Began with an account of how social media algorithms can help to spread misinformation which in turn can lead to protests and civil unrest. The phenomenon is well-document, such as in this <a href="https://www.irishexaminer.com/breakingnews/ireland/dozens-of-far-right-social-media-accounts-said-to-be-spreading-misinformation-in-ireland-929725.html">Irish Examiner item</a>. Then tried to illustrate how a basic understanding of the algorithms might enable one to maximise the spread of one's own information.
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Gave a (somewhat over simplified) description of the Google Page Rank algorithm.  The algorithm requires a method for computing eigenvectors of an n&times;n matrix for very large n; this computation will be discussed next lecture for the case n=2.

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In readiness for the computation of eigenvectors I introduced the <i>characteristic polynomial</i> of a 2&times;2 matrix.