Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electronic excitation spectrum of metallic carbon nanotubes   We have studied the discrete electronic spectrum of closed metallic nanotube
quantum dots. At low temperatures, the stability diagrams show a very regular
four-fold pattern that allows for the determination of the electron addition
and excitation energies. The measured nanotube spectra are in excellent
agreement with theoretical predictions based on the nanotube band structure.
Our results permit the complete identification of the electron quantum states
in nanotube quantum dots.

23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin