Point-pushing in 3-manifolds

We study the Birman exact sequence for compact 3-manifolds.Comment: 33 pages, 1 figure. v2: Incorrect Lemma 6.21 replaced. Corollary 7.4 (now 7.5) strengthened. Other small changes in exposition. An alternative, more algebraic, proof of Theorem 7.2 (with less exposition) is given in arXiv:1404.368

The Kakimizu complex of a connected sum of links

We show that |MS(L_1 # L_2)|=|MS(L_1)|\times|MS(L_2)|\times\mathbb{R} when $L_1$ and $L_2$ are any non-split and non-fibred links. Here $MS(L)$ denotes the Kakimizu complex of a link $L$, which records the taut Seifert surfaces for $L$. We also show that the analogous result holds if we study incompressible Seifert surfaces instead of taut ones.Comment: 23 pages, 8 figures. This result has been proved independently by Bassem Saa

The Birman exact sequence for 3-manifolds

We study the Birman exact sequence for compact $3$--manifolds, obtaining a complete picture of the relationship between the mapping class group of the manifold and the mapping class group of the submanifold obtained by deleting an interior point. This covers both orientable manifolds and non-orientable ones.Comment: 30 pages, no figures. v2: Major re-write following referee suggestions. To appear in Bull. Lond. Math. Soc.; v1: This paper gives an alternative, more algebraic, proof of the main result of arXiv:1310.7884 (with less exposition

Embedding the Pentagon

The Pentagon Model is an explicit supersymmetric extension of the Standard Model, which involves a new strongly-interacting SU(5) gauge theory at TeV-scale energies. We show that the Pentagon can be embedded into an SU(5) x SU(5) x SU(5) gauge group at the GUT scale. The doublet-triplet splitting problem, and proton decay compatible with experimental bounds, can be successfully addressed in this context. The simplest approach fails to provide masses for the lighter two generations of quarks and leptons; however, this problem can be solved by the addition of a pair of antisymmetric tensor fields and an axion.Comment: 39 page

Sato--Tate, cyclicity, and divisibility statistics on average for elliptic curves of small height

We obtain asymptotic formulae for the number of primes $p\le x$ for which the reduction modulo $p$ of the elliptic curve \E_{a,b} : Y^2 = X^3 + aX + b satisfies certain ``natural'' properties, on average over integers $a$ and $b$ with $|a|\le A$ and $|b| \le B$, where $A$ and $B$ are small relative to $x$. Specifically, we investigate behavior with respect to the Sato--Tate conjecture, cyclicity, and divisibility of the number of points by a fixed integer $m$