Pairing in excited nuclei: a review.

Area of Science:

• Nuclear physics
• Condensed matter physics
• Thermodynamics

Background:

• Pairing correlations are fundamental in many-body systems, influencing properties from atomic nuclei to superconductors.
• Understanding these correlations at finite temperatures and angular momenta is crucial for describing excited states.
• The review focuses on systems where finite-size effects significantly alter pairing behavior.

Purpose of the Study:

• To review recent studies on the thermodynamic properties of pairing in diverse many-body systems.
• To discuss unique pairing phenomena arising from system finiteness, such as pairing reentrance.
• To analyze the influence of thermal pairing on nuclear structure and decay properties.

Main Methods:

• Review of theoretical studies on pairing in many-body systems.
• Analysis of nuclear reactions (heavy-ion fusion, [Formula: see text]-induced reactions, inelastic scattering) to form excited nuclei.
• Examination of experimental data for phenomena like pairing reentrance.

Main Results:

• Finiteness of systems leads to non-vanishing pairing gaps and smoothed phase transitions.
• Pairing reentrance is observed in excited nuclei and solid-state ferromagnets.
• Thermal pairing affects temperature-dependent giant dipole resonance width and radiative strength functions.

Conclusions:

• Pairing properties exhibit rich behavior in finite systems, deviating from bulk behavior.
• Pairing reentrance is a significant phenomenon with experimental evidence in both nuclear and solid-state physics.
• Thermodynamic pairing effects are crucial for accurately describing nuclear properties at finite excitation.