Random nilpotent groups, polycyclic presentations, and Diophantine problems. Garreta, A., Miasnikov, A., & Ovchinnikov, D. Groups Complexity Cryptology, 9(2):99–115, November, 2017. Publisher: De Gruyter Section: Groups Complexity Cryptology
Random nilpotent groups, polycyclic presentations, and Diophantine problems [link]Paper  doi  abstract   bibtex   
We introduce a model of random finitely generated, torsion-free, 2-step nilpotent groups (in short, τ2\\textbackslashtau_\2\\-groups). To do so, we show that these are precisely the groups with presentation of the form 〈A,C∣[ai,aj]=∏t=1mctλt,i,j(1≤i<j≤n),[A,C]=[C,C]=1〉\\textbackslashlangle A,C\textbackslashmid[a_\i\,a_\j\]=\textbackslashprod_\t=1\\textasciicircum\m\c_\t\\textasciicircum\\textbackslashlambda_\t,i,j\\(1\textbackslashleq i<j% \textbackslashleq n),\textbackslash,[A,C]=[C,C]=1\textbackslashrangle\, where A=\a1,…,an\\A=\textbackslash\a_\1\,\textbackslashdots,a_\n\\textbackslash\\ and C=\c1,…,cm\\C=\textbackslash\c_\1\,\textbackslashdots,c_\m\\textbackslash\\. Hence, a random G can be selected by fixing A and C , and then randomly choosing integers λt,i,j\\textbackslashlambda_\t,i,j\\, with \textbarλt,i,j\textbar≤ℓ\\textbar\textbackslashlambda_\t,i,j\\textbar\textbackslashleq\textbackslashell\ for some ℓ\\textbackslashell\. We prove that if m≥n-1≥1\m\textbackslashgeq n-1\textbackslashgeq 1\, then the following hold asymptotically almost surely as ℓ→∞\\textbackslashell\textbackslashto\textbackslashinfty\: the ring ℤ\\textbackslashmathbb\Z\\ is e-definable in G , the Diophantine problem over G is undecidable, the maximal ring of scalars of G is ℤ\\textbackslashmathbb\Z\\, G is indecomposable as a direct product of non-abelian groups, and Z⁢(G)=〈C〉\Z(G)=\textbackslashlangle C\textbackslashrangle\. We further study when Z⁢(G)≤Is⁡(G′)\Z(G)\textbackslashleq\textbackslashoperatorname\Is\(G\textasciicircum\\textbackslashprime\)\. Finally, we introduce similar models of random polycyclic groups and random f.g. nilpotent groups of any nilpotency step, possibly with torsion. We quickly see, however, that the latter yields finite groups a.a.s.
@article{garreta_random_2017,
	title = {Random nilpotent groups, polycyclic presentations, and {Diophantine} problems},
	volume = {9},
	issn = {1869-6104},
	url = {https://www.degruyter.com/document/doi/10.1515/gcc-2017-0007/html},
	doi = {10.1515/gcc-2017-0007},
	abstract = {We introduce a model of random finitely generated, torsion-free, 2-step nilpotent groups (in short, τ2\{{\textbackslash}tau\_\{2\}\}-groups). To do so, we show that these are precisely the groups with presentation of the form 〈A,C∣[ai,aj]=∏t=1mctλt,i,j(1≤i\&lt;j≤n),[A,C]=[C,C]=1〉\{{\textbackslash}langle A,C{\textbackslash}mid[a\_\{i\},a\_\{j\}]={\textbackslash}prod\_\{t=1\}{\textasciicircum}\{m\}c\_\{t\}{\textasciicircum}\{{\textbackslash}lambda\_\{t,i,j\}\}(1{\textbackslash}leq i\&lt;j\% {\textbackslash}leq n),{\textbackslash},[A,C]=[C,C]=1{\textbackslash}rangle\}, where A=\{a1,…,an\}\{A={\textbackslash}\{a\_\{1\},{\textbackslash}dots,a\_\{n\}{\textbackslash}\}\} and C=\{c1,…,cm\}\{C={\textbackslash}\{c\_\{1\},{\textbackslash}dots,c\_\{m\}{\textbackslash}\}\}. Hence, a random G can be selected by fixing A and C , and then randomly choosing integers λt,i,j\{{\textbackslash}lambda\_\{t,i,j\}\}, with {\textbar}λt,i,j{\textbar}≤ℓ\{{\textbar}{\textbackslash}lambda\_\{t,i,j\}{\textbar}{\textbackslash}leq{\textbackslash}ell\} for some ℓ\{{\textbackslash}ell\}. We prove that if m≥n-1≥1\{m{\textbackslash}geq n-1{\textbackslash}geq 1\}, then the following hold asymptotically almost surely as ℓ→∞\{{\textbackslash}ell{\textbackslash}to{\textbackslash}infty\}: the ring ℤ\{{\textbackslash}mathbb\{Z\}\} is e-definable in G , the Diophantine problem over G is undecidable, the maximal ring of scalars of G is ℤ\{{\textbackslash}mathbb\{Z\}\}, G is indecomposable as a direct product of non-abelian groups, and Z⁢(G)=〈C〉\{Z(G)={\textbackslash}langle C{\textbackslash}rangle\}. We further study when Z⁢(G)≤Is⁡(G′)\{Z(G){\textbackslash}leq{\textbackslash}operatorname\{Is\}(G{\textasciicircum}\{{\textbackslash}prime\})\}. Finally, we introduce similar models of random polycyclic groups and random f.g. nilpotent groups of any nilpotency step, possibly with torsion. We quickly see, however, that the latter yields finite groups a.a.s.},
	language = {en},
	number = {2},
	urldate = {2021-04-21},
	journal = {Groups Complexity Cryptology},
	author = {Garreta, Albert and Miasnikov, Alexei and Ovchinnikov, Denis},
	month = nov,
	year = {2017},
	note = {Publisher: De Gruyter
Section: Groups Complexity Cryptology},
	pages = {99--115},
}

Downloads: 0