On an Equivalent Class of Norms for Bmo
نویسندگان
چکیده
The BMO norm of / is equivalent to sup (f\f(y)-u(x,t)\"Pt(x-y)dy\ , where Pt is the Poisson kernel. In this note, we show that Pt can be replaced by a nonnegative radial function h, which is positive in a neighbourhood of 0, with J h(x) dx = 1 and J rTM" (Inr)h(r) dr < oo, where h is the least decreasing radial majorant of h. 1980 Mathematics subject classification (Amer. Math. Soc): primary 42 B 30; secondary 42 B 99.
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