We identify a new cosmological problem for models which solve the strong CP puzzle with an invisible axion, unrelated to the domain wall problem. Because the axion is very weakly coupled, the energy density stored in the oscillations of the classical axion field does not dissipate rapidly; it exceeds the critical density needed to close the universe unless fa <~ 1012 GeV, where fa is the ~lxion decay constant. If this bound is saturated, axions may comprise the dark matter of the universe.Ever since the discovery [ 1 ] of the CP-violating parameter 0 of the strong interactions, the small value of 0 has posed a serious puzzle. Current experimental limits [2] on the electric dipole moment of the neutron require [3] ~< 10 -9. The small value of O is naturally explained in models.with a spontaneously broken Peccei-Quinn symmetry [4], but the resulting axion [5] has not been seen. In a recently proposed variant of the Peccei-Quinn scheme [6,7], the axion mass and its couplings to ordinary matter are inversely proportional to the large vacuum expectation value fa of an [SU(2)

We propose a mechanism for stabilizing the size of the extra dimension in the Randall-Sundrum scenario. The potential for the modulus field that sets the size of the fifth dimension is generated by a bulk scalar with quartic interactions localized on the two 3-branes. The minimum of this potential yields a compactification scale that solves the hierarchy problem without fine tuning of parameters.Comment: 8 pages, LaTeX; minor typo correcte

We introduce a new and well defined power counting for the effective field theory describing nucleon-nucleon interactions. Because of the large N N scattering lengths it differs from other applications of chiral perturbation theory and is facilitated by introducing an unusual subtraction scheme and renormalization group analysis. Calculation to subleading order in the expansion can be done analytically, and we present the results for both the 1 S 0 and

No abstract

No abstract