11,408 research outputs found
Context Vectors are Reflections of Word Vectors in Half the Dimensions
This paper takes a step towards theoretical analysis of the relationship
between word embeddings and context embeddings in models such as word2vec. We
start from basic probabilistic assumptions on the nature of word vectors,
context vectors, and text generation. These assumptions are well supported
either empirically or theoretically by the existing literature. Next, we show
that under these assumptions the widely-used word-word PMI matrix is
approximately a random symmetric Gaussian ensemble. This, in turn, implies that
context vectors are reflections of word vectors in approximately half the
dimensions. As a direct application of our result, we suggest a theoretically
grounded way of tying weights in the SGNS model
The Self-Organization of Meaning and the Reflexive Communication of Information
Following a suggestion of Warren Weaver, we extend the Shannon model of
communication piecemeal into a complex systems model in which communication is
differentiated both vertically and horizontally. This model enables us to
bridge the divide between Niklas Luhmann's theory of the self-organization of
meaning in communications and empirical research using information theory.
First, we distinguish between communication relations and correlations among
patterns of relations. The correlations span a vector space in which relations
are positioned and can be provided with meaning. Second, positions provide
reflexive perspectives. Whereas the different meanings are integrated locally,
each instantiation opens global perspectives--"horizons of meaning"--along
eigenvectors of the communication matrix. These next-order codifications of
meaning can be expected to generate redundancies when interacting in
instantiations. Increases in redundancy indicate new options and can be
measured as local reduction of prevailing uncertainty (in bits). The systemic
generation of new options can be considered as a hallmark of the
knowledge-based economy.Comment: accepted for publication in Social Science Information, March 21,
201
The brick polytope of a sorting network
The associahedron is a polytope whose graph is the graph of flips on
triangulations of a convex polygon. Pseudotriangulations and
multitriangulations generalize triangulations in two different ways, which have
been unified by Pilaud and Pocchiola in their study of flip graphs on
pseudoline arrangements with contacts supported by a given sorting network.
In this paper, we construct the brick polytope of a sorting network, obtained
as the convex hull of the brick vectors associated to each pseudoline
arrangement supported by the network. We combinatorially characterize the
vertices of this polytope, describe its faces, and decompose it as a Minkowski
sum of matroid polytopes.
Our brick polytopes include Hohlweg and Lange's many realizations of the
associahedron, which arise as brick polytopes for certain well-chosen sorting
networks. We furthermore discuss the brick polytopes of sorting networks
supporting pseudoline arrangements which correspond to multitriangulations of
convex polygons: our polytopes only realize subgraphs of the flip graphs on
multitriangulations and they cannot appear as projections of a hypothetical
multiassociahedron.Comment: 36 pages, 25 figures; Version 2 refers to the recent generalization
of our results to spherical subword complexes on finite Coxeter groups
(http://arxiv.org/abs/1111.3349
Critical points for the Hausdorff Dimension of pairs of pants
We study the dependence of the Hausdoroff dimension of the limit set of a hyperbolic Fuchsian group on the geometry of the associated Riemann surface. In particular, we study the type and location of extrema subject to restriction on the total length of the boundary geodesics. In addition, we compare different algorithms used for numerical computations
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