Convergence improvement for coupled cluster calculations

Convergence problems in coupled-cluster iterations are discussed, and a new iteration scheme is proposed. Whereas the Jacobi method inverts only the diagonal part of the large matrix of equation coefficients, we invert a matrix which also includes a relatively small number of off-diagonal coefficients, selected according to the excitation amplitudes undergoing the largest change in the coupled cluster iteration. A test case shows that the new IPM (inversion of partial matrix) method gives much better convergence than the straightforward Jacobi-type scheme or such well-known convergence aids as the reduced linear equations or direct inversion in iterative subspace methods.Comment: 7 pages, IOPP styl

Indifferente en Labiele Evenwichten in Economische Stelsels

In English: Unstable and Indifferent Equilibria in Economic Systems, Revue de l’Institut International de Statistique, Vol. 9, No.1/2, 1941, pp. 36-5

An Economic Study of the Effect of Android Platform Fragmentation on Security Updates

Vendors in the Android ecosystem typically customize their devices by modifying Android Open Source Project (AOSP) code, adding in-house developed proprietary software, and pre-installing third-party applications. However, research has documented how various security problems are associated with this customization process. We develop a model of the Android ecosystem utilizing the concepts of game theory and product differentiation to capture the competition involving two vendors customizing the AOSP platform. We show how the vendors are incentivized to differentiate their products from AOSP and from each other, and how prices are shaped through this differentiation process. We also consider two types of consumers: security-conscious consumers who understand and care about security, and na\"ive consumers who lack the ability to correctly evaluate security properties of vendor-supplied Android products or simply ignore security. It is evident that vendors shirk on security investments in the latter case. Regulators such as the U.S. Federal Trade Commission have sanctioned Android vendors for underinvestment in security, but the exact effects of these sanctions are difficult to disentangle with empirical data. Here, we model the impact of a regulator-imposed fine that incentivizes vendors to match a minimum security standard. Interestingly, we show how product prices will decrease for the same cost of customization in the presence of a fine, or a higher level of regulator-imposed minimum security.Comment: 22nd International Conference on Financial Cryptography and Data Security (FC 2018

Configuration interaction calculation of hyperfine and P,T-odd constants on ^{207}PbO excited states for the electron EDM experiments

We report first configuration interaction calculations of hyperfine constants A_\parallel and the effective electric field W_d acting on the electric dipole moment of the electron, in two excited electronic states of ^{207}PbO. The obtained hyperfine constants, A_\parallel = -3826 MHz for the a(1) state and A_\parallel = 4887 MHz for the B(1) state, are in very good agreement with the experimental data, -4113 MHz and 5000 \pm 200 MHz, respectively. We find W_d = -(6.1 ^{+1.8}_{-0.6}) 10^{24} Hz/(e cm) for a(1), and W_d = (8.0 \pm 1.6) 10^{24} Hz/(e cm) for B(1). The obtained values are analyzed and compared to recent relativistic coupled cluster results and a semiempirical estimate of W_d for the a(1) state.Comment: 6 pages, REVTeX4 style, submitted to Pthys.Rev.

Calculation of PandP_ and T_ odd effects in $"" sup 205_TIF including electron correlation

A method and codes for two-step correlation calculation of heavy-atom molecules have been developed, employing the generalized relativistic effective core potential and relativistic coupled cluster (RCC) methods at the first step, followed by nonvariational one-center restoration of proper four-component spinors in the heavy cores. Electron correlation is included for the first time in an ab initio calculation of the interaction of the permanent P,T-odd proton electric dipole moment with the internal electromagnetic field in a molecule. The calculation is performed for the ground state of TlF at the experimental equilibrium, R_e=2.0844 A, and at R=2.1 A, with spin-orbit and correlation effects included by RCC. Calculated results with single cluster amplitudes only are in good agreement (3% and 1%) with recent Dirac-Hartree-Fock (DHF) values of the magnetic parameter M; the larger differences occurring between present and DHF volume parameter (X) values, as well as between the two DHF calculations, are explained. Inclusion of electron correlation by GRECP/RCC with single and double excitations has a major effect on the P,T-odd parameters, decreasing M by 17% and X by 22%.Comment: 5 pages, REVTeX4 style Accepted for publication in Phys.Rev.Letter

On the performance of the intermediate Hamiltonian Fock-space coupled-cluster method on linear triatomic molecules: The electronic spectra of NpO2+, NpO22+, and Pu O22

International audienceIn this paper we explore the use of the novel relativistic intermediate Hamiltonian Fock-space coupled-cluster method in the calculation of the electronic spectrum for small actinyl ions (NpO2+, NpO22+, and PuO22+). It is established that the method, in combination with uncontracted double-zeta quality basis sets, yields excitation energies in good agreement with experimental values, and better than those obtained previously with other theoretical methods. We propose the reassignment of some of the peaks that were observed experimentally, and confirm other assignments

New evidence on Allyn Young's style and influence as a teacher

This paper publishes the hitherto unpublished correspondence between Allyn Abbott Young's biographer Charles Blitch and 17 of Young's former students or associates. Together with related biographical and archival material, the paper shows the way in which this adds to our knowledge of Young's considerable influence as a teacher upon some of the twentieth century's greatest economists. The correspondents are as follows: James W Angell, Colin Clark, Arthur H Cole, Lauchlin Currie, Melvin G de Chazeau, Eleanor Lansing Dulles, Howard S Ellis, Frank W Fetter, Earl J Hamilton, Seymour S Harris, Richard S Howey, Nicholas Kaldor, Melvin M Knight, Bertil Ohlin, Geoffrey Shepherd, Overton H Taylor, and Gilbert Walker