Path Integral For Quantum Gravity Research Articles

Why is the cosmological constant small?

I argue that singular metrics with finite action should be allowed in the path integral of quantum gravity. The path integral over such conformally flat configurations is studied. It is shown that the system is equivalent to a Coulomb gas. The cosmological constant acts as a charge density in thin gas. Due to Debye screening, the effective cosmological constant at macroscopic distances is very small. Quantum gravity may thus explain the vanishing of the cosmological constant.

The scattering of spin-1 particles by quantum gravitational bubbles

Quantum gravitational bubbles may be used to obtain a non-perturbative approximation to the path integral of quantum gravity. There are three basic types of bubblesCP 2,S 2 ×S 2, andK3, and in this paper the propagation of elementary spin-1 particles inCP 2 is investigated. To date information about the propagation of particles other than scalars has been obtained by making approximations to the basic bubble types. The work presented here represents the first exact calculation. It is found that spin-1 particles scatter very strongly, particularly at low energies, which is at odds with both physical observation and the earlier work on this subject. Possible explanations for this discrepancy are offered.