1,343 research outputs found
The Quest for Status and Endogenous Labor Supply. The Relative Wealth Framework
This paper introduces the quest for status into the Ramsey model with endogenous labor supply. We focus our attention on relative wealth preferences. In contrast to relative consumption preferences, they allow for the possibility that agents work too little in the long run, while under both specifications the steady-state levels of consumption and the stock of physical capital exceed their socially optimal counterparts. The initial phase of transitional dynamics is unambiguously characterized by under-consumption and excessive work effort. The social optimum can be replicated by taxing capital income, where the optimal tax rate increases as physical capital accumulates.Status, Relative consumption, Relative wealth, Endogenous labor supply
The Quest for Status and Endogenous Labor Supply: The Relative Wealth Framework
This paper introduces the quest for status into the Ramsey model with endogenous labor supply. We focus our attention on relative wealth preferences. In contrast to relative consumption preferences, they allow for the possibility that agents work too little in the long run, while under both specifications the steady-state levels of consumption and the stock of physical capital exceed their socially optimal counterparts. The initial phase of transitional dynamics is unambiguously characterized by under-consumption and excessive work effort. The social optimum can be replicated by taxing capital income, where the optimal tax rate increases as physical capital accumulates.Status, Relative Consumption, Relative Wealth, Endogenous Labor Supply
Spin glass models with Kac interactions
In this paper I will review my work on disordered systems -spin glass model
with two body and body interactions- with long but finite interaction
range . I will describe the relation of these model with Mean Field Theory
in the Kac limit and some attempts to go beyond mean field.Comment: Proceedings of the Stat-phys23 conferenc
Modeling microevolution in a changing environment: The evolving quasispecies and the Diluted Champion Process
Several pathogens use evolvability as a survival strategy against acquired
immunity of the host. Despite their high variability in time, some of them
exhibit quite low variability within the population at any given time, a
somehow paradoxical behavior often called the evolving quasispecies. In this
paper we introduce a simplified model of an evolving viral population in which
the effects of the acquired immunity of the host are represented by the
decrease of the fitness of the corresponding viral strains, depending on the
frequency of the strain in the viral population. The model exhibits evolving
quasispecies behavior in a certain range of its parameters, ans suggests how
punctuated evolution can be induced by a simple feedback mechanism.Comment: 15 pages, 12 figures. Figures redrawn, some additional clarifications
in the text. To appear in Journal of Statistical Mechanics: Theory and
Experimen
Ultrametricity in 3D Edwards-Anderson spin glasses
We perform an accurate test of Ultrametricity in the aging dynamics of the
three dimensional Edwards-Anderson spin glass. Our method consists in
considering the evolution in parallel of two identical systems constrained to
have fixed overlap. This turns out to be a particularly efficient way to study
the geometrical relations between configurations at distant large times. Our
findings strongly hint towards dynamical ultrametricity in spin glasses, while
this is absent in simpler aging systems with domain growth dynamics. A recently
developed theory of linear response in glassy systems allows to infer that
dynamical ultrametricity implies the same property at the level of equilibrium
states.Comment: 4 pages, 5 figure
Quantum Phase Transition in Lattice Model of Unconventional Superconductors
In this paper we shall introduce a lattice model of unconventional
superconductors (SC) like d-wave SC in order to study quantum phase transition
at vanishing temperature (). Finite- counterpart of the present model was
proposed previously with which SC phase transition at finite was
investigated. The present model is a noncompact U(1) lattice-gauge-Higgs model
in which the Higgs boson, the Cooper-pair field, is put on lattice links in
order to describe d-wave SC. We first derive the model from a microscopic
Hamiltonian in the path-integral formalism and then study its phase structure
by means of the Monte Carlo simulations. We calculate the specific heat,
monopole densities and the magnetic penetration depth (the gauge-boson mass).
We verified that the model exhibits a second-order phase transition from normal
to SC phases. Behavior of the magnetic penetration depth is compared with that
obtained in the previous analytical calculation using XY model in four
dimensions. Besides the normal to SC phase transition, we also found that
another second-order phase transition takes place within the SC phase in the
present model. We discuss physical meaning of that phase transition.Comment: 12 pages, 10 figures, references added, some discussion on the
results adde
On Mean Field Glassy Dynamics out of Equilibrium
We study the off equilibrium dynamics of a mean field disordered systems
which can be interpreted both as a long range interaction spin glass and as a
particle in a random potential. The statics of this problem is well known and
exhibits a low temperature spin glass phase with continuous replica symmetry
breaking. We study the equations of off equilibrium dynamics with analytical
and numerical methods. In the spin glass phase, we find that the usual
equilibrium dynamics (observed when the observation time is much smaller than
the waiting time) coexists with an aging regime. In this aging regime, we
propose a solution implying a hierarchy of crossovers between the observation
time and the waiting time.Comment: LaTeX, LPTENS preprint 94/0
- …