Emergent Phenomena In Atomic Nuclei From Large-scale Modeling: A Symmetry-guided Perspective

A Symmetry-Guided Perspective

Kristina D Launey

• Publisher: WSPC
• ISBN:
  9789813146068
• Topic: Ciencias físicas
• Subtopic: Física nuclear

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This book is a unique collection of reviews that share a common topic, emergent phenomena in atomic nuclei, while revealing the multifaceted nature of the subject, from quarks to heavy nuclei. It tells an amazing story of a decades-long journey of trials and successes, up to present days, with the aim to understand the vast array of experimental data and the fundamentals of strongly interacting fermions. The emphasis is on discovering emergent orderly patterns amidst the overarching complexity of many-particle quantum-mechanical systems. Recent findings are discussed within an interesting framework: a combination of nuclear theory and experiment, of group theory and computational science, and of pivotal models of astonishing simplicity and state-of-the-art models empowered by supercomputers.

A special theme resonates throughout the book: the important role of symmetries, exact and approximate, in exposing emergent features and guiding large-scale nuclear modeling. World-renowned experts offer their unique perspective on symmetries in the world of quarks and gluons, and that of protons and neurons — from chiral symmetry, through spin-isospin and quasi-spin symmetries, to symplectic symmetry, — as well as on the emergent nature of nuclear collectivity, clustering, and pairing, viewed from spectroscopy, microscopic considerations, and first principles. The book provides an excellent foundation that allows researchers and graduate students in physics and applied mathematics to review the current status of the subject, and to further explore the research literature through exhaustive sets of references that also point to studies underpinned by similar techniques in condensed matter and atomic physics along with quantum information.

--> Contents:

• Symmetries in Nuclei: From Experimental Signatures to Pivotal Nuclear Models (Overview):
  • Nuclear Collectivity — Its Emergent Nature Viewed from Phenomenology and Spectroscopy (John L Wood)
  • The Anatomy of Atomic Nuclei: Illuminating Many-Body Wave Functions Through Group-Theoretical Decomposition (Calvin W Johnson)
• Emergent Simplicity within Intricate Multi-Particle Dynamics: Nuclear Structure and Reactions:
  • The Emergence and Use of Symmetry in the Many-Nucleon Model of Atomic Nuclei (David J Rowe)
  • Toward Large-Scale Multi-Shell Calculations with Symmetry-Adapted Bases: Lessons From the Symplectic Shell Model (Jutta E Escher)
• Orderly Patterns from First Principles:
  • Lattice Quantum Chromodynamics: Symmetries and Applications (Thomas Luu and Andrea Shindler)
  • Ab Initio Lattice Effective Field Theory and Wigner's SU(4) Symmetry (Dean Lee)
  • Clustering in Light Nuclei with the Correlated Gaussian Approach (Yasuyuki Suzuki and Wataru Horiuchi)
  • Symmetry-Adapted No-Core Shell Model — The Ab Initio Picture of Nuclear Collectivity (Jerry P Draayer, Tomas Dytrych and Kristina D Launey)
• Symmetries and Emergent Features in Medium-Mass and Heavy Nuclei:
  • Auxiliary-Field Quantum Monte Carlo Methods in Nuclei (Yoram Alhassid)
  • Lie Density Functional Theory (George Rosensteel)
  • xactly Solvable Pairing in a Mean-Field Framework: Models and Applications (Feng Pan, Xin Guan and Jerry P Draayer)

