  With no free parameter (except the string scale $M_S$), dynamical flux
compactification in Type IIB string theory determines both the cosmological
constant (vacuum energy density) $\Lambda$ and the Planck mass $M_P$ in terms
of $M_S$, thus yielding their relation. Following elementary probability
theory, we find that a good fraction of the meta-stable de Sitter vacua in the
cosmic string theory landscape tend to have an exponentially small cosmological
constant $\Lambda$ compared to either the string scale $M_S$ or the Planck
scale $M_P$, i.e., $\Lambda \ll M_S^4 \ll M_P^4$. Here we illustrate the basic
stringy ideas with a simple scalar field $\phi^3$ (or $\phi^4$) model coupled
with fluxes to show how this may happen and how the usual radiative instability
problem is bypassed (since there are no parameters to be fine-tuned). These low
lying semi-classical de Sitter vacua tend to be accompanied by light scalar
bosons/axions, so the Higgs boson mass hierarchy problem may be ameliorated as
well.
