Take a pair of two disjoint nonpolar compact subsets
A and
B of the complex plane
C = $¥widehat{¥bf C}¥setminus${∞}, the complex sphere less the point at infinity, with connected complement $¥widehat{¥bf C}¥setminus$(
A ∪
B) and a simple arc γ in $¥widehat{¥bf C}¥setminus$(
A ∪
B). We form the two sheeted covering surface $¥widehat{¥bf C}$
γ of $¥widehat{¥bf C}$ by pasting $¥widehat{¥bf C}¥setminus$γ with another copy $¥widehat{¥bf C}¥setminus$γ crosswise along γ. Embed
A and
B in $¥widehat{¥bf C}$
γ either in the same sheet or in the different sheets and consider the variational 2-capacity cap(
A, $¥widehat{¥bf C}$
γ$¥setminus$
B) of
A contained in the open subset $¥widehat{¥bf C}$
γ$¥setminus$
B of $¥widehat{¥bf C}$
γ. Concerning the relation between the above capacity and the variational 2-capacity cap(
A, $¥widehat{¥bf C}¥setminus$
B) of
A contained in the open subset $¥widehat{¥bf C}¥setminus$
B of $¥widehat{¥bf C}$, we will establish the following capacity inequality for the two sheeted cover and its base:
0 < cap(
A, ¥widehat{¥bf C}$
γ$¥setminus$
B) < 2 · cap(
A, ¥widehat{¥bf C}¥setminus$
B),
where the bound 2 in the above inequality is the best possible in the sense that, for any 0<τ <2, there is a triple of
A,
B, and γ such that cap(
A, $¥widehat{¥bf C}$
γ$¥setminus$
B) > τ · cap(
A, $¥widehat{¥bf C}¥setminus$
B), where
A and
B may in the same sheet or in the different sheets.
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