24 research outputs found
Gorkov algebraic diagrammatic construction formalism at third order
Background. The Gorkov approach to self-consistent Green's function theory
has been formulated in [V. Som\`a, T. Duguet, C. Barbieri, Phys. Rev. C 84,
064317 (2011)]. Over the past decade, it has become a method of reference for
first-principle computations of semi-magic nuclear isotopes. The currently
available implementation is limited to a second-order self-energy and neglects
particle-number non-conserving terms arising from contracting three-particle
forces with anomalous propagators. For nuclear physics applications, this is
sufficient to address first-order energy differences, ground-state radii and
moments on an accurate enough basis. However, addressing absolute binding
energies, fine spectroscopic details of particle systems or delicate
quantities such as second-order energy differences associated to pairing gaps,
requires to go to higher truncation orders.
Purpose. The formalism is extended to third order in the algebraic
diagrammatic construction (ADC) expansion with two-body Hamiltonians.
Methods. The expansion of Gorkov propagators in Feynman diagrams is combined
with the algebraic diagrammatic construction up to the third order as an
organization scheme to generate the Gorkov self-energy.
Results. Algebraic expressions for the static and dynamic contributions to
the self-energy, along with equations for the matrix elements of the Gorkov
eigenvalue problem, are derived. It is first done for a general basis before
specifying the set of equations to the case of spherical systems displaying
rotational symmetry. Workable approximations to the full self-consistency
problem are also elaborated on. The formalism at third order it thus complete
for a general two-body Hamiltonian.
Conclusion. Working equations for the full Gorkov-ADC(3) are now available
for numerical implementation.Comment: 30 pages, 8 figures; published versio
Self-consistent Green's functions calculation of the nucleon mean-free path
The extension of Green's functions techniques to the complex energy plane
provides access to fully dressed quasi-particle properties from a microscopic
perspective. Using self-consistent ladder self-energies, we find both spectra
and lifetimes of such quasi-particles in nuclear matter. With a consistent
choice of the group velocity, the nucleon mean-free path can be computed. Our
results indicate that, for energies above 50 MeV at densities close to
saturation, a nucleon has a mean-free path of 4 to 5 femtometers.Comment: 5 pages, 4 figures. Minor changes, bibliography corrected. Accepted
version in Phys. Rev. Let
Microscopic optical potentials for medium-mass isotopes derived at the first order of the Watson multiple scattering theory
We perform a first-principle calculation of optical potentials for nucleon
elastic scattering off medium-mass isotopes. Fully based on a saturating chiral
Hamiltonian, the optical potentials are derived by folding nuclear density
distributions computed with ab initio self-consistent Green's function theory
with a nucleon-nucleon matrix computed with a consistent chiral
interaction. The dependence on the folding interaction as well as the
convergence of the target densities are investigated. Numerical results are
presented and discussed for differential cross sections and analyzing powers,
with focus on elastic proton scattering off Calcium and Nickel isotopes. Our
optical potentials generally show a remarkable agreement with the available
experimental data for laboratory energies in the range 65-200 MeV. We study the
evolution of the scattering observables with increasing proton-neutron
asymmetry by computing theoretical predictions of the cross section and
analyzing power over the Calcium and Nickel isotopic chains
Bogoliubov many-body perturbation theory for open-shell nuclei
A Rayleigh–Schrödinger many-body perturbation theory (MBPT) approach is introduced by making use of a particle-number-breaking Bogoliubov reference state to tackle (near-)degenerate open-shell fermionic systems. By choosing a reference state that solves the Hartree–Fock–Bogoliubov variational problem, the approach reduces to the well-tested Møller–Plesset, i.e., Hartree–Fock based, MBPT when applied to closed-shell systems. Due to its algorithmic simplicity, the newly developed framework provides a computationally simple yet accurate alternative to state-of-the-art non-perturbative manybody approaches. At the price of working in the quasi-particle basis associated with a single-particle basis of sufficient size, the computational scaling of the method is independent of the particle number.
This paper presents the first realistic applications of the method ranging from the oxygen to the nickel isotopic chains on the basis of a modern nuclear Hamiltonian derived from chiral effective field theory
Imaging the initial condition of heavy-ion collisions and nuclear structure across the nuclide chart
A major goal of the hot QCD program, the extraction of the properties of the
quark gluon plasma (QGP), is currently limited by our poor knowledge of the
initial condition of the QGP, in particular how it is shaped from the colliding
nuclei. To attack this limitation, we propose to exploit collisions of selected
species to precisely assess how the initial condition changes under variations
of the structure of the colliding ions. This knowledge, combined with
event-by-event measures of particle correlations in the final state of
heavy-ion collisions, will provide in turn a new way to probe the collective
structure of nuclei, and to confront and exploit the predictions of
state-of-the-art ab initio nuclear structure theories. The US nuclear community
should capitalize on this interdisciplinary connection by pursuing collisions
of well-motivated species at high-energy colliders.Comment: 23 pages, 6 figure
From the liquid drop model to lattice QCD: A brief history of nuclear interactions
International audienceThe present article aims to give a concise account of the main developments in nuclear structure theory, from its origin in the 1930s to date, taking the modelling of inter-nucleon interactions as guideline
Self-consistent Green's function theory for atomic nuclei
International audienceNuclear structure theory has recently gone through a major renewal with the development of ab initio techniques that can be applied to a large number of atomic nuclei, well beyond the light sector that had been traditionally targeted in the past. Self-consistent Green's function theory is one among these techniques. The present work aims to give an overview of the self-consistent Green's function approach for atomic nuclei, including examples of recent applications and a discussion on the perspectives for extending the method to nuclear reactions, doubly open-shell systems and heavy nuclei
Radii and Binding Energies in Helium and Oxygen Isotopes: A Puzzle for Nuclear Forces
International audienceWe discuss the importance of the root mean square matter radius as a key observable for testing the validity of the nuclear forces employed in nuclear structure calculations. The link between proton-nucleus scattering and radii is underlined, with the test case carried out for ^8He. When a systematic study of both nuclear radii and binding energies is feasible, as done in (even) oxygen isotopes from the valley of stability to the neutron drip line, we show that the combined comparison of measured radii and binding energies with ab initio calculations offers unique insight on input nuclear forces. The need to use newly developed interactions to improve the description of the radii is discussed