Modular lattices from finite projective planes

Tathagata Basak[1]

  • [1] Department of Mathematics Iowa State University Ames, IA 50011

Journal de Théorie des Nombres de Bordeaux (2014)

  • Volume: 26, Issue: 2, page 269-279
  • ISSN: 1246-7405

Abstract

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Using the geometry of the projective plane over the finite field 𝔽 q , we construct a Hermitian Lorentzian lattice L q of dimension ( q 2 + q + 2 ) defined over a certain number ring 𝒪 that depends on q . We show that infinitely many of these lattices are p -modular, that is, p L q ' = L q , where p is some prime in 𝒪 such that | p | 2 = q .The Lorentzian lattices L q sometimes lead to construction of interesting positive definite lattices. In particular, if q 3 mod 4 is a rational prime such that ( q 2 + q + 1 ) is norm of some element in [ - q ] , then we find a 2 q ( q + 1 ) dimensional even unimodular positive definite integer lattice M q such that Aut ( M q ) PGL ( 3 , 𝔽 q ) . We find that M 3 is the Leech lattice.

How to cite

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Basak, Tathagata. "Modular lattices from finite projective planes." Journal de Théorie des Nombres de Bordeaux 26.2 (2014): 269-279. <http://eudml.org/doc/275779>.

@article{Basak2014,
abstract = {Using the geometry of the projective plane over the finite field $\mathbb\{F\}_q$, we construct a Hermitian Lorentzian lattice $L_\{q\}$ of dimension $(q^\{2\} + q + 2)$ defined over a certain number ring $\mathcal\{O\}$ that depends on $q$. We show that infinitely many of these lattices are $p$-modular, that is, $p L^\{\prime \}_\{q\} = L_\{q\}$, where $p$ is some prime in $\mathcal\{O\}$ such that $\vert p\vert ^\{2\} =q$.The Lorentzian lattices $L_q$ sometimes lead to construction of interesting positive definite lattices. In particular, if $q \equiv 3 \bmod 4$ is a rational prime such that $(q^2 + q + 1)$ is norm of some element in $\mathbb\{Q\}[\sqrt\{-q\}]$, then we find a $2q(q+1)$ dimensional even unimodular positive definite integer lattice $M_\{q\}$ such that $\operatorname\{Aut\}(M_q) \supseteq \operatorname\{PGL\}(3,\mathbb\{F\}_q)$. We find that $M_3$ is the Leech lattice.},
affiliation = {Department of Mathematics Iowa State University Ames, IA 50011},
author = {Basak, Tathagata},
journal = {Journal de Théorie des Nombres de Bordeaux},
language = {eng},
month = {10},
number = {2},
pages = {269-279},
publisher = {Société Arithmétique de Bordeaux},
title = {Modular lattices from finite projective planes},
url = {http://eudml.org/doc/275779},
volume = {26},
year = {2014},
}

TY - JOUR
AU - Basak, Tathagata
TI - Modular lattices from finite projective planes
JO - Journal de Théorie des Nombres de Bordeaux
DA - 2014/10//
PB - Société Arithmétique de Bordeaux
VL - 26
IS - 2
SP - 269
EP - 279
AB - Using the geometry of the projective plane over the finite field $\mathbb{F}_q$, we construct a Hermitian Lorentzian lattice $L_{q}$ of dimension $(q^{2} + q + 2)$ defined over a certain number ring $\mathcal{O}$ that depends on $q$. We show that infinitely many of these lattices are $p$-modular, that is, $p L^{\prime }_{q} = L_{q}$, where $p$ is some prime in $\mathcal{O}$ such that $\vert p\vert ^{2} =q$.The Lorentzian lattices $L_q$ sometimes lead to construction of interesting positive definite lattices. In particular, if $q \equiv 3 \bmod 4$ is a rational prime such that $(q^2 + q + 1)$ is norm of some element in $\mathbb{Q}[\sqrt{-q}]$, then we find a $2q(q+1)$ dimensional even unimodular positive definite integer lattice $M_{q}$ such that $\operatorname{Aut}(M_q) \supseteq \operatorname{PGL}(3,\mathbb{F}_q)$. We find that $M_3$ is the Leech lattice.
LA - eng
UR - http://eudml.org/doc/275779
ER -

References

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