Understand
We investigate some cosmological consequences of a vector-tensor theory where an Abelian symmetry in the vector sector is slightly broken by a mass term and by ghost-free derivative self-interactions.
- When studying cosmological expansion in the presence of large bare cosmological constant $\Lambda_{cc}$, we find that the theory admits branches of de Sitter solutions in which the scale of the Hubble parameter is inversely proportional to a power of $\Lambda_{cc}$.
- Hence, a large value of $\Lambda_{cc}$ leads to a small size for the Hubble scale.
- In an appropriate limit, in which the symmetry breaking parameters are small, the theory recovers the Abelian symmetry plus an additional Galileon symmetry acting on the longitudinal vector polarization.
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