Solution

ID: past-exam-of-the-distribution-theory-course-of-the-university-of-oxford/2023/1/b/ii/solution

No. Consider the continuous even function
The formulas agree at , and at zero. Part (i) defines its even-weight principal-value distribution. However,
If this were a regular distribution represented by , testing on either side of zero would force almost everywhere there, by uniqueness of the locally integrable function representing a regular distribution. Changing the value at zero cannot remove the displayed divergence, contradicting local integrability of .
More generally, the exact condition is
Necessity is the preceding argument; sufficiency follows because is then a locally integrable function and its truncated integrals converge absolutely. The value alone provides no such rate of decay.

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