18,146 research outputs found
Magnon Heat Conductivity and Mean Free Paths in Two-Leg Spin Ladders: A Model-Independent Determination
The magnon thermal conductivity of the spin ladders
in has been investigated at low doping levels
, 0.125, 0.25, 0.5 and 0.75. The Zn-impurities generate nonmagnetic
defects which define an upper limit for and therefore allow
a clear-cut relation between and to
be established independently of any model. Over a large temperature range we
observe a progressive suppression of with increasing
Zn-content and find in particular that with respect to pure is strongly suppressed even in
the case of tiny impurity densities where ~{\AA}.
This shows unambiguously that large ~{\AA} which
have been reported for and on basis of a kinetic model are in the correct order
of magnitude
Predictions of the pseudo-complex theory of Gravity for EHT observations- II. Theory and predictions
We present a resum\'e on the modified theory of gravity, called
pseudo-complex General Relativity (pc-GR). It is the second in a series of
papers, where the first one (Boller et al. 2019, referred to as paper I)
discussed the observational consequences of pc-GR. In this paper, we
concentrate on the underlying theory. PC-GR involves an algebraic extension of
the standard theory of GR and it depends on two phenomenological parameters. An
element included in pc-GR that is not present in standard GR is the
energy-momentum tensor corresponding to an anisotropic ideal fluid, which we
call dark energy. The two parameters are related to the coupling of mass to the
dark energy and its fall-off as a function of r. The consequences and
predictions of this theory will be discussed in the context of the
observational results of the Even Horizon Telescope, expected soon. Our main
result is that due to the accumulation of dark energy near a large mass, the
modified theory predicts a dark ring followed by a bright ring in the emission
profile of the accretion disc. We also discuss the light ring in the equatorial
plane.Comment: 2 figure
Hidden assumptions in the derivation of the Theorem of Bell
John Bell's inequalities have already been considered by Boole in 1862. Boole
established a one-to-one correspondence between experimental outcomes and
mathematical abstractions of his probability theory. His abstractions are
two-valued functions that permit the logical operations AND, OR and NOT and are
the elements of an algebra. Violation of the inequalities indicated to Boole an
inconsistency of definition of the abstractions and/or the necessity to revise
the algebra. It is demonstrated in this paper, that a violation of Bell's
inequality by Einstein-Podolsky-Rosen type of experiments can be explained by
Boole's ideas. Violations of Bell's inequality also call for a revision of the
mathematical abstractions and corresponding algebra. It will be shown that this
particular view of Bell's inequalities points toward an incompleteness of
quantum mechanics, rather than to any superluminal propagation or influences at
a distance
On possible violation of the CHSH Bell inequality in a classical context
It has been shown that there is a small possibility to experimentally violate
the CHSH Bell inequality in a 'classical' context. The probability of such a
violation has been estimated in the framework of a classical probabilistic
model in the language of a random-walk representation.Comment: 9 pages, 1 figur
Ab initio study of semiconducting carbon nanotubes adsorbed on the Si(100) surface: diameter- and registration-dependent atomic configurations and electronic properties
We present a first-principles study of semiconducting carbon nanotubes
adsorbed on the unpassivated Si(100) surface. We have found metallicity for the
combined system caused by n-doping of the silicon slab representing the surface
by the SWNT. We confirm this metallicity for nanotubes of different diameters
and chiral angles, and find the effect to be independent of the orientation of
the nanotubes on the surface. We also present adsorption energetics and
configurations which show semiconducting SWNTs farther apart from the surface
and transferring less charge, in comparison with metallic SWNTs of similar
diameter.Comment: Replaces old (Jan 2006) version; more supporting material. 11 pages,
8 figures, 7 table
Durability testing at 5 atmospheres of advanced catalysts and catalyst supports for gas turbine engine combustors
The durability of CATCOM catalysts and catalyst supports was experimentally demonstrated in a combustion environment under simulated gas turbine engine combustor operating conditions. A test of 1000 hours duration was completed with one catalyst using no. 2 diesel fuel and operating at catalytically-supported thermal combustion conditions. The performance of the catalyst was determined by monitoring emissions throughout the test, and by examining the physical condition of the catalyst core at the conclusion of the test. Tests were performed periodically to determine changes in catalytic activity of the catalyst core. Detailed parametric studies were also run at the beginning and end of the durability test, using no. 2 fuel oil. Initial and final emissions for the 1000 hours test respectively were: unburned hydrocarbons (C3 vppm):0, 146, carbon monoxide (vppm):30, 2420; nitrogen oxides (vppm):5.7, 5.6
Non-linear rheology of active particle suspensions: Insights from an analytical approach
We consider active suspensions in the isotropic phase subjected to a shear
flow. Using a set of extended hydrodynamic equations we derive a variety of
{\em analytical} expressions for rheological quantities such as shear viscosity
and normal stress differences. In agreement to full-blown numerical
calculations and experiments we find a shear thickening or -thinning behaviour
depending on whether the particles are contractile or extensile. Moreover, our
analytical approach predicts that the normal stress differences can change
their sign in contrast to passive suspensions.Comment: 11 pages, 10 figures, appear in PR
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