Group and phase velocity mismatch fringes in triple sum-frequency spectroscopy

The effects of group and phase velocity mismatch are well-known in optical harmonic generation, but the non-degenerate cases remain unexplored. In this work we develop an analytic model which predicts velocity mismatch effects in non-degenerate triple sum-frequency mixing, TSF. We verify this model experimentally using two tunable, ultrafast, short-wave-IR lasers to demonstrate spectral fringes in the TSF output from a 500 $\mu$m thick sapphire plate. We find the spectral dependence of the TSF depends strongly on both the phase velocity and the group velocity differences between the input and output fields. We define practical strategies for mitigating the impact of velocity mismatches

Lithospheric deformation beneath the San Gabriel Mountains in the Southern California Transverse Ranges

High-resolution tomographic images from Los Angeles Region Seismic Experiment (LARSE) array and southern California Seismic Network (SCSN) teleseismic data suggest that the entire lithosphere below the San Gabriel Mountains and San Andreas fault in the Transverse Ranges has thickened in a narrow, vertical sheet. P wave travel time inversions of the combined data support the presence of the well-documented upper mantle high-velocity anomaly that extends ∼200 km into the mantle under the northernmost Los Angeles basin and Transverse Ranges, and is associated with mantle downwelling due to oblique convergence. We find that the high-velocity, high-density upper mantle anomaly comprises a 60–80 km wide sheet of mantle material that lies directly below a substantial crustal root in the San Gabriel Mountains. The velocity perturbations are as large as 3% in the anomaly, corresponding to a ∼2% density increase. The tomographic images suggest that deformation in the ductile lower crust and mantle lithosphere may be partially coupled mechanically and thermally if the thickening is occurring together in response to convergence and that it may be a local compressional feature

Ohio and the World

Commencement address given by the Honorable Foy David Kohler, Appointed Ambassador to the U. S. S. R., to the Summer 1962 graduating class of The Ohio State University, St. John Arena, Columbus, Ohio, August 24, 1962

Voice of America

Now, in just plain physical terms, what is the Voice of America? I have had a lot of ladies ask me where our station is and things like that; apparently conceiving the Voice of America as a radio station comparable to their local radio station, but with a few strange characters around who are multilingual and can say the same thing in many different languages. Well it isn\u27t that; it is a colossal radio operation. NBC and CBS combined are pretty small, as radio operations go, compared with what is, and particular­ly with what will be, the Voice of America

Vibrational coherence in electron spin resonance in nanoscale oscillators

We study a scheme for electrical detection, using electron spin resonance, of coherent vibrations in a molecular single electron level trapped near a conduction channel. Both equilibrium spin-currents and non-equilibrium spin- and charge currents are investigated. Inelastic side-band anti-resonances corresponding to the vibrational modes appear in the electron spin resonance spectrum.Comment: 4 pages, 3 figures: Published versio

Social scale and collective computation: Does information processing limit rate of growth in scale?

Collective computation is the process by which groups store and share information to arrive at decisions for collective behavior. How societies engage in effective collective computation depends partly on their scale. Social arrangements and technologies that work for small- and mid-scale societies are inadequate for dealing effectively with the much larger communication loads that societies face during the growth in scale that is a hallmark of the Holocene. An important bottleneck for growth may be the development of systems for persistent recording of information (writing), and perhaps also the abstraction of money for generalizing exchange mechanisms. Building on Shin et al., we identify a Scale Threshold to be crossed before societies can develop such systems, and an Information Threshold which, once crossed, allows more or less unlimited growth in scale. We introduce several additional articles in this special issue that elaborate or evaluate this Thresholds Model for particular types of societies or times and places in the world.1 Introduction 2 Seshat: The Global History Databank 2.1 Quantitative historical analysis uncovers a single dimension of complexity that structures global variation in human social organization 2.2 Scale and information-processing thresholds in Holocene social evolution 2.3 Evolution of collective computational abilities of (pre)historic societies 3 Empirical Fluctuation, or Stochastic Law? 4 Opening the Discussion on Collective Computation: Historical Survey and Introduction to the Case Studies 4.1 Marcus Hamilton: Collective computation and the emergence of hunter-gatherer small-worlds 4.2 Laura Ellyson: Applying Gregory Johnson’s concepts of scalar stress to scale and Information Thresholds in Holocene social evolution 4.3 Johannes Müller et al.: Tripolye mega-sites: “Collective computational abilities” of prehistoric proto-urban societies? 4.4 Steven Wernke: Explosive expansion, sociotechnical diversity, and fragile sovereignty in the domain of the Inka 4.5 Gary Feinman and David Carballo: Communication, computation, and governance: A multiscalar vantage on the prehispanic Mesoamerican World 4.6 Ian Morris: Scale, information-processing, and complementarities in Old-World Axial-Age societies 5 Conclusion 6 Postscript: the Second Social Media Revolutio

Argent, religion et pouvoir en Nouvelle-Calédonie : A. Ballande et les évêques, 1885-1935

Kohler Jean-Marie, Shineberg Dorothy. Argent, religion et pouvoir en Nouvelle-Calédonie. A.Ballande et les évêques, 1885-1935. In: Journal de la Société des océanistes, 95, 1992-2. pp. 151-183

On the minimization of Dirichlet eigenvalues of the Laplace operator

We study the variational problem \inf \{\lambda_k(\Omega): \Omega\ \textup{open in}\ \R^m,\ |\Omega| < \infty, \ \h(\partial \Omega) \le 1 \}, where $\lambda_k(\Omega)$ is the $k$'th eigenvalue of the Dirichlet Laplacian acting in $L^2(\Omega)$, \h(\partial \Omega) is the $(m-1)$- dimensional Hausdorff measure of the boundary of $\Omega$, and $|\Omega|$ is the Lebesgue measure of $\Omega$. If $m=2$, and $k=2,3, \cdots$, then there exists a convex minimiser $\Omega_{2,k}$. If $m \ge 2$, and if $\Omega_{m,k}$ is a minimiser, then $\Omega_{m,k}^*:= \textup{int}(\overline{\Omega_{m,k}})$ is also a minimiser, and $\R^m\setminus \Omega_{m,k}^*$ is connected. Upper bounds are obtained for the number of components of $\Omega_{m,k}$. It is shown that if $m\ge 3$, and $k\le m+1$ then $\Omega_{m,k}$ has at most $4$ components. Furthermore $\Omega_{m,k}$ is connected in the following cases : (i) $m\ge 2, k=2,$ (ii) $m=3,4,5,$ and $k=3,4,$ (iii) $m=4,5,$ and $k=5,$ (iv) $m=5$ and $k=6$. Finally, upper bounds on the number of components are obtained for minimisers for other constraints such as the Lebesgue measure and the torsional rigidity.Comment: 16 page

Non-Hamiltonian dynamics in optical microcavities resulting from wave-inspired corrections to geometric optics

We introduce and investigate billiard systems with an adjusted ray dynamics that accounts for modifications of the conventional reflection of rays due to universal wave effects. We show that even small modifications of the specular reflection law have dramatic consequences on the phase space of classical billiards. These include the creation of regions of non-Hamiltonian dynamics, the breakdown of symmetries, and changes in the stability and morphology of periodic orbits. Focusing on optical microcavities, we show that our adjusted dynamics provides the missing ray counterpart to previously observed wave phenomena and we describe how to observe its signatures in experiments. Our findings also apply to acoustic and ultrasound waves and are important in all situations where wavelengths are comparable to system sizes, an increasingly likely situation considering the systematic reduction of the size of electronic and photonic devices.Comment: 6 pages, 4 figures, final published versio