2,909 research outputs found
Formal Verification of Arithmetic Circuits by Function Extraction
The paper presents an algebraic approach to functional verification of gate-level, integer arithmetic circuits. It is based on extracting a unique bit-level polynomial function computed by the circuit directly from its gate-level implementation. The method can be used to verify the arithmetic function computed by the circuit against its known specification, or to extract an arithmetic function implemented by the circuit. Experiments were performed on arithmetic circuits synthesized and mapped onto standard cells using ABC system. The results demonstrate scalability of the method to large arithmetic circuits, such as multipliers, multiply-accumulate, and other elements of arithmetic datapaths with up to 512-bit operands and over 2 million gates. The results show that our approach wins over the state-of-the-art SAT/SMT solvers by several orders of magnitude of CPU time. The procedure has linear runtime and memory complexity, measured by the number of logic gates
Low energy n-\nuc{3}{H} scattering : a novel testground for nuclear interaction
The low energy n-\nuc{3}{H} elastic cross sections near the resonance peak
are calculated by solving the 4-nucleon problem with realistic NN interactions.
Three different methods -- Alt, Grassberger and Shandas (AGS), Hyperspherical
Harmonics and Faddeev-Yakubovsky -- have been used and their respective results
are compared. We conclude on a failure of the existing NN forces to reproduce
the n-\nuc{3}{H} total cross section.Comment: To be published in Phys. Rev.
Chemical Synthesis at Surfaces with Atomic Precision: Taming Complexity and Perfection
Scanning probe microscopy (SPM) is a powerful tool to study the structure and dynamics of molecules at surfaces and interfaces as well as to precisely manipulate atoms and molecules by applying an external force, by inelastic electron tunneling, or by means of an electric field. The rapid development of these SPM manipulation modes made it possible to achieve fine‐control over fundamental processes in the physics of interfaces as well as chemical reactivity, such as adsorption, diffusion, bond formation, and bond dissociation with precision at the single atom/molecule level. Their controlled use for the fabrication of atomic‐scale structures and synthesis of new, perhaps uncommon, molecules with programmed properties are reviewed. Opportunities and challenges towards the development of complex chemical systems are discussed, by analyzing potential future impacts in nanoscience and nanotechnology.journal articlereview2019 Dec 192019 11 28importe
Solutions of the Faddeev-Yakubovsky equations for the four nucleons scattering states
The Faddeev-Yakubowsky equations in configuration space have been solved for
the four nucleon system. The results with an S-wave interaction model in the
isospin approximation are presented. They concern the bound and scattering
states below the first three-body threshold. The elastic phase-shifts for the
N+NNN reaction in different () channels are given and the corresponding
low energy expansions are discussed. Particular attention is payed to the n+t
elastic cross section. Its resonant structure is well described in terms of a
simple NN interaction. First results concerning the S-matrix for the coupled
N+NNN-NN+NN channels and the strong deuteron-deuteron scattering length are
obtained.Comment: latex.tar.gz, 36 pages, 10 figures, 11 tables. To be published in
Physical Review
Four-nucleon shell-model calculations in a Faddeev-like approach
We use equations for Faddeev amplitudes to solve the shell-model problem for
four nucleons in the model space that includes up to 14 hbar Omega
harmonic-oscillator excitations above the unperturbed ground state. Two- and
three-body effective interactions derived from the Reid93 and Argonne V8'
nucleon-nucleon potentials are used in the calculations. Binding energies,
excitations energies, point-nucleon radii and electromagnetic and strangeness
charge form factors for 4He are studied. The structure of the Faddeev-like
equations is discussed and a formula for matrix elements of the permutation
operators in a harmonic-oscillator basis is given. The dependence on
harmonic-oscillator excitations allowed in the model space and on the
harmonic-oscillator frequency is investigated. It is demonstrated that the use
of the three-body effective interactions improves the convergence of the
results.Comment: 22 pages, 13 figures, REVTe
Total 4He Photoabsorption Cross Section Revisited: Correlated HH versus Effective Interaction HH
Two conceptually different hyperspherical harmonics expansions are used for
the calculation of the total 4He photoabsorption cross section. Besides the
well known method of CHH the recently introduced effective interaction approach
for the hyperspherical formalism is applied. Semi-realistic NN potentials are
employed and final state interaction is fully taken into account via the
Lorentz integral transform method. The results show that the effective
interaction leads to a very good convergence, while the correlation method
exhibits a less rapid convergence in the giant dipole resonance region. The
rather strong discrepancy with the experimental photodisintegration cross
sections is confirmed by the present calculations.Comment: LaTeX, 7 pages, 3 ps figure
The -3N problem with separable interactions
The -3N-interaction is studied within the four-body Faddeev-Yakubovsky
theory adopting purely separable forms for the two- and three-body
subamplitudes, limiting the basic two-body interactions to s-waves only. The
corresponding separable approximation for the integral kernels is obtained by
using the Hilbert-Schmidt procedure. Results are presented for the -H
scattering amplitude and for the total elastic cross section for energies below
the triton break-up threshold.Comment: revised version accepted for Phys. Rev. C, 16 pages revtex including
6 eps-figures, formal part shortene
Few-nucleon systems in translationally invariant harmonic oscillator basis
We present a translationally invariant formulation of the no-core shell model
approach for few-nucleon systems. We discuss a general method of
antisymmetrization of the harmonic-oscillator basis depending on Jacobi
coordinates. The use of a translationally invariant basis allows us to employ
larger model spaces than in traditional shell-model calculations. Moreover, in
addition to two-body effective interactions, three- or higher-body effective
interactions as well as real three-body interactions can be utilized. In the
present study we apply the formalism to solve three and four nucleon systems
interacting by the CD-Bonn nucleon-nucleon potential. Results of ground-state
as well as excited-state energies, rms radii and magnetic moments are
discussed. In addition, we compare charge form factor results obtained using
the CD-Bonn and Argonne V8' NN potentials.Comment: 25 pages. RevTex. 13 Postscript figure
Elastic p-3He and n-3H scattering with two- and three-body forces
We report on a microscopic calculation of n-3H and p-3He scattering employing
the Argonne v_{18} and v_8' nucleon-nucleon potentials with and without
additional three-nucleon force. An R-matrix analysis of the p-3He and n-3H
scattering data is presented. Comparisons are made for the phase shifts and a
selection of measurements in both scattering systems. Differences between our
calculation and the R-matrix results or the experimental data can be attributed
to only two partial waves (3P0 and 3P2). We find the effect of the Urbana IX
and the Texas-Los Alamos three-nucleon forces on the phase shifts to be
negligible.Comment: submitted to Phys. Rev.
The Ay Problem for p-3He Elastic Scattering
We present evidence that numerically accurate quantum calculations employing
modern internucleon forces do not reproduce the proton analyzing power, A_y,
for p-3He elastic scattering at low energies. These calculations underpredict
new measured analyzing powers by approximately 30% at E_{c.m.} = 1.20 MeV and
by 40% at E_{c.m.} = 1.69 MeV, an effect analogous to a well-known problem in
p-d and n-d scattering. The calculations are performed using the complex Kohn
variational principle and the (correlated) Hyperspherical Harmonics technique
with full treatment of the Coulomb force. The inclusion of the three-nucleon
interaction does not improve the agreement with the experimental data.Comment: Latex file, 4 pages, 2 figures, to be published on Phys. Rev. Let
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