## EVENT DETAILS AND ABSTRACT

**Number Theory**
**Title:** Increasing the number of fibered faces of arithmetic hyperbolic 3-manifolds.

**Speaker:** Professor Nathan Dunfield

**Speaker Info:** UIUC

**Brief Description:**

**Special Note**:

**Abstract:**

I will exhibit a closed hyperbolic 3-manifold which satisfies a very strong form of Thurston's Virtual Fibration
Conjecture. In particular, this manifold has finite covers which fiber over the circle in arbitrarily many fundamentally
distinct ways. More precisely, it has a tower of finite covers where the number of fibered faces of the Thurston norm ball
goes to infinity, in fact faster than any power of the logarithm of the degree of the cover. The example manifold M is
arithmetic, and the proof uses detailed number-theoretic information, at the level of the Hecke eigenvalues, to drive a
geometric argument based on Fried's dynamical characterization of the fibered faces. The origin of the basic fibration of M
over the circle is the modular elliptic curve E=X_0(49), which admits multiplication by the ring of integers of Q[sqrt(-7)].
We first base change the holomorphic differential on E to a cusp form on GL(2) over K=Q[sqrt(-3)], and then transfer over to a
quaternion algebra D/K ramified only at the primes above 7; the fundamental group of M is a quotient of the principal
congruence subgroup of level 7 of the multiplicative group of a maximal order of D. This is joint work with Dinakar
Ramakrishnan.

**Date:** Monday, January 12, 2009

**Time:** 3:00PM

**Where:** Lunt 107

**Contact Person:** Florian Herzig

**Contact email:** herzig@math.northwestern.edu

**Contact Phone:** 847-467-1898

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