Effective distance between nested Margulis tubes

We give sharp, effective bounds on the distance between tori of fixed injectivity radius inside a Margulis tube in a hyperbolic 3-manifold.Comment: 25 pages, 3 figures. v3 contains minor revisions. To appear in Transactions of the AM

Innovation in Isolation: Labor-Management Partnerships in the United States

In the United States, as in other advanced industrial countries, worker participation in management has taken on increasing importance, placing pressures on employers and unions to change how they deal with employees/members, and with each other. This paper examines two of the most impressive cases in the U.S.: the partnerships between General Motors (G.M.) and the United Autoworkers union (U.A W.) at Saturn and between BellSouth and the Communication Workers union (C.W.A.). We outline the evolution and the basic features of these innovations, as well as highlighting certain ongoing problems. These problems, we argue, confront the parties to employment relations in the U.S. more generally, reflecting profound ambivalence about such experiments, and their continued isolation as ‘islands of excellence ’. As such, these cases both illustrate the vast potential for labor-management partnerships as well as the dampening effect of the employment relations context in the U.S

Note on the space group selection rule for closed strings on orbifolds

It is well-known that the space group selection rule constrains the interactions of closed strings on orbifolds. For some examples, this rule has been described by an effective Abelian symmetry that combines with a permutation symmetry to a non-Abelian flavor symmetry like $D_4$ or $\Delta(54)$. However, the general case of the effective Abelian symmetries was not yet fully understood. In this work, we formalize the computation of the Abelian symmetry that results from the space group selection rule by imposing two conditions only: (i) well-defined discrete charges and (ii) their conservation. The resulting symmetry, which we call the space group flavor symmetry $D_S$, is uniquely specified by the Abelianization of the space group. For all Abelian orbifolds with $N=1$ supersymmetry we compute $D_S$ and identify new cases, for example, where $D_S$ contains a $Z_2$ dark matter-parity with charges 0 and 1 for massless and massive strings, respectively.Comment: 28 pages, 1 tabl

Irrotational Binary Neutron Stars in Quasiequilibrium in General Relativity

Neutron stars in binary orbit emit gravitational waves and spiral slowly together. During this inspiral, they are expected to have very little vorticity. It is in fact a good approximation to treat the system as having zero vorticity, i.e., as irrotational. Because the orbital period is much shorter than the radiation reaction time scale, it is also an excellent approximation to treat the system as evolving through a sequence of equilibrium states, in each of which the gravitational radiation is neglected. In Newtonian gravity, one can simplify the hydrodynamic equations considerably for an equilibrium irrotational binary by introducing a velocity potential. The equations reduce to a Poisson-like equation for the potential, and a Bernoulli-type integral for the density. We show that a similar simplification can be carried out in general relativity. The resulting equations are much easier to solve than other formulations of the problem.Comment: 14 pages, AASTeX, accepted in ApJ. Simplified final form of equation (eq. 52). Added Shibata re

Mirage Torsion

Z_NxZ_M orbifold models admit the introduction of a discrete torsion phase. We find that models with discrete torsion have an alternative description in terms of torsionless models. More specifically, discrete torsion can be 'gauged away' by changing the shifts by lattice vectors. Similarly, a large class of the so-called generalized discrete torsion phases can be traded for changing the background fields (Wilson lines) by lattice vectors. We further observe that certain models with generalized discrete torsion are equivalent to torsionless models with the same gauge embedding but based on different compactification lattices. We also present a method of classifying heterotic Z_NxZ_M orbifolds.Comment: 26 pages, 3 figures, v2: matches version published in JHE

Etruscan Bone Mirror Handles

"Figured carvings in ivory and bone form a small, precious group in the repertory of Etruscan art. Chronologically, they fall into two groups: the Archaic and the Late Classical and Hellenistic. Among the latter are handles for bronze mirrors, usually made of bone. Six examples and a fragment of a seventh have been known, all in Italy and most of them in Florence. The appearance of another handle, almost complete and very well preserved, is thus an important addition to our knowledge of Late Etruscan art. Said to have been found at Yuki, the handle is now in the Museum of Art and Archaeology of the University of Missouri-Columbia."--First paragraph.Includes bibliographical reference

A Syro-Palestinian Bowl Type

"A single type of artifact surviving from the ancient world can often give us a broad insight into many aspects of the culture from which it derives. Such a piece is a pottery bowl recently acquired by the Museum of Art and Archaeology at the University of Missouri-Columbia. The bowl is said to have come from the Syro-Palestinian coastal area, which in the Hellenistic period was under the strong Hellenizing influence that moved eastward in the wake of the conquests of Alexander the Great and took hold in the kingdoms ruled by his successors. Greek pottery, especially the so-called black-glazed wares (really covered with a sintered slip, often with stamped and rouletted decoration) and the molded relief bowls, were assiduously imported and then imitated in the Hellenized east. What is particularly interesting about the bowl published here is that it seems clearly to be a product of the Syro-Palestinian coastal area, imitating a shape that was imported from Greek lands. Its decoration, however, is unknown in Greece proper and is dependent, as we shall see, on east Mediterranean craft production."--First paragraph.Includes bibliographical reference