Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Negative Differential Conductivity in Carbon Nanotubes in the Presence
  of an External Electric Field   We study theoretically the electron transport properties in carbon nanotubes
under the influence of an external electric field E(t) using Boltzmann's
equation. The current-density equation is derived. Negative differential
conductivity is predicted when {\omega}{\tau}<<1 (quasi-static case). We
observed this in the neighbourhood where the constant electric field E_o is
equal to the amplitude of the AC electric field E_1 and the peak decreases with
increasing E_1. This phenomenon can also be used for the generation of
terahertz radiation without electric current instability.

25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
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The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an