Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thermohaline mixing: A physical mechanism governing the photospheric
  composition of low-mass giants   Numerous spectroscopic observations provide compelling evidence for a
non-canonical mixing process that modifies the surface abundances of Li, C and
N of low-mass red giants when they reach the bump in the luminosity function.
Eggleton et al. (2006) have proposed that a molecular weight inversion created
by the 3He(3He,2p)4He reaction may be at the origin of this mixing, and relate
it to the Rayleigh-Taylor instability. In the present work we argue that one is
actually dealing with a double diffusive instability referred to as
thermohaline convection and we discuss its influence on the red giant branch.
We compute stellar models of various initial metallicities using the
prescription by Ulrich (1972) (extended to the case of a non-perfect gas) for
the turbulent diffusivity produced by the thermohaline instability in stellar
radiation zones. Thermohaline mixing simultaneously accounts for the observed
behaviour of the carbon isotopic ratio and of the abundances of Li, C and N on
the upper part of the red giant branch. It reduces significantly the 3He
production with respect to canonical evolution models as required by
measurements of 3He/H in galactic HII regions. Thermohaline mixing is a
fundamental physical process that must be included in stellar evolution
modeling.

36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org