Harmonic maps couples to the Einstein equation

We study harmonic maps ∅ : (M,g) → (N, h) which are coupled to the metric g by the Einstein equation κ Ric[g

String Branchings on Complex Tori and Algebraic Representations of Generalized Krichever-Novikov Algebras

The propagation differential for bosonic strings on a complex torus with three symmetric punctures is investigated. We study deformation aspects between two point and three point differentials as well as the behaviour of the corresponding Krichever-Novikov algebras. The structure constants are calculated and from this we derive a central extension of the Krichever-Novikov algebras by means of b-c systems. The defining cocycle for this central extension deforms to the well known Virasoro cocycle for certain kinds of degenerations of the torus. AMS subject classification (1991): 17B66, 17B90, 14H52, 30F30, 81T40Comment: 11 pages, amste

Triple-Star Candidates Among the Kepler Binaries

We present the results of a search through the photometric database of eclipsing Kepler binaries (Prsa et al. 2011; Slawson et al. 2011) looking for evidence of hierarchical triple star systems. The presence of a third star orbiting the binary can be inferred from eclipse timing variations. We apply a simple algorithm in an automated determination of the eclipse times for all 2157 binaries. The "calculated" eclipse times, based on a constant period model, are subtracted from those observed. The resulting O-C (observed minus calculated times) curves are then visually inspected for periodicities in order to find triple-star candidates. After eliminating false positives due to the beat frequency between the ~1/2-hour Kepler cadence and the binary period, 39 candidate triple systems were identified. The periodic O-C curves for these candidates were then fit for contributions from both the classical Roemer delay and so-called "physical" delay, in an attempt to extract a number of the system parameters of the triple. We discuss the limitations of the information that can be inferred from these O-C curves without further supplemental input, e.g., ground-based spectroscopy. Based on the limited range of orbital periods for the triple star systems to which this search is sensitive, we can extrapolate to estimate that at least 20% of all close binaries have tertiary companions.Comment: 19 pages, 13 figures, 3 tables; ApJ, 2013, 768, 33; corrected Fig. 7, updated references, minor fixes to tex

Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica

A high-resolution ice-core record of atmospheric CO2 concentration over the Holocene epoch shows that the global carbon cycle has not been in steady state during the past 11,000 years. Analysis of the CO2 concentration and carbon stable-isotope records, using a one-dimensional carbon-cycle model,uggests that changes in terrestrial biomass and sea surface temperature were largely responsible for the observed millennial-scale changes of atmospheric CO2 concentrations

Robust self-replication of combinatorial information via crystal growth and scission

Understanding how a simple chemical system can accurately replicate combinatorial information, such as a sequence, is an important question for both the study of life in the universe and for the development of evolutionary molecular design techniques. During biological sequence replication, a nucleic acid polymer serves as a template for the enzyme-catalyzed assembly of a complementary sequence. Enzymes then separate the template and complement before the next round of replication. Attempts to understand how replication could occur more simply, such as without enzymes, have largely focused on developing minimal versions of this replication process. Here we describe how a different mechanism, crystal growth and scission, can accurately replicate chemical sequences without enzymes. Crystal growth propagates a sequence of bits while mechanically-induced scission creates new growth fronts. Together, these processes exponentially increase the number of crystal sequences. In the system we describe, sequences are arrangements of DNA tile monomers within ribbon-shaped crystals. 99.98% of bits are copied correctly and 78% of 4-bit sequences are correct after two generations; roughly 40 sequence copies are made per growth front per generation. In principle, this process is accurate enough for 1,000-fold replication of 4-bit sequences with 50% yield, replication of longer sequences, and Darwinian evolution. We thus demonstrate that neither enzymes nor covalent bond formation are required for robust chemical sequence replication. The form of the replicated information is also compatible with the replication and evolution of a wide class of materials with precise nanoscale geometry such as plasmonic nanostructures or heterogeneous protein assemblies

Attending to Attention: A Systematic Review of Attention and Reading

Background: Extensive research has conclusively linked inattention to poor reading performance. The process by which this relation occurs remains somewhat undefined, which makes it difficult for practitioners to identify key intervention targets. Objectives: This systematic review will synthesize current peer-reviewed research on the developmental relationship between inattention and reading. The primary aim of this review was to describe how inattention negatively relates to the development of literacy from preschool through middle childhood. A secondary aim of this review was to summarize recent research on the potential differential relationship between attention and literacy among students overrepresented in ratings of inattention, including boys and students of color. Design and Methods: PsycInfo, Education Full Text, ERIC, and ProQuest Education, and Dissertations and Theses were searched, using a broad search string. The initial search resulted in 1,262 potentially relevant studies published since the most recent authorization of the Every Child Succeeds Act (i.e., from December 2015-2019) for review. Out of 1,262 citations found, 70 empirical studies were screened and assessed for eligibility, and 16 met the specific inclusion criteria. A coding sheet was then used to synthesize data from the included studies. Results: Among preschool and elementary school children, inattention, whether measured through observer ratings or performance tasks, has a consistent, negative impact on reading skills as reported both by teachers, standardized instruments, and classroom performance outcomes. Results point to multiple pathways through which inattention may have a negative impact on reading outcomes. Evidence points to a negative and direct effect of inattention on the development of and performance in reading concurrently and over time. Inattention may have an additional, indirect, and negative effect on reading performance through its negative impact on early literacy and cognitive skills, including phonological awareness and processing, vocabulary, and working memory. There is a lack of research on potential differential processes by which attention relates to reading among subgroups of children who are at elevated risk for poor literacy outcomes. Conclusions and Implications: Assessing for and intervening in early attention problems in preschool and kindergarten is essential to promote optimal reading outcomes for all students. There is an urgent need for future research to investigate potential differential processes in the relation between attention and reading performance for children who are at an elevated risk for reading problems. School social workers are especially prepared and located to address the interaction of child and classroom factors within schools that impede student performance in early grades and set up challenges for later success

Are Subjects Making Financial Decisions in Lab Auctions or Are They Just Gambling?

Optimal bidding strategies in first-price and Dutch auctions are theoretically isomorphic but depend on bidder risk attitudes. However, laboratory experiments consistently find different behaviour between auction formats. This article explores whether the notion in psychology that financial and gambling risks are viewed differently can explain the discrepancy. Ultimately, the evidence does not support this hypothesis, but a bidder\u27s propensity to gamble is associated with how much risk he takes in both auctions whereas his propensity to take financial risks is not. The results suggest that subjects may view themselves as gambling in laboratory auctions rather than making financial decisions