8,540 research outputs found
The Green's function and the Ahlfors map
The classical Green's function associated to a simply connected domain in the
complex plane is easily expressed in terms of a Riemann mapping function. The
purpose of this paper is to express the Green's function of a finitely
connected domain in the plane in terms of a single Ahlfors mapping of the
domain, which is a proper holomorphic mapping of the domain onto the unit disc
that is the analogue of the Riemann map in the multiply connected setting.Comment: 14 page
Time's Arrow, A Halloween Concert, October 31, 1995
This is the concert program of the Time's Arrow, A Halloween Concert performance on Tuesday, October 31, 1995 at 8:00 p.m., at the Tsai Performance Center, 685 Commonwealth Avenue, Boston, Massachusetts. Works performed were An Idyll for the Misbegotten by George Crumb, La Vita Nuova by Nicholas Maw, Lucy and the Count by Jon Deak, and Mysteries of the Macabre by György Ligeti. Digitization for Boston University Concert Programs was supported by the Boston University Humanities Library Endowed Fund
Exact duality in semidefinite programming based on elementary reformulations
In semidefinite programming (SDP), unlike in linear programming, Farkas'
lemma may fail to prove infeasibility. Here we obtain an exact, short
certificate of infeasibility in SDP by an elementary approach: we reformulate
any semidefinite system of the form Ai*X = bi (i=1,...,m) (P) X >= 0 using only
elementary row operations, and rotations. When (P) is infeasible, the
reformulated system is trivially infeasible. When (P) is feasible, the
reformulated system has strong duality with its Lagrange dual for all objective
functions.
As a corollary, we obtain algorithms to generate the constraints of {\em all}
infeasible SDPs and the constraints of {\em all} feasible SDPs with a fixed
rank maximal solution.Comment: To appear, SIAM Journal on Optimizatio
The structure of the semigroup of proper holomorphic mappings of a planar domain to the unit disc
Given a bounded n-connected domain in the plane bounded by non-intersecting
Jordan curves, and given one point on each boundary curve, L. Bieberbach proved
that there exists a proper holomorphic mapping of the domain onto the unit disc
that is an n-to-one branched covering with the properties that it extends
continuously to the boundary and maps each boundary curve one-to-one onto the
unit circle, and it maps each given point on the boundary to the point 1 in the
unit circle. We modify a proof by H. Grunsky of Bieberbach's result to show
that there is a rational function of 2n+2 complex variables that generates all
of these maps. We also show how to generate all the proper holomorphic mappings
to the unit disc via the rational function.Comment: 17 page
Exploring Different Dimensions of Attention for Uncertainty Detection
Neural networks with attention have proven effective for many natural
language processing tasks. In this paper, we develop attention mechanisms for
uncertainty detection. In particular, we generalize standardly used attention
mechanisms by introducing external attention and sequence-preserving attention.
These novel architectures differ from standard approaches in that they use
external resources to compute attention weights and preserve sequence
information. We compare them to other configurations along different dimensions
of attention. Our novel architectures set the new state of the art on a
Wikipedia benchmark dataset and perform similar to the state-of-the-art model
on a biomedical benchmark which uses a large set of linguistic features.Comment: accepted at EACL 201
Spectral goodness of fit for network models
We introduce a new statistic, 'spectral goodness of fit' (SGOF) to measure
how well a network model explains the structure of an observed network. SGOF
provides an absolute measure of fit, analogous to the standard R-squared in
linear regression. Additionally, as it takes advantage of the properties of the
spectrum of the graph Laplacian, it is suitable for comparing network models of
diverse functional forms, including both fitted statistical models and
algorithmic generative models of networks. After introducing, defining, and
providing guidance for interpreting SGOF, we illustrate the properties of the
statistic with a number of examples and comparisons to existing techniques. We
show that such a spectral approach to assessing model fit fills gaps left by
earlier methods and can be widely applied
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