Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Investigating liquid surfaces down to the nanometer scale using grazing
  incidence x-ray scattering   Grazing incidence x-ray surface scattering has been used to investigate
liquid surfaces down to the molecular scale. The free surface of water is well
described by the capillary wave model (<z(q)z(-q)> ~ q-2 spectrum) up to
wavevectors > 10^8 m^-1. At larger wavevectors near-surface acoustic waves must
be taken into account. When the interface is bounded by a surfactant monolayer,
it exhibits a bending stiffness and the bending rigidity modulus can be
measured. However, bending effects generally cannot be described using the
Helfrich Hamiltonian and the characteristic exponent in the roughness power
spectrum can smaller than 4. Finally, upon compression, tethered monolayers
formed on a subphase containing divalent ions are shown to buckle in the third
dimension with a characteristic wavelength on the order of 10^8 m^-1.

37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
21
The categories of this paper are: adap-org