Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Negative permeability in magnetostatics and its experimental
  demonstration   The control of magnetic fields, essential for our science and technology, is
currently achieved by magnetic materials with positive permeability, including
ferromagnetic, paramagnetic, and diamagnetic types. Here we introduce materials
with negative static permeability as a new paradigm for manipulating magnetic
fields. As a first step, we extend the solutions of Maxwell magnetostatic
equations to include negative-permeability values. The understanding of these
new solutions allow us to devise a negative-permeability material as a suitably
tailored set of currents arranged in space, overcoming the fact that passive
materials with negative permeability do no exist in magnetostatics. We confirm
the theory by experimentally creating a spherical shell that emulates a
negative-permeability material in a uniform magnetic field. Our results open
new possibilities for creating and manipulating magnetic fields, which can be
useful for practical applications.

2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th