Today's #paperOfTheDay is "Why there is Nothing rather than something: A theory of the cosmological constant" from 1988. Like yesterday's paper, it deals with the intersection between quantum field theory and #generalRelativity, but the 30 years between them clearly show. Coleman's 1988 paper is an argument in the style of that time (which structurally is quite similar to much of the older #renormalon literature): Heuristic manipulations of formal objects such as the wave function of the universe, or divergent sums over all spacetime geometries. The outcome of this argument is that if #wormholes exist (caused by quantum effects at a scale that is much smaller than observations, but larger than the Planck scale), they can drive the cosmological constant to zero in an Euclidean path integral formulation of general relativity. As always with Coleman, the language is quite funny and frank about the paper's limitations: He writes "Although I find this theory in many ways very attractive, I must honestly stress its speculative character. It rests on wormhole dynamics and the Euclidean formulation of quantum gravity. This is doubly a house built on sand. [...] the Euclideon formulation of gravity is not a subject with firm foundations and clear rules of procedure; indeed, it is more like a trackless swamp". Observations like these have by now, 30 years later, led to a style of theoretical physics that is much more systematic and mathematical than in the 1980s, but also sometimes less intuitive. #dailyPaperChallenge https://doi.org/10.1016%2F0550-3213(88)90097-1