B. S. Visser

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We examine an oligopoly model where some consumers engage in costly non-sequential search to discover prices. There are three distinct price-dispersed equilibria characterized by low, moderate and high search intensity. The effects of an increase in the number of firms on search behavior, expected prices, price dispersion and welfare are sensitive (i) to(More)
A significant fraction of the energy density of the interstellar medium is in the form of high-energy charged particles (cosmic rays). The origin of these particles remains uncertain. Although it is generally accepted that the only sources capable of supplying the energy required to accelerate the bulk of Galactic cosmic rays are supernova explosions, and(More)
Very high energy gamma-rays probe the long-standing mystery of the origin of cosmic rays. Produced in the interactions of accelerated particles in astrophysical objects, they can be used to image cosmic particle accelerators. A first sensitive survey of the inner part of the Milky Way with the High Energy Stereoscopic System (HESS) reveals a population of(More)
This paper considers a market where a single seller must employ informative advertising to launch a new product of observable quality. We formulate a fairly general advertising technology that allows us to study three promotional strategies —mass, targeted and customer directed advertising. We show that when the advertising technology exhibits strong(More)
Observations of the shell-type supernova remnant SN1006 have been carried out with the H.E.S.S. system of Cherenkov telescopes during 2003 (18.2h with two operating telescopes) and 2004 (6.3h with all four telescopes). No evidence for TeV γ-ray emission from any compact or extended region associated with the remnant is seen and resulting upper limits at the(More)
We investigate the distribution of profits between a laboratory and two firms on the intermediate market for cost-reducing or/and demand-enhancing technology, and infer implications for the governance of R&D. The laboratory supplies tailor-made multi-dimensional R&D services at some costs, and maximizes its individual profits. Firms are interested in(More)
We consider a committee that makes a decision on a project on behalf of 'the public'. Members of the committee agree on the a priori value of the project, and hold additional private information about its consequences. They are experts who care both about the value of the project and about being considered well informed. Before voting on the project,(More)
  • Jan Marc Berk, Beata K Bierut, Robert Paul Berben, Bryan Chapple, Petra Gerlach-Kristen, Ellen Meade +3 others
  • 2009
In 2009 all ECB publications feature a motif taken from the €200 banknote. Fax +49 69 1344 6000 All rights reserved. Any reproduction, publication and reprint in the form of a different publication, whether printed or produced electronically, in whole or in part, is permitted only with the explicit written authorisation of the ECB or the author(s). The(More)
We report the detection of a point-like source of very high energy (VHE) γ-rays coincident within 1 ′ of Sgr A * , obtained with the H.E.S.S. array of Cherenkov telescopes. The γ-rays exhibit a power-law energy spectrum with a spectral index of −2.2 ± 0.09 ± 0.15 and a flux above the 165 GeV threshold of (1.82 ± 0.22) · 10 −7 m −2 s −1. The measured flux(More)