Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Towards a microscopic construction of flavour vacua from a space-time
  foam model   The effect on flavour oscillations of simple expanding background
space-times, motivated by some D-particle foam models, is calculated for a
toy-model of bosons with flavour degrees of freedom. The presence of D-particle
defects in the space-time, which can interact non trivially (via particle
capture) with flavoured particles in a flavour non-preserving way, generates
mixing in the effective field theory of low-energy string excitations.
Moreover, the recoil of the D-particle defect during the capture/scattering
process implies Lorentz violation, which however may be averaged to zero in
isotropic D-particle populations, but implies non-trivial effects in
correlators. Both features imply that the flavoured mixed state sees a
non-trivial flavour (Fock-space) vacuum of a type introduced earlier by Blasone
and Vitiello in a generic context of theories with mixing. We discuss the
orthogonality of the flavour vacua to the usual Fock vacua and the effect on
flavour oscillations in these backgrounds. Furthermore we analyse the equation
of state of the Flavour vacuum, and find that, for slow expansion rates induced
by D particle recoil, it is equivalent to that of a cosmological constant. Some
estimates of these novel non-perturbative contribution to the vacuum energy are
made. The contribution vanishes if the mass difference and the mixing angle of
the flavoured states vanish.

32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs