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Nuclear Theory·nucl-th

Wednesday·February 7, 2024

12 papers—4 primary·8 cross-listed

All12Primary4Cross-lists8
  1. 01

    Exploring freeze out and flow using exact solutions of conformal hydrodynamics

    Owen Bradley🇺🇸 · Christopher Plumberg🇺🇸

    Exact solutions to the equations of hydrodynamics provide valuable benchmark tests for numerical hydrodynamic codes and also provide useful insights into the nature of hydrodynamic flow. In this paper, we introduce two novel, closely related exact solutions with non-trivial rapidity dependence which are generalizations of the well-known Gubser flow solution to conformal hydrodynamics. We then use one of our solutions to explore the consequences of choosing between two different criteria for implementing the freeze out process in fluid dynamical simulations of nuclear collisions: freeze out at constant temperature vs. freeze out at constant Knudsen number. We find that, employing our exact solution, the differences between these freeze out criteria are heavily influenced by the presence of strong collective flow. Our results highlight the importance of accurately describing the freeze out process in collisions with large flow gradients, particularly in small systems.

    nucl-thhep-thnucl-exPRC(2024)·2 citations
  2. 02

    The spin alignment of rho mesons in a pion gas

    Yi-Liang Yin🇨🇳 · Wen-Bo Dong🇨🇳 · Jin-Yi Pang🇨🇳 · Shi Pu🇨🇳 · Qun Wang🇨🇳

    We study the spin alignment of neutral rho mesons in a pion gas using spin kinetic or Boltzmann equations. The coupling is given by the chiral effective theory. The collision terms at the leading and next-to-leading order in spin Boltzmann equations are derived. The evolution of the spin density matrix of the neutral rho meson is simulated with different initial conditions. The numerical results show that the interaction of pions and neutral rho mesons creates very small spin alignment in the central rapidity region if there is no rho meson in the system at the initial time. Such a small spin alignment in the central rapidity region will decay rapidly toward zero in later time. If there are rho mesons with a sizable spin alignment at the initial time the spin alignment will also decrease rapidly. We also considered the effect on from the elliptic flow of pions in the blast wave model. With vanishing spin alignment at the initial time, the deviation of from 1/3 is positive but very small.

    nucl-thPRC(2024)·10 citations
  3. 03

    On the calculation and use of effective single-particle energies. The example of the neutron - splitting along isotones

    Vittorio Somà🇫🇷 · Thomas Duguet🇫🇷

    The rich phenomenology of quantum many-body systems such as atomic nuclei is complex to interpret. Often, the behaviour (e.g. evolution with the number of constituents) of measurable/observable quantities such as binding or excitation energies can be best understood on the basis of a simplified picture involving auxiliary quantities that are not observable, i.e. whose values vary with parameters that are internal to the theoretical construction (contrarily to measurable/observable quantities). While being useful, the simplified interpretation is thus theoretical-scheme-dependent. This applies, in particular, to the so-called single-nucleon shell structure based on auxiliary effective single-particle energies (ESPEs). In this context, the present work aims at (i) recalling the way to compute ESPEs out of solutions of many-body Schrödinger's equation, (ii) illustrating the use of ESPEs within the frame of state-of-the-art ab initio calculations to interpret the outcome of a recent nuclear experiment and (iii) demonstrating the impact of several alterations to the computation of ESPEs. While the chosen alterations constitute approximations within the ab initio scheme, they are built-in when employing other theoretical constructs at play in nuclear physics. The present considerations are thus meant to empirically illustrate variations that can be expected between ESPEs computed within different (equally valid) theoretical schemes.

    nucl-thnucl-exPhil.Trans.A.Math.Phys.Eng.Sci.(2024)·4 citations
  4. 04

    Nuclear Isomers at the Extremes of their Properties

    Bhoomika Maheshwari · Ashok Kumar Jain

    The longer-lived excited nuclear states, referred as nuclear isomers, exist due to the hindered decays owing to their peculiar nucleonic structural surroundings. Some of these conditions, being exceptionally rare and limited to achieve, elevate certain isomers to the status of extreme and unusual isomers among their kin. For example, the coupling of single-particle orbitals is rare and so are decaying isomers. This review delves into some of such remarkable isomers scattered across the nuclear landscape while highlighting the possibilities to find more of them. Unique properties of some of them, harbor the potential for transformative applications in medicine and energy. An exciting example is that of the lowest energy isomer known so far in Th, which may help realize the dream of an ultra-precise nuclear clock in the coming decade. These isomers also offer an insight into the extremes of nuclear structure associated with them, which leads to their unusual status in energy, half-life, spin etc. The review attempts to highlight isomers with high-multipolarities, high-spins, high-energies, longest half-lives, extremely low energy, etc. A lack of theoretical understanding of the decay rates, half-lives and moments of these isomers is also pointed out.

    nucl-thnucl-exEur.Phys.J.ST(2024)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE