Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Towards a Model of Quarks and Leptons   We propose an extra-dimension framework on the orbifold $S^1/Z_2$ for
understanding the origin of the fermion mass and mixing hierarchies.
Introducing the flavor symmetry $G_F(=${\it non-Abelian}$\times${\it Abelian})
as well as the extra gauged $U(1)$ symmetries through the bulk, we regard the
$SU(2)$ singlet and doublet fermions in the Standard Model (SM) to be localized
at the separate 3-branes and let the extra $SU(2)$ singlet flavored fermions in
the bulk couple to the SM fermions at the 3-branes. The extra $U(1)$ symmetries
satisfy the $U(1)$ gravitational anomaly-free condition, playing a crucial role
in achieving the desirable fermion mass and mixing hierarchies and making the
flavored axion naturally light.
  The singlet scalar fields, the flavon fields, are responsible for the
spontaneous breaking of $G_F$ on the two 3-branes, while the $SU(2)$ singlet
flavored fermions are integrated out to give rise to the effective Yukawa
couplings for the SM fermions, endowed with the information of $G_F$ breaking
in the two sectors. The flavored axion from the PQ symmetry is also proposed
for solving the strong CP problem and being a dark matter candidate in our
model.

11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph