968 research outputs found
Relation between space-time inversion and particle-antiparticle symmetry and the microscopic essence of special relativity
After analyzing the implication of investigations on the C, P and T
transformations since 1956, we propose that there is a basic symmetry in
particle physics. The combined space-time inversion is equivalent to
particle-antiparticle transformation, denoted by . It is shown
that the relativistic quantum mechanics and quantum field theory do contain
this invariance explicitly or implicitly. In particular, (a) the appearance of
negative energy or negative probability density in single particle theory --
corresponding to the fact of existence of antiparticle, (b) spin- statistics
connection, (c) CPT theorem, (d) the Feynman propagator are linked together via
this symmetry. Furthermore, we try to derive the main results of special
relativity, especially, (e) the mass-energy relation, (f) the Lorentz
transformation by this one ``relativistic'' postulate and some
``nonrelativistic'' knowledge.Comment: 29 pages, Latex, 1 figur
A tail-based test for differential expression analysis and pathway analysis in RNA-sequencing data
RNA sequencing data have been abundantly generated in biomedical research for biomarker discovery and pathway analysis. Such data at the exon-level are usually heavily tailed and correlated. Conventional statistical tests based on the mean or median difference for differential expression likely suffer from low power when the between-group difference occurs mostly in the upper or lower tail of the distribution of gene expression. We propose a tail-based test to make comparisons between groups in terms of a specific distribution area rather than a single location. The proposed test, which is derived from quantile regression, adjusts for covariates and accounts for within-sample dependence among the exons through a specified correlation structure. Through Monte Carlo simulation studies, we show that the proposed test is generally more powerful and robust in detecting differential expression than commonly used tests based on the mean or a single quantile. An application to TCGA lung adenocarcinoma data demonstrates the promise of the proposed method in terms of biomarker discovery. We also extend the proposed test to perform pathway analysis for a set of genes within the same pathway or share similar biological function. Genes in such sets are known to be dependent of each other and our test accounts for their pairwise correlation. Through simulation comparison with commonly used pathway analysis methods, we show the proposed test yields better results. An application on non-small cell lung cancer pathways from KEGG pathway Database also demonstrates the proposed test is a powerful method in detecting differentially expressed pathways
Parameterized Algorithmics for Computational Social Choice: Nine Research Challenges
Computational Social Choice is an interdisciplinary research area involving
Economics, Political Science, and Social Science on the one side, and
Mathematics and Computer Science (including Artificial Intelligence and
Multiagent Systems) on the other side. Typical computational problems studied
in this field include the vulnerability of voting procedures against attacks,
or preference aggregation in multi-agent systems. Parameterized Algorithmics is
a subfield of Theoretical Computer Science seeking to exploit meaningful
problem-specific parameters in order to identify tractable special cases of in
general computationally hard problems. In this paper, we propose nine of our
favorite research challenges concerning the parameterized complexity of
problems appearing in this context
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