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cmp-lg/9807006
|
A Maximum-Entropy Partial Parser for Unrestricted Text
|
cmp-lg cs.CL
|
This paper describes a partial parser that assigns syntactic structures to
sequences of part-of-speech tags. The program uses the maximum entropy
parameter estimation method, which allows a flexible combination of different
knowledge sources: the hierarchical structure, parts of speech and phrasal
categories. In effect, the parser goes beyond simple bracketing and recognises
even fairly complex structures. We give accuracy figures for different
applications of the parser.
|
cmp-lg/9807007
|
Chunk Tagger - Statistical Recognition of Noun Phrases
|
cmp-lg cs.CL
|
We describe a stochastic approach to partial parsing, i.e., the recognition
of syntactic structures of limited depth. The technique utilises Markov Models,
but goes beyond usual bracketing approaches, since it is capable of recognising
not only the boundaries, but also the internal structure and syntactic category
of simple as well as complex NP's, PP's, AP's and adverbials. We compare
tagging accuracy for different applications and encoding schemes.
|
cmp-lg/9807008
|
A Linguistically Interpreted Corpus of German Newspaper Text
|
cmp-lg cs.CL
|
In this paper, we report on the development of an annotation scheme and
annotation tools for unrestricted German text. Our representation format is
based on argument structure, but also permits the extraction of other kinds of
representations. We discuss several methodological issues and the analysis of
some phenomena. Additional focus is on the tools developed in our project and
their applications.
|
cmp-lg/9807009
|
A Projection Architecture for Dependency Grammar and How it Compares to
LFG
|
cmp-lg cs.CL
|
This paper explores commonalities and differences between \dachs, a variant
of Dependency Grammar, and Lexical-Functional Grammar. \dachs\ is based on
traditional linguistic insights, but on modern mathematical tools, aiming to
integrate different knowledge systems (from syntax and semantics) via their
coupling to an abstract syntactic primitive, the dependency relation. These
knowledge systems correspond rather closely to projections in LFG. We will
investigate commonalities arising from the usage of the projection approach in
both theories, and point out differences due to the incompatible linguistic
premises. The main difference to LFG lies in the motivation and status of the
dimensions, and the information coded there. We will argue that LFG confounds
different information in one projection, preventing it to achieve a good
separation of alternatives and calling the motivation of the projection into
question.
|
cmp-lg/9807010
|
Automatically Creating Bilingual Lexicons for Machine Translation from
Bilingual Text
|
cmp-lg cs.CL
|
A method is presented for automatically augmenting the bilingual lexicon of
an existing Machine Translation system, by extracting bilingual entries from
aligned bilingual text. The proposed method only relies on the resources
already available in the MT system itself. It is based on the use of bilingual
lexical templates to match the terminal symbols in the parses of the aligned
sentences.
|
cmp-lg/9807011
|
Statistical Models for Unsupervised Prepositional Phrase Attachment
|
cmp-lg cs.CL
|
We present several unsupervised statistical models for the prepositional
phrase attachment task that approach the accuracy of the best supervised
methods for this task. Our unsupervised approach uses a heuristic based on
attachment proximity and trains from raw text that is annotated with only
part-of-speech tags and morphological base forms, as opposed to attachment
information. It is therefore less resource-intensive and more portable than
previous corpus-based algorithms proposed for this task. We present results for
prepositional phrase attachment in both English and Spanish.
|
cmp-lg/9807012
|
Character design for soccer commmentary
|
cmp-lg cs.CL
|
In this paper we present early work on an animated talking head commentary
system called {\bf Byrne}\footnote{David Byrne is the lead singer of the
Talking Heads.}. The goal of this project is to develop a system which can take
the output from the RoboCup soccer simulator, and generate appropriate
affective speech and facial expressions, based on the character's personality,
emotional state, and the state of play. Here we describe a system which takes
pre-analysed simulator output as input, and which generates text marked-up for
use by a speech generator and a face animation system. We make heavy use of
inter-system standards, so that future versions of Byrne will be able to take
advantage of advances in the technologies that it incorporates.
|
cmp-lg/9807013
|
Improving Data Driven Wordclass Tagging by System Combination
|
cmp-lg cs.CL
|
In this paper we examine how the differences in modelling between different
data driven systems performing the same NLP task can be exploited to yield a
higher accuracy than the best individual system. We do this by means of an
experiment involving the task of morpho-syntactic wordclass tagging. Four
well-known tagger generators (Hidden Markov Model, Memory-Based, Transformation
Rules and Maximum Entropy) are trained on the same corpus data. After
comparison, their outputs are combined using several voting strategies and
second stage classifiers. All combination taggers outperform their best
component, with the best combination showing a 19.1% lower error rate than the
best individual tagger.
|
cmp-lg/9808001
|
An Empirical Evaluation of Probabilistic Lexicalized Tree Insertion
Grammars
|
cmp-lg cs.CL
|
We present an empirical study of the applicability of Probabilistic
Lexicalized Tree Insertion Grammars (PLTIG), a lexicalized counterpart to
Probabilistic Context-Free Grammars (PCFG), to problems in stochastic
natural-language processing. Comparing the performance of PLTIGs with
non-hierarchical N-gram models and PCFGs, we show that PLTIG combines the best
aspects of both, with language modeling capability comparable to N-grams, and
improved parsing performance over its non-lexicalized counterpart. Furthermore,
training of PLTIGs displays faster convergence than PCFGs.
|
cmp-lg/9808002
|
Indexing with WordNet synsets can improve Text Retrieval
|
cmp-lg cs.CL
|
The classical, vector space model for text retrieval is shown to give better
results (up to 29% better in our experiments) if WordNet synsets are chosen as
the indexing space, instead of word forms. This result is obtained for a
manually disambiguated test collection (of queries and documents) derived from
the Semcor semantic concordance. The sensitivity of retrieval performance to
(automatic) disambiguation errors when indexing documents is also measured.
Finally, it is observed that if queries are not disambiguated, indexing by
synsets performs (at best) only as good as standard word indexing.
|
cmp-lg/9808003
|
Parallel Strands: A Preliminary Investigation into Mining the Web for
Bilingual Text
|
cmp-lg cs.CL
|
Parallel corpora are a valuable resource for machine translation, but at
present their availability and utility is limited by genre- and
domain-specificity, licensing restrictions, and the basic difficulty of
locating parallel texts in all but the most dominant of the world's languages.
A parallel corpus resource not yet explored is the World Wide Web, which hosts
an abundance of pages in parallel translation, offering a potential solution to
some of these problems and unique opportunities of its own. This paper presents
the necessary first step in that exploration: a method for automatically
finding parallel translated documents on the Web. The technique is conceptually
simple, fully language independent, and scalable, and preliminary evaluation
results indicate that the method may be accurate enough to apply without human
intervention.
|
cmp-lg/9808004
|
Word Length Frequency and Distribution in English: Observations, Theory,
and Implications for the Construction of Verse Lines
|
cmp-lg cs.CL
|
Recent observations in the theory of verse and empirical metrics have
suggested that constructing a verse line involves a pattern-matching search
through a source text, and that the number of found elements (complete words
totaling a specified number of syllables) is given by dividing the total number
of words by the mean number of syllables per word in the source text. This
paper makes this latter point explicit mathematically, and in the course of
this demonstration shows that the word length frequency totals in English
output are distributed geometrically (previous researchers reported an adjusted
Poisson distribution), and that the sequential distribution is random at the
global level, with significant non-randomness in the fine structure. Data from
a corpus of just under two million words, and a syllable-count lexicon of
71,000 word-forms is reported. The pattern-matching theory is shown to be
internally coherent, and it is observed that some of the analytic techniques
described here form a satisfactory test for regular (isometric) lineation in a
text.
|
cmp-lg/9808005
|
Combining Expression and Content in Domains for Dialog Managers
|
cmp-lg cs.CL
|
We present work in progress on abstracting dialog managers from their domain
in order to implement a dialog manager development tool which takes (among
other data) a domain description as input and delivers a new dialog manager for
the described domain as output. Thereby we will focus on two topics; firstly,
the construction of domain descriptions with description logics and secondly,
the interpretation of utterances in a given domain.
|
cmp-lg/9808006
|
Isometric Lineation in English Texts: An Empirical and Mathematical
Examination of its Character and Consequences
|
cmp-lg cs.CL
|
In this paper we build on earlier observations and theory regarding word
length frequency and sequential distribution to develop a mathematical
characterization of some of the language features distinguishing isometrically
lineated text from unlineated text, in other words the features distinguishing
isometrical verse from prose. It is shown that the frequency of syllables
making complete words produces a flat distribution for prose, while that for
verse exhibits peaks at the line length position and subsequent multiples of
that position. Data from several verse authors is presented, including a
detailed mathematical analysis of the dynamics underlying peak creation, and
comments are offered on the processes by which authors construct lines. We note
that the word-length sequence of prose is random, whereas lineation
necessitates non-random word-length sequencing, and that this has the probable
consequence of introducing a degree of randomness into the otherwise highly
ordered grammatical sequence. In addition we observe that this effect can be
ameliorated by a reduction in the mean word length of the text (confirming
earlier observations that verse tends to use shorter words) and the use of
lines varying from the core isometrical set. The frequency of variant lines is
shown to be coincident with the frequency of polysyllables, suggesting that the
use of variant lines is motivated by polysyllabic word placement. The
restrictive effects of different line lengths, the relationship between
metrical restriction and poetic effect, and the general character of metrical
rules are also discussed.
|
cmp-lg/9808007
|
Some Properties of Preposition and Subordinate Conjunction Attachments
|
cmp-lg cs.CL
|
Determining the attachments of prepositions and subordinate conjunctions is a
key problem in parsing natural language. This paper presents a trainable
approach to making these attachments through transformation sequences and
error-driven learning. Our approach is broad coverage, and accounts for roughly
three times the attachment cases that have previously been handled by
corpus-based techniques. In addition, our approach is based on a simplified
model of syntax that is more consistent with the practice in current
state-of-the-art language processing systems. This paper sketches syntactic and
algorithmic details, and presents experimental results on data sets derived
from the Penn Treebank. We obtain an attachment accuracy of 75.4% for the
general case, the first such corpus-based result to be reported. For the
restricted cases previously studied with corpus-based methods, our approach
yields an accuracy comparable to current work (83.1%).
|
cmp-lg/9808008
|
Deriving the Predicate-Argument Structure for a Free Word Order Language
|
cmp-lg cs.CL
|
In relatively free word order languages, grammatical functions are
intricately related to case marking. Assuming an ordered representation of the
predicate-argument structure, this work proposes a Combinatory Categorial
Grammar formulation of relating surface case cues to categories and types for
correctly placing the arguments in the predicate-argument structure. This is
achieved by assigning case markers GF-encoding categories. Unlike other CG
formulations, type shifting does not proliferate or cause spurious ambiguity.
