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Michael Vaughan-Lee

Publications and source records attributed to Michael Vaughan-Lee.

15 recordsLinked to original sources
arXiv2026

The exponents of $p$-groups of maximal class and their Schur multipliers

Let $P$ be a $p$-group of maximal class of order $p^n$ where $p,n>2$. If $n>p+1$ then the exponent of $P$ is $p^k$, where $k$ is the least integer greater or equal to $(n-1)/(p-1)$. If $n=p+1$ then $P$ has exponent $p^2$. And if $n\leq p$ then $P$ has exponent $p$ or $p^2$, with both possibilities arising. The Schur multiplier of $P$ has exponent at most $p^k$, where $k$ is the least integer greater than or equal to $(n-2)/(p-1)$.

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arXiv2025

On Zel'manov's global nilpotence theorem for Engel Lie algebras

I give a proof of Zel'manov's theorem that if $L$ is an $n$-Engel Lie algebra over a field $F$ of characteristic zero then $L$ is (globally) nilpotent. This is a very important result which extends Kostrikin's theorem that $L$ is locally nilpotent if the characteristic of $F$ is zero or some prime $p>n$. Zel'manov's proof contains some striking original ideas, and I wrote this note in an effort to understand his arguments. I hope that my efforts will be of use to other mathematicians in understanding this remarkable theorem.

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arXiv2024

5-Engel Lie algebras II

In my article 5-Engel algebras published on the arXiv in 2023 I proved that 5-Engel Lie algebras of characteristic zero or prime characteristic $p>7$ are nilpotent of class at most 11. In this note I investigate the ideal ID$(x)$ generated by an element $x$ in a 5-Engel Lie algebra. In characteristic 2 and 3 this ideal does not have to be nilpotent. For all primes $p>3$ I show that Id$(x)$ is nilpotent in 5-Engel Lie algebras of characteristic $p$, and I obtain explicit (best possible) bounds on the nilpotency class.

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arXiv2024

5-Engel Lie algebras

We prove that 5-Engel Lie algebras over a field of characteristic zero, or over a field of prime characteristic $p>7$, are nilpotent of class at most 11. We also prove that if $G$ is a finite 5-Engel $p$-group for $p>7$ then $G$ is nilpotent of class at most 10.

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arXiv2024

Bases for free Lie superalgebras

We describe a basis for free Lie superalgebras which uses the theory of basic commutators. The only description for bases for free Lie superalgebras that I have found in the literature is in the book "Infinite dimensional Lie superalgebras" by Bahturin et al. Their bases make use of the theory of Shirshov bases in free Lie algebras, and I believe that there is a case for writing up an alternative approach using basic commutators.

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arXiv2021

Schur's exponent conjecture II

Primoz Moravec published a very important paper in 2007 where he proved that if $G$ is a finite group of exponent $n$ then the exponent of the Schur multiplier of $G$ can be bounded by a function $f(n)$ depending only on $n$. Moravec does not give a value for $f(n)$, but actually his proof shows that we can take $f(n)=ne$ where $e$ is the order of $b^{-n}a^{-n}(ab)^{n}$ in the Schur multiplier of $R(2,n)$. (Here$R(2,n)$ is the largest finite two generator group of exponent $n$, and we take $a,b$ to be the generators of $R(2,n)$.) It is an easy hand calculation to show that $e=n$ for $n=2,3$, and it is a straightforward computation with the $p$-quotient algorithm to show that $e=n$ for $n=4,5,7$. The groups $R(2,8)$ and $R(2,9)$ are way out of range of the $p$-quotient algorithm, even with a modern supercomputer. But we are able toshow that $e\geq n$ for $n=8,9$. Moravec's proof also shows that if $G$ is a finite group of exponent $n$ with nilpotency class $c$, then the exponent of the Schur multiplier of $G$ is bounded by $ne$ where $e$ is the order of $b^{-n}a^{-n}(ab)^{n}$ in the Schur multiplier of the class $c$ quotient $R(2,n;c)$ of $R(2,n)$. If $q$ is a prime power we let $e_{q,c}$ be the order of $b^{-q}a^{-q}(ab)^{q}$ in the Schur multiplier of $R(2,q;c)$. We are able to show that $e_{p^{k},p^{2}-p-1}$ divides $p$ for all prime powers $p^{k}$. If $k>2$ then $e_{2^{k},c}$ equals 2 for $c<4$, equals 4 for $4\leq c\leq11$, and equals $8$ for $c=12$. If $k>1$ then $e_{3^{k},c}$ equals 1 for $c<3$, equals 3 for $3\leq c<12$, and equals 9 for $c=12$. We also investigate the order of $[b,a]$ in a Schur cover for $R(2,q;c)$.

