Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Universality of Tip Singularity Formation in Freezing Water Drops   A drop of water deposited on a cold plate freezes into an ice drop with a
pointy tip. While this phenomenon clearly finds its origin in the expansion of
water upon freezing, a quantitative description of the tip singularity has
remained elusive. Here we demonstrate how the geometry of the freezing front,
determined by heat transfer considerations, is crucial for the tip formation.
We perform systematic measurements of the angles of the conical tip, and reveal
the dynamics of the solidification front in a Hele-Shaw geometry. It is found
that the cone angle is independent of substrate temperature and wetting angle,
suggesting a universal, self-similar mechanism that does not depend on the rate
of solidification. We propose a model for the freezing front and derive
resulting tip angles analytically, in good agreement with observations.

21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