7,018 research outputs found
State-of-the-art survey of dissimilar metal joining by solid state welding
State-of-the-art of dissimilar metal joining by solid state diffusion bonding and roll and press welding, emphasizing stainless steel and aluminum allo
Cosmological Constant in LQG Vertex Amplitude
A new q-deformation of the Euclidean EPRL/FK vertex amplitude is proposed by
using the evaluation of the Vassiliev invariant associated with a 4-simplex
graph (related to two copies of quantum SU(2) group at different roots of
unity) embedded in a 3-sphere. We show that the large-j asymptotics of the
q-deformed vertex amplitude gives the Regge action with a cosmological
constant. In the end we also discuss its relation with a Chern-Simons theory on
the boundary of 4-simplex.Comment: 6 pages, 5 figures, result and presentation improve
Cluster growth in the dynamical Erdös-Rényi process with forest fires
We investigate the growth of clusters within the forest fire model of Ráth and Tóth [EJP, vol 14, paper no 45]. The model is a continuous-time Markov process, similar to the dynamical Erdős-Rényi random graph but with the addition of so-called fires. A vertex may catch fire at any moment and, when it does so, causes all edges within its connected cluster to burn, meaning that they instantaneously disappear. Each burned edge may later reappear.
We give a precise description of the process CtCt of the size of the cluster of a tagged vertex, in the limit as the number of vertices in the model tends to infinity. We show that CtCt is an explosive branching process with a time-inhomogeneous offspring distribution and instantaneous return to 1 on each explosion. Additionally, we show that the characteristic curves used to analyse the Smoluchowski-type coagulation equations associated to the model have a probabilistic interpretation in terms of the process CtCt
Finite Number of States, de Sitter Space and Quantum Groups at Roots of Unity
This paper explores the use of a deformation by a root of unity as a tool to
build models with a finite number of states for applications to quantum
gravity. The initial motivation for this work was cosmological breaking of
supersymmetry. We explain why the project was unsuccessful. What is left are
some observations on supersymmetry for q-bosons, an analogy between black holes
in de Sitter and properties of quantum groups, and an observation on a
noncommutative quantum mechanics model with two degrees of freedom, depending
on one parameter. When this parameter is positive, the spectrum has a finite
number of states; when it is negative or zero, the spectrum has an infinite
number of states. This exhibits a desirable feature of quantum physics in de
Sitter space, albeit in a very simple, non-gravitational context.Comment: 25 pages, 5 figure
Magellanic Cloud X-ray Sources: III. Completion of a ROSAT Survey
This paper concludes a series of three papers presenting ROSAT
High-Resolution Imager (HRI) observations of unidentified Einstein and
serendipitous ROSAT X-ray sources in the direction of the Magellanic Clouds.
Accurate positions and fluxes have been measured for these sources. Optical
photometry and spectroscopy were obtained to search for identifications in
order to determine the physical nature of these sources. The present paper
includes new data for 24 objects; identifications are given or confirmed for 30
sources. For six sources optical finding charts showing the X-ray positions are
provided. The results from this program are summarized, showing the populations
of luminous X-ray sources in the Magellanic Clouds are quite different from
those in the Galaxy.Comment: 28 pages, 2 figures; to appear in Astronomical Journa
Spacetime as a Feynman diagram: the connection formulation
Spin foam models are the path integral counterparts to loop quantized
canonical theories. In the last few years several spin foam models of gravity
have been proposed, most of which live on finite simplicial lattice spacetime.
The lattice truncates the presumably infinite set of gravitational degrees of
freedom down to a finite set. Models that can accomodate an infinite set of
degrees of freedom and that are independent of any background simplicial
structure, or indeed any a priori spacetime topology, can be obtained from the
lattice models by summing them over all lattice spacetimes. Here we show that
this sum can be realized as the sum over Feynman diagrams of a quantum field
theory living on a suitable group manifold, with each Feynman diagram defining
a particular lattice spacetime. We give an explicit formula for the action of
the field theory corresponding to any given spin foam model in a wide class
which includes several gravity models. Such a field theory was recently found
for a particular gravity model [De Pietri et al, hep-th/9907154]. Our work
generalizes this result as well as Boulatov's and Ooguri's models of three and
four dimensional topological field theories, and ultimately the old matrix
models of two dimensional systems with dynamical topology. A first version of
our result has appeared in a companion paper [gr-qc\0002083]: here we present a
new and more detailed derivation based on the connection formulation of the
spin foam models.Comment: 32 pages, 2 figure
Latent profile analysis of the Five Facet Mindfulness Questionnaire in a sample with a history of recurrent depression
This is the final version. Available from the publisher via the DOI in this record.Background: Extending previous research, we applied latent profile analysis in a sample of adults with a history of recurrent depression to identify subgroups with distinct response profiles on the Five Facet Mindfulness Questionnaire and understand how these relate to psychological functioning. Method: The sample was randomly divided into two subsamples to first examine the optimal number of latent profiles (test sample; n = 343) and then validate the identified solution (validation sample; n = 340). Results: In both test and validation samples, a four-profile solution was revealed where two profiles mapped broadly onto those previously identified in nonclinical samples: “high mindfulness” and “nonjudgmentally aware.” Two additional subgroups, “moderate mindfulness” and “very low mindfulness,” were observed. “High mindfulness” was associated with the most adaptive psychological functioning and “very low mindfulness” with the least adaptive. Conclusions: In most people with recurrent depression, mindfulness skills are expressed evenly across different domains. However, in a small minority a meaningful and replicable uneven profile indicating nonjudgmental awareness is observable. Current findings require replication and future research should examine the extent to which profiles change from periods of wellness to illness in people with recurrent depression and how profiles are influenced by exposure to mindfulness-based intervention.Economic and Social Research Council (ESRC)Sussex Partnership NHS Foundation TrustNational Institute for Health Research (NIHR)Wellcome Trus
Просвещение как форма популяризации культурно- художественных достижений этнических меньшинств Украины: тенденции 1990-2000-х годов
У статті розглянуто місце і роль просвітництва у популяризації культурно-
мистецьких надбань етноменшин. На основі специфічного методологічного
інструментарію проаналізовано відповідність популяризації культурно-мистецьких
надбань – стратегічними цілями – визнання поліетнічного характеру українського
суспільства, розбудові соціокультурного середовища і духовному розвитку етносів.
Підкреслено, що в Україні діяла розгалужена мережа музеїв, де діяли спеціальні підрозділи
– відділи, центри, експозиції тощо. Проаналізовані напрямки науково – дослідної роботи
музеїв та виокремлена її просвітницької складової.В статье рассмотрены место и роль просвещения в популяризации культурно -
художественных достижений этнических меньшинств. На основе специфического
методологического инструментария проанализированы соответствие популяризации культурно - художественных достижений - стратегическими целями - признание
полеэтнического характера украинского общества, развитии социокультурной среды и
духовном развитии этносов. Подчеркнуто, что в Украине действовала разветвленная сеть
музеев, в которых действовали специальные подразделения - отделы, центры, экспозиции и
т.д. Проанализованы направления научно - исследовательской работы музеев с выделением
ее просветительской составляющей.On the basis of archival, statistical materials, analytical inputs predecessors considered
the place and role of education in promoting cultural - artistic achievements of ethnic minorities.
Nonfiction includes the problems of cultural heritage of the Ukrainian people is partly considered
problem areas, shapes, nature education. Importance designated problem is primarily due to
the need to have a clear understanding of the mechanism solutions independent state problems
of interethnic relations. Found that in Ukraine there and operated an extensive network of
structures that were engaged in the popularization of cultural - artistic achievements of Ukraine’s
ethnic groups: governments, national - cultural societies, cultural institutions. We considered
the prospect of continuity and the protection and conservation of heritage. Considerable attention
is given to finding areas of education: conducting scientific - practical conferences, advocacy
through the museums, the publication of the relevant literature.
First in the historiography on the basis of specific methodological tools to analyze the relevant
promotion of cultural - artistic achievements - the strategic objectives - recognition of the field of an
ethnic nature of Ukrainian society, the development of social and cultural environment and spiritual
development of ethnic groups. Particular attention is given to explaining participation in the process
of popularizing the achievements of local history museums in Ukraine. Stress that Ukraine had an
extensive network of museums that had special units - departments, centers, exposure, etc.. Directions
of scientific - research museums and highlighted its educational component. Significant place in the
article devoted to subjects found clarification of the regional museum
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