Transverse breathing mode of an elongated Bose-Einstein condensate.

We study experimentally the transverse monopole mode of an elongated rubidium condensate. Because of the scaling invariance of the nonlinear Schrödinger (Gross-Pitaevskii) equation, the oscillation is monochromatic and sinusoidal at short times, even under strong excitation. For ultralow temperatures, the quality factor Q = omega(0)/gamma(0) can exceed 2000, where omega(0) and gamma(0) are the mode angular frequency and damping rate. This value is much larger than any previously reported for other eigenmodes of a condensate. We also present the temperature variation of omega(0) and gamma(0).