Background
Symmetries are a key concept in physics, and describe the invariance of a system under certain operations (for example, rotation). Breaking a symmetry refers to modifying the system in a way so that it is no longer invariant under the same operation.
A symmetry can be completely broken, or only partially broken with a lower symmetry remaining. For example: a circle always looks the same, regardless of the angle you rotate it by. A square also has a rotational symmetry, but you have to rotate by multiples of 90 degrees to get the same picture. Hence, the symmetry of the square is lower.
Question
In the scientific literature, people use the expression "to break down a symmetry" when referring to a reduction from high symmetry (circle) to a lower symmetry (square) as compared to a complete breaking (irregular shape). They might write
The original continuous symmetry was broken down to a symmetry under 90 degree rotations.
In my opinion, the expression "to break down" is not appropriate, because it means to separate into its parts or to destroy completely rather than to reduce to a smaller part. I would instead write
The original continuous symmetry was reduced to a symmetry under 90 degree rotations.
Does the use of "to break down" with this meaning deviate from the usual meaning of this phrase in other contexts?
Here are some examples, suggesting that the use of "to break down" in the sense of reducing to a smaller part is at least common in the field:
http://arxiv.org/pdf/0708.2115 (native speaker, authority in his field)
http://arxiv.org/pdf/1312.2934
http://www.science.uva.nl/~bais/broksym.pdf
http://en.wikipedia.org/wiki/W%E2%80%B2_and_Z%E2%80%B2_bosons