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**Claim A** There exists and there are unit vectors such that

,

for each ,

where denotes the orthogonal projection.

Now, consider the vectors , and notice that

and therefore

for all I wonder if this kind of argument can be turned into a proof that FISP2 is a consequence of claim A. Notice that the spectral theorem can be applied to represent the unitary operator on the Hilbert space as a multiplication operator, that is, where is a measurable function and a.e.

It is clear that claim A has the following equivalent formulation:

**Claim B** There exists and there is a function such that

,

for each

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