Technical Change, Learning, and Wages

This paper examines the relationship between technological change and wages using pooled cross-sectional industry-level data and several alternative indicators of the rate of introduction of new technology. Our main finding is that industries with a high rate of technical change pay higher wages to workers of given age and education, compared to less technologically advanced industries. This is Consistent with the notion that the introduction of new technology creates a demand for learning, that learning is a function of employee ability and effort, and that increases in wages are required to elicit increases in ability and effort. A related finding is that the wages of highly educated workers (especially recent graduates) relative to those of less educated workers are highest in technologically advanced industries; this is consistent with the notion that educated workers are better learners.

The Comparative Advantage of Educated Workers in Implementing New Technology: Some Empirical Evidence

In this paper we estimate variants of a labor demand equation derived from a (restricted variable) cost function in which "experience"on a technology (proxied by the mean age of the capital stock) enters "non-neutrally." Our specification of the underlying cost function isbased on the hypothesis that highly educated workers have a comparative advantage with respect to the adjustment to and implementation of new technologies. Our empirical results are consistent with the implication of this hypothesis, that the relative demand for educated workers declines as the capital stock (and presumably the technology embodied therein) ages. According to our estimates, the education-distribution of employment depends more strongly on the age of equipment than on the age of plant, and the effect of changes in equipment age on labor demand is magnified in R&D-intensive industries.

Wave packet approach to periodically driven scattering

For autonomous systems it is well known how to extract tunneling probabilities from wavepacket calculations. Here we present a corresponding approach for periodically time-dependent Hamiltonians, valid at all frequencies, field strengths, and transition orders. After mapping the periodically driven system onto a time-independent one with an additional degree of freedom, use is made of the correlation function formulation of scattering [J. Chem. Phys. {\bf 98}, 3884 (1993)]. The formalism is then applied to study the transmission properties of a resonant tunneling double barrier structure under the influence of a sinusoidal laser field, revealing an unexpected antiresonance in the zero photon transition for large field strengths.Comment: 4 pages, 2 figure

Leading Pollicott-Ruelle Resonances for Chaotic Area-Preserving Maps

Recent investigations in nonlinear sciences show that not only hyperbolic but also mixed dynamical systems may exhibit exponential relaxation in the chaotic regime. The relaxation rates, which lead the decay of probability distributions and correlation functions, are related to the classical evolution resolvent (Perron-Frobenius operator) pole logarithm, the so called Pollicott-Ruelle resonances. In this Brief Report, the leading Pollicott-Ruelle resonances are calculated analytically for a general class of area-preserving maps. Besides the leading resonances related to the diffusive modes of momentum dynamics (slow rate), we also calculate the leading faster rate, related to the angular correlations. The analytical results are compared to the existing results in the literature.Comment: 6 pages, 1 figure. See also: R. Venegeroles, Phys. Rev. Lett. 99, 014101 (2007) or arXiv:nlin/0608067v

Crystal structure of LaTiO_3.41 under pressure

The crystal structure of the layered, perovskite-related LaTiO_3.41 (La_5Ti_5O_{17+\delta}) has been studied by synchrotron powder x-ray diffraction under hydrostatic pressure up to 27 GPa (T = 295 K). The ambient-pressure phase was found to remain stable up to 18 GPa. A sluggish, but reversible phase transition occurs in the range 18--24 GPa. The structural changes of the low-pressure phase are characterized by a pronounced anisotropy in the axis compressibilities, which are at a ratio of approximately 1:2:3 for the a, b, and c axes. Possible effects of pressure on the electronic properties of LaTiO_3.41 are discussed.Comment: 5 pages, 6 figure

