18,271 research outputs found
Interpreting the evidence on life cycle skill formation
This paper presents economic models of child development that capture the essence of recent findings
from the empirical literature on skill formation. The goal of this essay is to provide a theoretical framework
for interpreting the evidence from a vast empirical literature, for guiding the next generation of empirical
studies, and for formulating policy. Central to our analysis is the concept that childhood has more than one
stage. We formalize the concepts of self-productivity and complementarity of human capital investments
and use them to explain the evidence on skill formation. Together, they explain why skill begets skill
through a multiplier process. Skill formation is a life cycle process. It starts in the womb and goes on
throughout life. Families play a role in this process that is far more important than the role of schools.
There are multiple skills and multiple abilities that are important for adult success. Abilities are both
inherited and created, and the traditional debate about nature versus nurture is scientiÞcally obsolete.
Human capital investment exhibits both self-productivity and complementarity. Skill attainment at one
stage of the life cycle raises skill attainment at later stages of the life cycle (self-productivity). Early
investment facilitates the productivity of later investment (complementarity). Early investments are not
productive if they are not followed up by later investments (another aspect of complementarity). This
complementarity explains why there is no equity-efficiency trade-off for early investment. The returns to
investing early in the life cycle are high. Remediation of inadequate early investments is difficult and very
costly as a consequence of both self-productivity and complementarity
Effects of rotation in the energy spectrum of
In this paper, motivated by the experimental evidence of rapidly rotating
molecules in fullerite, we study the low-energy electronic states of
rotating fullerene within a continuum model. In this model, the low-energy
spectrum is obtained from an effective Dirac equation including non-Abelian
gauge fields that simulate the pentagonal rings of the molecule. Rotation is
incorporated into the model by solving the effective Dirac equation in the
rotating referential frame. The exact analytical solution for the
eigenfunctions and energy spectrum is obtained, yielding the previously known
static results in the no rotation limit. Due to the coupling between rotation
and total angular momentum, that appears naturally in the rotating frame, the
zero modes of static are shifted and also suffer a Zeeman splitting
whithout the presence of a magnetic field
Inertial-Hall effect: the influence of rotation on the Hall conductivity
Inertial effects play an important role in classical mechanics but have been
largely overlooked in quantum mechanics. Nevertheless, the analogy between
inertial forces on mass particles and electromagnetic forces on charged
particles is not new. In this paper, we consider a rotating non-interacting
planar two-dimensional electron gas with a perpendicular uniform magnetic field
and investigate the effects of the rotation in the Hall conductiv
Inspection and diagnosis tests for structural safety evaluation: A case study
Diagnosis and assessment of existing structures is a developing area due to the appearance of a high number of building defects, structural and non-structural deterioration and precocious loss of quality, and, consequently, lower expected durability. With the aim of verifying the viability of rehabilitation or the need to demolish an existing fifteen year old parking building, several inspections and diagnostic non-destructive and destructive testing, visual inspection, were carried out to evaluate the structural safety conditions
A dynamical point of view of Quantum Information: entropy and pressure
Quantum Information is a new area of research which has been growing rapidly
since last decade. This topic is very close to potential applications to the so
called Quantum Computer. In our point of view it makes sense to develop a more
"dynamical point of view" of this theory. We want to consider the concepts of
entropy and pressure for "stationary systems" acting on density matrices which
generalize the usual ones in Ergodic Theory (in the sense of the Thermodynamic
Formalism of R. Bowen, Y. Sinai and D. Ruelle). We consider the operator
acting on density matrices over a finite
-dimensional complex Hilbert space where and , are
operators in this Hilbert space. is not a linear operator. In
some sense this operator is a version of an Iterated Function System (IFS).
Namely, the , , play the role of the
inverse branches (acting on the configuration space of density matrices )
and the play the role of the weights one can consider on the IFS. We
suppose that for all we have that . A
family determines a Quantum Iterated Function System
(QIFS) , $\mathcal{F}_W=\{\mathcal{M}_N,F_i,W_i\}_{i=1,...,
k}.
Accessing the Acceleration of the Universe with Sunyaev-Zel'dovich and X-ray Data from Galaxy Clusters
By using exclusively the Sunyaev-Zel'dovich effect and X-ray surface
brightness data from 25 galaxy clusters in the redshift range 0.023< z < 0.784
we access cosmic acceleration employing a kinematic description. Such result is
fully independent on the validity of any metric gravity theory, the possible
matter-energy contents filling the Universe, as well as on the SNe Ia Hubble
diagram.Comment: 3 pages, 4 figures, To appear in the Proceedings of the Twelfth
Marcel Grossmann Meeting on General Relativit
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