1,270 research outputs found
Density Functional Theory of the Hubbard-Holstein Model
We present a density functional theory (DFT) for lattice models with local
electron-electron (e-e) and electron-phonon (e-ph) interactions.
Exchange-correlation potentials are derived via dynamical mean field theory for
the infinite-dimensional Bethe lattice, and analytically for an isolated
Hubbard-Holstein site. These potentials exhibit discontinuities as a function
of the density, which depend on the relative strength of the e-e and e-ph
interactions. By comparing to exact benchmarks, we show that the DFT formalism
gives a good description of the linear conductance and real-time dynamics.Comment: 5 pages, 3 figures, supplemental material provided as pd
Redescription of Cervidellus vexilliger (de Man, 1880) Thorne, 1937 (Nematoda : Cephalobidae) and taxonomical consequences
#Cervidellus vexilliger, actuellement espèce type du genre #Ypsylonellus, est redécrit et un néotype est désigné parmi les spécimens d'un échantillon collecté dans la localité type : Haagse Bos, Pays-Bas. Une autre espèce très proche, correspondant à la diagnose de #C. neftasiensis, était également présente dans cet échantillon. La description originale de #C. vexilliger et les nouveaux spécimens provenant de la localité type suggèrent que #C. vexilliger est conspécifique de #C. serratus. #C. serratus est donc synonymisé avec #C. vexilliger et #Ypsilonellus est synonymisé avec #Cervidellus. Des diagnoses différentielles et une classification provisoire sont proposées pour les genres #Cervidellus et #Stegelletina. (Résumé d'auteur
A revision of the genus Pseudacrobeles Steiner, 1938 (Nematoda : Cephalobidae) : Part 2. Subgenus Bunobus subgen.n., problematical species, discussion and key
A revision of the genus Pseudacrobeles Steiner, 1938 (Nematoda : Cephalobidae) : Part 1. Subgenus Pseudacrobeles grad.n.
Comment on "Thermal Effects on the Casimir Force in the 0.1-5 micrometer Range"
In a recent paper (M. Bostrom and Bo E. Sernelius, Phys. Rev. Lett. 84, 4757
(2000)) the combined effect of finite conductivity and finite temperature on
the Casimir force is analyzed, and significant deviations from other
theoretical results and a recent experiment are obtained.
In this Comment, I show that the extrapolation to zero frequency is incorrect
because the authors have neglected that the wavenumber and frequency of the
electromagentic mode must simultaneously appraoch zeroComment: Final version (two previous versions, first was partly incorrect)
Rejected by PRL
Non-Perturbative Theory of Dispersion Interactions
Some open questions exist with fluctuation-induced forces between extended
dipoles. Conventional intuition derives from large-separation perturbative
approximations to dispersion force theory. Here we present a full
non-perturbative theory. In addition we discuss how one can take into account
finite dipole size corrections. It is of fundamental value to investigate the
limits of validity of the perturbative dispersion force theory.Comment: 9 pages, no figure
Modular termination verification for non-blocking concurrency
© Springer-Verlag Berlin Heidelberg 2016.We present Total-TaDA, a program logic for verifying the total correctness of concurrent programs: that such programs both terminate and produce the correct result. With Total-TaDA, we can specify constraints on a thread’s concurrent environment that are necessary to guarantee termination. This allows us to verify total correctness for nonblocking algorithms, e.g. a counter and a stack. Our specifications can express lock- and wait-freedom. More generally, they can express that one operation cannot impede the progress of another, a new non-blocking property we call non-impedance. Moreover, our approach is modular. We can verify the operations of a module independently, and build up modules on top of each other
On the diffeomorphism commutators of lattice quantum gravity
We show that the algebra of discretized spatial diffeomorphism constraints in
Hamiltonian lattice quantum gravity closes without anomalies in the limit of
small lattice spacing. The result holds for arbitrary factor-ordering and for a
variety of different discretizations of the continuum constraints, and thus
generalizes an earlier calculation by Renteln.Comment: 16 pages, Te
Increased porosity turns desorption to adsorption for gas bubbles near water-SiO2 interface
We consider theoretically the retarded van der Waals interaction of a small gas bubble in water with a porous SiO2 surface. We predict a possible transition from repulsion to attraction as the surface is made more porous. It highlights that bubbles will interact differently with surface regions with different porosity (i.e., with different optical properties)
Role of food web interactions in promoting resilience to nutrient enrichment in a brackish water eelgrass (Zostera marina) ecosystem
Understanding the ecological interactions that enhance the resilience of threatened ecosystems is essential in assuring their conservation and restoration. Top-down trophic interactions can increase resilience to bottom-up nutrient enrichment, however, as many seagrass ecosystems are threatened by both eutrophication and trophic modifications, understanding how these processes interact is important. Using a combination of approaches, we explored how bottom-up and top-down processes, acting individually or in conjunction, can affect eelgrass meadows and associated communities in the northern Baltic Sea. Field surveys along with fish diet and stable isotope analyses revealed that the eelgrass trophic network included two main top predatory fish species, each of which feeds on a separate group of invertebrate mesograzers (crustaceans or gastropods). Mesograzer abundance in the study area was high, and capable of mitigating the effects of increased algal biomass that resulted from experimental nutrient enrichment in the field. When crustacean mesograzers were experimentally excluded, gastropod mesograzers were able to compensate and limit the effects of nutrient enrichment on eelgrass biomass and growth. Our results suggest that top-down processes (i.e., suppression of algae by different mesograzer groups) may ensure eelgrass resilience to nutrient enrichment in the northern Baltic Sea, and the existence of multiple trophic pathways can provide additional resilience in the face of trophic modifications. However, the future resilience of these meadows is likely threatened by additional local stressors and global environmental change. Understanding the trophic links and interactions that ensure resilience is essential for managing and conserving these important ecosystems and the services they provide
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