17,943 research outputs found
Directional learning and the provisioning of public goods
We consider an environment where players are involved in a public goods game
and must decide repeatedly whether to make an individual contribution or not.
However, players lack strategically relevant information about the game and
about the other players in the population. The resulting behavior of players is
completely uncoupled from such information, and the individual strategy
adjustment dynamics are driven only by reinforcement feedbacks from each
player's own past. We show that the resulting "directional learning" is
sufficient to explain cooperative deviations away from the Nash equilibrium. We
introduce the concept of k-strong equilibria, which nest both the Nash
equilibrium and the Aumann-strong equilibrium as two special cases, and we show
that, together with the parameters of the learning model, the maximal
k-strength of equilibrium determines the stationary distribution. The
provisioning of public goods can be secured even under adverse conditions, as
long as players are sufficiently responsive to the changes in their own payoffs
and adjust their actions accordingly. Substantial levels of public cooperation
can thus be explained without arguments involving selflessness or social
preferences, solely on the basis of uncoordinated directional (mis)learning.Comment: 7 two-column pages, 3 figures; accepted for publication in Scientific
Report
Propagation of detonations in hydrazine vapor
In the range of greater hydrazine vapor pressure, detonation speed depends exclusively on the extent of the ammonia decomposition in the second reaction stage. As vapor pressure decreases, the ammonia disintegration speed becomes increasingly slower and the reaction reached in the reaction zone increasingly decreases until finally, in the vapor pressure range between 53 and 16 Torr, the contribution of the second stage to detonation propagation disappears, and only the first stage remains active. Since the disintegration speed of the hydrazine in this pressure range has decreased markedly as well, no level, but rather only spinning, detonations occur. Temporary separations of the impact front and the reaction zone in the process lead to fluctuations of the detonation speed
An assessment of sphere drag coefficient data
Wind tunnel test data for falling sphere drag coefficient determinatio
Neutrino mass and magnetic moment in supersymmetry without R-parity in the light of recent data
We consider the generation of neutrino Majorana mass and transition magnetic
moment by the lepton-number violating and/or couplings in
R-parity-violating supersymmetric models. We update (and improve) the existing
upper limits on the relevant couplings using the most recent data on neutrino
masses and mixings, indicating also the possible improvement by the GENIUS
project. We study the implication of this update on the induced neutrino
magnetic moment.Comment: 7 pages, Latex, uses axodraw.sty; refs updated, to appear in PL
Stability of cooperation under image scoring in group interactions
Image scoring sustains cooperation in the repeated two-player prisoner's
dilemma through indirect reciprocity, even though defection is the uniquely
dominant selfish behaviour in the one-shot game. Many real-world dilemma
situations, however, firstly, take place in groups and, secondly, lack the
necessary transparency to inform subjects reliably of others' individual past
actions. Instead, there is revelation of information regarding groups, which
allows for `group scoring' but not for image scoring. Here, we study how
sensitive the positive results related to image scoring are to information
based on group scoring. We combine analytic results and computer simulations to
specify the conditions for the emergence of cooperation. We show that under
pure group scoring, that is, under the complete absence of image-scoring
information, cooperation is unsustainable. Away from this extreme case,
however, the necessary degree of image scoring relative to group scoring
depends on the population size and is generally very small. We thus conclude
that the positive results based on image scoring apply to a much broader range
of informational settings that are relevant in the real world than previously
assumed.Comment: 6 two-column pages, 4 figures; accepted for publication in Scientific
Report
Cross sections for the production of fragments with Z greater than or equal to 8 by fragmentation of Z greater than or equal to 9 and less than or equal to 26 nuclei
Charge changing nuclear collisions in plastic nuclear track detectors were studied using a new experimental technique of automatic track measurement for etched tracks in plastic detectors. Partial cross sections for the production of fragments of charge Z approximately 8 were measured for projectile nuclei of charge 9 approximately Z approximately 26 in the detector material CR39 and in silver. for this purpose three independent experiments were performed using Bevalac beams. The first one was an exposure of a stack of CR39 plastic plates to 1.8 GeV/nucl. Ar-40 nuclei. The second one was an exposure of another CR39 stack of 1.7 GeV/nucl. Fe-56 projectiles. In the third experiment a mixed stack of CR39 plates and silver foils was irradiated with 1.7 GeV/nucl. Fe-56 nuclei. Thus the measurement of nuclear cross sections in a light target (CR39 = C12H18O7) and as well in a heavy target (silver) was possible
The Logic of Collective Rating
The introduction of participatory rating mechanisms on online sales platforms has had substantial impact on firms' sales and profits. In this note, we develop a dynamic model of consumer influences on ratings and of rating influences on consumers, focussing on standard five-star mechanisms as implemented by many platforms. The key components of our social influence model are the consumer trust in the “wisdom of crowds” during the purchase phase and indirect reciprocity during the rating decision. Our model provides an overarching explanation for well-corroborated empirical regularities. We quantify the performance of the voluntary rating mechanism in terms of realized consumer surplus with the no-mechanism and full-information benchmarks, and identify how it could be improved
Crack barriers improve the mechanical and thermal properties of non-metallic sinter materials
Means of improving the tensile strength of ceramic composites by introducing ductile intermediate layers capable of absorbing the elastic energy at the rupture front are studied. Tests with an Al203 laminate with niobium inclusions showed that crack propagation could be successfully precluded by dissipation of the energy by deformation and/or delamination at the inclusion/matrix interface
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