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Readership: Graduate students and researchers in nuclear physics.
-->Emergent Phenomena in Atomic Nuclei;Large-Scale Modeling;First Principles;Physically Relevant Symmetries;Nuclear Structure;Nuclear Reactions;Experimental Monopole Moments and Quadrupole Moments;Spectroscopy;Nuclear Collectivity;Large Deformation;Rotations;Clustering;Alpha Clusters;Pairing Gaps;Shape Coexistence;Hoyle State;Giant Resonances;U(1)_A Anomaly in QCD;Neutron Electric Dipole Moment;Electroweak Response Functions;Soft Dipole Mode;Electron Scattering;Light-Ion Scattering;Level Densities;Spin Distribution;Chaotic Behavior;Moment of Inertia;Mathematical Proof of Extended Hohenberg–Kohn Theorem;Lanczos Numerical Algorithm for Eigenvalues;Symplectic Symmetry;Chiral Symmetry;Point Symmetries;Wigner Supermultiplet;Quasi-Spin;SU(3);Sp(3,R);SU(4);Symmetry-Adapted No-Core Shell Model;Lattice Quantum Chromodynamics;Lattice Effective Field Theory;Symplectic Shell Model;Cluster Model;Correlated Gaussian Approach;Auxiliary-Field Quantum Monte Carlo;Exactly Solvable Pairing Model;Density Functional Theory;Light Nuclei;Medium-Mass Nuclei;Heavy Nuclei Key Features:

• Presents the latest status on the topic from a broad range of perspectives and is a unique collection of topics, including overview, historical developments (both in theory and experiment), together with findings of recent state-of-the-art large-scale models
• Each review provides sufficient details to introduce the reader to the subject and capture his/her interest, together with an exhaustive set of references for further exploration of the research literature. References also point to studies that utilize similar techniques in other fields
• Provides an excellent foundation that encompasses not only various emergent features in nuclei, from light to heavy, but also covers few-body systems and clusters, and even further, links to the underlying physics, quarks and gluons
• Contributors are highly respected experts in their fields, have won national and international awards and recognitions, as well as come from leading institutions in countries, such as USA, Canada, Germany, Japan, and China — J Wood, D Rowe, Y Alhassid, Y Suzuki, J Draayer, D Lee, C Johnson, J Escher, T Luu, A Shindler, G Rosensteel, F Pan, W Horiuchi, T Dytrych, and X Guan

PART 1

Symmetries in Nuclei: From Experimental Signatures to Pivotal Nuclear Models (Overview)

Chapter 1

Nuclear Collectivity — Its Emergent Nature Viewed from Phenomenology and Spectroscopy

John L. Wood
School of Physics, Georgia Institute of Technology
Atlanta, GA 30332, USA

The collective nature of the nucleus was formalized 63 years ago in the work of Aage Bohr. In other arenas of physics it took 63 years to progress from the “quantum” to the “quark”. Progress in elucidating the details of nuclear collectivity appears to have almost stood still by comparison. The Author gives a personal perspective on nuclear collectivity, using phenomenology and examples from spectroscopy, based on his 50 years as an active nuclear physicist.

Contents

1.Introduction

2.Basics of the Nuclear Many-Body Problem

2.1.Nuclear Monopole Moments

2.2.Nuclear Quadrupole Moments

2.3.Simple Nuclear Models

2.3.1.The shell model

2.3.2.The pairing model

2.3.3.The rotor model

3.Nuclear Collectivity — A Current View

3.1.The Cd Isotopes

3.2.The N = 90 Isotones

3.3.The Os and Pt isotopes

4.A Forward-Looking View of Nuclear Quadrupole Collectivity

5.Conclusions

Acknowledgements

References

1.Introduction

Nuclear collectivity is, by definition, a many-body phenomenon. Unlike the physics that one encounters when dealing with a quantum or a quark, or an independent nucleon in a shell-model or Nilsson-model state, nuclear collectivity is orders-of-magnitude more complicated. This difference in complexity is proven by experience: we do not possess a universally accepted, unified model of nuclear collectivity (even after 63 years of trying to achieve this). The present exposition is a personal view by the Author that addresses this issue and may help to understand the lack of progress. (It is worth noting that we are in the excellent company of high-temperature superconductivity and the fractional quantum Hall effect.)

The atomic nucleus is a finite many-body quantum system. Extraordinary advances have been made in probing nuclear structure by way of experimental ingenuity and sophisticated model building. The shell model has been a reassuring guide to understanding a significant number of nuclei, at least their low-lying states, through the key concepts of energy shells and independent particle degrees of freedom. The pairing model provides remarkable insight into structures that fall under the heading of “seniority” degrees of freedom (seniority = number of unpaired nucleons). The rotor model is realized in some nuclei at the level of sub-one-percent precision in low-energy excitations and selected electromagnetic properties. Yet, the majority of nuclei do not come close to matching these ideal model examples; and there is seemingly little insight to what is missing, despite vast amounts of data.

Confronted with lack of insight regarding a unified model of nuclear collectivity, from the perspective of the Author, most recent activity has turned to shorter-term exploration: discovering a new isotope, adding a few excited states, determining a mass or a mean-square charge radius, measuring an electromagnetic transition probability. There are rallies to the collapses of closed shells, but few concerted efforts to probe nuclear collectivity in a manner that will move nuclear structure towards a unified view that is universally accepted. The present exposition looks at facets of nuclear structure where there is a basis for agreement, and takes a personal view of where much work still needs to be done.

2.Basics of the Nuclear Many-Body Problem

A number of philosophical criteria are important to keep in mind:

“Everything should be made as simple as possible, but not simpler”

— Albert Einstein;

“We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. Therefore, to the same natural effects we must, so far as possible, assign the same causes”

— Isaac Newton (William of Ockham).

These two adages define useful bounds for model building; unfortunately many (most) models of nuclear collectivity overstep these bounds. But, without models we would be powerless to organize nuclear data and make any sense thereof.

The array of nuclear data is, after 63 years of having ideas from Bohr’s collective model in hand (66 years for the shell model, 57 years for the pairing model), vast. It should be noted that were it not for the Evaluated Nuclear Structure Data File (ENSDF), maintained by the International Network of Nuclear Structure and Decay Data Evaluators, the Community would be buried in largely meaningless numbers. Consultation of ENSDF (and their link to the Experimental Unevaluated Nuclear Data List, XUNDL) provides a remarkable “jump-start” to any nuclear structure investigation, experimental or theoretical. However, what is lacking is “horizontal” perspective. Occasionally a review is made of some specific feature of nuclear structure, e.g., the electric quadrupole transition probability, B(E2), from the first-excited 2⁺ state in a doubly even nucleus [1]; but such work requires great experience and enormous amounts of time.

At a more subtle level, despite organized databases and useful models for organizing the data, new phenomena emerge. Philip Anderson underlined the operative meaning of “emergent” [2]. In the face of emergent behavior, all that models can do is fail — this is of great value, because when a model fails we have learned something. Note, the failure of the Standard Model of particles and fields is being sought, avidly. It is from data that emergent behavior is recognized; but data generally have to be organized to realize this, recall the above point regarding horizontal reviews. However, the first signs of new emergent data may be subtle. (A very good example of this was the first indication that nuclei might be deformed, which emerged from optical hyperfine structure and the suspicion that there may be the presence of a quadrupole electric field [3].)

2.1.Nuclear Monopole Moments

Nuclear monopole moments, or nuclear mean-square charge radii, form one of the two fundamental and broad horizontal views of nuclear structure (the other is nuclear masses). It is formalized in the equation, R = R₀A^1/3, where R is the root-mean-square radius, R₀ = 1.2 fm, and A is the mass number. It reflects a remarkable property of atomic nuclei — they a...

Table of contents

• Cover
• Halftitle
• Title
• Copyright
• Preface
• Contents
• Part 1: Symmetries in Nuclei: From Experimental Signatures to Pivotal Nuclear Models (Overview)
• Part 2: Emergent Simplicity within Intricate Multi-particle Dynamics: Nuclear Structure and Reactions
• Part 3 Orderly Patterns from First Principles
• Part 4: Symmetries and Emergent Features in Medium-mass and Heavy Nuclei
• Author Index
• Subject Index