1,528 research outputs found
Neutron matter from chiral effective field theory interactions
The neutron-matter equation of state constrains the properties of many
physical systems over a wide density range and can be studied systematically
using chiral effective field theory (EFT). In chiral EFT, all many-body forces
among neutrons are predicted to next-to-next-to-next-to-leading order (N3LO).
We present details and additional results of the first complete N3LO
calculation of the neutron-matter energy, which includes the subleading
three-nucleon as well as the leading four-nucleon forces, and provides
theoretical uncertainties. In addition, we discuss the impact of our results
for astrophysics: for the supernova equation of state, the symmetry energy and
its density derivative, and for the structure of neutron stars. Finally, we
give a first estimate for the size of the N3LO many-body contributions to the
energy of symmetric nuclear matter, which shows that their inclusion will be
important in nuclear structure calculations.Comment: published version; 21 pages, 11 figures, 5 table
Neutron matter at next-to-next-to-next-to-leading order in chiral effective field theory
Neutron matter presents a unique system for chiral effective field theory
(EFT), because all many-body forces among neutrons are predicted to
next-to-next-to-next-to-leading order (N3LO). We present the first complete
N3LO calculation of the neutron matter energy. This includes the subleading
three-nucleon (3N) forces for the first time and all leading four-nucleon (4N)
forces. We find relatively large contributions from N3LO 3N forces. Our results
provide constraints for neutron-rich matter in astrophysics with controlled
theoretical uncertainties.Comment: 5 pages, 4 figures; improved version, 3N ring and 2pi-contact
contributions corrected, conclusions unchanged; v3: minor changes, published
versio
The chiral condensate in neutron matter
We calculate the chiral condensate in neutron matter at zero temperature
based on nuclear forces derived within chiral effective field theory. Two-,
three- and four-nucleon interactions are included consistently to
next-to-next-to-next-to-leading order (N3LO) of the chiral expansion. We find
that the interaction contributions lead to a modest increase of the condensate,
thus impeding the restoration of chiral symmetry in dense matter and making a
chiral phase transition in neutron-rich matter unlikely for densities that are
not significantly higher than nuclear saturation density.Comment: published version, 6 pages, 4 figure
Chiral Three-Nucleon Interactions in Light Nuclei, Neutron- Scattering, and Neutron Matter
We present quantum Monte Carlo calculations of light nuclei, neutron-
scattering, and neutron matter using local two- and three-nucleon ()
interactions derived from chiral effective field theory up to
next-to-next-to-leading order (NLO). The two undetermined low-energy
couplings are fit to the He binding energy and, for the first time, to the
spin-orbit splitting in the neutron- -wave phase shifts.
Furthermore, we investigate different choices of local -operator structures
and find that chiral interactions at NLO are able to simultaneously
reproduce the properties of systems and of neutron matter, in
contrast to commonly used phenomenological interactions.Comment: 5 pages, 3 figures, 1 table - updated version: small wording changes,
one reference chang
Quantum Monte Carlo calculations of light nuclei with local chiral two- and three-nucleon interactions
Local chiral effective field theory interactions have recently been developed
and used in the context of quantum Monte Carlo few- and many-body methods for
nuclear physics. In this work, we go over detailed features of local chiral
nucleon-nucleon interactions and examine their effect on properties of the
deuteron, paying special attention to the perturbativeness of the expansion. We
then turn to three-nucleon interactions, focusing on operator ambiguities and
their interplay with regulator effects. We then discuss the nuclear Green's
function Monte Carlo method, going over both wave-function correlations and
approximations for the two- and three-body propagators. Following this, we
present a range of results on light nuclei: Binding energies and distribution
functions are contrasted and compared, starting from several different
microscopic interactions.Comment: 21 pages, 14 figures, published version, Editor's Suggestio
Cotunneling-mediated transport through excited states in the Coulomb blockade regime
We present finite bias transport measurements on a few-electron quantum dot.
In the Coulomb blockade regime, strong signatures of inelastic cotunneling
occur which can directly be assigned to excited states observed in the
non-blockaded regime. In addition, we observe structures related to sequential
tunneling through the dot, occuring after it has been excited by an inelastic
cotunneling process. We explain our findings using transport calculations
within the real-time Green's function approach, including diagrams up to fourth
order in the tunneling matrix elements.Comment: 4 pages, 3 figure
Quantum Monte Carlo Calculations with Chiral Effective Field Theory Interactions
We present the first quantum Monte Carlo (QMC) calculations with chiral
effective field theory (EFT) interactions. To achieve this, we remove all
sources of nonlocality, which hamper the inclusion in QMC calculations, in
nuclear forces to next-to-next-to-leading order. We perform auxiliary-field
diffusion Monte Carlo (AFDMC) calculations for the neutron matter energy up to
saturation density based on local leading-order, next-to-leading order, and
next-to-next-to-leading order nucleon-nucleon interactions. Our results exhibit
a systematic order-by-order convergence in chiral EFT and provide
nonperturbative benchmarks with theoretical uncertainties. For the softer
interactions, perturbative calculations are in excellent agreement with the
AFDMC results. This work paves the way for QMC calculations with systematic
chiral EFT interactions for nuclei and nuclear matter, for testing the
perturbativeness of different orders, and allows for matching to lattice QCD
results by varying the pion mass.Comment: 6 pages, 3 figures, 1 tabl
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