Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Protoplanetary disc `isochrones' and the evolution of discs in the
  $\dot{M}-M_{\rm d}$ plane   In this paper, we compare simple viscous diffusion models for the disc
evolution with the results of recent surveys of the properties of young
protoplanetary discs. We introduce the useful concept of `disc isochrones' in
the accretion rate - disc mass plane and explore a set of Montecarlo
realization of disc initial conditions. We find that such simple viscous models
can provide a remarkable agreement with the available data in the Lupus star
forming region, with the key requirement that the average viscous evolutionary
timescale of the discs is comparable to the cluster age. Our models produce
naturally a correlation between mass accretion rate and disc mass that is
shallower than linear, contrary to previous results and in agreement with
observations. We also predict that a linear correlation, with a tighter
scatter, should be found for more evolved disc populations. Finally, we find
that such viscous models can reproduce the observations in the Lupus region
only in the assumption that the efficiency of angular momentum transport is a
growing function of radius, thus putting interesting constraints on the nature
of the microscopic processes that lead to disc accretion.

11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
23
The categories of this paper are: solv-int