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Martin R. Bridson Charles F. Miller III 《Proceedings of the American Mathematical Society》2004,132(1):59-65
We give examples of direct products of three hyperbolic groups in which there cannot exist an algorithm to decide which finitely presented subgroups are isomorphic.
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The formation of p-tert-butylcalix[4]arene mono-, bis-, tris-, and tetrakistriflates 3, 2, 4, and 5, respectively, and their respective reactions, under typical Pd-catalyzed carbonylative, Suzuki-Miyaura coupling, or deoxygenation conditions are described. A novel, nonsolvent-derived 1:1 clathrate (6) of benzophenone and 3 was formed from the palladium-catalyzed carbonylative reaction of phenylboronic acid and 2. The X-ray crystal structure of this first nonsolvent-derived clathrate of a calix[4]arene derivative is reported. Another 1:1 clathrate of triethylamine and 3 was formed during the attempted Pd-catalyzed deoxygenation of 2. 相似文献
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Bodwell GJ Bridson JN Cyrañski MK Kennedy JW Krygowski TM Mannion MR Miller DO 《The Journal of organic chemistry》2003,68(6):2089-2098
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We extend the range of observed behaviour among length functionsof optimal asynchronously automatic structures. We do so bymeans of a construction that yields asynchronously automaticgroups with finite aspherical presentations where the Dehn functionof the group is polynomial of arbitrary degree. Many of thesegroups can be embedded in the automorphism group of a free group.Moreover, the fact that the groups have aspherical presentationsmakes them useful tools in the search to determine the spectrumof exponents for second order Dehn functions. We contributeto this search by giving the first exact calculations of groupswith quadratic and superquadratic exponents. 2000 Mathematical Subject Classification: 20F06, 20F65, 20F69. 相似文献
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There is only one gap in the isoperimetric spectrum 总被引:1,自引:0,他引:1
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John N. Bridson Melbourne J. Schriver Shuguang Zhu 《Journal of chemical crystallography》1995,25(1):11-14
The X-ray crystal structure of 1,3-adamantane-dicarbonamide has been determined. Colourless, cube shaped crystals of C12H18N2O2 crystallize in the monoclinic space group C2/c (#15) with cell dimensionsa=7·934(3),b=15·543(3),c=9·404(2) Å, =93.63°;V=1157.4(5) Å3 andZ=4.1074 unique reflections withI
net
>2.00(I) on refinement afforded values ofR=0.039 andR
w
=0.040. 相似文献
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The groups Aut(F3) and Out(F3) satisfy strictly exponentialisoperimetric inequalities; in particular, they are not automatic.For n 3, Aut (Fn) and Out (Fn) do not admit bounded bicombingsof sub-exponential length, hence they cannot act properly andcocompactly by isometries on any simply-connected space of non-positivecurvature, and they are not biautomatic. 相似文献
10.
G. Baumslag M. R. Bridson C. F. Miller III H. Short 《Commentarii Mathematici Helvetici》2000,75(3):457-477
We give a criterion for fibre products to be finitely presented and use it as the basis of a construction that encodes the
pathologies of finite group presentations into pairs of groups where G is a product of hyperbolic groups and P is a finitely presented subgroup. This enables us to prove that there is a finitely presented subgroup P in a biautomatic group G such that the generalized word problem for is unsolvable and P has an unsolvable conjugacy problem. An additional construction shows that there exists a compact non-positively curved polyhedron
X such that is biautomatic and there is no algorithm to decide isomorphism among the finitely presented subgroups of .
Received: October 7, 1999. 相似文献