  We have studied sidebranching induced by fluctuations in dendritic growth.
The amplitude of sidebranching induced by internal (equilibrium) concentration
fluctuations in the case of solidification with solutal diffusion is computed.
This amplitude turns out to be significantly smaller than values reported in
previous experiments.The effects of other possible sources of fluctuations (of
an external origin)are examined by introducing non-conserved noise in a
phase-field model. This reproduces the characteristics of sidebranching found
in experiments. Results also show that sidebranching induced by external noise
is qualitatively similar to that of internal noise, and it is only
distinguished by its amplitude.
