5,024 research outputs found
Correlated Equilibria and Mean Field Games: A Simple Model
No full textIn the context of simple finite-state discrete time systems, we introduce a generalization of a mean field game solution, called a correlated solution, which can be seen as the mean field game analogue of a correlated equilibrium. Our notion of a solution is justified in two ways: we prove that correlated solutions arise as limits of exchangeable correlated equilibria in restricted (Markov open-loop) strategies for the underlying N-player games, and we show how to construct approximate N-player correlated equilibria starting from a correlated solution to the mean field game
N-player games and mean field games with absorption
No full textWe introduce a simple class of mean field games with absorbing boundary over a finite time horizon. In the corresponding N -player games, the evolution of players’ states is described by a system of weakly interacting Itô equations with absorption on first exit from a bounded open set. Once a player exits, her/his contribution is removed from the empirical measure of the system. Players thus interact through a renormalized empirical measure. In the definition of solution to the mean field game, the renormalization appears in form of a conditional law. We justify our definition of solution in the usual way, that is, by showing that a solution of the mean field game induces approximate Nash equilibria for the N -player games with approximation error tending to zero as N tends to infinity. This convergence is established provided the diffusion coefficient is non-degenerate. The degenerate case is more delicate and gives rise to counter-examples
Coarse correlated equilibria for continuous time mean field games in open loop strategies
No full textIn the framework of continuous time symmetric stochastic differential games in open loop strategies, we introduce a generalization of mean field game solution, called coarse correlated solution. This can be seen as the analogue of a coarse correlated equilibrium in the N-player game. We justify our definition by showing that a coarse correlated solution for the mean field game induces a sequence of approximate coarse correlated equilibria with vanishing error for the underlying N-player games. Existence of coarse correlated solutions for the mean field game is proved by a minimax theorem. An example with explicit solutions is discussed as well
Correlated equilibria for mean field games with progressive strategies
No full textIn a discrete space and time framework, we study the mean field game limit for a class of symmetric N-player games based on the notion of correlated equilibrium. We give a definition of correlated solution that allows to construct approximate N-player correlated equilibria that are robust with respect to progressive deviations. We illustrate our definition by way of an example with explicit solutions
A quantitative index of land-use intensity in grasslands: Integrating mowing, grazing and fertilization
No full textAbstract not availableNico Blüthgen, Carsten F. Dormann, Daniel Prati, Valentin H. Klaus, Till Kleinebecker, Norbert Hölzel, Fabian Alt, Steffen Boch, Sonja Gockel, Andreas Hemp, Jörg Müller, Jens Nieschulze, Swen C. Renner, Ingo Schöning, Uta Schumacher, Stephanie A. Socher, Konstans Wells, Klaus Birkhofer, François Buscot, l, Yvonne Oelmann, Christoph Rothenwöhrer, Christoph Scherber, Teja Tscharntke, Christiane N. Weiner, Markus Fischer, Elisabeth K.V. Kalko, Karl Eduard Linsenmai
Baboon responses to graded bark variants
No full textWe studied chacma baboons', Papio cynocephalus ursinus, responses to conspecific ‘barks’ in a free-ranging population in the Okavango Delta of Botswana. These barks grade from tonal, harmonically rich calls to calls having a noisier, harsher structure. Tonal or clear barks are typically given when the signaller is at risk of losing contact with the group or when a mother and infant have become separated (‘contact barks’). The harsher variants are given in response to predators (‘alarm barks’). In both contexts, however, we also observed acoustically intermediate forms. Using the habituation–recovery method we tested whether baboons discriminated between (1) clear contact barks versus harsh alarm barks, and (2) clear contact barks versus intermediate alarm barks. Calls were selected according to the results of a discriminant function analysis conducted on a suite of acoustic parameters. In these experiments, animals showed a significant recovery of response only after playback of the harsh alarm call. We performed another set of experiments using single exemplars of clear and intermediate contact barks, or intermediate and harsh alarm barks. Animals responded only to the playback of a harsh alarm bark. Apparently, only this harsh variant was placed in a category that warranted a response. We hypothesize that baboons' responses were to a large degree influenced by their assessment of context
