importance of habit stock relatively to present consumption, is found to stimulate growth and labor supply.Consumption behavior

Four-Dimensional Spin Foam Perturbation Theory

We define a four-dimensional spin-foam perturbation theory for the ${\rm BF}$-theory with a $B\wedge B$ potential term defined for a compact semi-simple Lie group $G$ on a compact orientable 4-manifold $M$. This is done by using the formal spin foam perturbative series coming from the spin-foam generating functional. We then regularize the terms in the perturbative series by passing to the category of representations of the quantum group $U_q(\mathfrak{g})$ where $\mathfrak{g}$ is the Lie algebra of $G$ and $q$ is a root of unity. The Chain-Mail formalism can be used to calculate the perturbative terms when the vector space of intertwiners $\Lambda\otimes \Lambda \to A$, where $A$ is the adjoint representation of $\mathfrak{g}$, is 1-dimensional for each irrep $\Lambda$. We calculate the partition function $Z$ in the dilute-gas limit for a special class of triangulations of restricted local complexity, which we conjecture to exist on any 4-manifold $M$. We prove that the first-order perturbative contribution vanishes for finite triangulations, so that we define a dilute-gas limit by using the second-order contribution. We show that $Z$ is an analytic continuation of the Crane-Yetter partition function. Furthermore, we relate $Z$ to the partition function for the $F\wedge F$ theory

A Cubical Set Approach to 2-Bundles with Connection and Wilson Surfaces

In the context of non-abelian gerbes we define a cubical version of categorical group 2-bundles with connection over a smooth manifold. We define their two-dimensional parallel transport, study its properties, and define non-abelian Wilson surface functionals.Comment: Improvement on the exposition. Approximately 60 pages, 2 figure