Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Inherent directionality explains the lack of feedback loops in empirical
  networks   We explore the hypothesis that the relative abundance of feedback loops in
many empirical complex networks is severely reduced owing to the presence of an
inherent global directionality. Aimed at quantifying this idea, we propose a
simple probabilistic model in which a free parameter $\gamma$ controls the
degree of inherent directionality. Upon strengthening such directionality, the
model predicts a drastic reduction in the fraction of loops which are also
feedback loops. To test this prediction, we extensively enumerated loops and
feedback loops in many empirical biological, ecological and socio-
technological directed networks. We show that, in almost all cases, empirical
networks have a much smaller fraction of feedback loops than network
randomizations. Quite remarkably, this empirical finding is quantitatively
reproduced, for all loop lengths, by our model by fitting its only parameter
$\gamma$. Moreover, the fitted value of $\gamma$ correlates quite well with
another direct measurement of network directionality, performed by means of a
novel algorithm. We conclude that the existence of an inherent network
directionality provides a parsimonious quantitative explanation for the
observed lack of feedback loops in empirical networks.

37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an