5,374 research outputs found
Spin Resolution of the Electron-Gas Correlation Energy: Positive same-spin contribution
The negative correlation energy per particle of a uniform electron gas of
density parameter and spin polarization is well known, but its
spin resolution into up-down, up-up, and down-down contributions is not.
Widely-used estimates are incorrect, and hamper the development of reliable
density functionals and pair distribution functions. For the spin resolution,
we present interpolations between high- and low-density limits that agree with
available Quantum Monte Carlo data. In the low-density limit for ,
we find that the same-spin correlation energy is unexpectedly positive, and we
explain why. We also estimate the up and down contributions to the kinetic
energy of correlation.Comment: new version, to appear in PRB Rapid Communicatio
Optimal transport distances to characterise electronic excitations
Understanding the character of electronic excitations is important in
computational and mechanistic studies, but their classification from numerical
simulations remains an open problem despite significant progress in
density-based and exciton wavefunction-based descriptors. We propose and
investigate a new diagnostic based on the Sinkhorn divergence from optimal
transport, which is highly sensitive to translations and hence promising for
the identification of charge transfer excitations. In spite of this, we show
through numerical simulations on a representative set of molecules that the new
diagnostic is not able to separate charge transfer from Rydberg excitations in
practice, which can be explained by its inability to distinguish between
translational and diffusive processes. We trained a -NN classification
algorithm on the optimal transport diagonistic, the popular
diagnostic as well as their combination, and assessed its performance in
labelling excitations, finding that (i) The combination improves the
classification, (ii) Rydberg excitations are not separated well in any setting,
suggesting that key information on the diffusivity of the excited state is
missing and (iii) the optimal transport diagnostic breaks down for charge
transfer in small molecules.Comment: 6 pages, 4 figure
Evaluation of uncertainties in regional climate change simulations
We have run two regional climate models (RCMs) forced by three sets of initial and boundary conditions to form a 2×3 suite of 10-year climate simulations for the continental United States at approximately 50 km horizontal resolution. The three sets of driving boundary conditions are a reanalysis, an atmosphere-ocean coupled general circulation model (GCM) current climate, and a future scenario of transient climate change. Common precipitation climatology features simulated by both models included realistic orographic precipitation, east-west transcontinental gradients, and reasonable annual cycles over different geographic locations. However, both models missed heavy cool-season precipitation in the lower Mississippi River basin, a seemingly common model defect. Various simulation biases (differences) produced by the RCMs are evaluated based on the 2×3 experiment set in addition to comparisons with the GCM simulation. The RCM performance bias is smallest, whereas the GCM-RCM downscaling bias (difference between GCM and RCM) is largest. The boundary forcing bias (difference between GCM current climate driven run and reanalysis-driven run) and intermodel bias are both largest in summer, possibly due to different subgrid scale processes in individual models. The ratio of climate change to biases, which we use as one measure of confidence in projected climate changes, is substantially larger than 1 in several seasons and regions while the ratios are always less than 1 in summer. The largest ratios among all regions are in California. Spatial correlation coefficients of precipitation were computed between simulation pairs in the 2×3 set. The climate change correlation is highest and the RCM performance correlation is lowest while boundary forcing and intermodel correlations are intermediate. The high spatial correlation for climate change suggests that even though future precipitation is projected to increase, its overall continental-scale spatial pattern is expected to remain relatively constant. The low RCM performance correlation shows a modeling challenge to reproduce observed spatial precipitation patterns
A Spectral Bernstein Theorem
We study the spectrum of the Laplace operator of a complete minimal properly
immersed hypersurface in . (1) Under a volume growth condition on
extrinsic balls and a condition on the unit normal at infinity, we prove that
has only essential spectrum consisting of the half line .
This is the case when , where
is the extrinsic distance to a point of and are the
principal curvatures. (2) If the satisfy the decay conditions
, and strict inequality is achieved at some point
, then there are no eigenvalues. We apply these results to minimal
graphic and multigraphic hypersurfaces.Comment: 16 pages. v2. Final version: minor revisions, we add Proposition 3.2.
Accepted for publication in the Annali di Matematica Pura ed Applicata, on
the 05/03/201
Global regularity of weak solutions to quasilinear elliptic and parabolic equations with controlled growth
We establish global regularity for weak solutions to quasilinear divergence
form elliptic and parabolic equations over Lipschitz domains with controlled
growth conditions on low order terms. The leading coefficients belong to the
class of BMO functions with small mean oscillations with respect to .Comment: 24 pages, to be submitte
Minimal archi-texture for neutrino mass matrices
The origin of the observed masses and mixing angles of quarks and leptons is
one of imperative subjects in and beyond the standard model. Toward a deeper
understanding of flavor structure, we investigate in this paper the minimality
of fermion mass (Yukawa) matrices in unified theory. That is, the simplest
matrix form is explored in light of the current experimental data for quarks
and leptons, including the recent measurements of quark CP violation and
neutrino oscillations. Two types of neutrino mass schemes are particularly
analyzed; (i) Majorana masses of left-handed neutrinos with unspecified
mechanism and (ii) Dirac and Majorana masses introducing three right-handed
neutrinos. As a result, new classes of neutrino mass matrices are found to be
consistent to the low-energy experimental data and high-energy unification
hypothesis. For distinctive phenomenological implications of the minimal
fermion mass textures, we discuss flavor-violating decay of charged leptons,
the baryon asymmetry of the universe via thermal leptogenesis, neutrino-less
double beta decay, and low-energy leptonic CP violation.Comment: 37 pages, 6 figure
The mixed problem for the Laplacian in Lipschitz domains
We consider the mixed boundary value problem or Zaremba's problem for the
Laplacian in a bounded Lipschitz domain in R^n. We specify Dirichlet data on
part of the boundary and Neumann data on the remainder of the boundary. We
assume that the boundary between the sets where we specify Dirichlet and
Neumann data is a Lipschitz surface. We require that the Neumann data is in L^p
and the Dirichlet data is in the Sobolev space of functions having one
derivative in L^p for some p near 1. Under these conditions, there is a unique
solution to the mixed problem with the non-tangential maximal function of the
gradient of the solution in L^p of the boundary. We also obtain results with
data from Hardy spaces when p=1.Comment: Version 5 includes a correction to one step of the main proof. Since
the paper appeared long ago, this submission includes the complete paper,
followed by a short section that gives the correction to one step in the
proo
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