Categories of all argument-encoding grammatical functions follow from the same
principle of category assignment. Normal order evaluation of the combinatory
form reveals the predicate-argument structure. Application of the method to
Turkish is shown.
|
cmp-lg/9808009
|
How to define a context-free backbone for DGs: Implementing a DG in the
LFG formalism
|
cmp-lg cs.CL
|
This paper presents a multidimensional Dependency Grammar (DG), which
decouples the dependency tree from word order, such that surface ordering is
not determined by traversing the dependency tree. We develop the notion of a
\emph{word order domain structure}, which is linked but structurally dissimilar
to the syntactic dependency tree. We then discuss the implementation of such a
DG using constructs from a unification-based phrase-structure approach, namely
Lexical-Functional Grammar (LFG). Particular attention is given to the analysis
of discontinuities in DG in terms of LFG's functional uncertainty.
|
cmp-lg/9808010
|
Letter to Sound Rules for Accented Lexicon Compression
|
cmp-lg cs.CL
|
This paper presents trainable methods for generating letter to sound rules
from a given lexicon for use in pronouncing out-of-vocabulary words and as a
method for lexicon compression.
As the relationship between a string of letters and a string of phonemes
representing its pronunciation for many languages is not trivial, we discuss
two alignment procedures, one fully automatic and one hand-seeded which produce
reasonable alignments of letters to phones.
Top Down Induction Tree models are trained on the aligned entries. We show
how combined phoneme/stress prediction is better than separate prediction
processes, and still better when including in the model the last phonemes
transcribed and part of speech information. For the lexicons we have tested,
our models have a word accuracy (including stress) of 78% for OALD, 62% for CMU
and 94% for BRULEX. The extremely high scores on the training sets allow
substantial size reductions (more than 1/20).
WWW site: http://tcts.fpms.ac.be/synthesis/mbrdico
|
cmp-lg/9808011
|
Primitive Part-of-Speech Tagging using Word Length and Sentential
Structure
|
cmp-lg cs.CL
|
It has been argued that, when learning a first language, babies use a series
of small clues to aid recognition and comprehension, and that one of these
clues is word length. In this paper we present a statistical part of speech
tagger which trains itself solely on the number of letters in each word in a
sentence.
|
cmp-lg/9808012
|
Separating Surface Order and Syntactic Relations in a Dependency Grammar
|
cmp-lg cs.CL
|
This paper proposes decoupling the dependency tree from word order, such that
surface ordering is not determined by traversing the dependency tree. We
develop the notion of a \emph{word order domain structure}, which is linked but
structurally dissimilar to the syntactic dependency tree. The proposal results
in a lexicalized, declarative, and formally precise description of word order;
features which lack previous proposals for dependency grammars. Contrary to
other lexicalized approaches to word order, our proposal does not require
lexical ambiguities for ordering alternatives.
|
cmp-lg/9808013
|
Partial Evaluation for Efficient Access to Inheritance Lexicons
|
cmp-lg cs.CL
|
Multiple default inheritance formalisms for lexicons have attracted much
interest in recent years. I propose a new efficient method to access such
lexicons. After showing two basic strategies for lookup in inheritance
lexicons, a compromise is developed which combines to a large degree (from a
practical point of view) the advantages of both strategies and avoids their
disadvantages. The method is a kind of (off-line) partial evaluation that makes
a subset of inherited information explicit before using the lexicon. I identify
the parts of a lexicon which should be evaluated, and show how partial
evaluation works for inheritance lexicons. Finally, the theoretical results are
confirmed by a complete implementation. Speedups by a factor of 10-100 are
reached.
|
cmp-lg/9808014
|
Spotting Prosodic Boundaries in Continuous Speech in French
|
cmp-lg cs.CL
|
A radio speech corpus of 9mn has been prosodically marked by a phonetician
expert, and non expert listeners. this corpus is large enough to train and test
an automatic boundary spotting system, namely a time delay neural network fed
with F0 values, vowels and pseudo-syllable durations. Results validate both
prosodic marking and automatic spotting of prosodic events.
|
cmp-lg/9808015
|
Error-Driven Pruning of Treebank Grammars for Base Noun Phrase
Identification
|
cmp-lg cs.CL
|
Finding simple, non-recursive, base noun phrases is an important subtask for
many natural language processing applications. While previous empirical methods
for base NP identification have been rather complex, this paper instead
proposes a very simple algorithm that is tailored to the relative simplicity of
the task. In particular, we present a corpus-based approach for finding base
NPs by matching part-of-speech tag sequences. The training phase of the
algorithm is based on two successful techniques: first the base NP grammar is
read from a ``treebank'' corpus; then the grammar is improved by selecting
rules with high ``benefit'' scores. Using this simple algorithm with a naive
heuristic for matching rules, we achieve surprising accuracy in an evaluation
on the Penn Treebank Wall Street Journal.
|
cmp-lg/9808016
|
Segregatory Coordination and Ellipsis in Text Generation
|
cmp-lg cs.CL
|
In this paper, we provide an account of how to generate sentences with
coordination constructions from clause-sized semantic representations. An
algorithm is developed to generate sentences with ellipsis, gapping,
right-node-raising, and non-constituent coordination constructions. Various
examples from linguistic literature will be used to demonstrate that the
algorithm does its job well.
|
cmp-lg/9808017
|
A Variant of Earley Parsing
|
cmp-lg cs.CL
|
The Earley algorithm is a widely used parsing method in natural language
processing applications. We introduce a variant of Earley parsing that is based
on a ``delayed'' recognition of constituents. This allows us to start the
recognition of a constituent only in cases in which all of its subconstituents
have been found within the input string. This is particularly advantageous in
several cases in which partial analysis of a constituent cannot be completed
and in general in all cases of productions sharing some suffix of their
right-hand sides (even for different left-hand side nonterminals). Although the
two algorithms result in the same asymptotic time and space complexity, from a
practical perspective our algorithm improves the time and space requirements of
the original method, as shown by reported experimental results.
|
cmp-lg/9809001
|
Towards an implementable dependency grammar
|
cmp-lg cs.CL
|
The aim of this paper is to define a dependency grammar framework which is
both linguistically motivated and computationally parsable. See the demo at
http://www.conexor.fi/analysers.html#testing
|
cmp-lg/9809002
|
Some Ontological Principles for Designing Upper Level Lexical Resources
|
cmp-lg cs.CL
|
The purpose of this paper is to explore some semantic problems related to the
use of linguistic ontologies in information systems, and to suggest some
organizing principles aimed to solve such problems. The taxonomic structure of
current ontologies is unfortunately quite complicated and hard to understand,
especially for what concerns the upper levels. I will focus here on the problem
of ISA overloading, which I believe is the main responsible of these
difficulties. To this purpose, I will carefully analyze the ontological nature
of the categories used in current upper-level structures, considering the
necessity of splitting them according to more subtle distinctions or the
opportunity of excluding them because of their limited organizational role.
|
cmp-lg/9809003
|
A Comparison of WordNet and Roget's Taxonomy for Measuring Semantic
Similarity
|
cmp-lg cs.CL
|
This paper presents the results of using Roget's International Thesaurus as
the taxonomy in a semantic similarity measurement task. Four similarity metrics
were taken from the literature and applied to Roget's The experimental
evaluation suggests that the traditional edge counting approach does
surprisingly well (a correlation of r=0.88 with a benchmark set of human
similarity judgements, with an upper bound of r=0.90 for human subjects
performing the same task.)
|
cond-mat/0002331
|
From naive to sophisticated behavior in multiagents based financial
market models
|
cond-mat.stat-mech cond-mat.dis-nn cs.CE nlin.AO physics.data-an q-fin.TR
|
We discuss the behavior of two magnitudes, physical complexity and mutual
information function of the outcome of a model of heterogeneous, inductive
rational agents inspired in the El Farol Bar problem and the Minority Game. The
first is a measure rooted in Kolmogorov-Chaitin theory and the second one a
measure related with information entropy of Shannon.
We make extensive computer simulations, as result of which, we propose an
ansatz for physical complexity and establish the dependence of exponent of that
ansatz from the parameters of the model. We discuss the accuracy of our results
and the relationship with the behavior of mutual information function as a
measure of time correlations of agents choice.
|
cond-mat/0009165
|
Occam factors and model-independent Bayesian learning of continuous
distributions
|
cond-mat cs.LG nlin.AO physics.data-an
|
Learning of a smooth but nonparametric probability density can be regularized
using methods of Quantum Field Theory. We implement a field theoretic prior
numerically, test its efficacy, and show that the data and the phase space
factors arising from the integration over the model space determine the free
parameter of the theory ("smoothness scale") self-consistently. This persists
even for distributions that are atypical in the prior and is a step towards a
model-independent theory for learning continuous distributions. Finally, we
point out that a wrong parameterization of a model family may sometimes be
advantageous for small data sets.
|
cond-mat/0010337
|
Optimization with Extremal Dynamics
|
cond-mat.stat-mech cs.NE math.OC
|
We explore a new general-purpose heuristic for finding high-quality solutions
to hard optimization problems. The method, called extremal optimization, is
inspired by self-organized criticality, a concept introduced to describe
emergent complexity in physical systems. Extremal optimization successively
replaces extremely undesirable variables of a single sub-optimal solution with
new, random ones. Large fluctuations ensue, that efficiently explore many local
optima. With only one adjustable parameter, the heuristic's performance has
proven competitive with more elaborate methods, especially near phase
transitions which are believed to coincide with the hardest instances. We use
extremal optimization to elucidate the phase transition in the 3-coloring
problem, and we provide independent confirmation of previously reported
extrapolations for the ground-state energy of +-J spin glasses in d=3 and 4.
|
cond-mat/0104066
|
Beyond the Zipf-Mandelbrot law in quantitative linguistics
|
cond-mat.stat-mech cs.CL nlin.AO
|
In this paper the Zipf-Mandelbrot law is revisited in the context of
linguistics. Despite its widespread popularity the Zipf--Mandelbrot law can
only describe the statistical behaviour of a rather restricted fraction of the
total number of words contained in some given corpus. In particular, we focus
our attention on the important deviations that become statistically relevant as
larger corpora are considered and that ultimately could be understood as
salient features of the underlying complex process of language generation.
Finally, it is shown that all the different observed regimes can be accurately
encompassed within a single mathematical framework recently introduced by C.
Tsallis.
|
cond-mat/0104214
|
Extremal Optimization for Graph Partitioning
|
cond-mat.stat-mech cs.NE math.OC
|
Extremal optimization is a new general-purpose method for approximating
solutions to hard optimization problems. We study the method in detail by way
of the NP-hard graph partitioning problem. We discuss the scaling behavior of
extremal optimization, focusing on the convergence of the average run as a
function of runtime and system size. The method has a single free parameter,
which we determine numerically and justify using a simple argument. Our
numerical results demonstrate that on random graphs, extremal optimization
maintains consistent accuracy for increasing system sizes, with an
approximation error decreasing over runtime roughly as a power law t^(-0.4). On
geometrically structured graphs, the scaling of results from the average run
suggests that these are far from optimal, with large fluctuations between
individual trials. But when only the best runs are considered, results
consistent with theoretical arguments are recovered.
|
cond-mat/0109121
|
Coordination of Decisions in a Spatial Agent Model
|
cond-mat.stat-mech cs.MA
|
For a binary choice problem, the spatial coordination of decisions in an
agent community is investigated both analytically and by means of stochastic
computer simulations. The individual decisions are based on different local
information generated by the agents with a finite lifetime and disseminated in
the system with a finite velocity. We derive critical parameters for the
emergence of minorities and majorities of agents making opposite decisions and
investigate their spatial organization. We find that dependent on two essential
parameters describing the local impact and the spatial dissemination of
information, either a definite stable minority/majority relation
(single-attractor regime) or a broad range of possible values (multi-attractor
regime) occurs. In the latter case, the outcome of the decision process becomes
rather diverse and hard to predict, both with respect to the share of the
majority and their spatial distribution. We further investigate how a
dissemination of information on different time scales affects the outcome of
the decision process. We find that a more ``efficient'' information exchange
within a subpopulation provides a suitable way to stabilize their majority
status and to reduce ``diversity'' and uncertainty in the decision process.
|
cond-mat/0109218
|
Entropic analysis of the role of words in literary texts
|
cond-mat.stat-mech cs.CL
|
Beyond the local constraints imposed by grammar, words concatenated in long
sequences carrying a complex message show statistical regularities that may
reflect their linguistic role in the message. In this paper, we perform a
systematic statistical analysis of the use of words in literary English
corpora. We show that there is a quantitative relation between the role of
content words in literary English and the Shannon information entropy defined
over an appropriate probability distribution. Without assuming any previous
knowledge about the syntactic structure of language, we are able to cluster
certain groups of words according to their specific role in the text.
|
cond-mat/0110165
|
Jamming Model for the Extremal Optimization Heuristic
|
cond-mat.stat-mech cs.NE physics.comp-ph
|
Extremal Optimization, a recently introduced meta-heuristic for hard
optimization problems, is analyzed on a simple model of jamming. The model is
motivated first by the problem of finding lowest energy configurations for a
disordered spin system on a fixed-valence graph. The numerical results for the
spin system exhibit the same phenomena found in all earlier studies of extremal
optimization, and our analytical results for the model reproduce many of these
features.
|
cond-mat/0201139
|
Long-range fractal correlations in literary corpora
|
cond-mat.stat-mech cs.CL nlin.AO
|
In this paper we analyse the fractal structure of long human-language records
by mapping large samples of texts onto time series. The particular mapping set
up in this work is inspired on linguistic basis in the sense that is retains
{\em the word} as the fundamental unit of communication. The results confirm
that beyond the short-range correlations resulting from syntactic rules acting
at sentence level, long-range structures emerge in large written language
samples that give rise to long-range correlations in the use of words.
|
cond-mat/0202190
|
Threshold Disorder as a Source of Diverse and Complex Behavior in Random
Nets
|
cond-mat.dis-nn cs.NE q-bio.NC
|
We study the diversity of complex spatio-temporal patterns in the behavior of
random synchronous asymmetric neural networks (RSANNs). Special attention is
given to the impact of disordered threshold values on limit-cycle diversity and
limit-cycle complexity in RSANNs which have `normal' thresholds by default.
Surprisingly, RSANNs exhibit only a small repertoire of rather complex
limit-cycle patterns when all parameters are fixed. This repertoire of complex
patterns is also rather stable with respect to small parameter changes. These
two unexpected results may generalize to the study of other complex systems. In
order to reach beyond this seemingly-disabling `stable and small' aspect of the
limit-cycle repertoire of RSANNs, we have found that if an RSANN has threshold
disorder above a critical level, then there is a rapid increase of the size of
the repertoire of patterns. The repertoire size initially follows a power-law
function of the magnitude of the threshold disorder. As the disorder increases
further, the limit-cycle patterns themselves become simpler until at a second
critical level most of the limit cycles become simple fixed points.
Nonetheless, for moderate changes in the threshold parameters, RSANNs are found
to display specific features of behavior desired for rapidly-responding
processing systems: accessibility to a large set of complex patterns.
|
cond-mat/0202383
|
Extended Comment on Language Trees and Zipping
|
cond-mat.stat-mech cs.CL cs.LG
|
This is the extended version of a Comment submitted to Physical Review
Letters. I first point out the inappropriateness of publishing a Letter
unrelated to physics. Next, I give experimental results showing that the
technique used in the Letter is 3 times worse and 17 times slower than a simple
baseline. And finally, I review the literature, showing that the ideas of the
Letter are not novel. I conclude by suggesting that Physical Review Letters
should not publish Letters unrelated to physics.
|
cond-mat/0203436
|
Entropy estimation of symbol sequences
|
cond-mat.stat-mech cs.CL cs.IT math.IT physics.data-an stat.ML
|
We discuss algorithms for estimating the Shannon entropy h of finite symbol
sequences with long range correlations. In particular, we consider algorithms
which estimate h from the code lengths produced by some compression algorithm.
Our interest is in describing their convergence with sequence length, assuming
no limits for the space and time complexities of the compression algorithms. A
scaling law is proposed for extrapolation from finite sample lengths. This is
applied to sequences of dynamical systems in non-trivial chaotic regimes, a 1-D
cellular automaton, and to written English texts.
|
cond-mat/0203591
|
Anticorrelations and subdiffusion in financial systems
|
cond-mat.dis-nn cond-mat.stat-mech cs.CE q-fin.ST
|
Statistical dynamics of financial systems is investigated, based on a model
of a randomly coupled equation system driven by a stochastic Langevin force.
