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Approximately orthogonality preserving mappings on Hilbert C_{0}(Z)-modules
In this paper, we will use the categorical approach to
Hilbert (C^{ast})-modules over a commutative (C^{ast})-algebra
to investigate the approximately orthogonality preserving mappings
on Hilbert (C^{ast})-modules over a commutative
(C^{ast})-algebra.
Indeed, we show that if (Psi:Gamma rightarrow Gamma^{prime}
) is a nonzero ( C_{0}(Z) )-linear
(( delta , varepsilon))-orthogonality preserving mapping
between the continuous fields of Hilbert spaces on a locally
compact Hausdorff space (Z), then (Psi) is injective, continuous
and also for every ( x, y in Gamma ) and (z in Z),
[
vert
langle Psi(x),Psi(y) rangle(z) - varphi^2(z) langle x,y
rangle(z) vert leq frac{4(varepsilon -
delta)}{(1-delta)(1+varepsilon)} Vert Psi(x) Vert Vert
Psi(y) Vert,
]
where (varphi(z) = sup { Vert Psi(u)(z)
Vert : u ~ text{is a unit vector in} ~ Gamma })