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arXiv:0811.1611 · AIP conference proceedings

Coupled-Channels Approach for Dissipative Quantum Dynamics in Near-Barrier Collisions

A. Díaz-Torres, David J. Hinde, M. Dasgupta, Gerard J Milburn, J. A. Tostevin, Karl Ernst Rehm, Birger B. Back, Henning Esbensen, C. J. Lister

Published Jan 1, 2009• 2 citations
arXivHTMLPDF

Abstract

A novel quantum dynamical model based on the dissipative quantum dynamics of open quantum systems is presented. It allows the treatment of both deep‐inelastic processes and quantum tunneling (fusion) within a fully quantum mechanical coupled‐channels approach. Model calculations show the transition from pure state (coherent) to mixed state (decoherent and dissipative) dynamics during a near‐barrier nuclear collision. Energy dissipation, due to irreversible decay of giant‐dipole excitations of the interacting nuclei, results in hindrance of quantum tunneling.

DOI
10.1063/1.3108859

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A novel quantum dynamical model based on the dissipative quantum dynamics of open quantum systems is presented. It allows the treatment of both deep‐inelastic processes and quantum tunneling (fusion) within a fully quantum mechanical coupled‐channels approach. Model calculations show the transition from pure state (coherent) to mixed state (decoherent and dissipative) dynamics during a near‐barrier nuclear collision. Energy dissipation, due to irreversible decay of giant‐dipole excitations of the interacting nuclei, results in hindrance of quantum tunneling.
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Atomic nuclei are complex, quantum many‐body systems whose structure manifests itself through intrinsic quantum states associated with different excitation modes or degrees of freedom. Collective modes (vibration and/or rotation) dominate at low energy (near the ground‐state). The associated states are usually employed, within a truncated model space, as a basis in (coherent) coupled channels approaches to low‐energy reaction dynamics. However, excluded states can be essential, and their effects on the open (nuclear) system dynamics are usually treated through complex potentials. Is this a complete description of open system dynamics? Does it include effects of quantum decoherence? Can decoherence be manifested in reaction observables? In this contribution, I discuss these issues and the main ideas of a coupled‐channels density‐matrix approach that makes it possible to quantify the role and importance of quantum decoherence in low‐energy nuclear reaction dynamics. Topical applications, which refer to understanding the astrophysically important collision 12C+12C and achieving a unified quantum dynamical description of relevant reaction processes of weakly‐bound nuclei, are highlighted.
Low-energy nuclear fusion reactions have been described using a dynamical coupled-channels density matrix method, based on the theory of open quantum systems. For the first time, this has been combined with an energy projection method, permitting the calculation of energy resolved fusion probabilities. The results are benchmarked against calculations using stationary Schrödinger dynamics and show excellent agreement. Calculations of entropy, energy dissipation and coherence were conducted, demonstrating the capability of this method. It is evident that the presence of quantum decoherence does not affect fusion probability. This framework provides a basis for quantum thermodynamic studies using thermal environments.
Atomic nuclei are complex, quantum many-body systems whose structure manifests itself through intrinsic quantum states associated with different excitation modes or degrees of freedom.Collective modes (vibration and/or rotation) dominate at low energy (near the ground-state).The associated states are usually employed, within a truncated model space, as a basis in (coherent) coupled channels approaches to low-energy reaction dynamics.However, excluded non-collective states can be essential, and their effects on the open (nuclear) system dynamics are usually treated through complex potentials.Is this a complete description of open system dynamics?Does it include effects of quantum decoherence?Can decoherence be manifested in reaction observables?This paper discusses these issues and the main ideas of a coupled-channels density-matrix approach that makes it possible to quantify the role and importance of quantum decoherence in low-energy nuclear reaction dynamics.Some topical applications are highlighted.
We propose an ontological reformulation of quantum mechanics based on a fundamental distinction between static states and dissipative processes. Static states are time‑independent configurations of charge or matter density, devoid of internal dynamics. Dissipative processes, in contrast, involve real changes in density, energy loss, and irreversibility. This distinction enables a coherent and realistic reinterpretation of electronic orbitals, spin, atomic transitions, nuclear decay, tunneling, and entanglement. We show that every emission or absorption event requires dissipation, and that in an ensemble of excited systems the number of ideal observable transitions is always smaller than the number of initially excited systems. We extend the framework to nuclear structure and quantum correlations, highlighting the conceptual continuity of the theory and its compatibility with the thermodynamics of information.
The coupled-channels density-matrix technique for nuclear reaction dynamics, which is based on the Liouville-von Neumann equation with Lindblad dissipative terms, is developed with the inclusion of full angular momentum couplings. It allows a quantitative study of the role and importance of quantum decoherence in nuclear scattering. Formulas of asymptotic observables that can reveal effects of quantum decoherence are given. A method for extracting energy-resolved scattering information from the time-dependent density matrix is introduced. As an example, model calculations are carried out for the low-energy collision of the 16O^{16}\mathrm{O}16O projectile on the 154Sm^{154}\mathrm{Sm}154Sm target.