9,414 research outputs found
Quantum differential operators on the quantum plane
The universal enveloping algebra U(g) of a Lie algebra g acts on its
representation ring R through D(R), the ring of differential operators on R. A
quantised universal enveloping algebra (or "quantum group") is a deformation of
a universal enveloping algebra and acts not through the differential operators
of its representation ring but through the quantised differential operators of
its representation ring. We present this situation for the quantum group of
sl_2.Comment: 18 pages, references added, address change
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A reason for unreason: returns based beliefs in game theory
Players cooperate in experiments more than game theory would predict. We introduce the ‘returns-based beliefs’ approach: the expected returns of a particular strategy in proportion to total expected returns of all strategies. Using a decision analytic solution concept, Luce’s (1959) probabilistic choice model, and ‘hyperpriors’ for ambiguity in players’ cooperability, our approach explains empirical observations in various classes of games including the Prisoner’s and Traveler’s Dilemmas. Testing the closeness of fit of our model on Selten and Chmura (2008) data for completely mixed 2 × 2 games shows that with loss aversion, returns-based beliefs explain the data better than other equilibrium concepts
Predicting Combinatorial Binding of Transcription Factors to Regulatory Elements in the Human Genome by Association Rule Mining
Cis-acting transcriptional regulatory elements in mammalian genomes typically contain specific combinations of binding sites for various transcription factors. Although some cisregulatory elements have been well studied, the combinations of transcription factors that regulate normal expression levels for the vast majority of the 20,000 genes in the human genome are unknown. We hypothesized that it should be possible to discover transcription factor combinations that regulate gene expression in concert by identifying over-represented combinations of sequence motifs that occur together in the genome. In order to detect combinations of transcription factor binding motifs, we developed a data mining approach based on the use of association rules, which are typically used in market basket analysis. We scored each segment of the genome for the presence or absence of each of 83 transcription factor binding motifs, then used association rule mining algorithms to mine this dataset, thus identifying frequently occurring pairs of distinct motifs within a segment. Results: Support for most pairs of transcription factor binding motifs was highly correlated across different chromosomes although pair significance varied. Known true positive motif pairs showed higher association rule support, confidence, and significance than background. Our subsets of high-confidence, high-significance mined pairs of transcription factors showed enrichment for co-citation in PubMed abstracts relative to all pairs, and the predicted associations were often readily verifiable in the literature. Conclusion: Functional elements in the genome where transcription factors bind to regulate expression in a combinatorial manner are more likely to be predicted by identifying statistically and biologically significant combinations of transcription factor binding motifs than by simply scanning the genome for the occurrence of binding sites for a single transcription factor.NIAAA Alcohol Training GrantNational Science FoundationCellular and Molecular Biolog
Variations in the Cyclotron Resonant Scattering Features during 2011 outburst of 4U 0115+63
We study the variations in the Cyclotron Resonant Scattering Feature (CRSF)
during 2011 outburst of the high mass X-ray binary 4U 0115+63 using
observations performed with Suzaku, RXTE, Swift and INTEGRAL satellites. The
wide-band spectral data with low energy coverage allowed us to characterize the
broadband continuum and detect the CRSFs. We find that the broadband continuum
is adequately described by a combination of a low temperature (kT ~ 0.8 keV)
blackbody and a power-law with high energy cutoff (Ecut ~ 5.4 keV) without the
need for a broad Gaussian at ~ 10 keV as used in some earlier studies. Though
winds from the companion can affect the emission from the neutron star at low
energies (< 3 keV), the blackbody component shows a significant presence in our
continuum model. We report evidence for the possible presence of two
independent sets of CRSFs with fundamentals at ~ 11 keV and ~ 15 keV. These two
sets of CRSFs could arise from spatially distinct emitting regions. We also
find evidence for variations in the line equivalent widths, with the 11 keV
CRSF weakening and the 15 keV line strengthening with decreasing luminosity.
Finally, we propose that the reason for the earlier observed anti-correlation
of line energy with luminosity could be due to modelling of these two
independent line sets (~ 11 keV and ~ 15 keV) as a single CRSF.Comment: 12 pages, 8 figures (4 in colour), 6 tables. Accepted for publication
in MNRAS. Typos corrected, Figure 8 changed and some changes to draf
The Frenet Serret Description of Gyroscopic Precession
The phenomenon of gyroscopic precession is studied within the framework of
Frenet-Serret formalism adapted to quasi-Killing trajectories. Its relation to
the congruence vorticity is highlighted with particular reference to the
irrotational congruence admitted by the stationary, axisymmetric spacetime.
General precession formulae are obtained for circular orbits with arbitrary
constant angular speeds. By successive reduction, different types of
precessions are derived for the Kerr - Schwarzschild - Minkowski spacetime
family. The phenomenon is studied in the case of other interesting spacetimes,
such as the De Sitter and G\"{o}del universes as well as the general
stationary, cylindrical, vacuum spacetimes.Comment: 37 pages, Paper in Late
Dominance and Innovation
Do dominant or less dominant firms innovate more? Theoretically it has been shown that within an asymmetric mixed strategy game of a patent race, the less dominant firm invests more than the dominant firm. But the empirical data on patent races is divided. In this paper, we argue that the decisions that concern strategic choice in innovation may be influenced by expected relative returns. Our approach, which we call the returns-based beliefs approach, is based upon subjective probabilities. It combines a decision analytic solution concept and Luce’s (1959) probabilistic choice model. In particular, we show how the use of the returns-based beliefs approach provides support for the thesis that dominant firms invest more in R&D within an asymmetric mixed strategy game. Consequently, we argue that the returns-based beliefs approach is more in line with recent empirical studies of innovation. We also provide empirical evidence using UK R&D data across a range of industries from 2001-2006 that shows that firms’ spending on R&D is related more to their own profitability than that of their competitors, which is consistent with the returns-based beliefs approach. We discuss the managerial implications of our theoretical approach and the empirical findings
Beyond the basics: Access and equity in the expansion of post-compulsory schooling in Vietnam
Human capital development, including the expansion and improvement of schooling, has played a crucial role in Vietnam’s strong and relatively inclusive economic growth in recent years. Universal access to primary and lower secondary education have been achieved, but progression to upper secondary remains, for the most part, rationed by entrance examinations and the payment of fees. Both supply and access have improved strongly at upper secondary level since the 1990s, in line with rising demand for higher skilled school-leavers. However, it is less clear whether access to upper secondary schooling, and its wider social and economic benefits, is provided equitably. In this paper we employ a unique longitudinal dataset to examine the patterns of both access and attainment in upper secondary education in Vietnam. We consider their implications for equitable educational progression and the extent to which, in light of these patterns, the system can be described as meritocratic
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