Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Generalized polarizabilities and electroexcitation of the nucleon   Generalized nucleon polarizabilities for virtual photons can be defined in
terms of electroproduction cross sections as function of the 4-momentum
transfer $Q^2$. In particular, the sum of the generalized electric and magnetic
polarizabilities $\Sigma=\alpha+\beta$ and the spin polarizability $\gamma$ can
be expressed by virtual photon absorption cross sections integrated over the
excitation energy. These quantities have been calculated within the framework
of the recently developed unitary isobar model for pion photo- and
electroproduction on the proton, which describes the available experimental
data up to an excitation energy of about 1 GeV. Our results have been compared
to the predictions of chiral perturbation theory.

15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
16
The categories of this paper are: stat
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph