Issues in the Theory of Human Capital : Education as Investment

After a few references to the early literature on human capital, from Petty via Smith, Engel, and Nicholson to Marshall, various issues in current theory of human capital are briefly reviewed. They include questions regarding categories of " tangible human capital" and "intangible nonhuman capital;" investment in raising children. in schooling, and in research and development; depreciation of human capital through obsolescence, loss of strength, illness, retirement, and death; conflicts between efficiency and equality in the educational system; wrong educational mix resulting in waste or even net loss; the problem of complementarity among different kinds of physical and human capital; and the complexity of econometric rese3rch on comparative returns to different investments

Fluctuation relations for a driven Brownian particle

We consider a driven Brownian particle, subject to both conservative and non-conservative applied forces, whose probability evolves according to the Kramers equation. We derive a general fluctuation relation, expressing the ratio of the probability of a given Brownian path in phase space with that of the time-reversed path, in terms of the entropy flux to the heat reservoir. This fluctuation relation implies those of Seifert, Jarzynski and Gallavotti-Cohen in different special cases

A novel and precise time domain description of MOSFET low frequency noise due to random telegraph signals

Nowadays, random telegraph signals play an important role in integrated circuit performance variability, leading for instance to failures in memory circuits. This problem is related to the successive captures and emissions of electrons at the many traps stochastically distributed at the silicon-oxide (Si-SiO2) interface of MOS transistors. In this paper we propose a novel analytical and numerical approach to statistically describe the fluctuations of current due to random telegraph signal in time domain. Our results include two distinct situations: when the density of interface trap density is uniform in energy, and when it is an u-shape curve as prescribed in literature, here described as simple quadratic function. We establish formulas for relative error as function of the parameters related to capture and emission probabilities. For a complete analysis experimental u-shape curves are used and compared with the theoretical aproach

Microscopic Derivation of Causal Diffusion Equation using Projection Operator Method

We derive a coarse-grained equation of motion of a number density by applying the projection operator method to a non-relativistic model. The derived equation is an integrodifferential equation and contains the memory effect. The equation is consistent with causality and the sum rule associated with the number conservation in the low momentum limit, in contrast to usual acausal diffusion equations given by using the Fick's law. After employing the Markov approximation, we find that the equation has the similar form to the causal diffusion equation. Our result suggests that current-current correlations are not necessarily adequate as the definition of diffusion constants.Comment: 10 pages, 1 figure, Final version published in Phys. Rev.

Transport Statistics of Bistable Systems

We consider the transport statistics of classical bistable systems driven by noise. The stochastic path integral formalism is used to investigate the dynamics and distribution of transmitted charge. Switching rates between the two stable states are found from an instanton calculation, leading to an effective two-state system on a long time scale. In the bistable current range, the telegraph noise dominates the distribution, whose logarithm is found to be universally described by a tilted ellipse.Comment: 4 pages, 3 figures, version to appear in Phys. Rev. Let

Por qué discrepan los economistas

Por qué discrepan los economista

Por qué discrepan los economistas

Por qué discrepan los economista