Large-scale Lorentz Symmetry Violation And Effective Quintessence In String Landscape

Recently,Vafa et al.proposed two string Swampland criteria,and when studying the constraints imposed by the two string Swampland criteria on cosmology,they found that the inflationary models are generally difficult to be compatible with these two criteria.Applying these two criteria to the accelerated expansion of the universe during the current period,it was found that the specific quitesence model can satisfy these constraints while satisfying the constraints imposed by the current observations.Based on the cosmological model of the large-scale Lorentz violation,we obtained the modified Friedmann equation.Three feasible approximations are given in the calculation process,and an effective vacuum energy density is defined,which behaves as a monotonically decreasing quintessence potential energy for the string landscape,for most of the bare positive vacuum energy density in the swampland,the evolution of effective cosmological constant with time will show a local minimum.Comparing the calculated results of the distance modulus with the astronomical observations,we can get that a negative cosmological constant also accelerate the expansion of the universe.Therefore,it is not necessary to use the metastable de Sitter vacuum to explain the accelerated expansion of the late universe.The difficulty of incompatibility between the swampland model and the accelerated expansion of the late universe caused by the swampland conjecture will be eliminated.