3,930 research outputs found
Unnatural Selection: A new formal approach to punctuated equilibrium in economic systems
Generalized Darwinian evolutionary theory has emerged as central to the description of economic process (e.g., Aldrich et. al., 2008). Here we demonstrate that, just as Darwinian principles provide necessary, but not sufficient, conditions for understanding the dynamics of social entities, in a similar manner the asymptotic limit theorems of information theory provide another set of necessary conditions that constrain the evolution of socioeconomic process. These latter constraints can, however, easily be formulated as a statistics-like analytic toolbox for the study of empirical data that is consistent with a generalized Darwinism, and this is no small thing
Extending the Modern Synthesis: The evolution of ecosystems
The Modern Evolutionary Synthesis formalizes the role of variation, heredity, differential reproduction and mutation in population genetics. Here we explore a mathematical structure, based on the asymptotic limit theorems of information theory, that instantiates the punctuated dynamic relations of organisms and their embedding environments. The mathematical overhead is considerable, and we conclude that the model must itself be extended even further to allow the possibility of the transfer of heritage information between different classes of organisms. In essence, we provide something of a formal roadmap for the modernization of the Modern Synthesis
On the Relative Usefulness of Fireballs
In CSL-LICS 2014, Accattoli and Dal Lago showed that there is an
implementation of the ordinary (i.e. strong, pure, call-by-name)
-calculus into models like RAM machines which is polynomial in the
number of -steps, answering a long-standing question. The key ingredient
was the use of a calculus with useful sharing, a new notion whose complexity
was shown to be polynomial, but whose implementation was not explored. This
paper, meant to be complementary, studies useful sharing in a call-by-value
scenario and from a practical point of view. We introduce the Fireball
Calculus, a natural extension of call-by-value to open terms for which the
problem is as hard as for the ordinary lambda-calculus. We present three
results. First, we adapt the solution of Accattoli and Dal Lago, improving the
meta-theory of useful sharing. Then, we refine the picture by introducing the
GLAMoUr, a simple abstract machine implementing the Fireball Calculus extended
with useful sharing. Its key feature is that usefulness of a step is
tested---surprisingly---in constant time. Third, we provide a further
optimization that leads to an implementation having only a linear overhead with
respect to the number of -steps.Comment: Technical report for the LICS 2015 submission with the same titl
Contextual equivalence in lambda-calculi extended with letrec and with a parametric polymorphic type system
This paper describes a method to treat contextual equivalence in polymorphically typed lambda-calculi, and also how to transfer equivalences from the untyped versions of lambda-calculi to their typed variant, where our specific calculus has letrec, recursive types and is nondeterministic. An addition of a type label to every subexpression is all that is needed, together with some natural constraints for the consistency of the type labels and well-scopedness of expressions. One result is that an elementary but typed notion of program transformation is obtained and that untyped contextual equivalences also hold in the typed calculus as long as the expressions are well-typed. In order to have a nice interaction between reduction and typing, some reduction rules have to be accompanied with a type modification by generalizing or instantiating types
Homeomorphic Embedding for Online Termination of Symbolic Methods
Well-quasi orders in general, and homeomorphic embedding in particular, have gained popularity to ensure the termination of techniques for program analysis, specialisation, transformation, and verification. In this paper we survey and discuss this use of homeomorphic embedding and clarify the advantages of such an approach over one using well-founded orders. We also discuss various extensions of the homeomorphic embedding relation. We conclude with a study of homeomorphic embedding in the context of metaprogramming, presenting some new (positive and negative) results and open problems
Subsumption algorithms for concept languages
We investigate the subsumption problem in logic-based knowledge representation languages of the KL-ONE family and give decision procedures. All our languages contain as a kernel the logical connectives conjunction, disjunction, and negation for concepts, as well as role quantification. The algorithms are rule-based and can be understood as variants of tableaux calculus with a special control strategy. In the first part of the paper, we add number restrictions and conjunction of roles to the kernel language. We show that subsumption in this language is decidable, and we investigate sublanguages for which the problem of deciding subsumption is PSPACE-complete. In the second part, we amalgamate the kernel language with feature descriptions as used in computational linguistics. We show that feature descriptions do not increase the complexity of the subsumption problem
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