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Theoretical Methods for Giant Resonances: https://arxiv.org/abs/2201.04578
Gianluca Colo'
The Random Phase Approximation (RPA) and its variations and extensions are, without any doubt, the most widely used tools to describe Giant Resonances within a microscopic theory. In this chapter, we will start by discussing how RPA comes out naturally if one seeks a state with a harmonic time dependence in the space of one particle-one hole excitations on top of the ground state. It will be also shown that RPA is the simplest approach in which a ``collective'' state emerges. These are basic arguments that appear in other textbooks but are also unavoidable as a starting point for further discussions. In the rest of the chapter, we will give emphasis to developments that have taken place in the last decades: alternatives to RPA like the Finite Amplitude Method (FAM), state-of-the-art calculations with well-established Energy Density Functionals (EDFs), and progress in {\em ab initio} calculations. We will discuss extensions of RPA using as a red thread the various enlargements of the one particle-one hole model space. The importance of the continuum, and the exclusive observables like the decay products of Giant Resonances, will be also touched upon.
Comments: Contribution to the "Handbook of Nuclear Physics", Springer, 2022, I. Tanihata, H. Toki and T. Kajino, Eds. (small issue with \hbar when submitting, this character does not show up as it should)
Theory of Nuclear Fission: https://arxiv.org/abs/2201.02719
Nicolas Schunck, David Regnier
Atomic nuclei are quantum many-body systems of protons and neutrons held together by strong nuclear forces. Under the proper conditions, nuclei can break into two (sometimes three) fragments which will subsequently decay by emitting particles. This phenomenon is called nuclear fission. Since different fission events may produce different fragmentations, the end-products of all fissions that occurred in a small chemical sample of matter comprise hundreds of different isotopes, including α particles, together with a large number of emitted neutrons, photons, electrons and antineutrinos. The extraordinary complexity of this process, which happens at length scales of the order of a femtometer, mostly takes less than a femtosecond but is not completely over until all the lingering β decays have completed - which can take years - is a fascinating window into the physics of atomic nuclei. While fission may be more naturally known in the context of its technological applications, it also plays a pivotal role in the synthesis of heavy elements in astrophysical environments. In both cases, experimental measurements are not sufficient to provide complete data. Simulations are needed, yet at levels of accuracy and precision that pose formidable challenges to nuclear theory. The goal of this article is to provide a comprehensive overview of the theoretical methods employed in the description of nuclear fission.
Comments: 106 pages, 28 figures, 1 table, 513 references; submitted for publication in Progress in Nuclear and Particle Physics
Microscopic Theory of Nuclear Fission: https://arxiv.org/abs/2201.02716
Nicolas Schunck
Nuclear fission represents the ultimate test for microscopic theories of nuclear structure and reactions. Fission is a large-amplitude, time-dependent phenomenon taking place in a self-bound, strongly-interacting many-body system. It should, at least in principle, emerge from the complex interactions of nucleons within the nucleus. The goal of microscopic theories is to build a consistent and predictive theory of nuclear fission by using as only ingredients protons and neutrons, nuclear forces and quantum many-body methods. Thanks to a constant increase in computing power, such a goal has never seemed more within reach. This chapter gives an overview both of the set of techniques used in microscopic theory to describe the fission process and of some recent successes achieved by this class of methods.
Comments: 37 pages, 8 figures; chapter for the upcoming Handbook in Nuclear Physics edited by I. Tanihata, H. Toki and T. Kajino
Sub-barrier fusion reactions: https://arxiv.org/abs/2201.08061
K. Hagino
The concept of compound nucleus was proposed by Niels Bohr in 1936 to explain narrow resonances observed in scattering of a slow neutron off atomic nuclei. A compound nucleus is a metastable state with a long lifetime, in which all the degrees of freedom are in a sort of thermal equilibrium. Fusion reactions are defined as reactions to form such compound nucleus by merging two atomic nuclei. Here a short description of heavy-ion fusion reactions at energies close the Coulomb barrier is presented. This includes: (i) an overview of a fusion process, (ii) a strong interplay between nuclear structure and fusion, (iii) fusion and multi-dimensional/multi-particle quantum tunneling, and (iv) fusion for superheavy elements.
Comments: 26 pages, 19 figures. Contribution to the "Handbook of Nuclear Physics", Springer, 2022, I. Tanihata, H. Toki and T. Kajino, eds
Theoretical Methods for Giant Resonances: https://arxiv.org/abs/2201.04578
Gianluca Colo'
The Random Phase Approximation (RPA) and its variations and extensions are, without any doubt, the most widely used tools to describe Giant Resonances within a microscopic theory. In this chapter, we will start by discussing how RPA comes out naturally if one seeks a state with a harmonic time dependence in the space of one particle-one hole excitations on top of the ground state. It will be also shown that RPA is the simplest approach in which a ``collective'' state emerges. These are basic arguments that appear in other textbooks but are also unavoidable as a starting point for further discussions. In the rest of the chapter, we will give emphasis to developments that have taken place in the last decades: alternatives to RPA like the Finite Amplitude Method (FAM), state-of-the-art calculations with well-established Energy Density Functionals (EDFs), and progress in {\em ab initio} calculations. We will discuss extensions of RPA using as a red thread the various enlargements of the one particle-one hole model space. The importance of the continuum, and the exclusive observables like the decay products of Giant Resonances, will be also touched upon.
Comments: Contribution to the "Handbook of Nuclear Physics", Springer, 2022, I. Tanihata, H. Toki and T. Kajino, Eds. (small issue with \hbar when submitting, this character does not show up as it should)
Theory of Nuclear Fission: https://arxiv.org/abs/2201.02719
Nicolas Schunck, David Regnier
Atomic nuclei are quantum many-body systems of protons and neutrons held together by strong nuclear forces. Under the proper conditions, nuclei can break into two (sometimes three) fragments which will subsequently decay by emitting particles. This phenomenon is called nuclear fission. Since different fission events may produce different fragmentations, the end-products of all fissions that occurred in a small chemical sample of matter comprise hundreds of different isotopes, including α particles, together with a large number of emitted neutrons, photons, electrons and antineutrinos. The extraordinary complexity of this process, which happens at length scales of the order of a femtometer, mostly takes less than a femtosecond but is not completely over until all the lingering β decays have completed - which can take years - is a fascinating window into the physics of atomic nuclei. While fission may be more naturally known in the context of its technological applications, it also plays a pivotal role in the synthesis of heavy elements in astrophysical environments. In both cases, experimental measurements are not sufficient to provide complete data. Simulations are needed, yet at levels of accuracy and precision that pose formidable challenges to nuclear theory. The goal of this article is to provide a comprehensive overview of the theoretical methods employed in the description of nuclear fission.
Comments: 106 pages, 28 figures, 1 table, 513 references; submitted for publication in Progress in Nuclear and Particle Physics
Microscopic Theory of Nuclear Fission: https://arxiv.org/abs/2201.02716
Nicolas Schunck
Nuclear fission represents the ultimate test for microscopic theories of nuclear structure and reactions. Fission is a large-amplitude, time-dependent phenomenon taking place in a self-bound, strongly-interacting many-body system. It should, at least in principle, emerge from the complex interactions of nucleons within the nucleus. The goal of microscopic theories is to build a consistent and predictive theory of nuclear fission by using as only ingredients protons and neutrons, nuclear forces and quantum many-body methods. Thanks to a constant increase in computing power, such a goal has never seemed more within reach. This chapter gives an overview both of the set of techniques used in microscopic theory to describe the fission process and of some recent successes achieved by this class of methods.
Comments: 37 pages, 8 figures; chapter for the upcoming Handbook in Nuclear Physics edited by I. Tanihata, H. Toki and T. Kajino
Sub-barrier fusion reactions: https://arxiv.org/abs/2201.08061
K. Hagino
The concept of compound nucleus was proposed by Niels Bohr in 1936 to explain narrow resonances observed in scattering of a slow neutron off atomic nuclei. A compound nucleus is a metastable state with a long lifetime, in which all the degrees of freedom are in a sort of thermal equilibrium. Fusion reactions are defined as reactions to form such compound nucleus by merging two atomic nuclei. Here a short description of heavy-ion fusion reactions at energies close the Coulomb barrier is presented. This includes: (i) an overview of a fusion process, (ii) a strong interplay between nuclear structure and fusion, (iii) fusion and multi-dimensional/multi-particle quantum tunneling, and (iv) fusion for superheavy elements.
Comments: 26 pages, 19 figures. Contribution to the "Handbook of Nuclear Physics", Springer, 2022, I. Tanihata, H. Toki and T. Kajino, eds
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