7,437 research outputs found
Magnetic multipole analysis of kagome and artificial ice dipolar arrays
We analyse an array of linearly extended monodomain dipoles forming square
and kagome lattices. We find that its phase diagram contains two (distinct)
finite-entropy kagome ice regimes - one disordered, one algebraic - as well as
a low-temperature ordered phase. In the limit of the islands almost touching,
we find a staircase of corresponding entropy plateaux, which is analytically
captured by a theory based on magnetic charges. For the case of a modified
square ice array, we show that the charges ('monopoles') are excitations
experiencing two distinct Coulomb interactions: a magnetic 'three-dimensional'
one as well as a logarithmic `two dimensional' one of entropic origin.Comment: 4 pages, 2 figures; v2: minor changes as in final published versio
Stabilization of colloidal palladium particles by a block copolymer of polystyrene and a block containing amide sidegroups
A block copolymer of polystyrene and poly(tert-butylmethacrylate) was prepared by anionic polymerization. The ester groups of the poly(tert-butylmethacrylate) were hydrolyzed, after wich the remaining carboxyl groups were reacted with pyrrolidine. The resulting block copolymer with amide sidegroups was used for stabilization of a palladium colloid in toluene
Considerations on gradual glutamate accumulation related to cognitive task performance
Long-lasting activities with high demand in cognitive control are known to result in cognitive fatigue. However, the reason for control cost inflation remains elusive. A neurometabolic account was proposed in a recent study combining magnetic resonance spectroscopy (MRS) with daylong execution of behavioral tasks. It suggests that control cost during high-demand work is related to the necessity of recycling potentially toxic substances, specifically glutamate, which may accumulate extracellularly. As MRS provides estimates of metabolite concentrations, further evaluations are possible how well this hypothesis fits with fundamental consequences from the dynamic equilibrium of intercompartmental glutamate distributions
Paired composite fermion wavefunctions
We construct a family of BCS paired composite fermion wavefunctions that
generalize, but remain in the same topological phase as, the Moore-Read
Pfaffian state for the half-filled Landau level. It is shown that for a wide
range of experimentally relevant inter-electron interactions the groundstate
can be very accurately represented in this form.Comment: 4 pages, 2 figure
Paired composite fermion phase of quantum Hall bilayers at \nu = 1/2 + 1/2
We provide numerical evidence for composite fermion pairing in quantum Hall
bilayer systems at filling for intermediate spacing between the
layers. We identify the phase as pairing, and construct high
accuracy trial wavefunctions to describe the groundstate on the sphere. For
large distances between the layers, and for finite systems, a competing "Hund's
rule" state, or composite fermion liquid, prevails for certain system sizes. We
argue that for larger systems, the pairing phase will persist to larger layer
spacing.Comment: 4 pages, 2 figures; v2: final version, as published in journa
On square positive extensions and cubature formulas
AbstractWe consider linear functionals Ld defined over Pd⊂P≔R[x1,…,xn] and study how to extend Ld to a square positive L:P→R, i.e. to a linear functional L with L(p2)⩾0 for all p∈P. We use the connection of square positive functionals to real ideals, to orthogonal polynomials, and to moment matrices. Finally, we report how such extension techniques are used to construct and analyse cubature formulas
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