A theoretical study of the propagation and attenuation of acoustic waves in the lunar surface Interim report

Acoustic wave propagation and attenuation in lunar space environmen

Estimating Functions of Probability Distributions from a Finite Set of Samples, Part 1: Bayes Estimators and the Shannon Entropy

We present estimators for entropy and other functions of a discrete probability distribution when the data is a finite sample drawn from that probability distribution. In particular, for the case when the probability distribution is a joint distribution, we present finite sample estimators for the mutual information, covariance, and chi-squared functions of that probability distribution.Comment: uuencoded compressed tarfile, submitte

Prosperity and depression in the European economy and during interwar years (1913-1950) : an introduction.

We survey aggregate growth in a sample of 27 European countries during the interwar period. We discuss the available data, possible explanations for a slowdown in growth rates and test the explanatory power of several hypotheses put forward in the literature.Aggregate Growth; Interwar Period; Europe;

Observability of characteristic binary-induced structures in circumbinary disks

Context: A substantial fraction of protoplanetary disks forms around stellar binaries. The binary system generates a time-dependent non-axisymmetric gravitational potential, inducing strong tidal forces on the circumbinary disk. This leads to a change in basic physical properties of the circumbinary disk, which should in turn result in unique structures that are potentially observable with the current generation of instruments. Aims: The goal of this study is to identify these characteristic structures, to constrain the physical conditions that cause them, and to evaluate the feasibility to observe them in circumbinary disks. Methods: To achieve this, at first two-dimensional hydrodynamic simulations are performed. The resulting density distributions are post-processed with a 3D radiative transfer code to generate re-emission and scattered light maps. Based on these, we study the influence of various parameters, such as the mass of the stellar components, the mass of the disk and the binary separation on observable features in circumbinary disks. Results: We find that the Atacama Large (sub-)Millimetre Array (ALMA) as well as the European Extremely Large Telescope (E-ELT) are capable of tracing asymmetries in the inner region of circumbinary disks which are affected most by the binary-disk interaction. Observations at submillimetre/millimetre wavelengths will allow the detection of the density waves at the inner rim of the disk and the inner cavity. With the E-ELT one can partially resolve the innermost parts of the disk in the infrared wavelength range, including the disk's rim, accretion arms and potentially the expected circumstellar disks around each of the binary components

Unitary rotation and gyration of pixellated images on rectangular screens

In the two space dimensions of screens in optical sy stems, rotations, gyrations, and fractional Fourier transformations form the Fourier subgroup of the symplectic group of linear canonical transformations: U(2) F $\subset$ Sp(4,R). Here we study the action of this Fourier group on pixellated images within generic rectangular $N_x$ $\times$ $N_y$ screens; its elements here compose properly and act unitarily, i.e., without loss of information.Comment: 7 pages, 5 figure

Application of the SRI cloud-tracking technique to rapid-scan GOES observations

An automatic cloud tracking system was applied to multilayer clouds associated with severe storms. The method was tested using rapid scan observations of Hurricane Eloise obtained by the GOES satellite on 22 September 1975. Cloud tracking was performed using clustering based either on visible or infrared data. The clusters were tracked using two different techniques. The data of 4 km and 8 km resolution of the automatic system yielded comparable in accuracy and coverage to those obtained by NASA analysts using the Atmospheric and Oceanographic Information Processing System

A tour on Hermitian symmetric manifolds

Hermitian symmetric manifolds are Hermitian manifolds which are homogeneous and such that every point has a symmetry preserving the Hermitian structure. The aim of these notes is to present an introduction to this important class of manifolds, trying to survey the several different perspectives from which Hermitian symmetric manifolds can be studied.Comment: 56 pages, expanded version. Written for the Proceedings of the CIME-CIRM summer course "Combinatorial Algebraic Geometry". Comments are still welcome

Measuring the Decorrelation Times of Fourier Modes in Simulations

We describe a method to study the rate at which modes decorrelate in numerical simulations. We study the XY model updated with the Metropolis and Wolff dynamics respectively and compute the rate at which each eigenvector of the dynamics decorrelates. Our method allows us to identify the decorrelation time for each mode separately. We find that the autocorrelation function of the various modes is markedly different for the `local' Metropolis compared to the `non-local' Wolff dynamics. Equipped with this new insight, it may be possible to devise highly efficient algorithms.Comment: 16 pp (LaTeX), PUPT-1378 , IASSNS-HEP-93/