Impact splash chondrule formation during planetesimal recycling

Chondrules are the dominant bulk silicate constituent of chondritic meteorites and originate from highly energetic, local processes during the first million years after the birth of the Sun. So far, an astrophysically consistent chondrule formation scenario, explaining major chemical, isotopic and textural features, remains elusive. Here, we examine the prospect of forming chondrules from planetesimal collisions. We show that intensely melted bodies with interior magma oceans became rapidly chemically equilibrated and physically differentiated. Therefore, collisional interactions among such bodies would have resulted in chondrule-like but basaltic spherules, which are not observed in the meteoritic record. This inconsistency with the expected dynamical interactions hints at an incomplete understanding of the planetary growth regime during the protoplanetary disk phase. To resolve this conundrum, we examine how the observed chemical and isotopic features of chondrules constrain the dynamical environment of accreting chondrite parent bodies by interpreting the meteoritic record as an impact-generated proxy of planetesimals that underwent repeated collision and reaccretion cycles. Using a coupled evolution-collision model we demonstrate that the vast majority of collisional debris feeding the asteroid main belt must be derived from planetesimals which were partially molten at maximum. Therefore, the precursors of chondrite parent bodies either formed primarily small, from sub-canonical aluminum-26 reservoirs, or collisional destruction mechanisms were efficient enough to shatter planetesimals before they reached the magma ocean phase. Finally, we outline the window in parameter space for which chondrule formation from planetesimal collisions can be reconciled with the meteoritic record and how our results can be used to further constrain early solar system dynamics.Comment: 20 pages, 11 figures, 2 tables; accepted for publication in Icarus; associated blog article at goo.gl/5bDqG

Extremely Small Energy Gap in the Quasi-One-Dimensional Conducting Chain Compound SrNbO3.41_{3.41}

Resistivity, optical, and angle-resolved photoemission experiments reveal unusual one-dimensional electronic properties of highly anisotropic SrNbO$_{3.41}$. Along the conducting chain direction we find an extremely small energy gap of only a few meV at the Fermi level. A discussion in terms of typical 1D instabilities (Peierls, Mott-Hubbard) shows that neither seems to provide a satisfactory explanation for the unique properties of SrNbO$_{3.41}$.Comment: 4 pages, 3 figure

Phase space structures and ionization dynamics of hydrogen atom in elliptically polarized microwaves

The multiphoton ionization of hydrogen atoms in a strong elliptically polarized microwave field exhibits complex features that are not observed for ionization in circular and linear polarized fields. Experimental data reveal high sensitivity of ionization dynamics to the small changes of the field polarization. The multidimensional nature of the problem makes widely used diagnostics of dynamics, such as Poincar\'{e} surfaces of section, impractical. We analyze the phase space dynamics using finite time stability analysis rendered by the fast Lyapunov Indicators technique. The concept of zero--velocity surface is used to initialize the calculations and visualize the dynamics. Our analysis provides stability maps calculated for the initial energy at the maximum and below the saddle of the zero-velocity surface. We estimate qualitatively the dependence of ionization thresholds on the parameters of the applied field, such as polarization and scaled amplitude

Multifractal eigenstates of quantum chaos and the Thue-Morse sequence

We analyze certain eigenstates of the quantum baker's map and demonstrate, using the Walsh-Hadamard transform, the emergence of the ubiquitous Thue-Morse sequence, a simple sequence that is at the border between quasi-periodicity and chaos, and hence is a good paradigm for quantum chaotic states. We show a family of states that are also simply related to Thue-Morse sequence, and are strongly scarred by short periodic orbits and their homoclinic excursions. We give approximate expressions for these states and provide evidence that these and other generic states are multifractal.Comment: Substantially modified from the original, worth a second download. To appear in Phys. Rev. E as a Rapid Communicatio

Influence of classical resonances on chaotic tunnelling

Dynamical tunnelling between symmetry-related stable modes is studied in the periodically driven pendulum. We present strong evidence that the tunnelling process is governed by nonlinear resonances that manifest within the regular phase-space islands on which the stable modes are localized. By means of a quantitative numerical study of the corresponding Floquet problem, we identify the trace of such resonances not only in the level splittings between near-degenerate quantum states, where they lead to prominent plateau structures, but also in overlap matrix elements of the Floquet eigenstates, which reveal characteristic sequences of avoided crossings in the Floquet spectrum. The semiclassical theory of resonance-assisted tunnelling yields good overall agreement with the quantum-tunnelling rates, and indicates that partial barriers within the chaos might play a prominent role