http://dx.doi.org/10.4153/CJM-2012-006-2
Canad. J. Math. 65(2013), 559-574
Published:2012-05-17 Printed: Jun 2013
A. Ya. Helemskii, Faculty of Mechanics and Mathematics, Moscow State University, Moscow 119992 Russia
Features coming soon:
Citations (via CrossRef)
Tools:
Search Google Scholar:
Abstract
We define and study the so-called extreme version of the notion of a
projective normed module. The relevant definition takes into account
the exact value of the norm of the module in question, in contrast
with the standard known definition that is formulated in terms of norm
topology.
After the discussion of the case where our normed algebra $A$ is just
$\mathbb{C}$, we concentrate on the case of the next degree of complication,
where $A$ is a sequence algebra, satisfying some natural conditions.
The main results give a full characterization of extremely projective
objects within the subcategory of the category of non-degenerate
normed $A$--modules, consisting of the so-called homogeneous modules.
We consider two cases, `non-complete' and `complete', and the
respective answers turn out to be essentially different.
In particular, all Banach non-degenerate homogeneous modules,
consisting of sequences, are extremely projective within the category
of Banach non-degenerate homogeneous modules. However, neither of
them, provided it is infinite-dimensional, is extremely projective
within the category of all normed non-degenerate homogeneous modules.
On the other hand, submodules of these modules, consisting of finite
sequences, are extremely projective within the latter category.
© Canadian Mathematical Society, 2013
|