Anticorrelations of price returns, and subdiffusion of prices is found from the
model, and and compared with those calculated from historical $/EURO exchange
rates.
|
cond-mat/0208414
|
Winner-Relaxing Self-Organizing Maps
|
cond-mat.dis-nn cs.NE nlin.AO q-bio.NC
|
A new family of self-organizing maps, the Winner-Relaxing Kohonen Algorithm,
is introduced as a generalization of a variant given by Kohonen in 1991. The
magnification behaviour is calculated analytically. For the original variant a
magnification exponent of 4/7 is derived; the generalized version allows to
steer the magnification in the wide range from exponent 1/2 to 1 in the
one-dimensional case, thus provides optimal mapping in the sense of information
theory. The Winner Relaxing Algorithm requires minimal extra computations per
learning step and is conveniently easy to implement.
|
cond-mat/0301307
|
Nonextensive statistical mechanics and economics
|
cond-mat.stat-mech cs.CE q-fin.ST
|
Ergodicity, this is to say, dynamics whose time averages coincide with
ensemble averages, naturally leads to Boltzmann-Gibbs (BG) statistical
mechanics, hence to standard thermodynamics. This formalism has been at the
basis of an enormous success in describing, among others, the particular
stationary state corresponding to thermal equilibrium. There are, however, vast
classes of complex systems which accomodate quite badly, or even not at all,
within the BG formalism. Such dynamical systems exhibit, in one way or another,
nonergodic aspects. In order to be able to theoretically study at least some of
these systems, a formalism was proposed 14 years ago, which is sometimes
referred to as nonextensive statistical mechanics. We briefly introduce this
formalism, its foundations and applications. Furthermore, we provide some
bridging to important economical phenomena, such as option pricing, return and
volume distributions observed in the financial markets, and the fascinating and
ubiquitous concept of risk aversion. One may summarize the whole approach by
saying that BG statistical mechanics is based on the entropy $S_{BG}=-k \sum_i
p_i \ln p_i$, and typically provides {\it exponential laws} for describing
stationary states and basic time-dependent phenomena, while nonextensive
statistical mechanics is instead based on the entropic form
$S_q=k(1-\sum_ip_i^q)/(q-1)$ (with $S_1=S_{BG}$), and typically provides, for
the same type of description, (asymptotic) {\it power laws}.
|
cond-mat/0301459
|
Collectives for the Optimal Combination of Imperfect Objects
|
cond-mat.dis-nn cond-mat.stat-mech cs.MA nlin.AO
|
In this letter we summarize some recent theoretical work on the design of
collectives, i.e., of systems containing many agents, each of which can be
viewed as trying to maximize an associated private utility, where there is also
a world utility rating the behavior of that overall system that the designer of
the collective wishes to optimize. We then apply algorithms based on that work
on a recently suggested testbed for such optimization problems (Challet &
Johnson, PRL, vol 89, 028701 2002). This is the problem of finding the
combination of imperfect nano-scale objects that results in the best aggregate
object. We present experimental results showing that these algorithms
outperform conventional methods by more than an order of magnitude in this
domain.
|
cond-mat/0303089
|
Multiplicative point process as a model of trading activity
|
cond-mat.stat-mech cs.CE math.SP nlin.AO nlin.CD q-fin.TR
|
Signals consisting of a sequence of pulses show that inherent origin of the
1/f noise is a Brownian fluctuation of the average interevent time between
subsequent pulses of the pulse sequence. In this paper we generalize the model
of interevent time to reproduce a variety of self-affine time series exhibiting
power spectral density S(f) scaling as a power of the frequency f. Furthermore,
we analyze the relation between the power-law correlations and the origin of
the power-law probability distribution of the signal intensity. We introduce a
stochastic multiplicative model for the time intervals between point events and
analyze the statistical properties of the signal analytically and numerically.
Such model system exhibits power-law spectral density S(f)~1/f**beta for
various values of beta, including beta=1/2, 1 and 3/2. Explicit expressions for
the power spectra in the low frequency limit and for the distribution density
of the interevent time are obtained. The counting statistics of the events is
analyzed analytically and numerically, as well. The specific interest of our
analysis is related with the financial markets, where long-range correlations
of price fluctuations largely depend on the number of transactions. We analyze
the spectral density and counting statistics of the number of transactions. The
model reproduces spectral properties of the real markets and explains the
mechanism of power-law distribution of trading activity. The study provides
evidence that the statistical properties of the financial markets are enclosed
in the statistics of the time interval between trades. A multiplicative point
process serves as a consistent model generating this statistics.
|
cond-mat/0304132
|
Causalities of the Taiwan Stock Market
|
cond-mat.stat-mech cs.CE q-fin.ST
|
Volatility, fitting with first order Landau expansion, stationarity, and
causality of the Taiwan stock market (TAIEX) are investigated based on daily
records. Instead of consensuses that consider stock market index change as a
random time series we propose the market change as a dual time series consists
of the index and the corresponding volume. Therefore, causalities between these
two time series are investigated.
|
cond-mat/0305508
|
Neural network modeling of data with gaps: method of principal curves,
Carleman's formula, and other
|
cond-mat.dis-nn cs.NE physics.data-an
|
A method of modeling data with gaps by a sequence of curves has been
developed. The new method is a generalization of iterative construction of
singular expansion of matrices with gaps. Under discussion are three versions
of the method featuring clear physical interpretation: linear - modeling the
data by a sequence of linear manifolds of small dimension; quasilinear -
constructing "principal curves: (or "principal surfaces"), univalently
projected on the linear principal components; essentially non-linear - based on
constructing "principal curves": (principal strings and beams) employing the
variation principle; the iteration implementation of this method is close to
Kohonen self-organizing maps. The derived dependencies are extrapolated by
Carleman's formulas. The method is interpreted as a construction of neural
network conveyor designed to solve the following problems: to fill gaps in
data; to repair data - to correct initial data values in such a way as to make
the constructed models work best; to construct a calculator to fill gaps in the
data line fed to the input.
|
cond-mat/0305527
|
Back-propagation of accuracy
|
cond-mat.dis-nn cs.NA cs.NE math.NA
|
In this paper we solve the problem: how to determine maximal allowable
errors, possible for signals and parameters of each element of a network
proceeding from the condition that the vector of output signals of the network
should be calculated with given accuracy? "Back-propagation of accuracy" is
developed to solve this problem. The calculation of allowable errors for each
element of network by back-propagation of accuracy is surprisingly similar to a
back-propagation of error, because it is the backward signals motion, but at
the same time it is very different because the new rules of signals
transformation in the passing back through the elements are different. The
method allows us to formulate the requirements to the accuracy of calculations
and to the realization of technical devices, if the requirements to the
accuracy of output signals of the network are known.
|
cond-mat/0305681
|
Seven clusters in genomic triplet distributions
|
cond-mat.dis-nn cs.CV physics.bio-ph physics.data-an q-bio.GN
|
In several recent papers new gene-detection algorithms were proposed for
detecting protein-coding regions without requiring learning dataset of already
known genes. The fact that unsupervised gene-detection is possible closely
connected to existence of a cluster structure in oligomer frequency
distributions. In this paper we study cluster structure of several genomes in
the space of their triplet frequencies, using pure data exploration strategy.
Several complete genomic sequences were analyzed, using visualization of tables
of triplet frequencies in a sliding window. The distribution of 64-dimensional
vectors of triplet frequencies displays a well-detectable cluster structure.
The structure was found to consist of seven clusters, corresponding to
protein-coding information in three possible phases in one of the two
complementary strands and in the non-coding regions with high accuracy (higher
than 90% on the nucleotide level). Visualizing and understanding the structure
allows to analyze effectively performance of different gene-prediction tools.
Since the method does not require extraction of ORFs, it can be applied even
for unassembled genomes. The information content of the triplet distributions
and the validity of the mean-field models are analysed.
|
cond-mat/0307083
|
Generation of Explicit Knowledge from Empirical Data through Pruning of
Trainable Neural Networks
|
cond-mat cs.NE physics.data-an
|
This paper presents a generalized technology of extraction of explicit
knowledge from data. The main ideas are 1) maximal reduction of network
complexity (not only removal of neurons or synapses, but removal all the
unnecessary elements and signals and reduction of the complexity of elements),
2) using of adjustable and flexible pruning process (the pruning sequence
shouldn't be predetermined - the user should have a possibility to prune
network on his own way in order to achieve a desired network structure for the
purpose of extraction of rules of desired type and form), and 3) extraction of
rules not in predetermined but any desired form. Some considerations and notes
about network architecture and training process and applicability of currently
developed pruning techniques and rule extraction algorithms are discussed. This
technology, being developed by us for more than 10 years, allowed us to create
dozens of knowledge-based expert systems. In this paper we present a
generalized three-step technology of extraction of explicit knowledge from
empirical data.
|
cond-mat/0307630
|
Product Distribution Field Theory
|
cond-mat.stat-mech cond-mat.dis-nn cs.MA nlin.AO
|
This paper presents a novel way to approximate a distribution governing a
system of coupled particles with a product of independent distributions. The
approach is an extension of mean field theory that allows the independent
distributions to live in a different space from the system, and thereby capture
statistical dependencies in that system. It also allows different Hamiltonians
for each independent distribution, to facilitate Monte Carlo estimation of
those distributions. The approach leads to a novel energy-minimization
algorithm in which each coordinate Monte Carlo estimates an associated
spectrum, and then independently sets its state by sampling a Boltzmann
distribution across that spectrum. It can also be used for high-dimensional
numerical integration, (constrained) combinatorial optimization, and adaptive
distributed control. This approach also provides a simple, physics-based
derivation of the powerful approximate energy-minimization algorithms
semi-formally derived in \cite{wowh00, wotu02c, wolp03a}. In addition it
suggests many improvements to those algorithms, and motivates a new (bounded
rationality) game theory equilibrium concept.
|
cond-mat/0312019
|
A theoretical investigation of ferromagnetic tunnel junctions with
4-valued conductances
|
cond-mat.mes-hall cond-mat.mtrl-sci cs.CE physics.ins-det quant-ph
|
In considering a novel function in ferromagnetic tunnel junctions consisting
of ferromagnet(FM)/barrier/FM junctions, we theoretically investigate multiple
valued (or multi-level) cell property, which is in principle realized by
sensing conductances of four states recorded with magnetization configurations
of two FMs; that is, (up,up), (up,down), (down,up), (down,down). To obtain such
4-valued conductances, we propose FM1/spin-polarized barrier/FM2 junctions,
where the FM1 and FM2 are different ferromagnets, and the barrier has spin
dependence. The proposed idea is applied to the case of the barrier having
localized spins. Assuming that all the localized spins are pinned parallel to
magnetization axes of the FM1 and FM2, 4-valued conductances are explicitly
obtained for the case of many localized spins. Furthermore, objectives for an
ideal spin-polarized barrier are discussed.
|
cond-mat/0402508
|
Information Theory - The Bridge Connecting Bounded Rational Game Theory
and Statistical Physics
|
cond-mat.stat-mech cond-mat.dis-nn cs.GT cs.MA nlin.AO
|
A long-running difficulty with conventional game theory has been how to
modify it to accommodate the bounded rationality of all real-world players. A
recurring issue in statistical physics is how best to approximate joint
probability distributions with decoupled (and therefore far more tractable)
distributions. This paper shows that the same information theoretic
mathematical structure, known as Product Distribution (PD) theory, addresses
both issues. In this, PD theory not only provides a principled formulation of
bounded rationality and a set of new types of mean field theory in statistical
physics. It also shows that those topics are fundamentally one and the same.
|
cond-mat/0402581
|
Dictionary based methods for information extraction
|
cond-mat.stat-mech cond-mat.other cs.IR q-bio.GN q-bio.OT
|
In this paper we present a general method for information extraction that
exploits the features of data compression techniques. We first define and focus
our attention on the so-called "dictionary" of a sequence. Dictionaries are
intrinsically interesting and a study of their features can be of great
usefulness to investigate the properties of the sequences they have been
extracted from (e.g. DNA strings). We then describe a procedure of string
comparison between dictionary-created sequences (or "artificial texts") that
gives very good results in several contexts. We finally present some results on
self-consistent classification problems.
|
cond-mat/0403233
|
Artificial Sequences and Complexity Measures
|
cond-mat.stat-mech cs.CL cs.IR cs.IT math.IT
|
In this paper we exploit concepts of information theory to address the
fundamental problem of identifying and defining the most suitable tools to
extract, in a automatic and agnostic way, information from a generic string of
characters. We introduce in particular a class of methods which use in a
crucial way data compression techniques in order to define a measure of
remoteness and distance between pairs of sequences of characters (e.g. texts)
based on their relative information content. We also discuss in detail how
specific features of data compression techniques could be used to introduce the
notion of dictionary of a given sequence and of Artificial Text and we show how
these new tools can be used for information extraction purposes. We point out
the versatility and generality of our method that applies to any kind of
corpora of character strings independently of the type of coding behind them.
We consider as a case study linguistic motivated problems and we present
results for automatic language recognition, authorship attribution and self
consistent-classification.
|
cond-mat/0407439
|
A Theoretical Study on Spin-Dependent Transport of "Ferromagnet/Carbon
Nanotube Encapsulating Magnetic Atoms/Ferromagnet" Junctions with 4-Valued
Conductances
|
cond-mat.mes-hall cond-mat.mtrl-sci cs.CE physics.chem-ph
|
As a novel function of ferromagnet (FM)/spacer/FM junctions, we theoretically
investigate multiple-valued (or multi-level) cell property, which is in
principle realized by sensing conductances of four states recorded with
magnetization configurations of two FMs; (up,up), (up,down), (down,up),
(down,down). In order to sense all the states, 4-valued conductances
corresponding to the respective states are necessary. We previously proposed
that 4-valued conductances are obtained in FM1/spin-polarized spacer (SPS)/FM2
junctions, where FM1 and FM2 have different spin polarizations, and the spacer
depends on spin [J. Phys.: Condens. Matter 15, 8797 (2003)]. In this paper, an
ideal SPS is considered as a single-wall armchair carbon nanotube encapsulating
magnetic atoms, where the nanotube shows on-resonance or off-resonance at the
Fermi level according to its length. The magnitude of the obtained 4-valued
conductances has an opposite order between the on-resonant nanotube and the
off-resonant one, and this property can be understood by considering electronic
states of the nanotube. Also, the magnetoresistance ratio between (up,up) and
(down,down) can be larger than the conventional one between parallel and
anti-parallel configurations.
|
cond-mat/0408190
|
From spin glasses to hard satisfiable formulas
|
cond-mat.stat-mech cond-mat.dis-nn cs.AI
|
We introduce a highly structured family of hard satisfiable 3-SAT formulas
corresponding to an ordered spin-glass model from statistical physics. This
model has provably "glassy" behavior; that is, it has many local optima with
large energy barriers between them, so that local search algorithms get stuck
and have difficulty finding the true ground state, i.e., the unique satisfying
assignment. We test the hardness of our formulas with two Davis-Putnam solvers,
Satz and zChaff, the recently introduced Survey Propagation (SP), and two local
search algorithms, Walksat and Record-to-Record Travel (RRT). We compare our
formulas to random 3-XOR-SAT formulas and to two other generators of hard
satisfiable instances, the minimum disagreement parity formulas of Crawford et
al., and Hirsch's hgen. For the complete solvers the running time of our
formulas grows exponentially in sqrt(n), and exceeds that of random 3-XOR-SAT
formulas for small problem sizes. SP is unable to solve our formulas with as
few as 25 variables. For Walksat, our formulas appear to be harder than any
other known generator of satisfiable instances. Finally, our formulas can be
solved efficiently by RRT but only if the parameter d is tuned to the height of
the barriers between local minima, and we use this parameter to measure the
barrier heights in random 3-XOR-SAT formulas as well.
|
cond-mat/0410270
|
On uniqueness theorems for Tsallis entropy and Tsallis relative entropy
|
cond-mat.stat-mech cs.IT math.IT
|
The uniqueness theorem for Tsallis entropy was presented in {\it H.Suyari,
IEEE Trans. Inform. Theory, Vol.50, pp.1783-1787 (2004)} by introducing the
generalized Shannon-Khinchin's axiom. In the present paper, this result is
generalized and simplified as follows: {\it Generalization}: The uniqueness
theorem for Tsallis relative entropy is shown by means of the generalized
Hobson's axiom. {\it Simplification}: The uniqueness theorem for Tsallis
entropy is shown by means of the generalized Faddeev's axiom.
|
cond-mat/0410271
|
A generalized Faddeev's axiom and the uniqueness theorem for Tsallis
entropy
|
cond-mat.stat-mech cs.IT math.IT
|
The uniequness theorem for the Tsallis entropy by introducing the generalized
Faddeev's axiom is proven. Our result improves the recent result, the
uniqueness theorem for Tsallis entropy by the generalized Shannon-Khinchin's
axiom in \cite{Suy}, in the sence that our axiom is simpler than his one, as
similar that Faddeev's axiom is simpler than Shannon-Khinchin's one.
|
cond-mat/0410460
|
A Computational Study of Rotating Spiral Waves and Spatio-Temporal
Transient Chaos in a Deterministic Three-Level Active System
|
cond-mat.other cs.NE nlin.CG
|
Spatio-temporal dynamics of a deterministic three-level cellular automaton
(TLCA) of Zykov-Mikhailov type (Sov. Phys. - Dokl., 1986, Vol.31, No.1, P.51)
is studied numerically. Evolution of spatial structures is investigated both
for the original Zykov-Mikhailov model (which is applicable to, for example,
Belousov-Zhabotinskii chemical reactions) and for proposed by us TLCA, which is
a generalization of Zykov-Mikhailov model for the case of two-channel
diffusion. Such the TLCA is a minimal model for an excitable medium of
microwave phonon laser, called phaser (D. N. Makovetskii, Tech. Phys., 2004,
Vol.49, No.2, P.224; cond-mat/0402640). The most interesting observed forms of
TLCA dynamics are as follows: (a) spatio-temporal transient chaos in form of
highly bottlenecked collective evolution of excitations by rotating spiral
waves (RSW) with variable topological charges; (b) competition of left-handed
and right-handed RSW with unexpected features, including self-induced
alteration of integral effective topological charge; (c) transient chimera
states, i.e. coexistence of regular and chaotic domains in TLCA patterns; (d)
branching of TLCA states with different symmetry which may lead to full
restoring of symmetry of imperfect starting pattern. Phenomena (a) and (c) are
directly related to phaser dynamics features observed earlier in real
experiments at liquid helium temperatures on corundum crystals doped by
iron-group ions. ACM: F.1.1, I.6, J.2; PACS:05.65.+b, 07.05.Tp, 82.20.Wt
|
cond-mat/0410594
|
A model of student's dilemma
|
cond-mat.other cond-mat.stat-mech cs.MA physics.soc-ph
|
Each year perhaps millions of young people face the following dilemma: should
I continue my education or rather start working with already acquired skills.
Right decision must take into account somebody's own abilities, accessibility
to education institutions, competition, and potential benefits. A multi-agent,
evolutionary model of this dilemma predicts a transition between stratified and
homogeneous phases, evolution that diminishes fitness, fewer applicants per
seat for decreased capacity of the university, and presence of poor students at
\'elite universities.
|
cond-mat/0412460
|
Exact Maxwell-Boltzmann, Bose-Einstein and Fermi-Dirac Statistics
|
cond-mat.stat-mech cs.IT math.IT quant-ph
|
The exact Maxwell-Boltzmann (MB), Bose-Einstein (BE) and Fermi-Dirac (FD)
entropies and probabilistic distributions are derived by the combinatorial
method of Boltzmann, without Stirling's approximation. The new entropy measures
are explicit functions of the probability and degeneracy of each state, and the
total number of entities, N. By analysis of the cost of a "binary decision",
exact BE and FD statistics are shown to have profound consequences for the
behaviour of quantum mechanical systems.
|
cond-mat/0412587
|
Spin dependent transport of ``nonmagnetic metal/zigzag nanotube
encapsulating magnetic atoms/nonmagnetic metal'' junctions
|
cond-mat.mes-hall cond-mat.mtrl-sci cs.CE physics.chem-ph quant-ph
|
Towards a novel magnetoresistance (MR) device with a carbon nanotube, we
propose ``nonmagnetic metal/zigzag nanotube encapsulating magnetic
atoms/nonmagnetic metal'' junctions. We theoretically investigate how
spin-polarized edges of the nanotube and the encapsulated magnetic atoms
influence on transport. When the on-site Coulomb energy divided by the
magnitude of transfer integral, $U/|t|$, is larger than 0.8, large MR effect
due to the direction of spins of magnetic atoms, which has the magnitude of the
MR ratio of about 100%, appears reflecting such spin-polarized edges.
