2,767 research outputs found
Roton Interactions In Superfluid Helium
Based on a hard-sphere model for superfluid helium we derive a microscopic theory for quasiparticle interactions in this liquid. A satisfactory upper bound for the roton-roton collision frequency is obtained from this model. This theory also leads to an attractive coupling of two rotons with opposite momenta but the coupling strength is an order of magnitude larger than the phenomenological estimates based on experiments. However, as our analysis reveals, this large coupling strength is compatible with other physical considerations presented in this paper and does not contradict experimental data. © 1976 The American Physical Society.1451932194
Non-Hausdorff Symmetries of C*-algebras
Symmetry groups or groupoids of C*-algebras associated to non-Hausdorff
spaces are often non-Hausdorff as well. We describe such symmetries using
crossed modules of groupoids. We define actions of crossed modules on
C*-algebras and crossed products for such actions, and justify these
definitions with some basic general results and examples.Comment: very minor changes. To appear in Math. An
Equivariant comparison of quantum homogeneous spaces
We prove the deformation invariance of the quantum homogeneous spaces of the
q-deformation of simply connected simple compact Lie groups over the
Poisson-Lie quantum subgroups, in the equivariant KK-theory with respect to the
translation action by maximal tori. This extends a result of Neshveyev-Tuset to
the equivariant setting. As applications, we prove the ring isomorphism of the
K-group of Gq with respect to the coproduct of C(Gq), and an analogue of the
Borsuk-Ulam theorem for quantum spheres.Comment: 21 page
Toward Green Mobility: The Evolution of Transport
We envisage a transport system producing zero emissions and sparing the surface landscape, while people, on average, range hundreds of kilometers daily. We believe this prospect of "green mobility" is consistent with historical evolution. We lay out the general principles, extracted from widespread observations of human behavior over long periods of time, and use them to explain past transport systems and project the next 50-100 years. We discuss in detail railroads, cars, aeroplanes, and magnetically levitated trains (maglevs)
Management of fiscal and monetary policies interdependence in South African economy : A Bayesian VAR approach
Abstract: Purpose of the study: This study revisits the management and interaction aspects between fiscal and monetary policies in South Africa using a Bayesian vector autoregressive model (BVA). Design/methodology/approach: Monthly data on the inflation rate, interest rate, money supply, tax revenue, government spending and government debt for the period 2009 - 2019 were sourced from the South African Reserve Bank. Findings: The impulse response analysis shows that positive shocks to money supply prompt monetary authority to raise the economy's interest rate, which increases the bank rate. Inflation does not respond to shock to government spending and could drive inflation in the South African economy from the supply side rather than the demand side. Tax revenue and money supply shocks are significant sources of variation in inflation. These variables account for 7 and 18 percent variation in government spending. Recommendations/value: The study concludes that monetary authority must employ supply-side measures to manage the price level
Quantum teardrops
Algebras of functions on quantum weighted projective spaces are introduced,
and the structure of quantum weighted projective lines or quantum teardrops are
described in detail. In particular the presentation of the coordinate algebra
of the quantum teardrop in terms of generators and relations and classification
of irreducible *-representations are derived. The algebras are then analysed
from the point of view of Hopf-Galois theory or the theory of quantum principal
bundles. Fredholm modules and associated traces are constructed. C*-algebras of
continuous functions on quantum weighted projective lines are described and
their K-groups computed.Comment: 18 page
Eutrofiering in Nederland.
Een derde onderzoek is uitgevoerd naar de eutrofieringstoestand in de (semi-) stagnante zoete oppervlaktewateren in ons land. Van 121 plassen en meren werden min of meer volledige gegevens ontvangen betreffende de fysische, chemische en biologische kenmerke
INFLUENCE OF PISTON DISPLACEMENT ON THE SCAVENGING AND SWIRLING FLOW IN TWO-STROKE DIESEL ENGINES
Aspects of the FM Kondo Model: From Unbiased MC Simulations to Back-of-an-Envelope Explanations
Effective models are derived from the ferromagnetic Kondo lattice model with
classical corespins, which greatly reduce the numerical effort. Results for
these models are presented. They indicate that double exchange gives the
correct order of magnitude and the correct doping dependence of the Curie
temperature. Furthermore, we find that the jump in the particle density
previously interpreted as phase separation is rather explained by ferromagnetic
polarons.Comment: Proceedings of Wandlitz Days of Magnetism 200
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