[Triumf-seminars] TRIUMF Theory Seminar today at 13:00

[TRIUMF Seminars]

Date/Time: Tue 2016-05-03 at 13:00

Location:  Theory Seminar Room 

Speaker:   Ingo Tews (Institute for Nuclear Theory, University of Washington)

Title:     Quantum Monte Carlo calculations with chiral effective field theory interactions

Abstract: The neutron-matter equation of state connects several physical systems over a wide density range, from cold atomic gases in the unitary limit at low densities, to neutron-rich nuclei at intermediate densities, up to neutron stars which reach supranuclear densities in their core. An accurate description of the neutron-matter equation of state is therefore crucial to describe these systems. To calculate the neutron-matter equation of state reliably, precise many-body methods in combination with a systematic theory for nuclear forces are needed.

Chiral effective field theory (EFT) is such a theory. It provides a systematic framework for the description of low-energy hadronic interactions and enables calculations with controlled theoretical uncertainties. Chiral EFT makes use of a momentum-space expansion of nuclear forces based on the symmetries of Quantum Chromodynamics, which is the fundamental theory of strong interactions. On the other hand, continuum Quantum Monte Carlo (QMC) methods are among the most precise many-body methods available to study strongly interacting systems at finite densities. Continuum QMC methods require as an input local interactions. However, chiral EFT, which is naturally formulated in momentum space, contains several sources of nonlocality. 

I will discuss how to construct local chiral two-nucleon and consistent three-nucleon (3N) interactions and present results of QMC calculations for neutron matter, light nuclei, and neutron-alpha scattering. I will discuss the effect of local regulator functions on the results. These regulators are a necessary ingredient in many-body calculations based on chiral effective field theory interactions, but artifacts are inevitable in current power counting schemes. I will investigate different choices of local 3N-operator structures and show, that chiral EFT interactions are able to simultaneously reproduce the properties of A=3,4,5 systems and of neutron matter, in contrast to commonly used phenomenological 3N interactions.



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