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1.
Luis Paris 《Proceedings of the American Mathematical Society》1997,125(3):731-738
Let be a Coxeter system, and let be a subset of . The subgroup of generated by is denoted by and is called a parabolic subgroup. We give the precise definition of the commensurator of a subgroup in a group. In particular, the commensurator of in is the subgroup of in such that has finite index in both and . The subgroup can be decomposed in the form where is finite and all the irreducible components of are infinite. Let be the set of in such that for all . We prove that the commensurator of is . In particular, the commensurator of a parabolic subgroup is a parabolic subgroup, and is its own commensurator if and only if .
2.
P. N. Dowling W. B. Johnson C. J. Lennard B. Turett 《Proceedings of the American Mathematical Society》1997,125(1):167-174
A renorming of , explored here in detail, shows that the copies of produced in the proof of the Kadec-Pelczynski theorem inside nonreflexive subspaces of cannot be produced inside general nonreflexive spaces that contain copies of . Put differently, James's distortion theorem producing one-plus-epsilon-isomorphic copies of inside any isomorphic copy of is, in a certain sense, optimal. A similar renorming of shows that James's distortion theorem for is likewise optimal.
3.
Let be given. For any we construct a function having the following properties: (a) has support in . (b) . (c) If denotes the Haar function and , then . (d) generates an affine Riesz basis whose frame bounds (which are given explicitly) converge to as .
4.
Michael E. Taylor 《Proceedings of the American Mathematical Society》1997,125(6):1711-1716
We show that, if is the representation of on given by (2.11), and is a bounded operator on , then belongs to if and only if
is a function on with values in the Banach space .
5.
H. Aimar L. Forzani F. J. Martí n-Reyes 《Proceedings of the American Mathematical Society》1997,125(7):2057-2064
In this note we consider singular integrals associated to Calderón-Zygmund kernels. We prove that if the kernel is supported in then the one-sided condition, , is a sufficient condition for the singular integral to be bounded in , , or from into weak- if . This one-sided condition becomes also necessary when we require the uniform boundedness of the singular integrals associated to the dilations of a kernel which is not identically zero in . The two-sided version of this result is also obtained: Muckenhoupts condition is necessary for the uniform boundedness of the singular integrals associated to the dilations of a general Calderón-Zygmund kernel which is not the function zero either in or in .
6.
There are very few cases known of nonabelian groups where the group of central units of , denoted , is nontrivial and where the structure of , including a complete set of generators, has been determined. In this note, we show that the central units of augmentation 1 in the integral group ring form an infinite cyclic group , and we explicitly find the generator .
7.
Hiroaki Aikawa 《Proceedings of the American Mathematical Society》1997,125(1):229-234
Let be a bounded domain in , , and let . We consider positive functions on such that for all bounded harmonic functions on . We determine Lipschitz domains having such with .
8.
J. Marshall Ash Gang Wang David Weinberg 《Proceedings of the American Mathematical Society》1997,125(1):219-228
If is a lacunary sequence of integers, and if for each , and are trigonometric polynomials of degree then must tend to zero for almost every whenever does. We conjecture that a similar result ought to hold even when the sequence has much slower growth. However, there is a sequence of integers and trigonometric polynomials such that tends to zero everywhere, even though the degree of does not exceed for each . The sequence of trigonometric polynomials tends to zero for almost every , although explicit formulas are developed to show that the sequence of corresponding conjugate functions does not. Among trigonometric polynomials of degree with largest Fourier coefficient equal to , the smallest one ``at' is while the smallest one ``near' is unknown.
9.
Keiji Izuchi 《Proceedings of the American Mathematical Society》1997,125(4):1153-1159
Let be a sequence of bounded linear operators on such that and for every . It is proved that for every .
10.
Mark L. Lewis 《Proceedings of the American Mathematical Society》1997,125(1):27-33
Let be an -group, let be a subnormal subgroup of , and let be a Hall subgroup of . If the character is primitive, then is a power of 2. Furthermore, if is odd, then .
11.
Claude Laflamme 《Proceedings of the American Mathematical Society》1997,125(10):3019-3025
We discuss F filters and show that the minimum size of a filter base generating an undiagonalizable filter included in some F filter is the better known bounded evasion number . An application to -sets from trigonometric series is given by showing that if is an -set and has size less than , then is again an -set.
12.
We give a necessary and sufficient condition on an operator for the existence of an operator in the nest algebra of a continuous nest satisfying (resp. . We also characterise the operators in which have the following property: For every continuous nest there exists an operator in satisfying (resp. .
13.
Junxi Zhao 《Proceedings of the American Mathematical Society》1997,125(1):101-109
Let be a complete commutative subspace lattice on a Hilbert space. When is purely atomic, we give a necessary and sufficient condition for for every in , where and denote the spectrum of in and respectively. In addition, we discuss the properties of the spectra and the invertibility conditions for operators in .
14.
W. Edwin Clark Boris Shekhtman 《Proceedings of the American Mathematical Society》1997,125(1):251-254
Let be an -dimensional vector space over an algebraically closed field . Define to be the least positive integer for which there exists a family of -dimensional subspaces of such that every -dimensional subspace of has at least one complement among the 's. Using algebraic geometry we prove that .
15.
Paul A. Binding Pavel Drá bek Yin Xi Huang 《Proceedings of the American Mathematical Society》1997,125(12):3555-3559
Consider
where and and let be the principal eigenvalue of the problem with . For , we discuss for which values of and the Fredholm alternative holds.
16.
W. J. Ricker 《Proceedings of the American Mathematical Society》1997,125(8):2401-2407
A classical result of W. Bade states that if is any complete Boolean algebra of projections in an arbitrary Banach space then, for every there exists an element (called a Bade functional for with respect to in the dual space , with the following two properties: (i) is non-negative on and, (ii) whenever satisfies It is shown that a Fréchet space has this property if and only if it does not contain an isomorphic copy of the sequence space
17.
Ju Seon Kim 《Proceedings of the American Mathematical Society》1997,125(5):1497-1501
Let be a hypersurface in , and let denote the mean curvature and the scalar curvature of respectively. We show that if is compact and , then is diffeomorphic to . Also we prove that if is complete, is constant and , then is or or .
18.
Cá ndido Piñ eiro 《Proceedings of the American Mathematical Society》1997,125(7):2073-2082
Let . Among other results, we prove that a Banach space has the property that every sequence lies inside the range of an -valued measure if and only if, for all sequences in satisfying that the operator is 1-summing, the operator is nuclear, being the conjugate number for . We also prove that, if is an infinite-dimensional -space for , then can't have the above property for any .
19.
Let be the moduli space of based (anti-self-dual) instantons on of charge and rank . There is a natural inclusion . We show that the direct limit space is homotopy equivalent to . Let be a line in the complex projective plane and let be the blow-up at a point away from . can be alternatively described as the moduli space of rank holomorphic bundles on with and and with a fixed holomorphic trivialization on .
20.
Paolo M. Soardi 《Proceedings of the American Mathematical Society》1997,125(12):3669-3673
We point out that the well known characterization of spaces () in terms of orthogonal wavelet bases extends to any separable rearrangement invariant Banach function space on (equipped with Lebesgue measure) with nontrivial Boyd's indices. Moreover we show that such bases are unconditional bases of .