6,308 research outputs found
Deferred Annuities and Strategic Asset Allocation
We derive the optimal portfolio choice and consumption pattern over the lifecycle for households facing labor income, capital market, and mortality risk. In addition to stocks and bonds, households also have access to deferred annuities. Deferred annuities offer a hedge against mortality risk and provide similar benefits as Social Security. We show that a considerable fraction of wealth should be annuitized to skim the return enhancing mortality credit. The remaining liquid wealth (stocks and bonds) is used to hedge labor income risk during work life and to earn the equity premium. We find a marginal difference between a strategy involving deferred annuities and one where the investor can purchase immediate life annuities.
Two-fluid tokamak equilibria with reversed magnetic shear and sheared flow
The aim of the present work is to investigate tokamak equilibria with
reversed magnetic shear and sheared flow, which may play a role in the
formation of internal transport barriers (ITBs), within the framework of
two-fluid model. The study is based on exact self-consistent solutions in
cylindrical geometry by means of which the impact of the magnetic shear, s, and
the "toroidal" (axial) and "poloidal" (azimuthal) ion velocity components on
the radial electric field, its shear and the shear of the ExB velocity is
examined. For a wide parametric regime of experimental concern it turns out
that the contributions of the toroidal and poloidal velocity and pressure
gradient terms to the electric field, its shear and ExB velocity shear are of
the same order of magnitude. The impact of s on ExB velocity shear through the
pressure gradient term is stronger than that through the velocity terms. The
results indicate that, alike MHD, the magnetic shear and the sheared toroidal
and poloidal velocities act synergetically in producing electric fields and
therefore ExB velocity shear profiles compatible with ones observed in
discharges with ITBs; owing to the pressure gadient term, however, the impact
of s on the electic field, its shear and the shear of ExB velocity is stronger
than that in MHD.Comment: 25 pages, 21 figure
Intrinsic motivation in open source software development
This papers sheds light on the puzzling evidence that even though open source software (OSS) is a public good, it is developed for free by highly qualified, young and motivated individuals, and evolves at a rapid pace. We show that once OSS development is understood as the private provision of a public good, these features emerge quite naturally. We adapt a dynamic private-provision-of-public-goods model to reflect key aspects of the OSS phenomenon. In particular, instead of relying on extrinsic motives for programmers (e.g. signaling) the present model is driven by intrinsic motives of OSS programmers, such as user-programmers, play value or homo ludens payoff, and gift culture benefits. Such intrinsic motives feature extensively in the wider OSS literature and contribute new insights to the economic analysis. --open source software,public goods,homo ludens,war of attrition
Euler-Lagrange correspondence of generalized Burgers cellular automaton
Recently, we have proposed a {\em Euler-Lagrange transformation} for cellular
automata(CA) by developing new transformation formulas. Applying this method to
the Burgers CA(BCA), we have succeeded in obtaining the Lagrange representation
of the BCA. In this paper, we apply this method to multi-value generalized
Burgers CA(GBCA) which include the Fukui-Ishibashi model and the quick-start
model associated with traffic flow. As a result, we have succeeded in
clarifying the Euler-Lagrange correspondence of these models. It turns out,
moreover that the GBCA can naturally be considered as a simple model of a
multi-lane traffic flow.Comment: 11 pages, 6 figures; accepted for publication in Int. J. Mod. Phys.
Integrability of a Generalized Ito System: the Painleve Test
It is shown that a generalized Ito system of four coupled nonlinear evolution
equations passes the Painleve test for integrability in five distinct cases, of
which two were introduced recently by Tam, Hu and Wang. A conjecture is
formulated on integrability of a vector generalization of the Ito system.Comment: LaTeX, 5 page
Cellular automaton rules conserving the number of active sites
This paper shows how to determine all the unidimensional two-state cellular
automaton rules of a given number of inputs which conserve the number of active
sites. These rules have to satisfy a necessary and sufficient condition. If the
active sites are viewed as cells occupied by identical particles, these
cellular automaton rules represent evolution operators of systems of identical
interacting particles whose total number is conserved. Some of these rules,
which allow motion in both directions, mimic ensembles of one-dimensional
pseudo-random walkers. Numerical evidence indicates that the corresponding
stochastic processes might be non-Gaussian.Comment: 14 pages, 5 figure
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