A Hybrid Public Good Experiment Eliciting Multi-Dimensional Choice Data

Similar to Fischbacher and Gachter (2010) we suggest an elicitation method for exploring the motivation of participants when contributing to a public good in the role of "leader" or "follower". In the Hybrid Public Good experiment each of two interacting contributors chooses an independent contribution level as well as three adjusted contribution levels when (s)he, as the only adjusting player, learns that the other's independent contribution is smaller, equal or larger than the own one. To approximate the border cases of simultaneous contributing as well as sequential contributions we systematically vary the probability that one player can adjust, based on such qualitative information, but maintain that no adaptation at all and adaptation by only one occurs with positive probability. Adaptation is framed in two ways, once by additively changing the own independent contribution and once by stating new contribution levels. Surprisingly, the framing effect becomes stronger with experience. Reacting to coinciding independent contributions implies impressive conformity in contributing. Reacting to higher, respectively lower independent contributions implies average upward, and, more strongly, downward adaptation

Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo

International audienceIntermediate-mass black holes (IMBHs) span the approximate mass range 100−105 M⊙, between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150 M⊙ providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200 M⊙ and effective aligned spin 0.8 at 0.056 Gpc−3 yr−1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc−3 yr−1.Key words: gravitational waves / stars: black holes / black hole physicsCorresponding author: W. Del Pozzo, e-mail: [email protected]† Deceased, August 2020