3,469 research outputs found
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
On the Spectral Lags and Peak-Counts of the Gamma-Ray Bursts Detected by the RHESSI Satellite
A sample of 427 gamma-ray bursts from a database (February 2002 - April 2008)
of the RHESSI satellite is analyzed statistically. The spectral lags and
peak-count rates, which have been calculated for the first time in this paper,
are studied completing an earlier analysis of durations and hardness ratios.
The analysis of the RHESSI database has already inferred the existence of a
third group with intermediate duration, apart from the so-called short and long
groups. First aim of this article is to discuss the properties of these
intermediate-duration bursts in terms of peak-count rates and spectral lags.
Second aim is to discuss the number of GRB groups using another statistical
method and by employing the peak-count rates and spectral lags as well. The
standard parametric (model-based clustering) and non-parametric (K-means
clustering) statistical tests together with the Kolmogorov-Smirnov and
Anderson-Darling tests are used. Two new results are obtained: A. The
intermediate-duration group has similar properties to the group of short
bursts. Intermediate and long groups appear to be different. B. The
intermediate-duration GRBs in the RHESSI and Swift databases seem to be
represented by different phenomena.Comment: 41 pages, 10 figures, 9 tables, accepted to be published in The
Astrophysical Journa
Local density of states and Friedel oscillations around a non-magnetic impurity in unconventional density wave
We present a mean-field theoretical study on the effect of a single
non-magnetic impurity in quasi-one dimensional unconventional density wave. The
local scattering potential is treated within the self-consistent -matrix
approximation. The local density of states around the impurity shows the
presence of resonant states in the vicinity of the Fermi level, much the same
way as in -density waves or unconventional superconductors. The assumption
for different forward and backscattering, characteristic to quasi-one
dimensional systems in general, leads to a resonance state that is double
peaked in the pseudogap. The Friedel oscillations around the impurity are also
explored in great detail, both within and beyond the density wave coherence
length . Beyond we find power law behavior as opposed to the
exponential decay of conventional density wave. The entropy and specific heat
contribution of the impurity are also calculated for arbitrary scattering
strengths.Comment: 13 pages, 4 figure
Aranyló rongylabda. Fragmentumok a magyar foci virágkoráról
Napjainkra a futball – igazodva a körĂĽlötte lĂ©vĹ‘ világhoz, vagy Ă©ppen formálva azt – globalizálĂłdott. A labdarĂşgás világmĂ©retű, Ăłriási ĂĽzlet, jĂłl eladhatĂł mĂ©diaesemĂ©ny, amely hatalmas reklámhordozĂł szereppel bĂr, hiszen a foci töretlen nĂ©pszerűsĂ©ge miatt hĂ©trĹ‘l hĂ©tre világszerte százezreket, milliĂłkat csábĂt a stadionokba, Ă©s ĂĽltet le a televĂziĂł kĂ©pernyĹ‘je elĂ©
Az informális tanulás törtĂ©neti szĂnterei
A közgondolkodás a tanulást elsĹ‘dlegesen a formális kĂ©pzĂ©shez köti, kevĂ©sbĂ© tulajdonĂt jelentĹ‘sĂ©get az informális tanulásnak,annak ellenĂ©re, hogy az jelentĹ‘s idĹ‘t Ă©s teret tölt ki az egyĂ©n Ă©letĂ©ben, mĂ©g a magasan kĂ©pzett szemĂ©lyek esetĂ©ben is. Az egĂ©sz Ă©letre kiterjedĹ‘ tanulás paradigmája is (amely magába foglalja az Ă©lethosszig tartĂł Ă©s az Ă©let minden terĂĽletĂ©t Ă©rintĹ‘ tanulást is) felĂ©rtĂ©keli az iskolán kĂvĂĽli tanulás funkciĂłját. Tanulságosnak látszik az informális tanulás törtĂ©neti vizsgálata is: annak bemutatása, hogy milyen jellegzetes szĂnterei voltak az informális (vagy más nĂ©ven: termĂ©szetes, hĂ©tköznapi) tanulásnak egy adott korban
Differenciált munkaformák. A műhelyfoglalkozás indoka és tapasztalatai
Az Ărás egyfelĹ‘l indoklását adja, hogy miĂ©rt van szĂĽksĂ©g a felsĹ‘oktatásban olyan műhelyfoglalkozásokra, amelyek a differenciálást, a tevĂ©kenysĂ©gcentrikus Ă©s Ă©lmĂ©nyszerű munkaformák alkalmazását segĂtik az oktatĂłk körĂ©ben. Ennek a jelentĹ‘sĂ©gĂ©t a tanárkĂ©pzĂ©sben látja, ahol kiemelt szerepet kap, hogy a szakterĂĽleti kĂ©pzĂ©s vonatkozásában is ilyen szemlĂ©lettel Ă©s mĂłdszerekkel találkozzanak a jövĹ‘ pedagĂłgusai. MásfelĹ‘l a kurzus tapasztalatait veszi számba, hangsĂşlyozva, hogy segĂteni kell a tanulással kapcsolatos szemlĂ©letváltást mind az oktatĂłk, mind pedig a hallgatĂłk körĂ©ben. EgyĂ©rtelműsĂti, hogy jĂłval több elĹ‘kĂ©szĂtĂ©st, felkĂ©szĂĽlĂ©st igĂ©nyel ennek a szemlĂ©letnek Ă©s gyakorlatnak a megvalĂłsĂtása, mint a hagyományos ĂłraszervezĂ©s, ezĂ©rt Ă©rdemes megfontolni a differenciálás, tevĂ©kenycentrikus, Ă©lmĂ©nyszerű munkaformák alkalmazásával járĂł többletmunka elismertetĂ©sĂ©t a felsĹ‘oktatásban (is
Defense mechanisms of empathetic players in the spatial ultimatum game
Experiments on the ultimatum game have revealed that humans are remarkably
fond of fair play. When asked to share an amount of money, unfair offers are
rare and their acceptance rate small. While empathy and spatiality may lead to
the evolution of fairness, thus far considered continuous strategies have
precluded the observation of solutions that would be driven by pattern
formation. Here we introduce a spatial ultimatum game with discrete strategies,
and we show that this simple alteration opens the gate to fascinatingly rich
dynamical behavior. Besides mixed stationary states, we report the occurrence
of traveling waves and cyclic dominance, where one strategy in the cycle can be
an alliance of two strategies. The highly webbed phase diagram, entailing
continuous and discontinuous phase transitions, reveals hidden complexity in
the pursuit of human fair play.Comment: 4 two-column pages, 5 figures; accepted for publication in Physical
Review Letter
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