479 research outputs found
A Remark on Unconditional Uniqueness in the Chern-Simons-Higgs Model
The solution of the Chern-Simons-Higgs model in Lorenz gauge with data for
the potential in and for the Higgs field in is
shown to be unique in the natural space for , where corresponds to finite energy. Huh and Oh
recently proved local well-posedness for , but uniqueness was obtained
only in a proper subspace of Bourgain type. We prove that any solution in
must in fact belong to the space
, hence it is the unique solution obtained by Huh and Oh
Gaussian entanglement induced by an extended thermal environment
We study stationary entanglement among three harmonic oscillators which are
dipole coupled to a one-dimensional or a three-dimensional bosonic environment.
The analysis of the open-system dynamics is performed with generalized quantum
Langevin equations which we solve exactly in Fourier representation. The focus
lies on Gaussian bipartite and tripartite entanglement induced by the highly
non-Markovian interaction mediated by the environment. This environment-induced
interaction represents an effective many-parties interaction with a spatial
long-range feature: a main finding is that the presence of a passive oscillator
is detrimental for the stationary two-mode entanglement. Furthermore, our
results strongly indicate that the environment-induced entanglement mechanism
corresponds to uncontrolled feedback which is predominantly coherent at low
temperatures and for moderate oscillator-environment coupling as compared to
the oscillator frequency.Comment: 15 page, 6 figure
Animal Successional Pathways for about 200 Years Near a Melting Glacier: A Norwegian Case Study
Here, we explore 200 years of arthropod succession by using dated moraines in a Norwegian glacier foreland. Surface active beetles (Coleoptera) and spiders (Aranea) were sampled by pitfall trapping, and springtails (Collembola) and mites (Acari) were extracted from soil samples. Newly deglaciated ground was rapidly colonised by a mixture of generalists and specialists, with various life strategies. Interestingly, the pioneer community was fed by three ‘invisible’ food sources: biofilm with terrestrial diatom algae, tiny pioneer mosses and chironomid midges whose larvae were pond-living and used ancient carbon that was released by the melting glacier as an energy source. The true ‘super-pioneers’ were biofilm-eating springtails, which tracked the melting ice edge closely. Most species of beetles and springtails colonised within 80 years, while spiders and oribatid mites needed a longer time span to colonise. Topography influenced the succession pattern. Among both surface-living macroarthropods and soil-living microarthropods, we distinguished between a ‘dry’ and a ‘wet’ successional pathway with different community structure. Most arthropod species persisted after colonisation, but certain species preferring open space or low temperature were gradually excluded. Comparisons are made with botanical succession. Sampling methods, material size, and taxonomic resolution were considered critical factors when studying arthropod succession
Fetishism and the social value of objects.
The idea of the fetish has a particular presence in the writings of both Marx and Freud. It implies for these two theorists of the social, a particular form of relation between human beings and objects. In the work of both the idea of the fetish involves attributing properties to objects that they do not 'really' have and that should correctly be recognised as human. While Marx's account of fetishism addresses the exchange-value of commodities at the level of the economic relations of production, it fails to deal in any detail with the use-value or consumption of commodities. In contrast Freud's concept of the fetish as a desired substitute for a suitable sex object explores how objects are desired and consumed. Drawing on both Marx and Freud, Baudrillard breaks with their analyses of fetishism as demonstrating a human relation with unreal objects. He explores the creation of value in objects through the social exchange of sign values, showing how objects are fetishised in ostentation. This paper argues that while Baudrillard breaks with the realism characteristic of Marx's and Freud's analyses of fetishism, he does not go far enough in describing the social and discursive practices in which objects are used and sometimes transformed into fetishes. It is proposed that the fetishisation of objects involves an overdetermination of their social value through a discursive negotiation of the capacities of objects that stimulates fantasy and desire for them
Topology Optimization of Two Fluid Heat Exchangers
A method for density-based topology optimization of heat exchangers with two
fluids is proposed. The goal of the optimization process is to maximize the
heat transfer from one fluid to the other, under maximum pressure drop
constraints for each of the fluid flows. A single design variable is used to
describe the physical fields. The solid interface and the fluid domains are
generated using an erosion-dilation based identification technique, which
guarantees well-separated fluids, as well as a minimum wall thickness between
them. Under the assumption of laminar steady flow, the two fluids are modelled
separately, but in the entire computational domain using the Brinkman
penalization technique for ensuring negligible velocities outside of the
respective fluid subdomains. The heat transfer is modelled using the
convection-diffusion equation, where the convection is driven by both fluid
flows. A stabilized finite element discretization is used to solve the
governing equations. Results are presented for two different problems: a
two-dimensional example illustrating and verifying the methodology; and a
three-dimensional example inspired by shell-and-tube heat exchangers. The
optimized designs for both cases show an improved heat transfer compared to the
baseline designs. For the shell-and-tube case, the full freedom topology
optimization approach is shown to yield performance improvements of up to 113%
under the same pressure drop
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