|
cond-mat/0412723
|
Modelling financial markets by the multiplicative sequence of trades
|
cond-mat.stat-mech cs.CE math.SP physics.data-an q-fin.ST
|
We introduce the stochastic multiplicative point process modelling trading
activity of financial markets. Such a model system exhibits power-law spectral
density S(f) ~ 1/f**beta, scaled as power of frequency for various values of
beta between 0.5 and 2. Furthermore, we analyze the relation between the
power-law autocorrelations and the origin of the power-law probability
distribution of the trading activity. The model reproduces the spectral
properties of trading activity and explains the mechanism of power-law
distribution in real markets.
|
cond-mat/0504025
|
Point process model of 1/f noise versus a sum of Lorentzians
|
cond-mat.stat-mech astro-ph cond-mat.dis-nn cs.CE math.ST nlin.AO physics.data-an q-bio.NC stat.TH
|
We present a simple point process model of $1/f^{\beta}$ noise, covering
different values of the exponent $\beta$. The signal of the model consists of
pulses or events. The interpulse, interevent, interarrival, recurrence or
waiting times of the signal are described by the general Langevin equation with
the multiplicative noise and stochastically diffuse in some interval resulting
in the power-law distribution. Our model is free from the requirement of a wide
distribution of relaxation times and from the power-law forms of the pulses. It
contains only one relaxation rate and yields $1/f^ {\beta}$ spectra in a wide
range of frequency. We obtain explicit expressions for the power spectra and
present numerical illustrations of the model. Further we analyze the relation
of the point process model of $1/f$ noise with the Bernamont-Surdin-McWhorter
model, representing the signals as a sum of the uncorrelated components. We
show that the point process model is complementary to the model based on the
sum of signals with a wide-range distribution of the relaxation times. In
contrast to the Gaussian distribution of the signal intensity of the sum of the
uncorrelated components, the point process exhibits asymptotically a power-law
distribution of the signal intensity. The developed multiplicative point
process model of $1/f^{\beta}$ noise may be used for modeling and analysis of
stochastic processes in different systems with the power-law distribution of
the intensity of pulsing signals.
|
cond-mat/0506037
|
Diagnosis of weaknesses in modern error correction codes: a physics
approach
|
cond-mat.stat-mech cond-mat.dis-nn cs.IT math.IT
|
One of the main obstacles to the wider use of the modern error-correction
codes is that, due to the complex behavior of their decoding algorithms, no
systematic method which would allow characterization of the Bit-Error-Rate
(BER) is known. This is especially true at the weak noise where many systems
operate and where coding performance is difficult to estimate because of the
diminishingly small number of errors. We show how the instanton method of
physics allows one to solve the problem of BER analysis in the weak noise range
by recasting it as a computationally tractable minimization problem.
|
cond-mat/0506652
|
The theoretical capacity of the Parity Source Coder
|
cond-mat.dis-nn cond-mat.stat-mech cs.IT math.IT
|
The Parity Source Coder is a protocol for data compression which is based on
a set of parity checks organized in a sparse random network. We consider here
the case of memoryless unbiased binary sources. We show that the theoretical
capacity saturate the Shannon limit at large K. We also find that the first
corrections to the leading behavior are exponentially small, so that the
behavior at finite K is very close to the optimal one.
|
cond-mat/0508216
|
Cluster Variation Method in Statistical Physics and Probabilistic
Graphical Models
|
cond-mat.stat-mech cs.IT math.IT
|
The cluster variation method (CVM) is a hierarchy of approximate variational
techniques for discrete (Ising--like) models in equilibrium statistical
mechanics, improving on the mean--field approximation and the Bethe--Peierls
approximation, which can be regarded as the lowest level of the CVM. In recent
years it has been applied both in statistical physics and to inference and
optimization problems formulated in terms of probabilistic graphical models.
The foundations of the CVM are briefly reviewed, and the relations with
similar techniques are discussed. The main properties of the method are
considered, with emphasis on its exactness for particular models and on its
asymptotic properties.
The problem of the minimization of the variational free energy, which arises
in the CVM, is also addressed, and recent results about both provably
convergent and message-passing algorithms are discussed.
|
cond-mat/0511159
|
Learning by message-passing in networks of discrete synapses
|
cond-mat.dis-nn cs.LG q-bio.NC
|
We show that a message-passing process allows to store in binary "material"
synapses a number of random patterns which almost saturates the information
theoretic bounds. We apply the learning algorithm to networks characterized by
a wide range of different connection topologies and of size comparable with
that of biological systems (e.g. $n\simeq10^{5}-10^{6}$). The algorithm can be
turned into an on-line --fault tolerant-- learning protocol of potential
interest in modeling aspects of synaptic plasticity and in building
neuromorphic devices.
|
cond-mat/0512017
|
Combinatorial Information Theory: I. Philosophical Basis of
Cross-Entropy and Entropy
|
cond-mat.stat-mech cs.IT math-ph math.IT math.MP physics.data-an
|
This study critically analyses the information-theoretic, axiomatic and
combinatorial philosophical bases of the entropy and cross-entropy concepts.
The combinatorial basis is shown to be the most fundamental (most primitive) of
these three bases, since it gives (i) a derivation for the Kullback-Leibler
cross-entropy and Shannon entropy functions, as simplified forms of the
multinomial distribution subject to the Stirling approximation; (ii) an
explanation for the need to maximize entropy (or minimize cross-entropy) to
find the most probable realization; and (iii) new, generalized definitions of
entropy and cross-entropy - supersets of the Boltzmann principle - applicable
to non-multinomial systems. The combinatorial basis is therefore of much
broader scope, with far greater power of application, than the
information-theoretic and axiomatic bases. The generalized definitions underpin
a new discipline of ``{\it combinatorial information theory}'', for the
analysis of probabilistic systems of any type.
Jaynes' generic formulation of statistical mechanics for multinomial systems
is re-examined in light of the combinatorial approach. (abbreviated abstract)
|
cond-mat/0601021
|
Characterizing correlations of flow oscillations at bottlenecks
|
cond-mat.stat-mech cs.MA
|
"Oscillations" occur in quite different kinds of many-particle-systems when
two groups of particles with different directions of motion meet or intersect
at a certain spot. We present a model of pedestrian motion that is able to
reproduce oscillations with different characteristics. The Wald-Wolfowitz test
and Gillis' correlated random walk are shown to hold observables that can be
used to characterize different kinds of oscillations.
|
cond-mat/0601487
|
Loop Calculus in Statistical Physics and Information Science
|
cond-mat.stat-mech cond-mat.dis-nn cs.IT math.IT
|
Considering a discrete and finite statistical model of a general position we
introduce an exact expression for the partition function in terms of a finite
series. The leading term in the series is the Bethe-Peierls (Belief
Propagation)-BP contribution, the rest are expressed as loop-contributions on
the factor graph and calculated directly using the BP solution. The series
unveils a small parameter that often makes the BP approximation so successful.
Applications of the loop calculus in statistical physics and information
science are discussed.
|
cond-mat/0601573
|
Amorphous packings of hard spheres in large space dimension
|
cond-mat.stat-mech cond-mat.dis-nn cs.IT math.GM math.IT
|
In a recent paper (cond-mat/0506445) we derived an expression for the
replicated free energy of a liquid of hard spheres based on the HNC free energy
functional. An approximate equation of state for the glass and an estimate of
the random close packing density were obtained in d=3. Here we show that the
HNC approximation is not needed: the same expression can be obtained from the
full diagrammatic expansion of the replicated free energy. Then, we consider
the asymptotics of this expression when the space dimension d is very large. In
this limit, the entropy of the hard sphere liquid has been computed exactly.
Using this solution, we derive asymptotic expressions for the glass transition
density and for the random close packing density for hard spheres in large
space dimension.
|
cond-mat/0602183
|
Nonlinear parametric model for Granger causality of time series
|
cond-mat.dis-nn cond-mat.stat-mech cs.LG physics.med-ph q-bio.QM
|
We generalize a previously proposed approach for nonlinear Granger causality
of time series, based on radial basis function. The proposed model is not
constrained to be additive in variables from the two time series and can
approximate any function of these variables, still being suitable to evaluate
causality. Usefulness of this measure of causality is shown in a physiological
example and in the study of the feed-back loop in a model of excitatory and
inhibitory neurons.
|
cond-mat/0602345
|
Numerical Modeling of Coexistence, Competition and Collapse of Rotating
Spiral Waves in Three-Level Excitable Media with Discrete Active Centers and
Absorbing Boundaries
|
cond-mat.other cs.NE nlin.CG
|
Spatio-temporal dynamics of excitable media with discrete three-level active
centers (ACs) and absorbing boundaries is studied numerically by means of a
deterministic three-level model (see S. D. Makovetskiy and D. N. Makovetskii,
on-line preprint cond-mat/0410460 ), which is a generalization of Zykov-
Mikhailov model (see Sov. Phys. -- Doklady, 1986, Vol.31, No.1, P.51) for the
case of two-channel diffusion of excitations. In particular, we revealed some
qualitatively new features of coexistence, competition and collapse of rotating
spiral waves (RSWs) in three-level excitable media under conditions of strong
influence of the second channel of diffusion. Part of these features are caused
by unusual mechanism of RSWs evolution when RSW's cores get into the surface
layer of an active medium (i.~e. the layer of ACs resided at the absorbing
boundary). Instead of well known scenario of RSW collapse, which takes place
after collision of RSW's core with absorbing boundary, we observed complicated
transformations of the core leading to nonlinear ''reflection'' of the RSW from
the boundary or even to birth of several new RSWs in the surface layer. To our
knowledge, such nonlinear ''reflections'' of RSWs and resulting die hard
vorticity in excitable media with absorbing boundaries were unknown earlier.
