1,971 research outputs found
A First Class Constraint Generates Not a Gauge Transformation, But a Bad Physical Change: The Case of Electromagnetism
No full textIn Dirac-Bergmann constrained dynamics, a first-class constraint typically does not _alone_ generate a gauge transformation. By direct calculation it is found that each first-class constraint in Maxwell's theory generates a change in the electric field E by an arbitrary gradient, spoiling Gauss's law. The secondary first-class constraint p^i,_i=0 still holds, but being a function of derivatives of momenta, it is not directly about E (a function of derivatives of A_mu). Only a special combination of the two first-class constraints, the Anderson-Bergmann (1951)-Castellani gauge generator G, leaves E unchanged. This problem is avoided if one uses a first-class constraint as the generator of a _canonical transformation_; but that partly strips the canonical coordinates of physical meaning as electromagnetic potentials and makes the electric field depend on the smearing function, bad behavior illustrating the wisdom of the Anderson-Bergmann (1951) Lagrangian orientation of interesting canonical transformations.
The need to keep gauge-invariant the relation dot{q}- dH/dp= -E_i -p^i=0 supports using the primary Hamiltonian rather than the extended Hamiltonian. The results extend the Lagrangian-oriented reforms of Castellani, Sugano, Pons, Salisbury, Shepley, _etc._ by showing the inequivalence of the extended Hamiltonian to the primary Hamiltonian (and hence the Lagrangian) even for _observables_, properly construed in the sense implying empirical equivalence.
Dirac and others have noticed the arbitrary velocities multiplying the primary constraints outside the canonical Hamiltonian while apparently overlooking the corresponding arbitrary coordinates multiplying the secondary constraints _inside_ the canonical Hamiltonian, and so wrongly ascribed the gauge quality to the primaries alone, not the primary-secondary team G. Hence the Dirac conjecture about secondary first-class constraints rests upon a false presupposition. The usual concept of Dirac observables should also be modified to employ the gauge generator G, not the first-class constraints separately, so that the Hamiltonian observables become equivalent to the Lagrangian ones such as the electromagnetic field F
A machine-learning system for the automated detection of megafauna and its applicability unseen footage
No full textSchoening T, Bergmann M, Nattkemper TW. A machine-learning system for the automated detection of megafauna and its applicability unseen footage. Presented at the GEOHAB, Rome
Gustav Bergmann, New Foundations of Ontology
No full textThe formal ontology here presented is what we might call a typed combinatorial Meinongian mereology. Its author seeks to formulate the laws, here called ‘canons’, regulating how entities can combine together in wholes of different sorts. The method, as in Bergmann’s earlier works, involves the construction of an ideal language of such a sort that the analysis of complex wholes can be achieved by transforming our natural-language representations of reality into what we might think of as artificial characteristic maps or diagrams which allow the relevant ontological structures to be read off immediately from the symbolic representations which results. In former works Bergmann had held that the symbolic language of Principia Mathematica could serve as the appropriate diagrammatic device for the standard first-order functional calculus and develops instead a new sort diagrammatic languag
Testing Mechanisms of Bergmann's Rule: Phenotypic Decline but No Genetic Change in Body Size in Three Testing Mechanisms of Bergmann's Rule: Phenotypic Decline but No Genetic Change in Body Size in Three Passerine Bird Populations
No full textJSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. abstract: Bergmann's rule predicts a decrease in body size with increasing temperature and has much empirical support. Surprisingly, we know very little about whether "Bergmann size clines" are due to a genetic response or are a consequence of phenotypic plasticity. Here, we use data on body size (mass and tarsus length) from three long-term ) study populations of great tits (Parus major) that experienced a temperature increase to examine mechanisms behind Bergmann's rule. We show that adult body mass decreased over the study period in all populations and that tarsus length increased in one population. Both body mass and tarsus length were heritable and under weak positive directional selection, predicting an increase, rather than a decrease, in body mass. There was no support for microevolutionary change, and thus the observed declines in body mass were likely a result of phenotypic plasticity. Interestingly, this plasticity was not in direct response to temperature changes but seemed to be due to changes in prey dynamics. Our results caution against interpreting recent phenotypic body size declines as adaptive evolutionary responses to temperature changes and highlight the importance of considering alternative environmental factors when testing size clines. The University of Chicago Press an
Finding ourselves: Theology, place, and human flourishing
No full textThis is the author's PDF version of the book chapter.This book chapter is about being "lost" and "found" and of the significance of space and place for "finding ourselves" as fully human. Tim Gorringe's work on culture and the built environment will inform some of the author's reflection on this
Molecular dynamics in a grand ensemble: Bergmann-Lebowitz model and adaptive resolution simulation
No full textThis article deals with the molecular dynamics simulation of open systems that can exchange energy and matter with a reservoir; the physics of the reservoir and its interactions with the system are described by the model introduced by Bergmann and Lebowitz (P G Bergmann and J L Lebowitz 1955 Phys. Rev. 99 578). Despite its conceptual appeal, the model did not gain popularity in the field of molecular simulation and, as a consequence, did not play a role in the development of open system molecular simulation techniques, even though it can provide the conceptual legitimation of simulation techniques that mimic open systems. We shall demonstrate that the model can serve as a tool in devising both numerical procedures and conceptual definitions of physical quantities that cannot be defined in a straightforward way by systems with a fixed number of molecules. In particular, we discuss the utility of the Bergmann-Lebowitz (BL) model for the calculation of equilibrium time correlation functions within the grand canonical adaptive resolution method (GC-AdResS) and report numerical results for the case of liquid water.Deutsche Forschungsgemeinschaft (DFG); Heisenberg grant [DE 1140/5-2]; DFG grant [DE 1140/7-1]; National High Technology Research and Development Program of China [2015AA011201]; North German Supercomputing Alliance (HLRN) [bec00100]; Heisenberg grant; [CRC 1114]SCI(E)[email protected]
Book review: Religion in the Anthropocene, edited by Celia Deane-Drummond, Sigurd Bergmann and Markus Vogt. Eugen, OR.: Cascade Books, 2017. 338pp. ISBN 978-1-4982-9191-0
No full textThis is the author accepted manuscript. The final version is available from Paternoster Periodicals via the link in this recordBook review of Celia Deane-Drummond, Sigurd Bergmann and Markus Vogt (eds), Religion in the Anthropocene
Eugen, OR.: Cascade Books, 2017. 338pp. ISBN 978-1-4982-9191-0
Energy momentum distributions of monopole metric in teleparallel gravity
No full text32nd International Physics Congress of Turkish-Physical-Society (TPS) -- SEP 06-09, 2016 -- Bodrum, TURKEYIn this study, we investigate energy and momentum distributions of Monopole metric. For this purpose, we have used Einstein, Bergmann-Thomson and Landau-Lifshitz energy and momentum densities in Teleparallel Gravity (TG). We obtained that: (i) The solutions of Einstein and Bergmann-Thomson energy and momentum distributions give the same results but Landau-Lifshitz energy distribution does not provide same results in TG. (ii) The momentum densities of Einstein, Bergmann-Thomson and Landau-Lifshitz are vanish in TG for monopole metric. (hi) The obtained energy-momentum solutions are different from the earlier results in General Relativity (GR).Turkish Phys So
An overview and rating of benthic image pre-processings for color constancy
No full textOsterloff J, Schoening T, Bergmann M, Nattkemper TW. An overview and rating of benthic image pre-processings for color constancy. Presented at the Marine Imaging Workshop, National Oceanography Centre, Southampton, UK
Categorization of 2-photon microscopy images of human articular cartilage into states of arthritis
No full textBergmann T, Fiebich TM, Nattkemper TW, Anselmetti D. Categorization of 2-photon microscopy images of human articular cartilage into states of arthritis. Presented at the Tagung der Biomedizinischen Technik (BMT), Freiburg, Germany
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