113 research outputs found
An effective field theory approach to two trapped particles
We discuss the problem of two particles interacting via short-range
interactions within a harmonic-oscillator trap. The interactions are organized
according to their number of derivatives and defined in truncated model spaces
made from a bound-state basis. Leading-order (LO) interactions are iterated to
all orders, while corrections are treated in perturbation theory. We show
explicitly that next-to-LO and next-to-next-to-LO interactions improve
convergence as the model space increases. In the large-model-space limit we
regain results from a pseudopotential. Arbitrary scattering lengths are
considered, as well as a generalization to include the non-vanishing range of
the interaction.Comment: 27 pages, 12 figure
Effective interactions for light nuclei: an effective (field theory) approach
One of the central open problems in nuclear physics is the construction of
effective interactions suitable for many-body calculations. We discuss a
recently developed approach to this problem, where one starts with an effective
field theory containing only fermion fields and formulated directly in a
no-core shell-model space. We present applications to light nuclei and to
systems of a few atoms in a harmonic-oscillator trap. Future applications and
extensions, as well as challenges, are also considered
Effective Theory for Trapped Few-Fermion Systems
We apply the general principles of effective field theories to the
construction of effective interactions suitable for few- and many-body
calculations in a no-core shell model framework. We calculate the spectrum of
systems with three and four two-component fermions in a harmonic trap. In the
unitary limit, we find that three-particle results are within 10% of known
semi-analytical values even in small model spaces. The method is very general,
and can be readily extended to other regimes, more particles, different species
(e.g., protons and neutrons in nuclear physics), or more-component fermions (as
well as bosons). As an illustration, we present calculations of the
lowest-energy three-fermion states away from the unitary limit and find a
possible inversion of parity in the ground state in the limit of trap size
large compared to the scattering length. Furthermore, we investigate the lowest
positive-parity states for four fermions, although we are limited by the
dimensions we can currently handle in this case.Comment: 8 pages, 5 figure
Induced fission of 240Pu
We study the fission dynamics of 240Pu within an implementation of the
Density Functional Theory (DFT) extended to superfluid systems and real-time
dynamics. We demonstrate the critical role played by the pairing correlations.
The evolution is found to be much slower than previously expected in this fully
non-adiabatic treatment of nuclear dynamics, where there are no symmetry
restrictions and all collective degrees of freedom (CDOF) are allowed to
participate in the dynamics.Comment: 8 pages, 4 figures, talk given at The 6th International Conference on
Fission and Properties of Neutron-Rich Nuclei, Sanibel Island, Florida,
November 6-2 (2016
Real time description of fission
Using the time-dependent superfluid local density approximation, the dynamics
of fission is investigated in real time from just beyond the saddle to fully
separated fragments. Simulations produced in this fully microscopic framework
can help to assess the validity of the current approaches to fission, and to
obtain estimate of fission observables. In this contribution, we concentrate on
general aspects of fission dynamics.Comment: Proceedings of the "15th Varenna Conference on Nuclear Reaction
Mechanisms," Varenna, Italy, June 201
Nuclear Fission: from more phenomenology and adjusted parameters to more fundamental theory and increased predictive power
Two major recent developments in theory and computational resources created
the favorable conditions for achieving a microscopic description of nuclear
fission almost eighty years after its discovery in 1939 by Hahn and Strassmann
(1930). The first major development was in theory, the extension of the
Time-Dependent Density Functional Theory (TDDFT) to superfluid fermion systems.
The second development was in computing, the emergence of powerful enough
supercomputers capable of solving the complex systems of equations describing
the time evolution in three dimensions without any restrictions of hundreds of
strongly interacting nucleons. Even though the available nuclear energy density
functionals (NEDFs) are phenomenological still, their accuracy is improving
steadily and the prospects of being able to perform calculations of the nuclear
fission dynamics and to predict many properties of the fission fragments,
otherwise not possible to extract from experiments, are within reach, all
without making recourse anymore to uncontrollable assumptions and simplified
phenomenological models.Comment: 6 pages, account of invited talk given at FUSION17, Hobart, Tasmania,
February 20-24, 201
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