12,793 research outputs found
Pentaquark Exotic Baryons in the Skyrme Model
We investigate the pentaquark() exotic baryons as soliton-antiflavored
heavy mesons bound states in the limit of infinitely heavy meson mass. Our
approach respects the chiral symmetry as well as the heavy quark symmetry. The
results reveal a possibility for the loosely bound non-strange -baryon(s).Comment: LaTeX, 11 pages, SNUTP-94/06 (revised
Universal scaling at non-thermal fixed points of a two-component Bose gas
Quasi-stationary far-from-equilibrium critical states of a two-component Bose
gas are studied in two spatial dimensions. After the system has undergone an
initial dynamical instability it approaches a non-thermal fixed point. At this
critical point the structure of the gas is characterised by ensembles of
(quasi-)topological defects such as vortices, skyrmions and solitons which give
rise to universal power-law behaviour of momentum correlation functions. The
resulting power-law spectra can be interpreted in terms of
strong-wave-turbulence cascades driven by particle transport into
long-wave-length excitations. Scaling exponents are determined on both sides of
the miscible-immiscible transition controlled by the ratio of the intra-species
to inter-species couplings. Making use of quantum turbulence methods, we
explain the specific values of the exponents from the presence of transient
(quasi-)topological defects.Comment: 13 pages, 12 figure
The Evolution of Extortion in Iterated Prisoner's Dilemma Games
Iterated games are a fundamental component of economic and evolutionary game
theory. They describe situations where two players interact repeatedly and have
the possibility to use conditional strategies that depend on the outcome of
previous interactions. In the context of evolution of cooperation, repeated
games represent the mechanism of reciprocation. Recently a new class of
strategies has been proposed, so called 'zero determinant strategies'. These
strategies enforce a fixed linear relationship between one's own payoff and
that of the other player. A subset of those strategies are 'extortioners' which
ensure that any increase in the own payoff exceeds that of the other player by
a fixed percentage. Here we analyze the evolutionary performance of this new
class of strategies. We show that in reasonably large populations they can act
as catalysts for the evolution of cooperation, similar to tit-for-tat, but they
are not the stable outcome of natural selection. In very small populations,
however, relative payoff differences between two players in a contest matter,
and extortioners hold their ground. Extortion strategies do particularly well
in co-evolutionary arms races between two distinct populations: significantly,
they benefit the population which evolves at the slower rate - an instance of
the so-called Red King effect. This may affect the evolution of interactions
between host species and their endosymbionts.Comment: contains 4 figure
Learning to Reach Agreement in a Continuous Ultimatum Game
It is well-known that acting in an individually rational manner, according to
the principles of classical game theory, may lead to sub-optimal solutions in a
class of problems named social dilemmas. In contrast, humans generally do not
have much difficulty with social dilemmas, as they are able to balance personal
benefit and group benefit. As agents in multi-agent systems are regularly
confronted with social dilemmas, for instance in tasks such as resource
allocation, these agents may benefit from the inclusion of mechanisms thought
to facilitate human fairness. Although many of such mechanisms have already
been implemented in a multi-agent systems context, their application is usually
limited to rather abstract social dilemmas with a discrete set of available
strategies (usually two). Given that many real-world examples of social
dilemmas are actually continuous in nature, we extend this previous work to
more general dilemmas, in which agents operate in a continuous strategy space.
The social dilemma under study here is the well-known Ultimatum Game, in which
an optimal solution is achieved if agents agree on a common strategy. We
investigate whether a scale-free interaction network facilitates agents to
reach agreement, especially in the presence of fixed-strategy agents that
represent a desired (e.g. human) outcome. Moreover, we study the influence of
rewiring in the interaction network. The agents are equipped with
continuous-action learning automata and play a large number of random pairwise
games in order to establish a common strategy. From our experiments, we may
conclude that results obtained in discrete-strategy games can be generalized to
continuous-strategy games to a certain extent: a scale-free interaction network
structure allows agents to achieve agreement on a common strategy, and rewiring
in the interaction network greatly enhances the agents ability to reach
agreement. However, it also becomes clear that some alternative mechanisms,
such as reputation and volunteering, have many subtleties involved and do not
have convincing beneficial effects in the continuous case
The width of for large in chiral quark soliton model
In the chiral quark soliton model the smallness of width is due to
the cancellation of the coupling constants which are of different order in
. We show that taking properly into account the flavor structure of
relevant SU(3) representations for arbitrary number of colors enahnces the
nonleading term by an additional factor of , making the cancellation
consistent with the counting. Moreover, we show that, for the same
reason, width is suppressed by a group-theoretical factor with respect to and discuss the dependence of the
phase space factors for these two decays.Comment: 9 pages, 3 eps figures, in v2 reference added, minor typos correcte
Studying Paths of Participation in Viral Diffusion Process
Authors propose a conceptual model of participation in viral diffusion
process composed of four stages: awareness, infection, engagement and action.
To verify the model it has been applied and studied in the virtual social chat
environment settings. The study investigates the behavioral paths of actions
that reflect the stages of participation in the diffusion and presents
shortcuts, that lead to the final action, i.e. the attendance in a virtual
event. The results show that the participation in each stage of the process
increases the probability of reaching the final action. Nevertheless, the
majority of users involved in the virtual event did not go through each stage
of the process but followed the shortcuts. That suggests that the viral
diffusion process is not necessarily a linear sequence of human actions but
rather a dynamic system.Comment: In proceedings of the 4th International Conference on Social
Informatics, SocInfo 201
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