Is Cosmological Constant Needed in Higgs Inflation?
  The detection of B-mode shows a very powerful constraint to theoretical
inflation models through the measurement of the tensor-to-scalar ratio $r$.
Higgs boson is the most likely candidate of the inflaton field. But usually,
Higgs inflation models predict a small value of $r$, which is not quite
consistent with the recent results from BICEP2. In this paper, we explored
whether a cosmological constant energy component is needed to improve the
situation. And we found the answer is yes. For the so-called Higgs chaotic
inflation model with a quadratic potential, it predicts $r\approx 0.2$,
$n_s\approx0.96$ with e-folds number $N\approx 56$, which is large enough to
overcome the problems such as the horizon problem in the Big Bang cosmology.
The required energy scale of the cosmological constant is roughly $\Lambda \sim
(10^{14} \text{GeV})^2 $, which means a mechanism is still needed to solve the
fine-tuning problem in the later time evolution of the universe, e.g. by
introducing some dark energy component.
