4,536 research outputs found
Orthogonal polynomials in the normal matrix model with a cubic potential
We consider the normal matrix model with a cubic potential. The model is
ill-defined, and in order to reguralize it, Elbau and Felder introduced a model
with a cut-off and corresponding system of orthogonal polynomials with respect
to a varying exponential weight on the cut-off region on the complex plane. In
the present paper we show how to define orthogonal polynomials on a specially
chosen system of infinite contours on the complex plane, without any cut-off,
which satisfy the same recurrence algebraic identity that is asymptotically
valid for the orthogonal polynomials of Elbau and Felder. The main goal of this
paper is to develop the Riemann-Hilbert (RH) approach to the orthogonal
polynomials under consideration and to obtain their asymptotic behavior on the
complex plane as the degree of the polynomial goes to infinity. As the
first step in the RH approach, we introduce an auxiliary vector equilibrium
problem for a pair of measures on the complex plane. We then
formulate a matrix valued RH problem for the orthogonal polynomials
in hand, and we apply the nonlinear steepest descent method of Deift-Zhou to
the asymptotic analysis of the RH problem. The central steps in our study are a
sequence of transformations of the RH problem, based on the equilibrium vector
measure , and the construction of a global parametrix. The main
result of this paper is a derivation of the large asymptotics of the
orthogonal polynomials on the whole complex plane. We prove that the
distribution of zeros of the orthogonal polynomials converges to the measure
, the first component of the equilibrium measure. We also obtain
analytical results for the measure relating it to the distribution of
eigenvalues in the normal matrix model which is uniform in a domain bounded by
a simple closed curve.Comment: 57 pages, 8 figure
Some considerations in the selection of aircraft for earth resource observations
Comparison of logistics problems and cost aspects in selection of aircraft for earth resources survey
Disorder-Induced Static Antiferromagnetism in Cuprate Superconductors
Using model calculations of a disordered d-wave superconductor with on-site
Hubbard repulsion, we show how dopant disorder can stabilize novel states with
antiferromagnetic order. We find that the critical strength of correlations or
impurity potential necessary to create an ordered magnetic state in the
presence of finite disorder is reduced compared to that required to create a
single isolated magnetic droplet. This may explain why in cuprates like LSCO
low-energy probes have identified a static magnetic component which persists
well into the superconducting state, whereas in cleaner systems like YBCO it is
absent or minimal. Finally we address the case of nominally clean LSCO samples
at optimal doping, where such ordered magnetic moments are absent, but where
they can be induced by small concentrations of strong scatterers.Comment: 4 pages, 5 figure
Efficient Coordination in Weakest-Link Games
Existing experimental research on behavior in weakest-link games shows overwhelmingly the inability of people to coordinate on the efficient equilibrium, especially in larger groups. We hypothesize that people will be able to coordinate on efficient outcomes, provided they have sufficient freedom to choose their interaction neighborhood. We conduct experiments with medium sized and large groups and show that neighborhood choice indeed leads to coordination on the fully efficient equilibrium, irrespective of group size. This leads to substantial welfare effects. Achieved welfare is between 40 and 60 percent higher in games with neighborhood choice than without neighborhood choice. We identify exclusion as the simple but very effective mechanism underlying this result. In early rounds, high performers exclude low performers who in consequence ‘learn’ to become high performers.efficient coordination, weakest-link, minimum effort, neighborhood choice, experiment
The Paradoxical Content of the Title Son of Man
The problem with which this thesis will be occupied is the determination of the content of the title Son of Man and demonstrating the sources of this content. An investigation of this sort will prove that the content of Son of Man” is anything but simple; it is paradoxical. Since this title is Jesus\u27 favorite self-designation, writer and reader are justified to expect growth in the knowledge of our Lord and Savior, Jesus Christ.
Disorder- and Field-Induced Antiferromagnetism in Cuprate Superconductors
The underdoped high-Tc materials are characterized by a competition between
Cooper pairing and antiferromagnetic (AF) order. Important differences between
the superconducting (SC) state of these materials and conventional
superconductors include the d-wave pairing symmetry and a remarkable magnetic
response to nonmagnetic perturbations, whereby droplets of spin-density wave
(SDW) order can form around impurities and the cores of vortices. In a simple
picture, whenever SC is suppressed locally, SDW order is nucleated. Within a
mean-field theory of d-wave SC in an applied magnetic field including disorder
and Hubbard correlations, we show in fact that the creation of SDW order is not
simply due to suppression of the SC order parameter, but rather due to a
correlation-induced splitting of the electronic bound state created by the
perturbation. Since the bound state exists because of the sign change of the
order parameter along quasiparticle trajectories, the induced SDW order is a
direct consequence of the d-wave symmetry. Furthermore the formation of
anti-phase domain walls is important for obtaining the correct temperature
dependence of the induced magnetism as measured by neutron diffraction.Comment: 22 pages, 9 figure
Mapping of strongly correlated steady-state nonequilibrium to an effective equilibrium
By mapping steady-state nonequilibrium to an effective equilibrium, we
formulate nonequilibrium problems within an equilibrium picture where we can
apply existing equilibrium many-body techniques to steady-state electron
transport problems. We study the analytic properties of many-body scattering
states, reduce the boundary condition operator in a simple form and prove that
this mapping is equivalent to the correct linear-response theory. In an example
of infinite-U Anderson impurity model, we approximately solve for the
scattering state creation operators, based on which we derive the bias operator
Y to construct the nonequilibrium ensemble in the form of the Boltzmann factor
exp(-beta(H-Y)). The resulting Hamiltonian is solved by the non-crossing
approximation. We obtain the Kondo anomaly conductance at zero bias, inelastic
transport via the charge excitation on the quantum dot and significant
inelastic current background over a wide range of bias. Finally, we propose a
self-consistent algorithm of mapping general steady-state nonequilibrium.Comment: 15 pages, 9 figure
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