The couplings of a light scalar to ordinary matter induce non-vanishing fields φ inside and around stars. In turn, the masses and couplings of ordinary particles depend on φ in general. Thus, fundamental coupling constants can be altered by dense matter nearby. We estimate the resulting effect on the cooling of neutron stars, the neutrino burst from supernova 1987 A and the period of the pulsar recently discovered in its remnant, and obtain bounds on the mass and couplings of scalar particles. We also comment on cosmological and other constraints on such scalar particles, and discuss in particular bounds on the mass of the dilaton in string theories.
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One of the authors( C.W.) would like to thankt he memberosf lTP for the kind hospitalitiyn SantaB ar-bara,w herep arto f this work wasp erformeadn dsup-portedb y the National ScienceF oundationu nder Grant No. PHY82-17853,s upplementebdy funds from the National Aeronautics and Space Administration.