Integral relations and the adiabatic expansion method for 1+2 reactions above the breakup threshold: Helium trimers with soft-core potentials

The integral relations formalism introduced in \cite{bar09,rom11}, and designed to describe 1+$N$ reactions, is extended here to collision energies above the threshold for the target breakup. These two relations are completely general, and in this work they are used together with the adiabatic expansion method for the description of 1+2 reactions. The neutron-deuteron breakup, for which benchmark calculations are available, is taken as a test of the method. The s-wave collision between the $^4$He atom and $^4$He$_2$ dimer above the breakup threshold and the possibility of using soft-core two-body potentials plus a short-range three-body force will be investigated. Comparisons to previous calculations for the three-body recombination and collision dissociation rates will be shown.Comment: To be published in Physical Review

How many-body correlations and α\alpha-clustering shape 6^6He

The Borromean $^6$He nucleus is an exotic system characterized by two `halo' neutrons orbiting around a compact $^4$He (or $\alpha$) core, in which the binary subsystems are unbound. The simultaneous reproduction of its small binding energy and extended matter and point-proton radii has been a challenge for {\em ab initio} theoretical calculations based on traditional bound-state methods. Using soft nucleon-nucleon interactions based on chiral effective field theory potentials, we show that supplementing the model space with $^4$He+$n$+$n$ cluster degrees of freedom largely solves this issue. We analyze the role played by the $\alpha$-clustering and many-body correlations, and study the dependence of the energy spectrum on the resolution scale of the interaction.Comment: 5 pages, 4 figure

Advances in the ab initio description of nuclear three-cluster systems

We introduce the extension of the ab initio no-core shell model with continuum to describe three-body cluster systems. We present results for the ground state of 6He and show improvements with respect to the description obtained within the no-core shell model and the no-core shell model/resonating group methods.Comment: Proceedings of the 21st International Conference on Few-Body Problems in Physics. May 18-22, 2015. Chicago, Illinois, US

General integral relations for the description of scattering states using the hyperspherical adiabatic basis

In this work we investigate 1+2 reactions within the framework of the hyperspherical adiabatic expansion method. To this aim two integral relations, derived from the Kohn variational principle, are used. A detailed derivation of these relations is shown. The expressions derived are general, not restricted to relative $s$ partial waves, and with applicability in multichannel reactions. The convergence of the ${\cal K}$-matrix in terms of the adiabatic potentials is investigated. Together with a simple model case used as a test for the method, we show results for the collision of a $^4$He atom on a \dimer dimer (only the elastic channel open), and for collisions involving a $^6$Li and two $^4$He atoms (two channels open).Comment: Accepted for publication in Physical Review

Variational description of continuum states in terms of integral relations

Two integral relations derived from the Kohn Variational Principle (KVP) are used for describing scattering states. In usual applications the KVP requires the explicit form of the asymptotic behavior of the scattering wave function. This is not the case when the integral relations are applied since, due to their short range nature, the only condition for the scattering wave function $\Psi$ is that it be the solution of $(H-E)\Psi=0$ in the internal region. Several examples are analyzed for the computation of phase-shifts from bound state type wave functions or, in the case of the scattering of charged particles, it is possible to obtain phase-shifts using free asymptotic conditions. As a final example we discuss the use of the integral relations in the case of the Hyperspherical Adiabatic method.Comment: 34 pages, 7 figures, accepted in Phys. Rev.

Unified ab initio approaches to nuclear structure and reactions

The description of nuclei starting from the constituent nucleons and the realistic interactions among them has been a long-standing goal in nuclear physics. In addition to the complex nature of the nuclear forces, with two-, three- and possibly higher many-nucleon components, one faces the quantum-mechanical many-nucleon problem governed by an interplay between bound and continuum states. In recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from QCD-employing Hamiltonians constructed within chiral effective field theory. After a brief overview of the field, we focus on ab initio many-body approaches - built upon the No-Core Shell Model - that are capable of simultaneously describing both bound and scattering nuclear states, and present results for resonances in light nuclei, reactions important for astrophysics and fusion research. In particular, we review recent calculations of resonances in the $^6$He halo nucleus, of five- and six-nucleon scattering, and an investigation of the role of chiral three-nucleon interactions in the structure of $^9$Be. Further, we discuss applications to the $^7$Be$(p,\gamma)^8$B radiative capture. Finally, we highlight our efforts to describe transfer reactions including the $^3$H$(d,n)^4$He fusion.Comment: Contribution to the Special Physica Scripta Edition - 40 year anniversary - Nobel Prize '75, 71 pages, 29 figure

No-Core Shell Model Analysis of Light Nuclei

The fundamental description of both structural properties and reactions of light nuclei in terms of constituent protons and neutrons interacting through nucleon-nucleon and three-nucleon forces is a long-sought goal of nuclear theory. I will briefly present a promising technique, built upon the {\em ab initio} no-core shell model, which emerged recently as a candidate to reach such a goal: the no-core shell model/resonating-group method. This approach, capable of describing simultaneously both bound and scattering states in light nuclei, complements a microscopic cluster technique with the use of two-nucleon realistic interactions, and a microscopic and consistent description of the nucleon clusters. I will discuss applications to light nuclei binary scattering processes and fusion reactions that power stars and Earth based fusion facilities, such as the deuterium-$^3$He fusion, and outline the progress toward the inclusion of the three-nucleon force into the formalism and the treatment of three-body clusters.Comment: 8 pages, 6 figures, Proceedings of the 20th International IUPAP Conference on Few-Body Problems in Physics, 20 - 25 August, 2012, Fukuoka, Japa

From Iron Lady’s portrait to Mutti Angela’s photography: the iconic treatment of German Chancellor Angela Merkel

La investigación condensada en estas páginas se basa en el poder de denotación de la fotografía y en la utilidad del análisis de contenido para esclarecer cuál es la representación de Angela Merkel acuñada en 2015 por cinco diarios españoles de referencia. Concretamente, prima la intención de comprobar si los rasgos característicos de una metáfora extemporánea como es el rol de Dama de Hierro permean la imagen que los diarios generalistas proyectan sobre la canciller alemana, y si las actitudes que se le atribuyen coexisten con otras propias de la tradicional interpretación de la naturaleza femínea. Al término del artículo se propone el empleo de una tabla de identificación que permite reconocer en una instantánea si ésta responde a la idiosincrasia de los dos roles más comunes vinculados a Merkel.The research presented in these pages rests on the photography’s denotation power, as well as on the usefulness of the content analysis technique in order to clarify which is Angela Merkel’s representation. So as to, five Spanish newspapers are analysed during 2015. Specifically, the prevalent intention is to check if the characteristic features of an extemporaneous metaphor —as it is the role of Iron Lady— pervade the image projected by the mainstream press onto the German Chancellor. In addition, it is investigated whether the attributed attitudes coexist with traditional female interpretation features. Moreover, at the end of the article, the use of an identification table is proposed. It would help to recognize if a picture responds to the idiosyncrasies of the two most common roles linked to Merkel