On a problem of H. Berens

Notes on a Problem of H. Cohn

✍ András Biró 📂 Article 📅 1999 🏛 Elsevier Science 🌐 English ⚖ 103 KB

We prove some partial results concerning the following problem: Assume that F is a finite field, a i is a complex number for each i # F such that a 0 =0, a 1 =1, |a i | =1 for all i # F "[0], and i # F a i+j aÄ i =&1 for all i # F "[0]. Does it follow that the function i Ä a i is a multiplicative ch

On a problem of H.-G. Steiner

✍ Hans Zassenhaus 📂 Article 📅 1970 🏛 Elsevier Science 🌐 English ⚖ 269 KB

On a problem of M. H. Stone

✍ G. Grätzer; E. T. Schmidt 📂 Article 📅 1957 🏛 Akadmiai Kiad 🌐 English ⚖ 280 KB

On a problem of H. N. Gupta

✍ Andreas Blass; Victor Pambuccian 📂 Article 📅 1996 🏛 Springer 🌐 English ⚖ 127 KB

It is shown that the axiom 'For any points x, y, z such that y is between x and z, there is a right triangle having x and z as endpoints of the hypotenuse and y as foot of the altitude to the hypotenuse', when added to three-dimensional Euclidean geometry over arbitrary ordered fields, is weaker tha

On a Problem of D. H. Lehmer

✍ Hua Ning Liu; Wen Peng Zhang 📂 Article 📅 2005 🏛 Institute of Mathematics, Chinese Academy of Scien 🌐 English ⚖ 150 KB

A Problem in Linear Matrix Approximation

✍ H. Berens; M. Finzel 📂 Article 📅 1995 🏛 John Wiley and Sons 🌐 English ⚖ 560 KB

## Abstract Let __A__ be a normal operator in ℬ︁(H), H a complex Hilbert space, and let ℛ ~A~ = ≷ {__AX__ ‐ __XA:X ∈ ℬ︁__(__H__)} be the commutator subspace of ℬ︁(__H__) associated with __A__. If __B__ in ℬ︁(__H__) commutes with __A__, then __B__ is orthogonal to ℛ~A~ with respect to the spectral n