Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Analytical solution of the dynamical spherical MIT bag   We prove that when the bag surface is allowed to move radially, the equations
of motion derived from the MIT bag Lagrangian with massless quarks and a
spherical boundary admit only one solution, which corresponds to a bag
expanding at the speed of light. This result implies that some new physics
ingredients, such as coupling to meson fields, are needed to make the dynamical
bag a consistent model of hadrons.

9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat
18
The categories of this paper are: econ
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg