Natural orbital functional theory and pairing correlation effects in electron momentum density

Occupation numbers of natural orbitals capture the physics of strong electron correlations in momentum space. A Natural Orbital Density Functional Theory based on the antisymmetrized geminal product provides these occupation numbers and the corresponding electron momentum density. A practical implementation of this theory approximates the natural orbitals by the Kohn-Sham orbitals and uses a mean-field approach to estimate pairing amplitudes leading to corrections for the independent particle model. The method is applied to weakly doped \mbox{La_2$CuO$_4}.Comment: 9 pages, 3 figures. Review paper contribution for the special issue (V.40, No.3 2014) of Fizika Nizkikh Temperatur on New Trends of Fermiology (shorter version

Compton scattering beyond the impulse approximation

We treat the non-relativistic Compton scattering process in which an incoming photon scatters from an N-electron many-body state to yield an outgoing photon and a recoil electron, without invoking the commonly used frameworks of either the impulse approximation (IA) or the independent particle model (IPM). An expression for the associated triple differential scattering cross section is obtained in terms of Dyson orbitals, which give the overlap amplitudes between the N-electron initial state and the (N-1) electron singly ionized quantum states of the target. We show how in the high energy transfer regime, one can recover from our general formalism the standard IA based formula for the cross section which involves the ground state electron momentum density (EMD) of the initial state. Our formalism will permit the analysis and interpretation of electronic transitions in correlated electron systems via inelastic x-ray scattering (IXS) spectroscopy beyond the constraints of the IA and the IPM.Comment: 7 pages, 1 figur

Phenotypic Overlap between MMP-13 and the Plasminogen Activation System during Wound Healing in Mice

BACKGROUND: Proteolytic degradation of extracellular matrix is a crucial step in the healing of incisional skin wounds. Thus, healing of skin wounds is delayed by either plasminogen-deficiency or by treatment with the broad-spectrum metalloproteinase (MP) inhibitor Galardin alone, while the two perturbations combined completely prevent wound healing. Both urokinase-type plasminogen activator and several matrix metallo proteinases (MMPs), such as MMP-3, -9 and -13, are expressed in the leading-edge keratinocytes of skin wounds, which may account for this phenotypic overlap between these classes of proteases. METHODOLOGY: To further test that hypothesis we generated Mmp13;Plau and Mmp13;Plg double-deficient mice in a cross between Mmp13- and Plau-deficient mice as well as Mmp13- and Plg-deficient mice. These mice were examined for normal physiology in a large cohort study and in a well-characterized skin wound healing model, in which we made incisional 20 mm-long full-thickness skin wounds. PRINCIPAL FINDINGS: While mice that are deficient in Mmp13 have a mean healing time indistinguishable to wild-type mice, wound healing in both Plau- and Plg-deficient mice is significantly delayed. Histological analysis of healed wounds revealed a significant increase in keratin 10/14 immunoreactive layers of kerationcytes in the skin surface in Mmp13;Plau double-deficient mice. Furthermore, we observe, by immunohistological analysis, an aberrant angiogenic pattern during wound healing induced by Plau-deficiency, which has not previously been described. CONCLUSIONS: We demonstrate a phenotypic overlap, defined as an additional delay in wound healing in the double-deficient mice compared to the individual single-deficient mice, between MMP-13 and the plasminogen activation system in the process of wound healing, but not during gestation and in postnatal development. Thus, a dual targeting of uPA and MMP-13 might be a possible future strategy in designing therapies aimed at tissue repair or other pathological processes, such as cancer invasion, where proteolytic degradation is a hallmark

Calculation of dispersion energy shifts in molecular electronic spectra using sum rules

The use of factorization formulas due to Casimir and Polder gives exact expressions for van der Waals energies in terms of the dynamic properties of the subsystems. It is natural to approximate the appearing polarizabilities in terms of rational fractions</p

Density of states in narrow energy bands

The density of states in the one-band short-range interaction model approximated with Hubbard's decoupling is equal to the I-independent band theoretical result at E = T-o and E = T-o + E. Improved decoupling procedures remove this anomaly.</p

Correlation functions and thermal rate constants

Thermal rate constants k(T) and cumulative reaction probabilities N(E) can be computed as a sum of correlation functions C-nm = &lt;(n)/f((H) over tilde/phi (m)). In this paper we discuss the use of two different Krylov subspace methods to compute these correlation functions for large systems. The first approach is based on the Lanczos algorithm to transform the Hamiltonian to tridiagonal form. As shown by Mandelshtam (J. Chem, Phys. 1998, 108, 9999) and Chen and Guo (J, Chem. Phys. 1999, 111, 9944), ail correlation functions can be computed from a single recursion. The second approach treats a number of linear systems of equations using a Krylov subspace solver. Here the quasiminimal residual (QMR) method was used. For the first approach, we found that we needed the same number of Lanczos recursions as the size of the matrix. If Ilo re-orthogonalization is used, the number of recursions grows further. The linear solver approach, on the other hand, converges fast for each linear system, but many systems must be solved.</p

The maximum entropy method and relaxation for multiple collisions involving highly charged ions

Advantages and disadvantages of the maximum entropy method (MEM) in application to the theory of relaxation are studied. The time evolution of distributions and of associated moments must obey stringent conditions for both finite and infinite intervals. The theoretical considerations are illustrated with examples from charge-state distributions arising in beam-foil spectroscopy. The examples indicate that the possibility to include more than two moments (extension to non-Gaussian case) is severely limited (though feasible) in the static case due to nonpositive definiteness as well as stiffness of the Hessian matrices appearing in the computations. This takes place already for the finite charge-state distribution intervals. For infinite intervals, this is a severe problem as required by the Marcinkiewicz theorem, affecting characteristic functions and, hence, the description of the time evolution of distributions. </p