Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A mechanism for evolution of the physical concepts network   We suggest an underlying mechanism that governs the growth of a network of
concepts, a complex network that reflects the connections between different
scientific concepts based on their co-occurrences in publications. To this end,
we perform empirical analysis of a network of concepts based on the preprints
in physics submitted to the arXiv.org. We calculate the network characteristics
and show that they cannot follow as a result of several simple commonly used
network growth models. In turn, we suggest that a simultaneous account of two
factors, i.e., growth by blocks and preferential selection, gives an
explanation of empirically observed properties of the concepts network.
Moreover, the observed structure emerges as a synergistic effect of these both
factors: each of them alone does not lead to a satisfactory picture.

4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph