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41.
A construction for Segal operations for K-theory of categories with cofibrations, weak equivalences and a biexact pairing is given and coherence properties of the operations are studied. The model for K-theory, which is used, allows coherence to be studied by means of (symmetric) monoidal functors. In the case of Waldhausen A-theory it is shown how to recover the operations used in Waldhausen (Lecture Notes in Mathematics, Vol. 967, Springer, Berlin, 1982, pp. 390-409) for the A-theory Kahn-Priddy theorem. The total Segal operation for A-theory, which assembles exterior power operations, is shown to carry a natural infinite loop map structure. The basic input is the un-delooped model for K-theory, which has been developed from a construction by Grayson and Gillet for exact categories in Gunnarsson et al. (J. Pure Appl. Algebra 79 (1992) 255), and Grayson's setup for operations in Grayson (K-theory (1989) 247). The relevant material from these sources is recollected followed by observations on equivariant objects and pairings. Grayson's conditions are then translated to the context of categories with cofibrations and weak equivalences. The power operations are shown to be well behaved w.r.t. suspension and are extended to algebraic K-theory of spaces. Staying close with the philosophy of Waldhausen (1982) Waldhausen's maps are found. The Kahn-Priddy theorem follows from splitting the “free part” off the equivariant theory. The treatment of coherence of the total operation in A-theory involves results from Laplaza (Lecture Notes in Mathematics, Vol. 281, Springer, Berlin, 1972, pp. 29-65) and restriction to spherical objects in the source of the operation. 相似文献
42.
43.
J. Kalliongis 《Mathematische Zeitschrift》2002,241(4):801-828
For compact irreducible sufficiently large 3-manifolds containing 2-sided projective planes, we consider the following Realization
Problem: Given a finite subgroup of the outer automorphism group of the fundamental group, is there a finite group of homeomorphisms,
which induces this subgroup?
Received: 16 November 1999; in final form: 18 January 2001 / Published online: 8 November 2002 相似文献
44.
A.R. Phani M. PassacantandoS. Santucci 《Journal of Physics and Chemistry of Solids》2002,63(3):383-392
Crack free, dense and transparent CdTiO3 thin films have been prepared by sol-gel technique using titanium butoxide and cadmium acetate. The formation of the CdTiO3 phase started from 500°C annealing temperature onwards. The complete orthorhombic structure of CdTiO3 was formed on Silicon (100) substrate at an annealing temperature of 600°C for 5 h. As the annealing temperature increased from 600 to 700°C, we have observed the cadmium silicate phase at the interface of Si and CdTiO3 phase. Structural, morphological and elemental evolution of these CdTiO3 thin films produced by sol-gel synthesis were characterised by grazing incidence X-ray diffraction (GIXRD), tapping mode atomic force microscopy (TMAFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) respectively. 相似文献
45.
本文使用激光诱导瞬态吸收光谱装置,研究了C60激发三重态在乙腈/甲苯混合溶剂中的光物理性质,得到了3C60的激发态寿命、自猝灭速率常数和时间分辩的瞬态吸收光谱.此外,实验中引入了哌嗪作为激发三重态猝灭剂.我们发现哌嗪能有效的猝灭3C60,猝灭速率常数kq接近扩散控制极限.改变混合溶剂的比例,相应的猝灭速率常数值也发生变化,即kq随混合溶剂极性的增加而增加,随溶剂粘度的增加而减小.稳态光解实验反映了反应物向产物转化过程中在紫外-可见波段吸收强度的变化. 相似文献
46.
Summary In this paper a Gauss-Jordan algorithm with column interchanges is presented and analysed. We show that, in contrast with Gaussian elimination, the Gauss-Jordan algorithm has essentially differing properties when using column interchanges instead of row interchanges for improving the numerical stability. For solutions obtained by Gauss-Jordan with column interchanges, a more satisfactory bound for the residual norm can be given. The analysis gives theoretical evidence that the algorithm yields numerical solutions as good as those obtained by Gaussian elimination and that, in most practical situations, the residuals are equally small. This is confirmed by numerical experiments. Moreover, timing experiments on a Cyber 205 vector computer show that the algorithm presented has good vectorisation properties. 相似文献
47.
The high-temperature cubic phase of non-stoichiometric strontium ferrite SrFeOx (2.5≤x≤3.0) has been studied by in situ neutron powder diffraction in air over the temperature range 300-1273 K. The composition of SrFeOx changes within the range 2.56≤x≤2.81 from 1273 to 673 K, respectively.Rietveld refinements of the diffraction patterns show that the high-temperature cubic phase of SrFeOx is consistent with a face-centred Fm3c structure. This structure leads to agreement with previous density measurements. This cell allows the high-temperature structure of SrFeOx to be described in terms of a solid solution of the composition end members. Cubic SrFeOx at high temperature is found to closely obey Vegard's law. The density of cubic SrFeOx is also found to exhibit a linear relationship with composition. 相似文献
48.
Nicolas Bergeron 《Mathematische Zeitschrift》2002,241(1):101-125
Let M be an arithmetic hyperbolic manifold and be a codimension 1 geodesic cycle. In this paper, we study the asymptotic growth of the -norm of the lifts of F in the congruence tower above M. We obtain an explicit value for the growth rate of this norm. In particular, we provide a new proof of a celebrated result
of Millson [Mi] on the homology of the arithmetic hyperbolic manifolds. The method is quite general and gives a new way of
getting non zero homology classes in certain locally symmetric spaces.
Received: 20 April 2001; in final form: 26 September 2001 / Published online: 28 February 2002 相似文献
49.
Chuanming Zong 《Monatshefte für Mathematik》2002,134(3):247-255
In this article we study the simultaneous packing and covering constants of two-dimensional centrally symmetric convex domains.
Besides an identity result between translative case and lattice case and a general upper bound, exact values for some special
domains are determined. Similar to Mahler and Reinhardt’s result about packing densities, we show that the simultaneous packing
and covering constant of an octagon is larger than that of a circle.
(Received 17 January 2001; in revised form 13 July 2001) 相似文献
50.
Let M be a Riemannian m-dimensional manifold with m ≥ 3, endowed with non zero parallel p-form. We prove that there is no minimal isometric immersions of M in a Riemannian manifold N with constant strictly negative sectional curvature. Next we show that, under the conform flatness of the manifold N and some assumptions on the Ricci curvature of N, there is no α-pluriharmonic isometric immersion. 相似文献