65 research outputs found
Dynamical Scaling Behavior of Percolation Clusters in Scale-free Networks
In this work we investigate the spectra of Laplacian matrices that determine
many dynamic properties of scale-free networks below and at the percolation
threshold. We use a replica formalism to develop analytically, based on an
integral equation, a systematic way to determine the ensemble averaged
eigenvalue spectrum for a general type of tree-like networks. Close to the
percolation threshold we find characteristic scaling functions for the density
of states rho(lambda) of scale-free networks. rho(lambda) shows characteristic
power laws rho(lambda) ~ lambda^alpha_1 or rho(lambda) ~ lambda^alpha_2 for
small lambda, where alpha_1 holds below and alpha_2 at the percolation
threshold. In the range where the spectra are accessible from a numerical
diagonalization procedure the two methods lead to very similar results.Comment: 9 pages, 6 figure
Scaling Properties of Random Walks on Small-World Networks
Using both numerical simulations and scaling arguments, we study the behavior
of a random walker on a one-dimensional small-world network. For the properties
we study, we find that the random walk obeys a characteristic scaling form.
These properties include the average number of distinct sites visited by the
random walker, the mean-square displacement of the walker, and the distribution
of first-return times. The scaling form has three characteristic time regimes.
At short times, the walker does not see the small-world shortcuts and
effectively probes an ordinary Euclidean network in -dimensions. At
intermediate times, the properties of the walker shows scaling behavior
characteristic of an infinite small-world network. Finally, at long times, the
finite size of the network becomes important, and many of the properties of the
walker saturate. We propose general analytical forms for the scaling properties
in all three regimes, and show that these analytical forms are consistent with
our numerical simulations.Comment: 7 pages, 8 figures, two-column format. Submitted to PR
Critical Exponents from Five-Loop Strong-Coupling phi^4-Theory in 4- epsilon Dimensions
With the help of strong-coupling theory, we calculate the critical exponents
of O(N)-symmetric phi^4-theories in 4- epsilon dimensions up to five loops with
an accuracy comparable to that achieved by Borel-type resummation methods.Comment: Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
paper also at http://www.physik.fu-berlin.de/~kleinert/29
Self-avoiding walks and connective constants in small-world networks
Long-distance characteristics of small-world networks have been studied by
means of self-avoiding walks (SAW's). We consider networks generated by
rewiring links in one- and two-dimensional regular lattices. The number of
SAW's was obtained from numerical simulations as a function of the number
of steps on the considered networks. The so-called connective constant,
, which characterizes the long-distance
behavior of the walks, increases continuously with disorder strength (or
rewiring probability, ). For small , one has a linear relation , and being constants dependent on the underlying
lattice. Close to one finds the behavior expected for random graphs. An
analytical approach is given to account for the results derived from numerical
simulations. Both methods yield results agreeing with each other for small ,
and differ for close to 1, because of the different connectivity
distributions resulting in both cases.Comment: 7 pages, 5 figure
Invaded cluster simulations of the XY model in two and three dimensions
The invaded cluster algorithm is used to study the XY model in two and three
dimensions up to sizes 2000^2 and 120^3 respectively. A soft spin O(2) model,
in the same universality class as the 3D XY model, is also studied. The static
critical properties of the model and the dynamical properties of the algorithm
are reported. The results are K_c=0.45412(2) for the 3D XY model and
eta=0.037(2) for the 3D XY universality class. For the 2D XY model the results
are K_c=1.120(1) and eta=0.251(5). The invaded cluster algorithm does not show
any critical slowing for the magnetization or critical temperature estimator
for the 2D or 3D XY models.Comment: 30 pages, 11 figures, problem viewing figures corrected in v
Practitioner’s Section: Integrated Resource Efficiency Analysis for Reducing Climate Impacts in the Chemical Industry
