Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Structure of Liquids: More order than expected   Disordered systems like liquids, gels, glasses, or granular materials are not
only ubiquitous in daily life and in industrial applications but they are also
crucial for the mechanical stability of cells or the transport of chemical and
biological agents in living organisms [1-3]. Despite the importance of these
systems, their microscopic structure is understood only on a rudimentary level,
thus in stark contrast to the case of gases and crystals [1,4]. Experimental
and theoretical investigations indicate that disordered systems have a
structural order on the length scale of a few particle diameters but which then
quickly vanishes at larger distances [5]. This conclusion is, however, based
mainly on the behavior of two-point correlation functions such as the static
structure factor or the radial distribution function [5.6]. Whether or not
disordered systems have an order that extents to larger length scales is
therefore a highly important question that is still open [7-10]. Here we use
computer simulations to show that liquids have an intricate structural order
given by alternating layers with icosahedral and dodecahedral symmetries and
which extends to surprisingly large distances. We show that the temperature
dependence of the corresponding length scale can be detected in the static
structure factor, making it directly accessible to scattering experiments.
These results, obtained by a novel type of four point correlation function that
probes directly the particle density in three dimensions, show that liquids are
far more ordered than envisaged so far but that this structural information is
encoded in non-standard correlation functions.

2
The categories of this paper are: math
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org