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arXiv2020

Schur's exponent conjecture -- counterexamples of exponent 5 and exponent 9

There is a long-standing conjecture attributed to I Schur that if $G$ is a finite group with Schur multiplier $M(G)$ then the exponent of $M(G)$ divides the exponent of $G$. It is easy to see that this conjecture holds for exponent 2 and exponent 3, but it has been known since 1974 that the conjecture fails for exponent 4. In this note I give an example of a group $G$ with exponent 5 with Schur multiplier $M(G)$ of exponent 25, and an example of a group $A$ of exponent 9 with Schur multiplier $M(A)$ of exponent 27.

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arXiv2020

Understanding Wall's theorem on dependence of Lie relators in Burnside groups

G.E. Wall gave two different proofs of a remarkable result about the multilinear Lie relators satisfied by groups of prime power exponent $q$. He showed that if $q$ is a power of the prime $p$, and if $f$ is a multilinear Lie relator in $n$ variables where $n\neq1\operatorname{mod}(p-1)$, then $f=0$ is a consequence of multilinear Lie relators in fewer than $n$ variables. For years I have struggled to understand his proofs, and while I still have not the slightest clue about his first proof published in the Journal of Algebra, I finally have some understanding of his second proof published in a conference proceedings. In this note I offer my insights into Wall's second proof of this theorem.

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arXiv2018

Graham Higman's PORC theorem

Graham Higman published two important papers in 1960. In the first of these papers he proved that for any positive integer $n$ the number of groups of order $p^{n}$ is bounded by a polynomial in $p$, and he formulated his famous PORC conjecture about the form of the function $f(p^{n})$ giving the number of groups of order $p^{n}$. In the second of these two papers he proved that the function giving the number of $p$-class two groups of order $p^{n}$ is PORC. He established this result as a corollary to a very general result about vector spaces acted on by the general linear group. This theorem takes over a page to state, and is so general that it is hard to see what is going on. Higman's proof of this general theorem contains several new ideas and is quite hard to follow. However in the last few years several authors have developed and implemented algorithms for computing Higman's PORC formulae in special cases of his general theorem. These algorithms give perspective on what are the key points in Higman's proof, and also simplify parts of the proof. In this note I give a proof of Higman's general theorem written in the light of these recent developments.

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arXiv2017

Choosing elements from finite fields

In two important papers from 1960 Graham Higman introduced the notion of PORC functions, and he proved that for any given positive integer $n$ the number of $p$-class two groups of order $p^n$ is a PORC function of $p$. A key result in his proof of this theorem is the following: "The number of ways of choosing a finite number of elements from the finite field of order $q^n$ subject to a finite number of monomial equations and inequalities between them and their conjugates over GF($q$), considered as a function of $q$, is PORC." Higman's proof of this result involves five pages of homological algebra. Here we give a short elementary proof of the result. Our proof is constructive, and gives an algorithms for computing the relevant PORC functions.

math.GR↗
arXiv2017

Orbits of irreducible binary forms over GF$(p)$

In this note I give a formula for calculating the number of orbits of irreducible binary forms of degree $n$ over GF$(p)$ under the action of GL$(2,p)$. This formula has applications to the classification of class two groups of exponent $p$ with derived groups of order $p^2$.

math.GR↗
arXiv2017

The class three groups of order $p^9$ with exponent $p$

We give a complete list of the class two groups with exponent $p$ and order dividing $p^8$. For each group in the list we compute the number of immediate descendants of order $p^9$ with exponent $p$. In each case the number of descendants is PORC, and so the total number of class three groups of order $p^9$ with exponent $p$ is PORC. Nevertheless, there are groups of order $p^8$ with exponent $p$ which have a non-PORC number of class three descendants of order $p^9$ with exponent $p$.

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arXiv2015

The automorphisms of class two groups of prime exponent

We give a complete list of all the 70 class two groups of exponent p (p>2) and order p^k for k<9. For each of these groups the number of conjugacy classes is a polynomial in p, and the order of the automorphism group is a polynomial in p. In contrast, Marcus du Sautoy and Michael Vaughan-Lee have given an example of a class two group of exponent p and order p^9 for which neither the number of conjugacy classes, nor the order of the automorphism group is polynomial on residue classes (PORC).

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arXiv2011

Non-PORC behaviour of a class of descendant $p$-groups

We prove that the number of immediate descendants of order $p^10$ of $G_p$ is not PORC (Polynomial On Residue Classes) where $G_p$ is the $p$-group of order $p^9$ defined by du Sautoy's nilpotent group encoding the elliptic curve $y^2=x^3-x$. This has important implications for Higman's PORC conjecture.

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