Reducing greenhouse gas emissions of the material-intensive chemical industry requires an integrated analysis and optimization of the complex production systems including raw material and energy use, resulting costs and environmental and climate impacts. To meet this challenge, the research project InReff (Integrated Resource Efficiency Analysis for Reducing Climate Impacts in the Chemical Industry) has been established. It aims at the development of an IT-supported modeling and evaluation framework which is able to comprehensively address issues of resource efficiency and climate change within the chemical industry, e.g. the minimization of material and energy intensity and consequently greenhouse gas emissions, without compromising on production performance. The paper presents background information on resource efficiency and the research project, an ideal-typical decision model for resource efficiency analysis, the conceptual approach for an IT-based integration platform as well as the case study design at the industrial project partners’ sites. These first results are linked to future activities and further research questions are highlighted in the concluding section
Crossover phenomena in spin models with medium-range interactions and self-avoiding walks with medium-range jumps
We study crossover phenomena in a model of self-avoiding walks with
medium-range jumps, that corresponds to the limit of an -vector
spin system with medium-range interactions. In particular, we consider the
critical crossover limit that interpolates between the Gaussian and the
Wilson-Fisher fixed point. The corresponding crossover functions are computed
using field-theoretical methods and an appropriate mean-field expansion. The
critical crossover limit is accurately studied by numerical Monte Carlo
simulations, which are much more efficient for walk models than for spin
systems. Monte Carlo data are compared with the field-theoretical predictions
concerning the critical crossover functions, finding a good agreement. We also
verify the predictions for the scaling behavior of the leading nonuniversal
corrections. We determine phenomenological parametrizations that are exact in
the critical crossover limit, have the correct scaling behavior for the leading
correction, and describe the nonuniversal lscrossover behavior of our data for
any finite range.Comment: 43 pages, revte
Efficacy and Toxicity of Different Chemotherapy Protocols for Concurrent Chemoradiation in Non-Small Cell Lung Cancer—A Secondary Analysis of the PET Plan Trial
(1) Background: The optimal chemotherapy (CHT) regimen for concurrent chemoradiation
(cCRT) is not well defined. In this secondary analysis of the international randomized PET-Plan
trial, we evaluate the efficacy of different CHT. (2) Methods: Patients with inoperable NSCLC
were randomized at a 1:1 ratio regarding the target volume definition and received isotoxically
dose-escalated cCRT using cisplatin 80 mg/m2
(day 1, 22) and vinorelbin 15 mg/m2
(day 1, 8, 22, 29)
(P1) or cisplatin 20 mg/m2
(day 1–5, 29–33) and vinorelbin 12.5 mg/m2
(day 1, 8, 15, 29, 36, 43) (P2) or
carboplatin AUC1 (day 1–5, 29–33) and vinorelbin 12.5 mg/m2
(day 1, 8, 15, 29, 36, 43) (P3) or other
CHT at the treating physician’s discretion. (3) Results: Between 05/2009 and 11/2016, 205 patients
were randomized and 172 included in the per-protocol analysis. Patients treated in P1 or P2 had a
better overall survival (OS) compared to P3 (p = 0.015, p = 0.01, respectively). Patients treated with
carboplatin had a worse OS compared to cisplatin (HR 1.78, p = 0.03), but the difference did not
remain significant after adjusting for age, ECOG, cardiac function creatinine and completeness of
CHT. (4) Conclusions: Carboplatin doublets show no significant difference compared to cisplatin,
after adjusting for possibly relevant factors, probably due to existing selection bias
Critical behavior of the three-dimensional XY universality class
We improve the theoretical estimates of the critical exponents for the
three-dimensional XY universality class. We find alpha=-0.0146(8),
gamma=1.3177(5), nu=0.67155(27), eta=0.0380(4), beta=0.3485(2), and
delta=4.780(2). We observe a discrepancy with the most recent experimental
estimate of alpha; this discrepancy calls for further theoretical and
experimental investigations. Our results are obtained by combining Monte Carlo
simulations based on finite-size scaling methods, and high-temperature
expansions. Two improved models (with suppressed leading scaling corrections)
are selected by Monte Carlo computation. The critical exponents are computed
from high-temperature expansions specialized to these improved models. By the
same technique we determine the coefficients of the small-magnetization
expansion of the equation of state. This expansion is extended analytically by
means of approximate parametric representations, obtaining the equation of
state in the whole critical region. We also determine the specific-heat
amplitude ratio.Comment: 61 pages, 3 figures, RevTe
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