**Cosmological Constant in Regge Quantum Gravity**

Abstract:

We will present a recent result regarding the cosmological constant problem.
In the framework of the piecewise-linear approaches to the construction of
the gravitational path integral, there are three contributions to the total
cosmological constant (CC): the bare term, the matter vacuum fluctuations
term, and the quantum gravity term. The existence of the quantum gravity
term is necessary due to the requirement of the finiteness of the
gravitational path integral, while its smallness is a nonperturbative
consequence of the semiclassical limit of the theory. As it turns out, one
can exactly cancel the bare term with the matter vacuum fluctuations term,
leaving the quantum gravity term as the sole contribution to CC, which is
moreover automatically small. This result opens the door to an alternative
explanation of the observed smallness of the cosmological constant.