Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Classical and quantum massive string   The classical and the quantum massive string model based on a modified BDHP
action is analyzed in the range of dimensions $1<d<25$. The discussion
concerning classical theory includes a formulation of the geometrical
variational principle, a phase-space description of the two-dimensional
dynamics, and a detailed analysis of the target space geometry of classical
solutions. The model is quantized using "old" covariant method. In particular
an appropriate construction of DDF operators is given and the no-ghost theorem
is proved. For a critical value of one of free parameters of the model the
quantum theory acquires an extra symmetry not present on the classical level.
In this case the quantum model is equivalent to the noncritical Polyakov string
and to the old Fairlie-Chodos-Thorn massive string.

14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
6
The categories of this paper are: astro-ph