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Denny H. Leung

Publications and source records attributed to Denny H. Leung.

43 records · Page 3Linked to original sources
arXiv1994

Isomorphic classification of atomic weak L^p spaces

Let $\msp$ be a measure space and let $1 < p < \infty$. The {\em weak $L^p$}\/ space $\wlp$ consists of all measurable functions $f$ such that \[ \|f\| = \sup_{t>0}t^{\frac{1}{p}}f^*(t) < \infty,\] where $f^*$ is the decreasing rearrangement of $|f|$. It is a Banach space under a norm which is equivalent to the expression above. In this paper, we pursue the problem of classifying weak $L^p$ spaces isomorphically when $\msp$ is purely atomic. It is also shown that if $\msp$ is a countably generated $σ$-finite measure space, then $\wlp$ (if infinite dimensional) must be isomorphic to either $\ell^\infty$ or $\seq$. The results of this article were presented at the conference in Columbia, Missouri in May, 1994.

math.FA↗
arXiv1994

Embedding Orlicz Sequence Spaces into $C(α)$

Let $M$ be a non-degenerate Orlicz function such that there exist $\ep > 0$ and $0 < s < 1$ with $\su M(\ep s^i)/M(s^i) < \infty$. It is shown that the Orlicz sequence space $h_M$ is isomorphic to a subspace of $C(\om^\om)$. It is also shown that for any non-degenerate Orlicz function $M$, $h_M$ does not embed into $C(\al)$ for any $\al < \om^\om$.

math.FA↗
arXiv1993

Some stability properties of $c_0$-saturated spaces

A Banach space is $c_0$-saturated if all of its closed infinite dimensional subspaces contain an isomorph of $c_0$. In this article, we study the stability of this property under the formation of direct sums and tensor products. Some of the results are: (1) a slightly more general version of the fact that $c_0$-sums of $c_0$-saturated spaces are $c_0$-saturated; (2) $C(K,E)$ is $c_0$-saturated if both $C(K)$ and $E$ are; (3) the tensor product $JH\tilde{\otimes}_εJH$ is $c_0$-saturated, where $JH$ is the James Hagler space.

math.FA↗
arXiv1993

Some isomorphically polyhedral Orlicz sequence spaces

A Banach space is polyhedral if the unit ball of each of its finite dimensional subspaces is a polyhedron. It is known that a polyhedral Banach space has a separable dual and is $c_0$-saturated, i.e., each closed infinite dimensional subspace contains an isomorph of $c_0$. In this paper, we show that the Orlicz sequence space $h_M$ is isomorphic to a polyhedral Banach space if $\lim_{t\to 0}M(Kt)/M(t) = \infty$ for some $K < \infty$. We also construct an Orlicz sequence space $h_M$ which is $c_0$-saturated, but which is not isomorphic to any polyhedral Banach space. This shows that being $c_0$-saturated and having a separable dual are not sufficient for a Banach space to be isomorphic to a polyhedral Banach space.

math.FA↗
arXiv1992

On $c_0$-saturated Banach spaces

A Banach space E is c_0-saturated if every closed infinite dimensional subspace of E contains an isomorph of c_0. A c_0-saturated Banach space with an unconditional basis which has a quotient space isomorphic to l^2 is constructed.

math.FA↗
arXiv1991

Banach spaces with Property (w)

A Banach space E is said to have Property (w) if every (bounded linear) operator from E into E' is weakly compact. We give some interesting examples of James type Banach spaces with Property (w). We also consider the passing of Property (w) from E to C(K,E).

math.FA↗