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# Author Archives: Peter Cameron

## Something I didn’t know

I didn’t know this, though probably I should have. Maybe you didn’t know it either. We work in a semigroup, a system with an operation (called multiplication) satisfying the associative law. A generalised inverse of an element A is an … Continue reading

Posted in exposition
Tagged associative law, commute, generalised inverse, matrices, polynomial
4 Comments

## The Wall conjecture extended

Tim Wall boldly conjectured in 1961 that the number of maximal subgroups of a finite group G is at most |G|−1. (This would be best possible, since the the elementary abelian 2-group attains this bound.) He proved that the conjecture … Continue reading

## A challenge

Let a(n) be defined in the following manner. Write n as an ordered sum of positive integers in all possible ways. (The number of such expressions is 2n−1; showing this is a pleasant exercise, but it is not relevant for … Continue reading

## Very good news!

Cheryl Praeger has been awarded the Australian Prime Minister’s Prize for Science. Here is an announcement on the ABC website. Congratulations Cheryl! And my thanks to Liz for sending me the news.

## Ginger Baker

At my age, it very often happens that someone who was part of the background of my younger self dies. Yesterday it was Ginger Baker. The obituary said more about his extraordinary life and his short temper than his drumming, … Continue reading

## A puzzle

Last weekend we walked from Kinross to Falkland. Kinross is on the shore of Loch Leven (not the sea-loch of the same name on the west coast), which is drained by the River Leven (which flows into the Firth of … Continue reading

## G2D2, 5: The logo revisited

There has been further discussion of the G2 logo; here is a brief summary. Elena Konstantinova tells me that it was designed by Vava Stefoglo; her portfolio is here. She is not a mathematician but received a good education in … Continue reading