Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pyroelectric vector and related polarization effects   The principal fact that the pyroelectric vector $\Pb^0$ typical of polar
crystals is invisible in equilibrium has been verified. Nevertheless, the
general formula for $\Pb^0$ as a definite bulk quantity associated only with
the inversion properties of a given charge distribution in the bulk has been
obtained. Its application to ferroelectric perovskites BaTiO$_3$, PbTiO$_3$,
and KNbO$_3$ is discussed.

33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn