Galactic Center ADAF Ruled out By Polarization

Recent observations of linear polarization at high frequency towards the galactic center radio source, Sgr A*, place strong constraints on the nature of the radio emission region. We discuss how these constraints rule out the larger accretion rate need for low efficiency accretion flows, such as advection-dominated accretion flows, and we present a toy model which can explain the radio to sub-mm spectrum and polarization of Sgr A*

The minimal volume orientable hyperbolic 2-cusped 3-manifolds

We prove that the Whitehead link complement and the (-2, 3, 8) pretzel link complement are the minimal volume orientable hyperbolic 3-manifolds with two cusps, with volume 3.66... = 4 x Catalan's constant. We use topological arguments to establish the existence of an essential surface which provides a lower bound on volume and strong constraints on the manifolds that realize that lower bound.Comment: 10 pages, 5 figures, incorporated referees comments, includes hyperref link

Lower bounds on volumes of hyperbolic Haken 3-manifolds

In this paper, we find lower bounds for volumes of hyperbolic 3-manifolds with various topological conditions. Let V_3 = 1.01494 denote the volume of a regular ideal simplex in hyperbolic 3-space. As a special case of the main theorem, if a hyperbolic manifold M contains an acylindrical surface S, then Vol(M)>= -2 V_3 chi(S). We also show that if beta_1(M)>= 2, then Vol(M)>= 4/5 V_3.Comment: 20 pages, 15 figure