Norms of Minimal Projections
نویسندگان
چکیده
منابع مشابه
Norms of Minimal Projections
It is proved that the projection constants of twoand three-dimensional spaces are bounded by 4/3 and (1 + √ 5)/2, respectively. These bounds are attained precisely by the spaces whose unit balls are the regular hexagon and dodecahedron. In fact, a general inequality for the projection constant of a real or complex n-dimensional space is obtained and the question of equality therein is discussed...
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It is shown that for many finite dimensional normed vector spaces V over C, a linear projection P : V → V will have nice structure if P + λ(I − P ) is an isometry for some complex unit not equal to one. From these results, one can readily determine the structure of bicircular projections, i.e., those linear projections P such that P + μ(I − P ) is a an isometry for every complex unit μ. The key...
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Given an n-tuple {a1, ..., an} of self-adjoint operators on an infinite dimensional Hilbert space H, we say that a projection p in B(H) is locally minimal for {a1, ..., an} if each pajp (for j = 1, ..., n) is a scalar multiple of p. In Theorem 1.8 we show that for any such {a1, ..., an} and any positive integer k there exists a projection p of rank k that is locally minimal for {a1, ..., an}. I...
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ژورنال
عنوان ژورنال: Journal of Functional Analysis
سال: 1994
ISSN: 0022-1236
DOI: 10.1006/jfan.1994.1010