Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Absence of Vortex Lattice Melting in a Conventional Superconductor   The state of the vortex lattice extremely close to the superconducting to
normal transition in an applied magnetic field is investigated in high purity
niobium. We observe that thermal fluctuations of the order parameter broaden
the superconducting to normal transition into a crossover but no sign of a
first order vortex lattice melting transition is detected in measurements of
the heat capacity or the small angle neutron scattering (SANS) intensity.
Direct observation of the vortices via SANS always finds a well ordered vortex
lattice. The fluctuation broadening is considered in terms of the Lowest Landau
Level theory of critical fluctuations and scaling is found to occur over a
large H_{c2}(T) range.

13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
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
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn