163 research outputs found
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
Ab initio no-core solutions for Li
We solve for properties of Li in the ab initio No-Core Full Configuration
approach and we separately solve for its ground state and
resonance with the Gamow Shell Model in the Berggren basis. We employ both the
JISP16 and chiral NNLO realistic nucleon-nucleon interactions and
investigate the ground state energy, excitation energies, point proton
root-mean-square radius and a suite of electroweak observables. We also extend
and test methods to extrapolate the ground state energy, point proton
root-mean-square radius, and electric quadrupole moment. We attain improved
estimates of these observables in the No-Core Full Configuration approach by
using basis spaces up through N=18 that enable more definitive
comparisons with experiment. Using the Density Matrix Renormalization Group
approach with the JISP16 interaction, we find that we can significantly improve
the convergence of the Gamow Shell Model treatment of the Li ground state
and resonance by adopting a natural orbital single-particle
basis.Comment: 25 pages, 18 figure
Ab initio no core full configuration approach for light nuclei
Comprehensive understanding of the structure and reactions of light nuclei poses theoretical and computational challenges. Still, a number of ab initio approaches have been developed to calculate the properties of atomic nuclei using fundamental interactions among nucleons. Among them, we work with the ab initio no core full configuration (NCFC) method and ab initio no core Gamow Shell Model (GSM). We first review these approaches and present some recent results
Toward a complete theory for predicting inclusive deuteron breakup away from stability
We present an account of the current status of the theoretical treatment of
inclusive reactions in the breakup-fusion formalism, pointing to some
applications and making the connection with current experimental capabilities.
Three independent implementations of the reaction formalism have been recently
developed, making use of different numerical strategies. The codes also
originally relied on two different but equivalent representations, namely the
prior (Udagawa-Tamura, UT) and the post (Ichimura-Austern-Vincent, IAV)
representations.
The different implementations have been benchmarked, and then applied to the
Ca isotopic chain. The neutron-Ca propagator is described in the Dispersive
Optical Model (DOM) framework, and the interplay between elastic breakup (EB)
and non-elastic breakup (NEB) is studied for three Ca isotopes at two different
bombarding energies. The accuracy of the description of different reaction
observables is assessed by comparing with experimental data of on
Ca. We discuss the predictions of the model for the extreme case of
an isotope (Ca) currently unavailable experimentally, though possibly
available in future facilities (nominally within production reach at FRIB). We
explore the use of reactions as surrogates for processes,
by using the formalism to describe the compound nucleus formation in a
reaction as a function of excitation energy, spin, and parity.
The subsequent decay is then computed within a Hauser-Feshbach formalism.
Comparisons between the and induced gamma decay
spectra are discussed to inform efforts to infer neutron captures from
reactions. Finally, we identify areas of opportunity for future
developments, and discuss a possible path toward a predictive reaction theory
Orbital dependent nucleonic pairing in the lightest known isotopes of tin
By studying the 109Xe-->105Te-->101Sn superallowed alpha-decay chain, we
observe low-lying states in 101Sn, the one-neutron system outside doubly magic
100Sn. We find that the spins of the ground state (J = 7=2) and first excited
state (J = 5=2) in 101Sn are reversed with respect to the traditional level
ordering postulated for 103Sn and the heavier tin isotopes. Through simple
arguments and state-of-the-art shell model calculations we explain this
unexpected switch in terms of a transition from the single-particle regime to
the collective mode in which orbital-dependent pairing correlations, dominate.Comment: 5 pages 3 figure
Charge radii and neutron correlations in helium halo nuclei
Within the complex-energy configuration interaction framework, we study
correlations of valence neutrons to explain the behavior of charge radii in the
neutron halo nuclei He. We find that the experimentally observed
decrease of the charge radius between He and He is caused by a subtle
interplay between three effects: dineutron correlations, a spin-orbit
contribution to the charge radius, and a core swelling effect. We demonstrate
that two-neutron angular correlations in the resonance of He differ
markedly from the ground-state correlations in He.Comment: 5 pages, 5 figure
Whole genome duplication is an early event leading to aneuploidy in -wild type glioblastoma
Glioblastoma, the most frequent and lethal form of glioma, displays chromosome instability and recurrent somatic copy number alterations (SCNA). Chromothripsis and whole genome duplication (WGD) have been recently identified in cancer. In the present study, we analyzed SCNA and determine the ploidy pattern in 123 -wild-type glioblastomas, using SNP array data. WGD and chromothripsis events were validated using, respectively, FISH and CTLPScanner. WGD was detected in 11.4% glioblastomas (14/123) and was associated with mutation ( = 0.0068). It was an early event occurring after the recurrent SCNA observed in diffuse high-grade gliomas. Glioblastomas with WGD were more aneuploid compared to glioblastomas without WGD ( < 0.0001). Chromothripsis occurred in 29.3% glioblastomas (36/123) and mostly affected chromosomes 7, 9 and 12, with amplification of oncogenes (EGFR, /), and homozygous deletion of tumor suppressor genes (). There was a significant association between chromothripsis and gene rearrangement at a given locus. WGD is an early genetic event significantly associated to mutation and leading to chromosome instability and aneuploidy in -wild-type glioblastoma. Chromothripsis recurrently targets oncogenes and tumor suppressor genes that are key players in gliomagenesis and tumor progression. The occurrence of chromothripsis points to underlying gene rearrangements (including gene fusions), potential therapeutic targets in glioblastoma
Living on the edge of stability, the limits of the nuclear landscape
A first-principles description of nuclear systems along the drip lines
presents a substantial theoretical and computational challenge. In this paper,
we discuss the nuclear theory roadmap, some of the key theoretical approaches,
and present selected results with a focus on long isotopic chains. An important
conclusion, which consistently emerges from these theoretical analyses, is that
three-nucleon forces are crucial for both global nuclear properties and
detailed nuclear structure, and that many-body correlations due to the coupling
to the particle continuum are essential as one approaches particle drip lines.
In the quest for a comprehensive nuclear theory, high performance computing
plays a key role.Comment: Contribution to proceedings of Nobel Symposium 152: Physics with
radioactive beams, June 2012, Gothenburg, Swede
- …