Tricriticality and Reentrance in a Naive Spin-Glass Model

In this paper a spin-1 spin-glass model under the presence of a uniform crystal field is investigated. It is shown that the model presents both continuous and first-order phase transition separated by a tricritical point. The phase diagram is obtained within the replica-symmetric solution and exhibits reentrance phenomena at low temperatures. Possibly it is the simplest model which can describe inverse freezing phenomena.Comment: 12 pages, 1 figur

Induced higher-derivative massive gravity on a 2-brane in 4D Minkowski space

In this paper we revisit the problem of localizing gravity in a 2-brane embedded in a 4D Minkowski space to address induction of high derivative massive gravity. We explore the structure of propagators to find well-behaved higher-derivative massive gravity induced on the brane. Exploring a special case in the generalized mass term of the graviton propagator we find a model of consistent higher order gravity with an additional unitary massive spin-2 particle and two massless particles: one spin-0 particle and one spin-1 particle. The condition for the absence of tachyons is satisfied for both `right' and `wrong' signs of the Einstein-Hilbert term on the 2-brane. We also find the Pauli-Fierz mass term added to the new massive gravity in three dimensions and recover the low dimensional DGP model.Comment: Latex, 12 pages, no figure; refs added, version to appear in PL

Multipliers and Capital: What is the role of Imperfect Competition?

In static general equilibrium models considering imperfectly competitive goods markets, the effectiveness of fiscal policy to stir output is shown to be greater than in the walrasian case. However, labour is the only input in these models. Here, I develop a simple intertemporal model allowing us to study the steady-state role of optimal capital stock in the fiscal policy transmission mechanism. I demonstrate the results depend strongly on the set of parameter values chosen and on the output definition. Using plausible calibrations the multiplier is larger in the walrasian case for small initial government purchases, and smaller for intermediate values.Multiplier, Fiscal Policy, Imperfect Competition