Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A mystery of conformal coupling   An origin and necessity of so called conformal (or,Penrose-Chernikov-Tagirov)
coupling of scalar field to the metric of n-dimensional Riemannian space-time
is discussed in brief. The corresponding general-relativistic field equation
implies a one-particle (quantum mechanical) Schrodinger Hamiltonian which
depends on the space-time dimensionality n, contrary to the Hamiltonian
constructed by quantization of geodesic motion, which is the same for any value
of n. In general, the Hamiltonians can coincide only for n = 4, the
dimensionality of the ordinarily observed Universe. In view of the fundamental
role of a scalar field in various cosmological models, this fact may be of
interest for models of brane worlds where n > 4 .

1
The categories of this paper are: cs
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph