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Nuclear Theory·nucl-th

Monday·March 7, 2022

13 papers—5 primary·8 cross-listed

All13Primary5Cross-lists8
  1. 01

    Analyzing rotational bands in odd-mass nuclei using Effective Field Theory and Bayesian methods

    I. K. Alnamlah · E. A. Coello Pérez · D. R. Phillips

    We recently developed an Effective Field Theory (EFT) for rotational bands in odd-mass nuclei. Here we use EFT expressions to perform a Bayesian analysis of data on the rotational energy levels of Tc, Gd, Dy, Er, Tm, W, U and Pu. The error model in our Bayesian analysis includes both experimental and EFT truncation uncertainties. It also accounts for the fact that low-energy constants (LECs) at even and odd orders are expected to have different sizes. We use Markov Chain Monte Carlo (MCMC) sampling to explore the joint posterior of the EFT and error-model parameters and show both the LECs and the expansion parameter, , can be reliably determined. We extract the LECs up to fourth order in the EFT and find that, provided we correctly account for EFT truncation errors in our likelihood, results for lower-order LECs are stable as we go to higher orders. LEC results are also stable with respect to the addition of higher-energy data. We extract the expansion parameter for all the nuclei listed above and find a clear correlation between the extracted and the expected based on the single-particle and vibrational energy scales. However, the that actually determines the convergence of the EFT expansion is markedly smaller than would be naively expected based on those scales.

    nucl-thFront.in Phys.(2022)·7 citations
  2. 02

    Nudged elastic band approach to nuclear fission pathways

    Eric Flynn · Daniel Lay · Sylvester Agbemava · Pablo Giuliani · Kyle Godbey · Witold Nazarewicz · Jhilam Sadhukhan

    The nuclear fission process is a dramatic example of the large-amplitude collective motion in which the nucleus undergoes a series of shape changes before splitting into distinct fragments. This motion can be represented by a pathway in the many-dimensional space of collective coordinates. The collective action along the fission pathway determines the spontaneous fission half-lives as well as mass and charge distributions of fission fragments. We study the performance and precision of various methods to determine the minimum action and minimum-energy fission trajectories in the collective space. We apply the nudged elastic band method (NEB), grid-based methods, and Euler Lagrange approach to the collective action minimization in two and three dimensional collective spaces. The performance of various approaches to the fission pathway problem is assessed by studying the collective motion along both analytic energy surfaces and realistic potential energy surfaces obtained with the Hartree-Fock-Bogoliubov theory. The uniqueness and stability of the solutions is studied. The NEB method is capable of efficient determination of the exit points on the outer turning surface that characterize the most probable fission pathway and constitute the key input for fission studies. This method can also be used to accurately compute the critical points (i.e., local minima and saddle points) on the potential energy surface of the fissioning nucleus that determine the static fission path. The NEB method is the tool of choice for finding the least-action and minimum energy fission trajectories. It will be particularly useful in large-scale fission calculation of superheavy nuclei and neutron-rich fissioning nuclei contributing to the astrophysical r-process recycling.

    nucl-thPRC(2022)·14 citations
  3. 03

    Stochastic hydrodynamics and hydro-kinetics: Similarities and differences

    Aritra De🇺🇸 · Chun Shen🇺🇸 · Joseph I. Kapusta🇺🇸

    The hydro-kinetic formalism has been used as a complementary approach to solving the Stochastic Differential Equations (SDE) corresponding to noisy hydrodynamics. The hydro-kinetic formalism consists of a deterministic set of relaxation type equations that tracks the evolution of 2-point correlation functions of stochastic hydrodynamic quantities. Hence they are comparatively easier to solve than the SDEs, which are computationally intensive and need to deal with arbitrarily large gradients. This work compares the two approaches for the propagation and diffusion of conserved charge fluctuations in the Bjorken hydrodynamic model. For white noise, the two approaches agree. For colored Catteneo noise, which is causal, the two approaches diverge. This is because white noise only induces two-point correlations, while Catteneo noise also induces higher-order correlations. This difference is quantified from the effects of causal evolution and influence from higher-order correlations induced by the Catteneo noise.

    nucl-thPRC(2022)·8 citations
  4. 04

    Direct URCA process in light of PREX-2

    Vivek Baruah Thapa🇮🇳 · Monika Sinha🇮🇳

    We study the implications of the recent development in nuclear symmetry energy constraints from PREX-2 data on dense matter equation of state and its impact on dURCA threshold density. In this work, we construct the equation of state within the framework of covariant density functional theory implementing coupling schemes of non-linear and density-dependent models and exploring the coupling parameter space of isovector-vector meson to baryons constrained by the isospin asymmetry parameter values deduced from recent PREX-2 data. The modified parameter sets are applied to evaluate the dense matter properties. We find that the updated data suggests the occurrence of dURCA process within neutron star even with mass as low as one solar mass.

    nucl-thastro-ph.HE8 citations
  5. 05

    Gauge fields renormalization groups and thermofractals

    Airton Deppman🇧🇷 · Eugenio Megias🇪🇸 · Debora P. Menezes🇧🇷

    The perturbative approach to QCD has been shown to be limited, and the difficulties to obtain accurate calculations in the low-energy region seems to be insurmountable. A recent approach uses the fractal structures of Yang-Mills Field Theory to circumvent those difficulties, allowing for the determination of an analytic expression for the running coupling. The results obtained are in agreement with several experimental findings, and explain many of the observed phenomena at high-energy collisions. In this work, we address some of the conceptual aspects of the fractal approach, which are expressed in terms of the renormalization group equation and the self-energy corrections to the parton mass. We associate these well-known concepts with the origins of the fractal structure in the quantum field theory.

    nucl-thhep-thquant-phJ.Phys.Conf.Ser.(2022)·0 citations

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first authorsco-authorsvia INSPIRE