94,393 research outputs found
Classification of multidimensional inflationary models
We define under which circumstances two multi-warped product spacetimes can
be considered equivalent and then we classify the spaces of constant curvature
in the Euclidean and Lorentzian signature. For dimension D=2, we get
essentially twelve representations, for D=3 exactly eighteen. More general, for
every even D, 5D+2 cases exist, whereas for every odd D, 5D+3 cases exist. For
every D, exactly one half of them has the Euclidean signature. Our definition
is well suited for the discussion of multidimensional cosmological models, and
our results give a simple algorithm to decide whether a given metric represents
the inflationary de Sitter spacetime (in unusual coordinates) or not.Comment: 21 pages, LaTeX, no figures, J. Math. Phys. in prin
Creation and Manipulation of Anyons in the Kitaev Model
We analyze the effect of local spin operators in the Kitaev model on the
honeycomb lattice. We show, in perturbation around the isolated-dimer limit,
that they create Abelian anyons together with fermionic excitations which are
likely to play a role in experiments. We derive the explicit form of the
operators creating and moving Abelian anyons without creating fermions and show
that it involves multi-spin operations. Finally, the important experimental
constraints stemming from our results are discussed.Comment: 4 pages, 3 figures, published versio
Asymptotic Freedom in Curvature-Satured Gravity
For a spatially flat Friedmann model with line element , the 00-component of the Einstein field equation
reads containing no derivative. For a nonlinear
Lagrangian , we obtain a second--order differential equation for
instead of the expected fourth-order equation. We discuss this equation for
the curvature-saturated model proposed by Kleinert and Schmidt. Finally, we
argue that asymptotic freedom is fulfilled in
curvature-saturated gravity.Comment: 9 pages, World Scientific LATEX, to appear in "Fluctuating Paths and
Fields", WSPC Singapore 2001, Eds: W. Janke, A. Pelster, H.-J. Schmidt, M.
Bachman
How to measure spatial distances?
The use of time--like geodesics to measure temporal distances is better
justified than the use of space--like geodesics for a measurement of spatial
distances. We give examples where a ''spatial distance'' cannot be
appropriately determined by the length of a space--like geodesic.Comment: 4 pages, latex, no figure
Internal Motility in Stiffening Actin-Myosin Networks
We present a study on filamentous actin solutions containing heavy meromyosin
subfragments of myosin II motor molecules. We focus on the viscoelastic phase
behavior and internal dynamics of such networks during ATP depletion. Upon
simultaneously using micro-rheology and fluorescence microscopy as
complementary experimental tools, we find a sol-gel transition accompanied by a
sudden onset of directed filament motion. We interpret the sol-gel transition
in terms of myosin II enzymology, and suggest a "zipping" mechanism to explain
the filament motion in the vicinity of the sol-gel transition.Comment: 4 pages, 3 figure
Reduced basis method for computational lithography
A bottleneck for computational lithography and optical metrology are long
computational times for near field simulations. For design, optimization, and
inverse scatterometry usually the same basic layout has to be simulated
multiple times for different values of geometrical parameters. The reduced
basis method allows to split up the solution process of a parameterized model
into an expensive offline and a cheap online part. After constructing the
reduced basis offline, the reduced model can be solved online very fast in the
order of seconds or below. Error estimators assure the reliability of the
reduced basis solution and are used for self adaptive construction of the
reduced system. We explain the idea of reduced basis and use the finite element
solver JCMsuite constructing the reduced basis system. We present a 3D
optimization application from optical proximity correction (OPC).Comment: BACUS Photomask Technology 200
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