Z2 massive axions, domain walls and inflation

We have analyzed a U(1) model which is broken explicitly to a Z2 model. The proposal results in generating two types of stable domain walls, in contrast with the more common NDW=1 version which is already used to explain axion invisibility for the UPQ(1) model. We have tried to take into account any possible relation with previous studies. We have studied some of the domain properties, proposing an approximate solution which satisfies boundary conditions and the static virial theorem, simultaneously. Invoking the mentioned approximation, we have been able to obtain an analytical insight about the effect of parameters on the domain wall features, particularly on their surface energy density which is of great importance in cosmological studies when one tries to avoid domain wall energy domination problem. Next, we have mainly focused on the likely inflationary scenarios resulting from the model, including saddle point inflation, again insisting on analytical discussions to be able to follow the role of parameters. We have tried to relate inflationary scenarios to the known categories to take advantage of the previous detailed studies under the inflationary topic over the decades. We have concluded that any successful inflationary scenario requires large fields within the present model. Calculations are mainly done analytically, although numerical results are also obtained to reinforce the analytical results.