Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Simple Theory of Ionic Activity in Concentrated Electrolytes   The Debye-H\" uckel formula for ionic activity coefficients is extended for
concentrated solutions by solving a simple model of many-body Coulomb
correlations and adding the Born solvation energy. Given the bulk permittivity,
our formula is able to fit activity data for diverse electrolytes with only one
parameter to adjust the correlation length, which interpolates between the
Bjerrum length and the mean ion spacing. The results show that ionic activity
in most electrolytes is dominated by three types of electrostatic forces: (i)
mean-field charge screening, (ii) solvation, and (iii) Coulomb correlations,
both "over-screening" (charge oscillations) and "under-screening" (extending
beyond the Debye screening length).

24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys