Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structural Transition Models for a class of Irreversible Aggregates   A progress report on two recent theoretical approaches proposed to understand
the physics of irreversible fractal aggregates showing up a structural
transition from a rather dense to a more multibranched growth is presented. In
the first approach the transition is understood by solving the Poisson equation
on a squared lattice. The second approach is based on the discretization of the
Biharmonic equation. Within these models the transition appears when the growth
velocity at the fractal surface presents a minimum. The effects of the
surrounding medium and geometrical constraints for the seed particles are
considered. By using the optical diffraction method, the structural transition
is further characterized by a decrease in the fractal dimension for this
peculiar class of aggregates.

19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph