1,594 research outputs found
Sum-factorization techniques in Isogeometric Analysis
The fast assembling of stiffness and mass matrices is a key issue in
isogeometric analysis, particularly if the spline degree is increased. We
present two algorithms based on the idea of sum factorization, one for matrix
assembling and one for matrix-free methods, and study the behavior of their
computational complexity in terms of the spline order . Opposed to the
standard approach, these algorithms do not apply the idea element-wise, but
globally or on macro-elements. If this approach is applied to Gauss quadrature,
the computational complexity grows as instead of as
previously achieved.Comment: 34 pages, 8 figure
Quenching the XXZ spin chain: quench action approach versus generalized Gibbs ensemble
Following our previous work [PRL 113 (2014) 09020] we present here a detailed
comparison of the quench action approach and the predictions of the generalized
Gibbs ensemble, with the result that while the quench action formalism
correctly captures the steady state, the GGE does not give a correct
description of local short-distance correlation functions. We extend our
studies to include another initial state, the so-called q-dimer state. We
present important details of our construction, including new results concerning
exact overlaps for the dimer and q-dimer states, and we also give an exact
solution of the quench-action-based overlap-TBA for the q-dimer. Furthermore,
we extend our computations to include the xx spin correlations besides the zz
correlations treated previously, and give a detailed discussion of the
underlying reasons for the failure of the GGE, especially in the light of new
developments.Comment: 42 pages, 6 figures, revtex4-1 clas
Studying the Perturbed Wess-Zumino-Novikov-Witten SU(2)k Theory Using the Truncated Conformal Spectrum Approach
We study the Wess-Zumino-Novikov-Witten (WZNW) theory perturbed by
the trace of the primary field in the adjoint representation, a theory
governing the low-energy behaviour of a class of strongly correlated electronic
systems. While the model is non-integrable, its dynamics can be investigated
using the numerical technique of the truncated conformal spectrum approach
combined with numerical and analytical renormalization groups (TCSA+RG). The
numerical results so obtained provide support for a semiclassical analysis
valid at . Namely, we find that the low energy behavior is sensitive to
the sign of the coupling constant, . Moreover for this
behavior depends on whether is even or odd. With even, we find
definitive evidence that the model at low energies is equivalent to the massive
sigma model. For odd, the numerical evidence is more equivocal, but
we find indications that the low energy effective theory is critical.Comment: 30 pages, 19 eps figures, LaTeX2e file. Version 2: manuscript
accepted for publication; small changes in text and in one of the figure
Bacterial degradation of polychlorinted biphenyls in sludge from an industrial sewer lagoon
A laboratory experiment was conducted to determine if polychlorinated biphenyls (PCB's) found in an industrial sewer sludge can be effectively degraded by mutant bacteria. The aerated sludge was inoculated daily with mutant bacteria in order to augment the existing bacteria with bacteria that were considered to be capable of degrading PCB's. The pH, nitrogen, and phosphorus levels were monitored daily to maintain an optimum growing medium for the bacteria. A gas chromatographic method was used to determine the PCB concentrations of the sludge initially and also throughout the experiment. Results and discussion of the bacterial treatment of polychlorinated biphenyls are presented
The Polar Regions of Cassiopeia A: The Aftermath of a Gamma Ray Burst?
Probably not, but it is interesting nevertheless to investigate just how
close Cas A might have come to generating such an event. Focusing on the
northeast jet filaments, we analyze the polar regions of the recently acquired
very deep 1 Ms Chandra X-ray observation. We infer that the so-called "jet"
regions are indeed due to jets emanating from the explosion center, and not due
to polar cavities in the circumstellar medium at the time of explosion. We
place limits on the equivalent isotropic explosion energy in the polar regions
(around 2.3 x 10^52 ergs), and the opening angle of the x-ray emitting ejecta
(around 7 degrees), which give a total energy in the NE jet of order 10^50
ergs; an order of magnitude or more lower than inferred for "typical" GRBs.
While the Cas A progenitor and explosion exhibit many of the features
associated with GRB hosts, e.g. extensive presupernova mass loss and rotation,
and jets associated with the explosion, we speculate that the recoil of the
compact central object, with velocity 330 km/s, may have rendered the jet
unstable. In such cases the jet rapidly becomes baryon loaded, if not truncated
altogether. Although unlikely to have produced a gamma ray burst, the jets in
Cas A suggest that such outflows may be common features of core-collapse SNe.Comment: 35 pages, 7 figures, accepted by Ap
Particle Formation and Ordering in Strongly Correlated Fermionic Systems: Solving a Model of Quantum Chromodynamics
In this paper we study a (1+1)-dimensional version of the famous
Nambu-Jona-Lasinio model of Quantum Chromodynamics (QCD2) both at zero and
finite hadron density. We use non-perturbative techniques (non-Abelian
bosonization and Truncated Conformal Space Approach). At zero density we
describe a formation of fermion three-quark (nucleons and -baryons) and
boson (two-quark mesons, six-quark deuterons) bound states and also a formation
of a topologically nontrivial phase. At finite hadron density, the model has a
rich phase diagram which includes phases with density wave and superfluid
quasi-long-range (QLR) order and also a phase of a baryon Tomonaga-Luttinger
liquid (strange metal). The QLR order results as a condensation of scalar
mesons (the density wave) or six-quark bound states (deuterons).Comment: 31 pages, pdflatex file, 7 figures; typos corrected, the version from
Phys. Rev.
Exact Maximal Height Distribution of Fluctuating Interfaces
We present an exact solution for the distribution P(h_m,L) of the maximal
height h_m (measured with respect to the average spatial height) in the steady
state of a fluctuating Edwards-Wilkinson interface in a one dimensional system
of size L with both periodic and free boundary conditions. For the periodic
case, we show that P(h_m,L)=L^{-1/2}f(h_m L^{-1/2}) for all L where the
function f(x) is the Airy distribution function that describes the probability
density of the area under a Brownian excursion over a unit interval. For the
free boundary case, the same scaling holds but the scaling function is
different from that of the periodic case. Numerical simulations are in
excellent agreement with our analytical results. Our results provide an exactly
solvable case for the distribution of extremum of a set of strongly correlated
random variables.Comment: 4 pages revtex (two-column), 1 .eps figure include
Hello, Frisco! : I Called You Up To Say Hello!
https://digitalcommons.library.umaine.edu/mmb-vp/3149/thumbnail.jp
Altruistic CEOs can be as risky as greedy ones
The most successful leaders exhibit moderate self-interest, argue Katalin Takacs-Haynes, Matthew Josefy and Michael A. Hit
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