42,515 research outputs found
Analyticity of the density of electronic wavefunctions
We prove that the electronic densities of atomic and molecular eigenfunctions
are real analytic in away from the nuclei.Comment: 19 page
Reweighting towards the chiral limit
We propose to perform fully dynamical simulations at small quark masses by
reweighting in the quark mass. This approach avoids some of the technical
difficulties associated with direct simulations at very small quark masses. We
calculate the weight factors stochastically, using determinant breakup and low
mode projection to reduce the statistical fluctuations. We find that the weight
factors fluctuate only moderately on nHYP smeared dynamical Wilson-clover
ensembles, and we could successfully reweight 16^4, (1.85fm)^4 volume
configurations from m_q = 20MeV to m_q = 5MeV quark masses, reaching the
epsilon-regime. We illustrate the strength of the method by calculating the low
energy constant F from the epsilon-regime pseudo-scalar correlator.Comment: 17 pages, 8 figure
Sharp regularity results for many-electron wave functions
We show that electronic wave functions Psi of atoms and molecules have a
representation Psi=F*phi, where F is an explicit universal factor, locally
Lipschitz, and independent of the eigenvalue and the solution Psi itself, and
phi has locally bounded second derivatives. This representation turns out to be
optimal as can already be demonstrated with the help of hydrogenic wave
functions. The proofs of these results are, in an essential way, based on a new
elliptic regularity result which is of independent interest. Some identities
that can be interpreted as cusp conditions for second order derivatives of Psi
are derived.Comment: 43 page
kmos: A lattice kinetic Monte Carlo framework
Kinetic Monte Carlo (kMC) simulations have emerged as a key tool for
microkinetic modeling in heterogeneous catalysis and other materials
applications. Systems, where site-specificity of all elementary reactions
allows a mapping onto a lattice of discrete active sites, can be addressed
within the particularly efficient lattice kMC approach. To this end we describe
the versatile kmos software package, which offers a most user-friendly
implementation, execution, and evaluation of lattice kMC models of arbitrary
complexity in one- to three-dimensional lattice systems, involving multiple
active sites in periodic or aperiodic arrangements, as well as site-resolved
pairwise and higher-order lateral interactions. Conceptually, kmos achieves a
maximum runtime performance which is essentially independent of lattice size by
generating code for the efficiency-determining local update of available events
that is optimized for a defined kMC model. For this model definition and the
control of all runtime and evaluation aspects kmos offers a high-level
application programming interface. Usage proceeds interactively, via scripts,
or a graphical user interface, which visualizes the model geometry, the lattice
occupations and rates of selected elementary reactions, while allowing
on-the-fly changes of simulation parameters. We demonstrate the performance and
scaling of kmos with the application to kMC models for surface catalytic
processes, where for given operation conditions (temperature and partial
pressures of all reactants) central simulation outcomes are catalytic activity
and selectivities, surface composition, and mechanistic insight into the
occurrence of individual elementary processes in the reaction network.Comment: 21 pages, 12 figure
The state space of short-range Ising spin glasses: the density of states
The state space of finite square and cubic Ising spin glass models is
analysed in terms of the global and the local density of states. Systems with
uniform and gaussian probability distribution of interactions are compared.
Different measures for the local state density are presented and discussed. In
particular the question whether the local density of states grows exponentially
or not is considered. The direct comparison of global and local densities leads
to consequences for the structure of the state space.Comment: 18 pages (including 6 figures); submitted to Z.f.Physik
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