S. Coleman, "Why there is nothing rather than something: a theory of the cosmological constant," Nuclear Physics B, 310, 643-68, 12 December 1988.
Sidney Coleman (Harvard University, Cambridge, Mass.): "The cosmological constant is a quantity that appears in Einstein's gravitational field equations. It can be thought of as the energy density of the ground state of quantum field theory, empty space. Experiment gives an upper bound on the constant (consistent with it vanishing altogether). Rough theoretical estimates predict a value several dozen orders of magnitude greater than the experimental upper bound. This is possibly the worst prediction in 20th-century physics and has been an embarrassment for many years.
"My paper extended earlier work by Hawking and Linde to offer a novel theory of the vanishing of the cosmological constant. The theory was (and is) highly speculative and I'm not sure why it has received so much more attention...