2,258 research outputs found
M-brane Models from Non-Abelian Gerbes
We make the observation that M-brane models defined in terms of 3-algebras
can be interpreted as higher gauge theories involving Lie 2-groups. Such gauge
theories arise in particular in the description of non-abelian gerbes. This
observation allows us to put M2- and M5-brane models on equal footing, at least
as far as the gauge structure is concerned. Furthermore, it provides a useful
framework for various generalizations; in particular, it leads to a fully
supersymmetric generalization of a previously proposed set of tensor multiplet
equations.Comment: 17 pages, v2: new SUSY models, version published in JHE
Self-dual String and Higher Instanton Solutions
We present and discuss explicit solutions to the non-abelian self-dual string
equation as well as to the non-abelian self-duality equation in six dimensions.
These solutions are generalizations of the 't Hooft-Polyakov monopole and the
BPST instanton to higher gauge theory. We expect that these solutions are
relevant to the effective description of M2- and M5-branes.Comment: 23 pages, 2 figures, v2 presentation improved, minor errors
corrected, new subsection with comment
Higher gauge theory and M-theory
In this thesis, the emerging field of higher gauge theory will be discussed, particularly
in relation to problems arising in M-theory, such as selfdual strings and the
so-called (2,0) theory. This thesis will begin with a Nahm-like construction for selfdual
strings using loop space, the space of loops on spacetime. This construction maps
solutions of the Basu-Harvey equation, the BPS equation arising in the description
of multiple M2-branes, to solutions of a selfdual string equation on loop space. Furthermore,
all ingredients of the construction reduce to those of the ordinary Nahm
construction when compactified on a circle with all loops restricted to those wrapping
the circle. The rest of this thesis, however, will not involve loop space. We will
see a Nahm-like construction for the case of infinitely many selfdual strings, suspended
between two M5-branes. This is possible since the limit taken renders the
fields describing the M5-branes abelian. This avoids the problem which the rest of
this thesis focuses on: What fields describe multiple M5-branes? The answer is likely
to involve higher gauge theory, a categorification of gauge theory which describes the
parallel transport of extended objects. Any theories which involves 3-algebras, including
current M2-brane models and the Lambert-Papageorgakis M5-brane model,
are examples of higher gauge theories. Recently, a class of models with N = (1, 0)
supersymmetry have been found, with significant overlap with algebraic structures
in higher gauge theory. This overlap suggests that the full N = (2, 0) theory could
involve semistrict L∞-algebras. Finally, we will see some explicit selfdual string
solutions, which may fit into these frameworks
Six-Dimensional (1,0) Superconformal Models and Higher Gauge Theory
We analyze the gauge structure of a recently proposed superconformal field
theory in six dimensions. We find that this structure amounts to a weak
Courant-Dorfman algebra, which, in turn, can be interpreted as a strong
homotopy Lie algebra. This suggests that the superconformal field theory is
closely related to higher gauge theory, describing the parallel transport of
extended objects. Indeed we find that, under certain restrictions, the field
content and gauge transformations reduce to those of higher gauge theory. We
also present a number of interesting examples of admissible gauge structures
such as the structure Lie 2-algebra of an abelian gerbe, differential crossed
modules, the 3-algebras of M2-brane models and string Lie 2-algebras.Comment: 31+1 pages, presentation slightly improved, version published in JM
Struggle for balance; Three views of finanical management
Illustrations and photographs not included in Web versio
The George-Anne
Performers: Bee PalmerPiano, Voice and Chord
Evaluation of a coastal acoustic buoy for cetacean detections, bearing accuracy and exclusion zone monitoring
The Maryland Department of Natural Resources and the Maryland Offshore Wind Development Fund at the Maryland Energy Administration cosponsored this work. This report was prepared as an account of work sponsored by an agency of the United States Government.There is strong socio-political support for offshore wind development in US territorial waters and construction is planned off several east coast states. Some of the planned development sites coincide with important habitat for critically endangered North Atlantic right whales. Both exclusion zones and passive acoustic monitoring are important tools for managing interactions between marine mammals and human activities. Understanding where animals are with respect to exclusion zones is important to avoid costly construction delays while minimizing the potential for negative impacts. Impact piling from construction of hundreds of offshore wind turbines likely require exclusion zones as large as 10 km. We have developed a three-hydrophone passive acoustic monitoring system that provides bearing information along with marine mammal detections to allow for informed management decisions in real-time. Multiple units form a monitoring system designed to determine whether marine mammal calls originate from inside or outside of an exclusion zone. In October 2021, we undertook a full system validation, with a focus on evaluating the detection range and bearing accuracy of the system with respect to right whale upcalls. Five units were deployed in Mid-Atlantic waters and we played more than 3500 simulated right whale upcalls at known locations to characterize the detection function and bearing accuracy of each unit. The modelled results of the detection function error were then used to compare the effectiveness of a bearing-based system to a single sensor that can only detect a signal but not ascertain directivity. Field trials indicated maximum detection ranges from 4-7.3 km depending on source and ambient noise levels. Simulations showed that incorporating bearing detections provide a substantial improvement in false alarm rates (6 to 12 times depending on number of units, placement and signal to noise conditions) for a small increase in the risk of missed detections inside of an exclusion zone (1%-3%). We show that the system can be used for monitoring exclusion zones and clearly highlight the value of including bearing estimation into exclusion zone monitoring plans while noting that placement and configuration of units should reflect anticipated ambient noise conditions.Publisher PDFPeer reviewe
Candidate Gene Identification for a Lethal Chlorophyll-Deficient Mutant in Soybean
Chlorophyll-deficient mutants have been studied persistently to understand genetic mechanisms controlling metabolic pathways. A spontaneous chlorophyll-deficient lethal mutant was observed in self-pollinated progeny of a soybean cultivar “BSR 101”. Observed segregation patterns indicated single-gene recessive inheritance for this lethal-yellow mutant. The objectives of this investigation were to develop a genetic linkage map of the region containing the lethal-yellow (YL_PR350) gene and identify putative candidate genes for this locus. The YL_PR350 gene was mapped to chromosome 15 and is flanked by BARCSOYSSR_15_1591 and BARCSOYSSR_15_1597. This region physically spans ~153 kb and there are 14 predicted genes that lie in this region. The predicted gene Glyma.15g275900 is an excellent candidate for the YL_PR350 gene as it is homologous to an Arabidopsis gene, At3g08010, which codes for a chloroplast-localized protein (ATAB2) involved in the biogenesis of Photosystem I and II. This thylakoid membrane protein is crucial for photosynthesis in Arabidopsis. Future characterization of the candidate gene may enhance our knowledge about photosynthesis, a complex metabolic process critical for sustainability of plants
Thymic involution and rising disease incidence with age
For many cancer types, incidence rises rapidly with age as an apparent power law, supporting the idea that cancer is caused by a gradual accumulation of genetic mutations. Similarly, the incidence of many infectious diseases strongly increases with age. Here, combining data from immunology and epidemiology, we show that many of these dramatic age-related increases in incidence can be modeled based on immune system decline, rather than mutation accumulation. In humans, the thymus atrophies from infancy, resulting in an exponential decline in T cell production with a half-life of ∼16 years, which we use as the basis for a minimal mathematical model of disease incidence. Our model outperforms the power law model with the same number of fitting parameters in describing cancer incidence data across a wide spectrum of different cancers, and provides excellent fits to infectious disease data. This framework provides mechanistic insight into cancer emergence, suggesting that age-related decline in T cell output is a major risk factor
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