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Nuclear Theory·nucl-th

Thursday·May 16, 2019

8 papers—5 primary·3 cross-listed

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  1. 01

    Bound to unbound states transitions of heavy quarkonia in the cooling phase of QGP

    Nirupam Dutta🇮🇳 · Partha Bagchi🇮🇳 · Jobin Sebastian🇮🇳

    Emphasizing the possibility of moderate suppression of heavy quarkonium states, we invite some attention towards the issue of real time evolution of quarkonia during the cooling phase of quark gluon plasma(QGP). In this context, we have used time dependent perturbation theory to show that , , can further be dissociated in the medium at a temperature below their dissociation thresholds even though they survive the Debye screening. We have presented and compared the dissociation probabilities and dissociation rates of these states in real and complex valued potential in this article. We realise that our method is an approximate way to analyse the short time behaviour of quarkonium in real valued potential and for long time behaviour one must adopt a non perturbative technique for solving schrödinger equation of quarkonium bound states in evolving QGP. On the other hand the perturbation technique seems to be valid enough to deal with the same for a complex valued quark anti-quark potential.

    nucl-thhep-phJ.Subatomic Part.Cosmol.(2025)·4 citations
  2. 02

    Statistical properties of thermal neutron capture cross section calculated with randomly generated resonance parameters

    N. Furutachi · F. Minato · O. Iwamoto

    We investigated the probability distribution of the thermal neutron capture cross section () deduced stochastically with the resonance parameters randomly sampled from Wigner and Porter-Thomas distributions. We found that the typical probability distribution has an asymmetric shape. While there is a long tail on the large side due to a resonance happening to be close to the thermal energy, the multi-resonance contribution considerably reduces the probability on the small side. We also found that the probability distributions have a similar shape if nuclei have an average resonance spacing sufficiently larger than an average radiation width. We compared the typical probability distribution with the distribution of the experimental values of 193 nuclei, and found a good agreement between them.

    nucl-thPRC(2019)·0 citations
  3. 03

    Rossby modes in neutron stars as sources of gravitational waves

    Sujan Roy🇮🇳 · Somnath Mukhopadhyay🇮🇳 · Joydev Lahiri🇮🇳 · Debasis Atta · Partha Roy Chowdhury🇮🇳 · D. N. Basu🇮🇳

    In the present work, we explore the Rossby mode instabilities in neutron stars as sources of gravitational waves. The intensity and time evolution of the emitted gravitational waves in terms of the amplitude of the strain tensor are estimated in the slow rotation approximation using -equilibrated neutron star matter obtained from density dependent M3Y effective interaction. For a wide range of neutron star masses, the fiducial gravitational and various viscous time scales, the critical frequencies and the time evolutions of the frequencies are calculated. The dissipative mechanism of the Rossby modes is considered to be driven by the shear viscosity along the boundary layer of the solid crust-liquid core interface as well as in the core and the bulk viscosity. It is found that neutron stars with slower frequency of rotation, for the same mass, radius and surface temperature, are expected to emit gravitational waves of higher intensity.

    nucl-thastro-ph.HEAnnals Phys.(2020)·6 citations
  4. 04

    Model-independent form-factor constraints for electromagnetic spin-1 currents

    Helmut Haberzettl🇺🇸

    Using local gauge invariance in the form of the Ward-Takahashi identity and the fact that properly constructed current operators must be free of kinematic singularities, it is shown that the magnetic moment and the quadrupole moment of an elementary spin-1 particle with mass and charge are related by , thus constraining the normalizations of the Sachs form factors. This relation holds true as a matter of course at the tree level in the standard model, but we prove it remains true in general for dressed spin-1 states derived from elementary fields. General expressions for spin-1 propagators and currents with arbitrary hadronic dressing are given showing the result to be independent of any dressing effect or model approach.

    nucl-thhep-phPRD(2019)·11 citations
  5. 05

    Extrapolation of nuclear structure observables with artificial neural networks

    W.G. Jiang · G. Hagen · T. Papenbrock

    Calculations of nuclei are often carried out in finite model spaces. Thus, finite-size corrections enter, and it is necessary to extrapolate the computed observables to infinite model spaces. In this work, we employ extrapolation methods based on artificial neural networks for observables such as the ground-state energy and the point-proton radius. We extrapolate results from no-core shell model and coupled-cluster calculations to very large model spaces and estimate uncertainties. Training the network on different data typically yields extrapolation results that cluster around distinct values. We show that a preprocessing of input data, and the inclusion of correlations among the input data, reduces the problem of multiple solutions and yields more stable extrapolated results and consistent uncertainty estimates. We perform extrapolations for ground-state energies and radii in He, Li, and O, and compare the predictions from neural networks with results from infrared extrapolations.

    nucl-thPRC(2019)·57 citations

Affiliations

first authorsco-authorsvia INSPIRE