Is lensing of point sources a problem for future CMB experiments?

Weak gravitational lensing from large-scale structure enhances and reduces the fluxes from extragalactic point sources with an rms amplitude of order 15%. In cosmic microwave background (CMB) experiments, sources exceeding some flux threshold are removed, which means that lensing will modulate the brightness map of the remaining unresolved sources. Since this mean brightness is of order 100 micro-Kelvin at 30 GHz for a reasonable flux cut, one might be concerned that this modulation could cause substantial problems for future CMB experiments. We present a detailed calculation of this effect and, fortunately, find that its power spectrum is always smaller than the normal point source power spectrum. Thus although this effect should be taken into account when analysing future high-precision CMB measurements, it will not substantially reduce the accuracy with which cosmological parameters can be measured.Comment: Expanded to match published version. 14 pages, with 3 figures included. Color figures at http://www.sns.ias.edu/~max/lensing.html (faster from the US), from http://www.mpa-garching.mpg.de/~max/lensing.html (faster from Europe) or from [email protected]

Weak Lensing By Nearby Structures

Weak gravitational lensing due to nearby structures, such as the Coma cluster, and the Local Supercluster can be expected to polarize images of distant galaxies by ${\cal O}(0.2$ with coherence over scales of tens of square degrees. The Sloan Survey, which will image \gsim 10^4 galaxies $\rm deg^{-2}$ over $\pi$ steradians, should be sensitive to polarizations of $\sim 0.1$, where $A$ is the area in square degrees. By measuring the polarization, one could determine $\Omega$ in local structures and compare this value to that derived from a variety of other techniques.Comment: 14 pages, phyzz

Are OECD Export Specialisation Patterns 'Sticky'? Relations to the Convergence-Divergence Debate

The aim of the present paper is twofold. We want to present and test a methodology capable to deal more satisfactorily with the question of stability of international export specialisation patterns and, secondly, we want to relate this issue to the convergence-divergence debate in growth theory and the rapidly increasing strand of literature on national systems of innovation.We conclude that the relative export structures are moving together in the long term. However, the speed of convergence is fairly slow, indicating that national export specialisation patterns are quite stubborn or 'sticky'. These findings are complementary to the new knowledge generated wit convergence-divergence debate in growth theory and the rapidly increasing strand of literature on natonal systems of innovation.Specialisation; International Trade Patterns; Growth and Trade

The spatial correlation properties of dark galaxy halos in a CDM universe

We use the Hierarchical Particle Mesh (HPM) N-body code written by J. V. Villumsen (Villumsen, 1989) to investigate the two-point spatial correlation function, xi(r), of dark galaxy halos as a function of halo mass and local environment (i.e. high, low, or average mass density). We assume a standard cold dark matter (CDM) universe (omega = 1, delta = 0, H sub 0 = 50,km/sec/Mpc). Because of the large dynamic ranges in mass and length that can be obtained with the HPM code, it is well-suited to an investigation of this sort

The Long Term Development of OECD Export Specialisation Patterns: De-specialisation and "Stickiness"

The paper examines an issue related to the discussion of national specificity - whether the group of OECD countries are characterised by a high degree of stability of their export specialisation patterns at the country level or not. During a period of nearly three decades from 1965 to 1992, 20 OECD countries are examined. In addition we test whether the countries, have become more or less specialised in terms of trade specialisation in the period in question. In order to fulfill these aims we examine the sensitivity for, firstly; the level of aggregation, and secondly; the kind of statistical methodology applied. In this context we distinguish between specialisation (or de-specialisation) in trade patterns on the one hand, and divergence (or on the contrary convergence) in trade patterns on the other. A specialisation process refers to a process in which specialisation intra-country becomes more dispersed (and counter-wise for de-specialisation). On the contrary, a divergence process refers to a process in which countries become more different in terms of specialisation in a particular sector, across countries (and counter-wise for convergence). The results show that elements of 'stickiness' and incremental change are combined for what concerns the intra-country analysis. In addition there is a (however slow) tendency for countries to de-specialise in terms of exports. The sector-wise results display convergence both in terms of beta- and sigma -convergence.Technological change; cumulativeness; international export specialisation patterns; nati

Technoligical Life Cycles Regional Clusters Facing Disruption

The phenomenon of technological life cycles is argued to be of great importance in the development of regional clusters. New 'disruptive' technologies may initiate the emergence of new regional industrial clusters and/or create new opportunities for further development of existing ones. However, they may also result in stagnation and decline of the latter. The term disruptive refers to such significant changes in the basic technologies that may change the industrial landscape, even in the shorter run. The paper examines the key features of a regional cluster, where the economic development patterns are quite closely related to the emergence of new key technologies.Technological life cycles, regional clusters, communication technology