Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: FIMP Dark Matter from Leptogenesis in Fast Expanding Universe   Within the framework of canonical type-I seesaw, a feebly interacting massive
particle (FIMP) $\chi$ is introduced as a dark matter candidate. The
leptogenesis mechanism and dark matter relic density share a common origin via
decays of Majorana neutrinos $N$. Provided an additional species $\varphi$
whose energy density red-shifts as $\rho_{\varphi}\propto a^{-(4+n)}$, the
Hubble expansion rate is larger than the standard scenario, i.e., the Universe
expands faster. The consequences of such a fast expanding Universe on
leptogenesis as well as FIMP dark matter are investigated in detail. We
demonstrate a significant impact on the final baryon asymmetry and dark matter
abundance due to the existence of $\varphi$ for the strong washout scenario.
While for the weak washout scenario, the effects of FEU are relatively small.
We introduce scale factors $F_L$ and $F_\chi$ to describe the corresponding
effects of FEU. A semi-analytical approach to derive the efficiency factors
$\eta_L$ and $\eta_\chi$ in FEU is also discussed. The viable parameter space
for success thermal leptogenesis and correct FIMP DM relic density is obtained
for standard cosmology and FEU. Our results show that it is possible to
distinguish different cosmology scenarios for strong washout cases.

17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th