Insight into the early steps of root hair formation revealed by the procuste1 cellulose synthase mutant of Arabidopsis thaliana
No full textBackground: formation of plant root hairs originating from epidermal cells involves selection of a polar initiation site and production of an initial hair bulge which requires local cell wall loosening. In Arabidopsis the polar initiation site is located towards the basal end of epidermal cells. However little is currently understood about the mechanism for the selection of the hair initiation site or the mechanism by which localised hair outgrowth is achieved. The Arabidopsis procuste1 (prc1-1) cellulose synthase mutant was studied in order to investigate the role of the cell wall loosening during the early stages of hair formation. Results: the prc1-1 mutant exhibits uncontrolled, preferential bulging of trichoblast cells coupled with mislocalised hair positioning. Combining the prc1-1 mutant with root hair defective6-1 (rhd6-1), which on its own is almost completely devoid of root hairs results in a significant restoration of root hair formation. The pEXPANSIN7::GFP (pEXP7::GFP) marker which is specifically expressed in trichoblast cell files of wild-type roots, is absent in the rhd6-1 mutant. However, pEXP7::GFP expression in the rhd6-1/prc1-1 double mutant is restored in a subset of epidermal cells which have either formed a root hair or exhibit a bulged phenotype consistent with a function for EXP7 during the early stages of hair formation. Conclusion: these results show that RHD6 acts upstream of the normal cell wall loosening event which involves EXP7 expression and that in the absence of a functional RHD6 the loosening and accompanying EXP7 expression is blocked. In the prc1-1 mutant background, the requirement for RHD6 during hair initiation is reduced which may result from a weaker cell wall structure mimicking the cell wall loosening events during hair formation
Do inflation targeters outperform non-targeters?
No full textTen years of empirical studies of inflation targeting have not uncovered clear evidence that monetary policy that incorporates formal targets imparts better inflation performance. The authors survey the literature and find that the "no difference" verdict concerning inflation targeting has been robust to a wide range of countries and methods of analysis, starting with a study by Dueker and Fischer (1996a). The authors present updated Markov-switching estimates from the original Dueker and Fischer (1996a) article and show that their early conclusions about inflation targeting among early adopters have not been overturned with an additional decade of data. These findings to date do not rule out the possibility, however, that formal inflation targets could prove pivotal if the global environment of disinflation were to reverse course.Inflation (Finance)
sj-docx-3-hol-10.1177_09596836221121766 – Supplemental material for Buffering new risks? Environmental, social and economic changes in the Turkana Basin during and after the African Humid Period
No full textSupplemental material, sj-docx-3-hol-10.1177_09596836221121766 for Buffering new risks? Environmental, social and economic changes in the Turkana Basin during and after the African Humid Period by Elisabeth Hildebrand, Katherine M Grillo, Kendra L Chritz, Markus L Fischer, Steven T Goldstein, Anneke Janzen, Annett Junginger, Rahab N Kinyanjui, Emmanuel Ndiema, Elizabeth Sawchuk, Amanuel Beyin and Susan K Pfeiffer in The Holocene</p
sj-pdf-4-hol-10.1177_09596836221121766 – Supplemental material for Buffering new risks? Environmental, social and economic changes in the Turkana Basin during and after the African Humid Period
No full textSupplemental material, sj-pdf-4-hol-10.1177_09596836221121766 for Buffering new risks? Environmental, social and economic changes in the Turkana Basin during and after the African Humid Period by Elisabeth Hildebrand, Katherine M Grillo, Kendra L Chritz, Markus L Fischer, Steven T Goldstein, Anneke Janzen, Annett Junginger, Rahab N Kinyanjui, Emmanuel Ndiema, Elizabeth Sawchuk, Amanuel Beyin and Susan K Pfeiffer in The Holocene</p
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