699 research outputs found
The Strategy-Proofness Landscape of Merging
Merging operators aim at defining the beliefs/goals of a group of agents from
the beliefs/goals of each member of the group. Whenever an agent of the group
has preferences over the possible results of the merging process (i.e., the
possible merged bases), she can try to rig the merging process by lying on her
true beliefs/goals if this leads to better merged base according to her point
of view. Obviously, strategy-proof operators are highly desirable in order to
guarantee equity among agents even when some of them are not sincere. In this
paper, we draw the strategy-proof landscape for many merging operators from the
literature, including model-based ones and formula-based ones. Both the general
case and several restrictions on the merging process are considered
Fluid-fluid demixing transitions in colloid--polyelectrolyte star mixtures
We derive effective interaction potentials between hard, spherical colloidal
particles and star-branched polyelectrolytes of various functionalities and
smaller size than the colloids. The effective interactions are based on a
Derjaguin-like approximation, which is based on previously derived potentials
acting between polyelectrolyte stars and planar walls. On the basis of these
interactions we subsequently calculate the demixing binodals of the binary
colloid--polyelectrolyte star mixture, employing standard tools from
liquid-state theory. We find that the mixture is indeed unstable at moderately
high overall concentrations. The system becomes more unstable with respect to
demixing as the star functionality and the size ratio grow.Comment: 24 pages, 9 figures, submitted to Journal of Physics: Condensed
Matte
Directional approach to spatial structure of solutions to the Navier-Stokes equations in the plane
We investigate a steady flow of incompressible fluid in the plane. The motion
is governed by the Navier-Stokes equations with prescribed velocity
at infinity. The main result shows the existence of unique solutions for
arbitrary force, provided sufficient largeness of . Furthermore a
spacial structure of the solution is obtained in comparison with the Oseen
flow. A key element of our new approach is based on a setting which treats the
directino of the flow as \emph{time} direction. The analysis is done in
framework of the Fourier transform taken in one (perpendicular) direction and a
special choice of function spaces which take into account the inhomogeneous
character of the symbol of the Oseen system. From that point of view our
technique can be used as an effective tool in examining spatial asymptotics of
solutions to other systems modeled by elliptic equations
Magnetic systems at criticality: different signatures of scaling
Different aspects of critical behaviour of magnetic materials are presented
and discussed. The scaling ideas are shown to arise in the context of purely
magnetic properties as well as in that of thermal properties as demonstrated by
magnetocaloric effect or combined scaling of excess entropy and order
parameter. Two non-standard approaches to scaling phenomena are described. The
presented concepts are exemplified by experimental data gathered on four
representatives of molecular magnets.Comment: 33 pages, 16 figure
Polyelectrolyte stars in planar confinement
We employ monomer-resolved Molecular Dynamics simulations and theoretical
considerations to analyze the conformations of multiarm polyelectrolyte stars
close to planar, uncharged walls. We identify three mechanisms that contribute
to the emergence of a repulsive star-wall force, namely: the confinement of the
counterions that are trapped in the star interior, the increase in
electrostatic energy due to confinement as well as a novel mechanism arising
from the compression of the stiff polyelectrolyte rods approaching the wall.
The latter is not present in the case of interaction between two
polyelectrolyte stars and is a direct consequence of the impenetrable character
of the planar wall.Comment: 34 pages, 8 figures. Revised version of the manuscript. To appear in
J. Chem. Phys. May, 200
Decrement Operators in Belief Change
While research on iterated revision is predominant in the field of iterated
belief change, the class of iterated contraction operators received more
attention in recent years. In this article, we examine a non-prioritized
generalisation of iterated contraction. In particular, the class of weak
decrement operators is introduced, which are operators that by multiple steps
achieve the same as a contraction. Inspired by Darwiche and Pearl's work on
iterated revision the subclass of decrement operators is defined. For both,
decrement and weak decrement operators, postulates are presented and for each
of them a representation theorem in the framework of total preorders is given.
Furthermore, we present two sub-types of decrement operators
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