Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Basic relations for the period variation models of variable stars   Models of period variations are basic tools for period analyzes of variable
stars. We introduce phase function and instant period and formulate basic
relations and equations among them. Some simple period models are also
presented.

8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph