Speaker
Description
Scalar fields are know to have various roles in the early Universe such as inflaton. Among of them, some real scalar fields are known to fragment into spatially localized and long-lived solitons called oscillons or I-balls. We prove the adiabatic invariance of the oscillons/I-balls for a potential that allows periodic motion even in the presence of non-negligible spatial gradient energy. We show that such potential is uniquely determined to be the quadratic one with a logarithmic correction, for which the oscillons/I-balls are absolutely stable. For slightly different forms of the scalar potential dominated by the quadratic one, the oscillons/I-balls are only quasi-stable, because the adiabatic charge is only approximately conserved. We check the conservation of the adiabatic charge of the I-balls in numerical simulation by slowly varying the coefficient of logarithmic corrections. This unambiguously shows that the longevity of oscillons/I-balls is due to the adiabatic invariance.
