181,804 research outputs found
A Canonical Locally Named Representation of Binding
No full textThis paper is about completely formal representation of languages with binding. We have previously written about a representation following an approach going back to Frege, based on first-order syntax using distinct syntactic classes for locally bound variables vs. global or free variables (Sato and Pollack, J Symb Comput 45:598–616, 2010). The present paper differs from our previous work by being more abstract. Whereas we previously gave a particular concrete function for canonically choosing the names of binders, here we characterize abstractly the properties required of such a choice function to guarantee canonical representation, and focus on the metatheory of the representation, proving that it is in substitution preserving isomorphism with the nominal Isabelle representation of pure lambda terms. This metatheory is formalized in Isabelle/HOL. The final section outlines a formalization in Matita of a challenging language with multiple binding and simultaneous substitution. The Isabelle and Matita proof files are available online
ON IWASAWA THEORY OF ELLIPTIC CURVES OVER Q AT PRIMES OF SUPERSINGULAR REDUCTION OVER Z_p-EXTENSIONS OF NUMBER FIELDS
No full textIn this paper, we make a study of the Iwasawa theory of an elliptic curve at a supersingular prime p along an arbitrary Z(p)-extension of a number field K in the case when p splits completely in K. Generalizing work of Kobayashi and Perrin-Riou , we define restricted Selmer groups and lambda(+/-), mu(+/-)-invariants; we then derive asymptotic formulas describing the growth of the Selmer group in terms of these invariants. To be able to work with non-cyclotomic Z(p)-extensions, a new local result is proven that gives a complete description of the formal group of an elliptic curve at a supersingular prime along any ramified Z(p)-extension of Q(p)
A Computational Model of Symbiotic Composition in Evolutionary Transitions
Get PDFSeveral of the major transitions in evolutionary history, such as the symbiogenic origin of eukaryotes from prokaryotes, share the feature that existing entities became the components of composite entities at a higher level of organisation. This composition of pre-adapted extant entities into a new whole is a fundamentally different source of variation from the gradual accumulation of small random variations, and it has some interesting consequences for issues of evolvability. Intuitively, the pre-adaptation of sets of features in reproductively independent specialists suggests a form of ‘divide and conquer’ decomposition of the adaptive domain. Moreover, the compositions resulting from one level may become the components for compositions at the next level, thus scaling-up the variation mechanism. In this paper, we explore and develop these concepts using a simple abstract model of symbiotic composition to examine its impact on evolvability. To exemplify the adaptive capacity of the composition model, we employ a scale-invariant fitness landscape exhibiting significant ruggedness at all scales. Whilst innovation by mutation and by conventional evolutionary algorithms becomes increasingly more difficult as evolution continues in this landscape, innovation by composition is not impeded as it discovers and assembles component entities through successive hierarchical levels
A complex analogue of the Goodman-Pollack-Wenger theorem
Get PDFA \textit{-transversal} to family of sets in is a
-dimensional affine subspace that intersects each set of the family. In 1957
Hadwiger provided a necessary and sufficient condition for a family of pairwise
disjoint, planar convex sets to have a -transversal. After a series of three
papers among the authors Goodman, Pollack, and Wenger from 1988 to 1990,
Hadwiger's Theorem was extended to necessary and sufficient conditions for
-transversals to finite families of convex sets in with
no disjointness condition on the family of sets. We prove an analogue of the
Goodman-Pollack-Wenger theorem in the complex setting.Comment: Correction: A complex Goodman-Pollack-Wenger theorem is proven as in
the main theorem of the first version. It does not imply a corresponding
result for real transversals as initially state
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Recommended from our members
Biohazards in biological research: proceedings
No full textThe 1973 publication "Biohazards in Biological Research," edited by S. Hellman, M. Oxman, and R. Pollack, focuses on the risks and safety concerns associated with biological research. In his comments, Robert Pollack addresses the need for improved safety protocols and stricter controls in laboratories working with potentially hazardous biological agents. He emphasizes the uneven standards in the certification and handling of biological materials, such as primary monkey cells and hybrid viruses, and the inconsistencies in the availability of certified, safe biological products like poliovaccine. Pollack calls for immediate action to implement safer practices, particularly in laboratories that handle dangerous viruses, cells, or animals. He also highlights the necessity for central certification of virus seed stocks and suggests that governmental and private research agencies must provide the necessary funds to ensure safety in research. Pollack warns that without adequate funding and safety measures, research may either continue with unnecessary risks or be halted entirely. Additionally, he stresses the importance of conducting prospective studies on the incidence of disease, including cancers, in laboratory workers to assess the potential harm of the agents being studied
RG 9015-001-001 Frank R. Zebley Collection, Along the Brandywine Photograph Collection
No full textPollack Mill on Beaver Cree
RG 9015-001-001 Frank R. Zebley Collection, Along the Brandywine Photograph Collection
No full textPollack Mill on Beaver Cree
Embodied Evolution: Distributing an evolutionary algorithm in a population of robots
No full textWe introduce Embodied Evolution (EE) as a new methodology for evolutionary robotics (ER). EE uses a population of physical robots that autonomously reproduce with one another while situated in their task environment. This constitutes a fully distributed evolutionary algorithm embodied in physical robots. Several issues identified by researchers in the evolutionary robotics community as problematic for the development of ER are alleviated by the use of a large number of robots being evaluated in parallel. Particularly, EE avoids the pitfalls of the simulate-and-transfer method and allows the speed-up of evaluation time by utilizing parallelism. The more novel features of EE are that the evolutionary algorithm is entirely decentralized, which makes it inherently scalable to large numbers of robots, and that it uses many robots in a shared task environment, which makes it an interesting platform for future work in collective robotics and Artificial Life. We have built a population of eight robots and successfully implemented the first example of Embodied Evolution by designing a fully decentralized, asynchronous evolutionary algorithm. Controllers evolved by EE outperform a hand-designed controller in a simple application. We introduce our approach and its motivations, detail our implementation and initial results, and discuss the advantages and limitations of EE
- …