ACM classes: F.1.1, I.6, J.2; PACS numbers: 05.65.+b, 07.05.Tp, 82.20.Wt
|
cond-mat/0602661
|
On the high density behavior of Hamming codes with fixed minimum
distance
|
cond-mat.stat-mech cond-mat.dis-nn cs.IT math.IT
|
We discuss the high density behavior of a system of hard spheres of diameter
d on the hypercubic lattice of dimension n, in the limit n -> oo, d -> oo,
d/n=delta. The problem is relevant for coding theory. We find a solution to the
equations describing the liquid up to very large values of the density, but we
show that this solution gives a negative entropy for the liquid phase when the
density is large enough. We then conjecture that a phase transition towards a
different phase might take place, and we discuss possible scenarios for this
transition. Finally we discuss the relation between our results and known
rigorous bounds on the maximal density of the system.
|
cond-mat/0603189
|
Loop series for discrete statistical models on graphs
|
cond-mat.stat-mech cond-mat.dis-nn cs.IT math.IT
|
In this paper we present derivation details, logic, and motivation for the
loop calculus introduced in \cite{06CCa}. Generating functions for three
inter-related discrete statistical models are each expressed in terms of a
finite series. The first term in the series corresponds to the Bethe-Peierls
(Belief Propagation)-BP contribution, the other terms are labeled by loops on
the factor graph. All loop contributions are simple rational functions of spin
correlation functions calculated within the BP approach. We discuss two
alternative derivations of the loop series. One approach implements a set of
local auxiliary integrations over continuous fields with the BP contribution
corresponding to an integrand saddle-point value. The integrals are replaced by
sums in the complimentary approach, briefly explained in \cite{06CCa}. A local
gauge symmetry transformation that clarifies an important invariant feature of
the BP solution, is revealed in both approaches. The partition function remains
invariant while individual terms change under the gauge transformation. The
requirement for all individual terms to be non-zero only for closed loops in
the factor graph (as opposed to paths with loose ends) is equivalent to fixing
the first term in the series to be exactly equal to the BP contribution.
Further applications of the loop calculus to problems in statistical physics,
computer and information sciences are discussed.
|
cond-mat/0604267
|
Survey propagation for the cascading Sourlas code
|
cond-mat.stat-mech cs.IT math.IT
|
We investigate how insights from statistical physics, namely survey
propagation, can improve decoding of a particular class of sparse error
correcting codes. We show that a recently proposed algorithm, time averaged
belief propagation, is in fact intimately linked to a specific survey
propagation for which Parisi's replica symmetry breaking parameter is set to
zero, and that the latter is always superior to belief propagation in the high
connectivity limit. We briefly look at further improvements available by going
to the second level of replica symmetry breaking.
|
cond-mat/0606125
|
Microscopic activity patterns in the Naming Game
|
cond-mat.dis-nn cs.MA physics.soc-ph
|
The models of statistical physics used to study collective phenomena in some
interdisciplinary contexts, such as social dynamics and opinion spreading, do
not consider the effects of the memory on individual decision processes. On the
contrary, in the Naming Game, a recently proposed model of Language formation,
each agent chooses a particular state, or opinion, by means of a memory-based
negotiation process, during which a variable number of states is collected and
kept in memory. In this perspective, the statistical features of the number of
states collected by the agents becomes a relevant quantity to understand the
dynamics of the model, and the influence of topological properties on
memory-based models. By means of a master equation approach, we analyze the
internal agent dynamics of Naming Game in populations embedded on networks,
finding that it strongly depends on very general topological properties of the
system (e.g. average and fluctuations of the degree). However, the influence of
topological properties on the microscopic individual dynamics is a general
phenomenon that should characterize all those social interactions that can be
modeled by memory-based negotiation processes.
|
cond-mat/0606696
|
Statistical mechanics of error exponents for error-correcting codes
|
cond-mat.dis-nn cond-mat.stat-mech cs.IT math.IT
|
Error exponents characterize the exponential decay, when increasing message
length, of the probability of error of many error-correcting codes. To tackle
the long standing problem of computing them exactly, we introduce a general,
thermodynamic, formalism that we illustrate with maximum-likelihood decoding of
low-density parity-check (LDPC) codes on the binary erasure channel (BEC) and
the binary symmetric channel (BSC). In this formalism, we apply the cavity
method for large deviations to derive expressions for both the average and
typical error exponents, which differ by the procedure used to select the codes
from specified ensembles. When decreasing the noise intensity, we find that two
phase transitions take place, at two different levels: a glass to ferromagnetic
transition in the space of codewords, and a paramagnetic to glass transition in
the space of codes.
|
cond-mat/0608312
|
On Cavity Approximations for Graphical Models
|
cond-mat.stat-mech cond-mat.dis-nn cs.IT math.IT
|
We reformulate the Cavity Approximation (CA), a class of algorithms recently
introduced for improving the Bethe approximation estimates of marginals in
graphical models. In our new formulation, which allows for the treatment of
multivalued variables, a further generalization to factor graphs with arbitrary
order of interaction factors is explicitly carried out, and a message passing
algorithm that implements the first order correction to the Bethe approximation
is described. Furthermore we investigate an implementation of the CA for
pairwise interactions. In all cases considered we could confirm that CA[k] with
increasing $k$ provides a sequence of approximations of markedly increasing
precision. Furthermore in some cases we could also confirm the general
expectation that the approximation of order $k$, whose computational complexity
is $O(N^{k+1})$ has an error that scales as $1/N^{k+1}$ with the size of the
system. We discuss the relation between this approach and some recent
developments in the field.
|
cond-mat/0611567
|
Generalized Statistics Framework for Rate Distortion Theory
|
cond-mat.stat-mech cs.IT math.IT
|
Variational principles for the rate distortion (RD) theory in lossy
compression are formulated within the ambit of the generalized nonextensive
statistics of Tsallis, for values of the nonextensivity parameter satisfying $
0 < q < 1 $ and $ q > 1 $. Alternating minimization numerical schemes to
evaluate the nonextensive RD function, are derived. Numerical simulations
demonstrate the efficacy of generalized statistics RD models.
|
cond-mat/0611717
|
Non-equilibrium phase transition in negotiation dynamics
|
cond-mat.stat-mech cs.MA physics.soc-ph q-bio.PE
|
We introduce a model of negotiation dynamics whose aim is that of mimicking
the mechanisms leading to opinion and convention formation in a population of
individuals. The negotiation process, as opposed to ``herding-like'' or
``bounded confidence'' driven processes, is based on a microscopic dynamics
where memory and feedback play a central role. Our model displays a
non-equilibrium phase transition from an absorbing state in which all agents
reach a consensus to an active stationary state characterized either by
polarization or fragmentation in clusters of agents with different opinions. We
show the exystence of at least two different universality classes, one for the
case with two possible opinions and one for the case with an unlimited number
of opinions. The phase transition is studied analytically and numerically for
various topologies of the agents' interaction network. In both cases the
universality classes do not seem to depend on the specific interaction
topology, the only relevant feature being the total number of different
opinions ever present in the system.
|
cond-mat/0701218
|
Generalized Statistics Framework for Rate Distortion Theory with Bregman
Divergences
|
cond-mat.stat-mech cs.IT math.IT
|
A variational principle for the rate distortion (RD) theory with Bregman
divergences is formulated within the ambit of the generalized (nonextensive)
statistics of Tsallis. The Tsallis-Bregman RD lower bound is established.
Alternate minimization schemes for the generalized Bregman RD (GBRD) theory are
derived. A computational strategy to implement the GBRD model is presented. The
efficacy of the GBRD model is exemplified with the aid of numerical
simulations.
|
cond-mat/0703351
|
Error Correction and Digitalization Concepts in Biochemical Computing
|
cond-mat.soft cond-mat.dis-nn cond-mat.mtrl-sci cs.CE q-bio.BM quant-ph
|
We offer a theoretical design of new systems that show promise for digital
biochemical computing, including realizations of error correction by utilizing
redundancy, as well as signal rectification. The approach includes information
processing using encoded DNA sequences, DNAzyme biocatalyzed reactions and the
use of DNA-functionalized magnetic nanoparticles. Digital XOR and NAND logic
gates and copying (fanout) are designed using the same components.
|
cond-mat/9703183
|
Finite size scaling of the bayesian perceptron
|
cond-mat.stat-mech cond-mat.dis-nn cs.AI cs.LG
|
We study numerically the properties of the bayesian perceptron through a
gradient descent on the optimal cost function. The theoretical distribution of
stabilities is deduced. It predicts that the optimal generalizer lies close to
the boundary of the space of (error-free) solutions. The numerical simulations
are in good agreement with the theoretical distribution. The extrapolation of
the generalization error to infinite input space size agrees with the
theoretical results. Finite size corrections are negative and exhibit two
different scaling regimes, depending on the training set size. The variance of
the generalization error vanishes for $N \rightarrow \infty$ confirming the
property of self-averaging.
|
cond-mat/9810144
|
Relaxation in graph coloring and satisfiability problems
|
cond-mat.dis-nn cs.AI
|
Using T=0 Monte Carlo simulation, we study the relaxation of graph coloring
(K-COL) and satisfiability (K-SAT), two hard problems that have recently been
shown to possess a phase transition in solvability as a parameter is varied. A
change from exponentially fast to power law relaxation, and a transition to
freezing behavior are found. These changes take place for smaller values of the
parameter than the solvability transition. Results for the coloring problem for
colorable and clustered graphs and for the fraction of persistent spins for
satisfiability are also presented.
