The singular support of a generalized function 
is the complement of the largest open
set on which 
is smooth. Roughly speaking, it is the closed
set where the distribution does not correspond to a smooth
function.
Singular Support
See also
Fourier Transform, Generalized Function, SupportThis entry contributed by Todd Rowland
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References
Folland, G. B. Introduction to Partial Differential Equations, 2nd ed. Princeton, NJ: Princeton University Press, 1996.Referenced on Wolfram|Alpha
Singular SupportCite this as:
Rowland, Todd. "Singular Support." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/SingularSupport.html