Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On a Second Critical Point in the First Order Metal - Insulator
  Transitions   For the first order Metal Insulator Transitions we show that together with
the d.c conductance zero there is a second critical point, where the dielectric
constant becomes zero and further turns negative. At this point the metallic
reflectivity sharply increases. The two points can be separated by a Phase
Separation State in a 3D disordered system, but may tend to merge in 2D. For
illustration we evaluate the dielectric function in a simple effective medium
approximation and show that at the second point it turns negative. We reproduce
the experimental data on a typical Mott insulator like MnO, demonstrating the
presence of the two points clearly. We discuss other experiments for studies of
the phase separation state and a similar phase separation in superconductors
with insulating inclusions.

20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
2
The categories of this paper are: math
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin