13,585 research outputs found
Light-Cone Quantization of Electrodynamics
Light-cone quantization of (3+1)-dimensional electrodynamics is discussed,
using discretization as an infrared regulator and paying careful attention to
the interplay between gauge choice and boundary conditions. In the zero
longitudinal momentum sector of the theory a general gauge fixing is performed
and the corresponding relations that determine the constrained modes of the
gauge field are obtained. The constraints are solved perturbatively and the
structure of the theory is studied to lowest nontrivial order. (Talk presented
at ``Theory of Hadrons and Light-Front QCD,'' Polana Zgorzelisko, Poland,
August 1994.)Comment: 6 pages, LaTeX, OSU-NT-94-0
Physical Coupling Schemes and QCD Exclusive Processes
I discuss application of the BLM method to obtain commensurate scale
relations connecting QCD exclusive amplitudes to other observables, in
particular the heavy quark potential.Comment: 7 pages, Latex, uses l-school.sty. Talk given at "New Nonperturbative
Methods and Quantization on the Light Cone," Les Houches, France, 24 Feb.-7
March 1997. To appear in the proceeding
-algebras associated to -correspondences and applications to mirror quantum spheres
The structure of the -algebras corresponding to even-dimensional mirror
quantum spheres is investigated. It is shown that they are isomorphic to both
Cuntz-Pimsner algebras of certain -correspondences and -algebras of
certain labelled graphs. In order to achieve this, categories of labelled
graphs and -correspondences are studied. A functor from labelled graphs to
-correspondences is constructed, such that the corresponding associated
-algebras are isomorphic. Furthermore, it is shown that
-correspondences for the mirror quantum spheres arise via a general
construction of restricted direct sum.Comment: 27 page
Declarative Specification
Deriving formal specifications from informal requirements is extremely difficult since one has to overcome the conceptual gap between an application domain and the domain of formal specification methods. To reduce this gap we introduce application-specific specification languages, i.e., graphical and textual notations that can be unambiguously mapped to formal specifications in a logic language. We describe a number of realised approaches based on this idea, and evaluate them with respect to their domain specificity vs. generalit
Simplicity of C*-algebras associated to row-finite locally convex higher-rank graphs
In previous work, the authors showed that the C*-algebra C*(\Lambda) of a
row-finite higher-rank graph \Lambda with no sources is simple if and only if
\Lambda is both cofinal and aperiodic. In this paper, we generalise this result
to row-finite higher-rank graphs which are locally convex (but may contain
sources). Our main tool is Farthing's "removing sources" construction which
embeds a row-finite locally convex higher-rank graph in a row-finite
higher-rank graph with no sources in such a way that the associated C*-algebras
are Morita equivalent.Comment: 18 pages, 1 figure, figure drawn using Tikz/PGF. Version 2: the
hypothesis "with no sources" has been removed from Theorem 3.4; it appeared
there in error since the main point of the theorem is that it applies in the
absence of this hypothesis (cf Theorem 3.1 of arXiv:math/0602120
De Novo Assembly of Nucleotide Sequences in a Compressed Feature Space
Sequencing technologies allow for an in-depth analysis
of biological species but the size of the generated datasets
introduce a number of analytical challenges. Recently, we
demonstrated the application of numerical sequence representations
and data transformations for the alignment of short
reads to a reference genome. Here, we expand out approach
for de novo assembly of short reads. Our results demonstrate
that highly compressed data can encapsulate the signal suffi-
ciently to accurately assemble reads to big contigs or complete
genomes
On the origins of Mendelian disease genes in man: the impact of gene duplication
Over 3,000 human diseases are known to be linked to heritable genetic variation, mapping to over 1,700 unique genes. Dating of the evolutionary age of these disease-associated genes has suggested that they have a tendency to be ancient, specifically coming into existence with early metazoa. The approach taken by past studies, however, assumes that the age of a disease is the same as the age of its common ancestor, ignoring the fundamental contribution of duplication events in the evolution of new genes and function. Here, we date both the common ancestor and the duplication history of known human disease-associated genes. We find that the majority of disease genes (80%) are genes that have been duplicated in their evolutionary history. Periods for which there are more disease-associated genes, for example, at the origins of bony vertebrates, are explained by the emergence of more genes at that time, and the majority of these are duplicates inferred to have arisen by whole-genome duplication. These relationships are similar for different disease types and the disease-associated gene's cellular function. This indicates that the emergence of duplication-associated diseases has been ongoing and approximately constant (relative to the retention of duplicate genes) throughout the evolution of life. This continued until approximately 390 Ma from which time relatively fewer novel genes came into existence on the human lineage, let alone disease genes. For single-copy genes associated with disease, we find that the numbers of disease genes decreases with recency. For the majority of duplicates, the disease-associated mutation is associated with just one of the duplicate copies. A universal explanation for heritable disease is, thus, that it is merely a by-product of the evolutionary process; the evolution of new genes (de novo or by duplication) results in the potential for new diseases to emerge
Groupoid algebras as Cuntz-Pimsner algebras
We show that if is a second countable locally compact Hausdorff \'etale
groupoid carrying a suitable cocycle , then the reduced
-algebra of can be realised naturally as the Cuntz-Pimsner algebra of
a correspondence over the reduced -algebra of the kernel of . If
the full and reduced -algebras of coincide, we deduce that the full
and reduced -algebras of coincide. We obtain a six-term exact sequence
describing the -theory of in terms of that of .Comment: 5 pages. V2: James Fletcher discovered an error Lemma 9. No other
results are affected. In this version, statements (2) and (3), and the proof,
of Lemma 9 have been corrected. Remark 10 has been added to give details of
the error. An erratum will appear in Math Scand, referring to this version of
the arXiv posting for detail
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