Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Low-frequency Gravitational Wave Detection via Double Optical Clocks in
  Space   We propose a Doppler tracking system for gravitational wave detection via
Double Optical Clocks in Space (DOCS). In this configuration two spacecrafts
(each containing an optical clock) are launched to space for Doppler shift
observations. Compared to the similar attempt of gravitational wave detection
in the Cassini mission, the radio signal of DOCS that contains the relative
frequency changes avoids completely noise effects due for instance to
troposphere, ionosphere, ground-based antenna and transponder. Given the high
stabilities of the two optical clocks (Allan deviation $\sim 4.1\times
10^{-17}$ @ 1000 s), an overall estimated sensitivity of $5 \times 10^{-19}$
could be achieved with an observation time of 2 years, and would allow to
detect gravitational waves in the frequency range from $\sim 10^{-4}$ Hz to
$\sim 10^{-2}$ Hz.

29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph