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 Gamow Shell Model calculations with realistic interactions

No-Core Gamow Shell Model (NCGSM) is applied for the first time to study selected well-bound and unbound states of helium isotopes. This model is formulated on the complex energy plane and, by using a complete Berggren ensemble, treats bound, resonant, and scattering states on equal footing. We use the Density Matrix Renormalization Group method to solve the many-body Schr\"{o}dinger equation. To test the validity of our approach, we benchmarked the NCGSM results against Faddeev and Faddeev-Yakubovsky exact calculations for $^3$H and $^4$He nuclei. We also performed {\textit ab initio} NCGSM calculations for the unstable nucleus $^5$He and determined the ground state energy and decay width, starting from a realistic N$^3$LO chiral interaction.Comment: 17 pages, 14 figures. Revised version. Discussion on microscopic overlap functions, SFs and ANCs is added. Added references. Accepted for publication at PR

Three and Four Harmonically Trapped Particles in an Effective Field Theory Framework

We study systems of few two-component fermions interacting via short-range interactions within a harmonic-oscillator trap. The dominant interactions, which are two-body, are organized according to the number of derivatives and defined in a two-body truncated model space made from a bound-state basis. Leading-order (LO) interactions are solved for exactly using the formalism of the No-Core Shell Model, whereas corrections are treated as many-body perturbations. We show explicitly that next-to-LO and next-to-next-to-LO interactions improve convergence as the model space increases. We present results at unitarity for three- and four-fermion systems, which show excellent agreement with the exact solution (for the three-body problem) and results obtained by others methods (in the four-body case). We also present results for finite scattering lengths and non-zero range of the interaction, including (at positive scattering length) observation of a change in the structure of the three-body ground state and extraction of the atom-dimer scattering length.Comment: 18 pages, 10 figure

Antibound States and Halo Formation in the Gamow Shell Model

The open quantum system formulation of the nuclear shell model, the so-called Gamow Shell Model (GSM), is a multi-configurational SM that employs a single-particle basis given by the Berggren ensemble consisting of Gamow states and the non-resonant continuum of scattering states. The GSM is of particular importance for weakly bound/unbound nuclear states where both many-body correlations and the coupling to decay channels are essential. In this context, we investigate the role of l=0 antibound (virtual) neutron single-particle states in the shell model description of loosely bound wave functions, such as the ground state wave function of a halo nucleus 11Li

Two and Three Nucleons in a Trap and the Continuum Limit

We describe systems of two and three nucleons trapped in a harmonic-oscillator potential with interactions from the pionless effective field theory up to next-to-leading order (NLO). We construct the two-nucleon interaction using two-nucleon scattering information. We calculate the trapped levels in the three-nucleon system with isospin $T=1/2$ and determine the three-nucleon force needed for stability of the triton. We extract neutron-deuteron phase shifts, and show that the quartet scattering length is in good agreement with experimental data.Comment: 19 pages, 15 figure

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 $(d,p)$ 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 $(d,p)$ on $^{40,48}$Ca. We discuss the predictions of the model for the extreme case of an isotope ($^{60}$Ca) currently unavailable experimentally, though possibly available in future facilities (nominally within production reach at FRIB). We explore the use of $(d,p)$ reactions as surrogates for $(n,\gamma)$ processes, by using the formalism to describe the compound nucleus formation in a $(d,p\gamma)$ reaction as a function of excitation energy, spin, and parity. The subsequent decay is then computed within a Hauser-Feshbach formalism. Comparisons between the $(d,p\gamma)$ and $(n,\gamma)$ induced gamma decay spectra are discussed to inform efforts to infer neutron captures from $(d,p\gamma)$ reactions. Finally, we identify areas of opportunity for future developments, and discuss a possible path toward a predictive reaction theory

Three particles in a finite volume: The breakdown of spherical symmetry

Lattice simulations of light nuclei necessarily take place in finite volumes, thus affecting their infrared properties. These effects can be addressed in a model-independent manner using Effective Field Theories. We study the model case of three identical bosons (mass m) with resonant two-body interactions in a cubic box with periodic boundary conditions, which can also be generalized to the three-nucleon system in a straightforward manner. Our results allow for the removal of finite volume effects from lattice results as well as the determination of infinite volume scattering parameters from the volume dependence of the spectrum. We study the volume dependence of several states below the break-up threshold, spanning one order of magnitude in the binding energy in the infinite volume, for box side lengths L between the two-body scattering length a and L = 0.25a. For example, a state with a three-body energy of -3/(ma^2) in the infinite volume has been shifted to -10/(ma^2) at L = a. Special emphasis is put on the consequences of the breakdown of spherical symmetry and several ways to perturbatively treat the ensuing partial wave admixtures. We find their contributions to be on the sub-percent level compared to the strong volume dependence of the S-wave component. For shallow bound states, we find a transition to boson-diboson scattering behavior when decreasing the size of the finite volume.Comment: 21 pages, 4 figures, 2 table

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

Three-Body Halo States in Effective Field Theory: Renormalization and Three-Body Interactions in the Helium-6 System

In this paper we study the renormalization of Halo effective field theory applied to the Helium-6 halo nucleus seen as an alpha-neutron-neutron three-body state. We include the 0(+) dineutron channel together with both the 3/2(-) and 1/2(-) neutron-alpha channels into the field theory and study all of the six lowest-order three-body interactions that are present. Furthermore, we discuss three different prescriptions to handle the unphysical poles in the P-wave two-body sector. In the simpler field theory without the 1/2(-) channel present we find that the bound-state spectrum of the field theory is renormalized by the inclusion of a single three-body interaction. However, in the field theory with both the 3/2(-) and 1/2(-) included, the system can not be renormalized by only one three-body operator