|
cond-mat/9902011
|
Cortical Potential Distributions and Cognitive Information Processing
|
cond-mat.dis-nn adap-org cond-mat.stat-mech cs.NE math-ph math.MP nlin.AO physics.bio-ph q-bio
|
The use of cortical field potentials rather than the details of spike trains
as the basis for cognitive information processing is proposed. This results in
a space of cognitive elements with natural metrics. Sets of spike trains may
also be considered to be points in a multidimensional metric space. The
closeness of sets of spike trains in such a space implies the closeness of
points in the resulting function space of potential distributions.
|
cond-mat/9906206
|
Ocular dominance patterns in mammalian visual cortex: A wire length
minimization approach
|
cond-mat.soft cond-mat.dis-nn cs.NE physics.bio-ph q-bio
|
We propose a theory for ocular dominance (OD) patterns in mammalian primary
visual cortex. This theory is based on the premise that OD pattern is an
adaptation to minimize the length of intra-cortical wiring. Thus we can
understand the existing OD patterns by solving a wire length minimization
problem. We divide all the neurons into two classes: left-eye dominated and
right-eye dominated. We find that segregation of neurons into monocular regions
reduces wire length if the number of connections with the neurons of the same
class differs from that with the other class. The shape of the regions depends
on the relative fraction of neurons in the two classes. If the numbers are
close we find that the optimal OD pattern consists of interdigitating stripes.
If one class is less numerous than the other, the optimal OD pattern consists
of patches of the first class neurons in the sea of the other class neurons. We
predict the transition from stripes to patches when the fraction of neurons
dominated by the ipsilateral eye is about 40%. This prediction agrees with the
data in macaque and Cebus monkeys. This theory can be applied to other binary
cortical systems.
|
cs/0001002
|
Minimum Description Length and Compositionality
|
cs.CL cs.AI
|
We present a non-vacuous definition of compositionality. It is based on the
idea of combining the minimum description length principle with the original
definition of compositionality (that is, that the meaning of the whole is a
function of the meaning of the parts).
The new definition is intuitive and allows us to distinguish between
compositional and non-compositional semantics, and between idiomatic and
non-idiomatic expressions. It is not ad hoc, since it does not make any
references to non-intrinsic properties of meaning functions (like being a
polynomial). Moreover, it allows us to compare different meaning functions with
respect to how compositional they are. It bridges linguistic and corpus-based,
statistical approaches to natural language understanding.
|
cs/0001004
|
Multiplicative Algorithm for Orthgonal Groups and Independent Component
Analysis
|
cs.LG
|
The multiplicative Newton-like method developed by the author et al. is
extended to the situation where the dynamics is restricted to the orthogonal
group. A general framework is constructed without specifying the cost function.
Though the restriction to the orthogonal groups makes the problem somewhat
complicated, an explicit expression for the amount of individual jumps is
obtained. This algorithm is exactly second-order-convergent. The global
instability inherent in the Newton method is remedied by a
Levenberg-Marquardt-type variation. The method thus constructed can readily be
applied to the independent component analysis. Its remarkable performance is
illustrated by a numerical simulation.
|
cs/0001006
|
Compositionality, Synonymy, and the Systematic Representation of Meaning
|
cs.CL cs.LO
|
In a recent issue of Linguistics and Philosophy Kasmi and Pelletier (1998)
(K&P), and Westerstahl (1998) criticize Zadrozny's (1994) argument that any
semantics can be represented compositionally. The argument is based upon
Zadrozny's theorem that every meaning function m can be encoded by a function
\mu such that (i) for any expression E of a specified language L, m(E) can be
recovered from \mu(E), and (ii) \mu is a homomorphism from the syntactic
structures of L to interpretations of L.
In both cases, the primary motivation for the objections brought against
Zadrozny's argument is the view that his encoding of the original meaning
function does not properly reflect the synonymy relations posited for the
language.
In this paper, we argue that these technical criticisms do not go through. In
particular, we prove that \mu properly encodes synonymy relations, i.e. if two
expressions are synonymous, then their compositional meanings are identical.
This corrects some misconceptions about the function \mu, e.g. Janssen (1997).
We suggest that the reason that semanticists have been anxious to preserve
compositionality as a significant constraint on semantic theory is that it has
been mistakenly regarded as a condition that must be satisfied by any theory
that sustains a systematic connection between the meaning of an expression and
the meanings of its parts. Recent developments in formal and computational
semantics show that systematic theories of meanings need not be compositional.
|
cs/0001008
|
Predicting the expected behavior of agents that learn about agents: the
CLRI framework
|
cs.MA cs.LG
|
We describe a framework and equations used to model and predict the behavior
of multi-agent systems (MASs) with learning agents. A difference equation is
used for calculating the progression of an agent's error in its decision
function, thereby telling us how the agent is expected to fare in the MAS. The
equation relies on parameters which capture the agent's learning abilities,
such as its change rate, learning rate and retention rate, as well as relevant
aspects of the MAS such as the impact that agents have on each other. We
validate the framework with experimental results using reinforcement learning
agents in a market system, as well as with other experimental results gathered
from the AI literature. Finally, we use PAC-theory to show how to calculate
bounds on the values of the learning parameters.
|
cs/0001010
|
A Real World Implementation of Answer Extraction
|
cs.CL
|
In this paper we describe ExtrAns, an answer extraction system. Answer
extraction (AE) aims at retrieving those exact passages of a document that
directly answer a given user question. AE is more ambitious than information
retrieval and information extraction in that the retrieval results are phrases,
not entire documents, and in that the queries may be arbitrarily specific. It
is less ambitious than full-fledged question answering in that the answers are
not generated from a knowledge base but looked up in the text of documents. The
current version of ExtrAns is able to parse unedited Unix "man pages", and
derive the logical form of their sentences. User queries are also translated
into logical forms. A theorem prover then retrieves the relevant phrases, which
are presented through selective highlighting in their context.
|
cs/0001012
|
Measures of Distributional Similarity
|
cs.CL
|
We study distributional similarity measures for the purpose of improving
probability estimation for unseen cooccurrences. Our contributions are
three-fold: an empirical comparison of a broad range of measures; a
classification of similarity functions based on the information that they
incorporate; and the introduction of a novel function that is superior at
evaluating potential proxy distributions.
|
cs/0001015
|
Multi-Agent Only Knowing
|
cs.AI cs.LO
|
Levesque introduced a notion of ``only knowing'', with the goal of capturing
certain types of nonmonotonic reasoning. Levesque's logic dealt with only the
case of a single agent. Recently, both Halpern and Lakemeyer independently
attempted to extend Levesque's logic to the multi-agent case. Although there
are a number of similarities in their approaches, there are some significant
differences. In this paper, we reexamine the notion of only knowing, going back
to first principles. In the process, we simplify Levesque's completeness proof,
and point out some problems with the earlier definitions. This leads us to
reconsider what the properties of only knowing ought to be. We provide an axiom
system that captures our desiderata, and show that it has a semantics that
corresponds to it. The axiom system has an added feature of interest: it
includes a modal operator for satisfiability, and thus provides a complete
axiomatization for satisfiability in the logic K45.
|
cs/0001018
|
Adaptive simulated annealing (ASA): Lessons learned
|
cs.MS cs.CE
|
Adaptive simulated annealing (ASA) is a global optimization algorithm based
on an associated proof that the parameter space can be sampled much more
efficiently than by using other previous simulated annealing algorithms. The
author's ASA code has been publicly available for over two years. During this
time the author has volunteered to help people via e-mail, and the feedback
obtained has been used to further develop the code. Some lessons learned, in
particular some which are relevant to other simulated annealing algorithms, are
described.
|
cs/0001020
|
Exploiting Syntactic Structure for Natural Language Modeling
|
cs.CL
|
The thesis presents an attempt at using the syntactic structure in natural
language for improved language models for speech recognition. The structured
language model merges techniques in automatic parsing and language modeling
using an original probabilistic parameterization of a shift-reduce parser. A
maximum likelihood reestimation procedure belonging to the class of
expectation-maximization algorithms is employed for training the model.
Experiments on the Wall Street Journal, Switchboard and Broadcast News corpora
show improvement in both perplexity and word error rate - word lattice
rescoring - over the standard 3-gram language model. The significance of the
thesis lies in presenting an original approach to language modeling that uses
the hierarchical - syntactic - structure in natural language to improve on
current 3-gram modeling techniques for large vocabulary speech recognition.
|
cs/0001021
|
Refinement of a Structured Language Model
|
cs.CL
|
A new language model for speech recognition inspired by linguistic analysis
is presented. The model develops hidden hierarchical structure incrementally
and uses it to extract meaningful information from the word history - thus
enabling the use of extended distance dependencies - in an attempt to
complement the locality of currently used n-gram Markov models. The model, its
probabilistic parametrization, a reestimation algorithm for the model
parameters and a set of experiments meant to evaluate its potential for speech
recognition are presented.
|
cs/0001022
|
Recognition Performance of a Structured Language Model
|
cs.CL
|
A new language model for speech recognition inspired by linguistic analysis
is presented. The model develops hidden hierarchical structure incrementally
and uses it to extract meaningful information from the word history - thus
enabling the use of extended distance dependencies - in an attempt to
complement the locality of currently used trigram models. The structured
language model, its probabilistic parameterization and performance in a
two-pass speech recognizer are presented. Experiments on the SWITCHBOARD corpus
show an improvement in both perplexity and word error rate over conventional
trigram models.
|
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