4,126 research outputs found
Subgraph covers -- An information theoretic approach to motif analysis in networks
Many real world networks contain a statistically surprising number of certain
subgraphs, called network motifs. In the prevalent approach to motif analysis,
network motifs are detected by comparing subgraph frequencies in the original
network with a statistical null model. In this paper we propose an alternative
approach to motif analysis where network motifs are defined to be connectivity
patterns that occur in a subgraph cover that represents the network using
minimal total information. A subgraph cover is defined to be a set of subgraphs
such that every edge of the graph is contained in at least one of the subgraphs
in the cover. Some recently introduced random graph models that can incorporate
significant densities of motifs have natural formulations in terms of subgraph
covers and the presented approach can be used to match networks with such
models. To prove the practical value of our approach we also present a
heuristic for the resulting NP-hard optimization problem and give results for
several real world networks.Comment: 10 pages, 7 tables, 1 Figur
Non-Perturbative U(1) Gauge Theory at Finite Temperature
For compact U(1) lattice gauge theory (LGT) we have performed a finite size
scaling analysis on lattices for fixed by
extrapolating spatial volumes of size to . Within the
numerical accuracy of the thus obtained fits we find for , 5 and~6
second order critical exponents, which exhibit no obvious
dependence. The exponents are consistent with 3d Gaussian values, but not with
either first order transitions or the universality class of the 3d XY model. As
the 3d Gaussian fixed point is known to be unstable, the scenario of a yet
unidentified non-trivial fixed point close to the 3d Gaussian emerges as one of
the possible explanations.Comment: Extended version after referee reports. 6 pages, 6 figure
A Gravitational Redshift Determination of the Mean Mass of White Dwarfs. DBA and DB Stars
We measure apparent velocities (v_app) of absorption lines for 36 white
dwarfs (WDs) with helium-dominated atmospheres -- 16 DBAs and 20 DBs -- using
optical spectra taken for the European Southern Observatory SN Ia progenitor
survey (SPY). We find a difference of 6.9+/-6.9 km/s in the average apparent
velocity of the H-alpha lines versus that of the HeI 5876AA for our DBAs. This
is a measure of the blueshift of this He line due to pressure effects. By using
this as a correction, we extend the gravitational redshift method employed by
Falcon et al. (2010) to use the apparent velocity of the HeI 5876AA line and
conduct the first gravitational redshift investigation of a group of WDs
without visible hydrogen lines. We use biweight estimators to find an average
apparent velocity, _BI, (and hence average gravitational redshift,
_BI) for our WDs; from that we derive an average mass, _BI. For the
DBAs, we find _BI = 40.8+/-4.7 km/s and derive _BI = 0.71 +0.04 -0.05
Msun. Though different from of DAs (32.57 km/s) at the 91% confidence
level and suggestive of a larger DBA mean mass than that for normal DAs derived
using the same method (0.647 +0.013 -0.014 Msun; Falcon et al. 2010), we do not
claim this as a stringent detection. Rather, we emphasize that the difference
between _BI of the DBAs and of normal DAs is no larger than 9.2
km/s, at the 95% confidence level; this corresponds to roughly 0.10 Msun. For
the DBs, we find ^He_BI = 42.9+/-8.49 km/s after applying the blueshift
correction and determine _BI = 0.74 +0.08 -0.09 Msun. The difference between
^He_BI of the DBs and of DAs is less than or equal to 11.5 km/s
(~0.12 Msun), at the 95% confidence level. The gravitational redshift method
indicates much larger mean masses than the spectroscopic determinations of the
same sample by Voss et al. (2007)...Comment: Accepted to the Astrophysical Journal, 10 pages double-column, 3
figures, 5 table
Waste management based on circular economy principles
Waste management has strategic implications in contemporary world. The demand in combination of economic development with environmental safety is urging to focus on capacities of non-linear economy. Waste management should redirect its efforts to reduction, recycling and treatment techniques, which view the wastes as resources. The goal of this paper is to study theoretical and practical issues of waste management based on circular economy principles from perspective of cross-disciplinary eco-economic collaboration. © 2020 The Authors, published by EDP Sciences.Russian Foundation for Basic Research, РФФР: 20 -010-00558“ The reported study was funded by RFBR, project number 20 -010-0055
Wither the sliding Luttinger liquid phase in the planar pyrochlore
Using series expansion based on the flow equation method we study the zero
temperature properties of the spin-1/2 planar pyrochlore antiferromagnet in the
limit of strong diagonal coupling. Starting from the limit of decoupled crossed
dimers we analyze the evolution of the ground state energy and the elementary
triplet excitations in terms of two coupling constants describing the inter
dimer exchange. In the limit of weakly coupled spin-1/2 chains we find that the
fully frustrated inter chain coupling is critical, forcing a dimer phase which
adiabatically connects to the state of isolated dimers. This result is
consistent with findings by O. Starykh, A. Furusaki and L. Balents (Phys. Rev.
B 72, 094416 (2005)) which is inconsistent with a two-dimensional sliding
Luttinger liquid phase at finite inter chain coupling.Comment: 6 pages, 4 Postscript figures, 1 tabl
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