Nuclear Theory·nucl-th

Tuesday·February 13, 2018

11 papers—6 primary·5 cross-listed

01
Cosmological Lithium Problems
C.A. Bertulani · Shubhchintak · A.M. Mukhamedzhanov
We briefly describe the cosmological lithium problems followed by a summary of our recent theoretical work on the magnitude of the effects of electron screening, the possible existence of dark matter parallel universes and the use of non-extensive (Tsallis) statistics during big bang nucleosynthesis. Solutions within nuclear physics are also discussed and recent measurements of cross-sections based on indirect experimental techniques are summarized.
nucl-thEPJ Web Conf.(2018)·3 citations
02
The surface properties of neutron-rich exotic nuclei within relativistic mean field formalisms
M. Bhuyan · B. V. Carlson · S. K. Patra · Shan-Gui Zhou
In this theoretical study, we establish a correlation between the neutron skin thickness and the nuclear symmetry energy for the even $-$ even isotopes of Fe, Ni, Zn, Ge, Se and Kr within the framework of the axially deformed self-consistent relativistic mean field for the non-linear NL3 $^{*}$ and density-dependent DD-ME1 interactions. The coherent density functional method is used to formulate the symmetry energy, the neutron pressure and the curvature of finite nuclei as a function of the nuclear radius. We have performed broad studies for the mass dependence on the symmetry energy in terms of the neutron-proton asymmetry for mass 70 $\leq$ A $\leq$ 96. From this analysis, we found a notable signature of a shell closure at $N$ = 50 in the isotopic chains of Fe, Ni, Zn, Ge, Se and Kr nuclei. The present study reveals an interrelationship between the characteristics of infinite nuclear matter and the neutron skin thickness of finite nuclei
nucl-thPRC(2018)·62 citations
03
Real-time evolution method and its application to 3 $α$ cluster system
R. Imai · T. Tada · M. Kimura
A new theoretical method is proposed to describe the ground and excited cluster states of atomic nuclei. The method utilizes the equation-of-motion of the Gaussian wave packets to generate the basis wave functions having various cluster configurations. The generated basis wave functions are superposed to diagonalize the Hamiltonian. In other words, this method uses the real time as the generator coordinate. The application to the $3 α$ system as a benchmark shows that the new method works efficiently and yields the result consistent with or better than the other cluster models. Brief discussion on the structure of the excited $0^{+}$ and $1^{-}$ states is also made.
nucl-thnucl-exPRC(2019)·26 citations
04
Isospin Conservation in Neutron Rich Systems of Heavy Nuclei
Ashok Kumar Jain · Swati Garg
It is generally believed that isospin would diminish in its importance as we go towards heavy mass region due to isospin mixing caused by the growing Coulomb forces. However, it was realized quite early that isospin could become an important and useful quantum number for all nuclei including heavy nuclei due to neutron richness of the systems~\cite{robson}. Lane and Soper~\cite{lane} also showed in a theoretical calculation that isospin indeed remains quite good in heavy mass neutron rich systems. In this paper, we present isospin based calculations~\cite{jain,swati} for the fission fragment distributions obtained from heavy-ion fusion fission reactions. We discuss in detail the procedure adopted to assign the isospin values and the role of neutron multiplicity data in obtaining the total fission fragment distributions. We show that the observed fragment distributions can be reproduced rather reasonably well by the calculations based on the idea of conservation of isospin. This is probably the very first direct experimental evidence of the validity of isospin in heavy nuclei, which arises largely due to the neutron-rich nature of heavy nuclei and their fragments. This result may eventually become useful for the theories of nuclear fission and also in other practical applications.
nucl-thEPJ Web Conf.(2018)·4 citations
05
Exploring the decay probability of neutron-rich superheavy nuclei
M. Bhuyan · B. V. Carlson
The modes of decay for the even-even isotopes of superheavy nuclei of Z = 118 and 120 with neutron number $160 \leq N \leq 204$ are investigated in the framework of the axially deformed relativistic mean field model. The asymmetry parameter $η$ and the relative neutron-proton asymmetry of the surface to the center ( $R_{η}$ ) are estimated for the ground state density distributions of the nuclei. We suggest that the resulting asymmetry parameter $η$ and the relative neutron-proton asymmetry $R_{η}$ of the density play a crucial role in the preformation factor of the decay half life.
nucl-th0 citations
06
On the nature of the shape coexistence and the quantum phase transition phenomena: lead region and Zr isotopes
J.E. García-Ramos · K. Heyde
The goal of this contribution is to analyze the connection between shape coexistence and quantum phase transition, two seemingly unrelated phenomena that share common aspects, namely, the rapid change in the ground state structure along an isotope chain or the presence of several minima at the mean-field level. To illustrate the similarities and differences between both phenomena, we will focus in the Pb region, in particular in Pt and Hg isotopes, as well as in Zr isotopes.
nucl-thEPJ Web Conf.(2018)·12 citations
07
Gauge Invariant Noether's Theorem and The Proton Spin Crisis
Gouranga C Nayak🇺🇸
Due to proton spin crisis it is necessary to understand the gauge invariant definition of the spin and orbital angular momentum of the quark and gluon from first principle. In this paper we derive the gauge invariant Noether's theorem by using combined Lorentz transformation plus local gauge transformation. We find that the notion of the gauge invariant definition of the spin (or orbital) angular momentum of the electromagnetic field does not exist in Dirac-Maxwell theory although the notion of the gauge invariant definition of the spin (or orbital) angular momentum of the electron exists. We find that the gauge invariant definition of the spin angular momentum of the electromagnetic field in the literature is not correct because of the non-vanishing surface term in Dirac-Maxwell theory although the corresponding surface term vanishes for linear momentum. We also show that the Belinfante-Rosenfeld tensor is not required to obtain symmetric and gauge invariant energy momentum tensor of the electron and the electromagnetic field in Dirac-Maxwell theory.
↳ hep-phnucl-thJHEP(2018)·7 citations
08
Determination of $s$ - and $p$ -wave $I = 1/2$ $K π$ scattering amplitudes in $N_{f} = 2 + 1$ lattice QCD
Ruairí Brett🇺🇸 · John Bulava🇩🇰 · Jacob Fallica🇺🇸 · Andrew Hanlon🇩🇪 · Ben Hörz🇩🇪 · Colin Morningstar🇺🇸
The elastic $I = 1/2$ , $s$ - and $p$ -wave kaon-pion scattering amplitudes are calculated using a single ensemble of anisotropic lattice QCD gauge field configurations with $N_{f} = 2 + 1$ flavors of dynamical Wilson-clover fermions at $m_{π} = 230 MeV$ . A large spatial extent of $L = 3.7 fm$ enables a good energy resolution while partial wave mixing due to the reduced symmetries of the finite volume is treated explicitly.The $p$ -wave amplitude is well described by a Breit-Wigner shape with parameters $m_{K^{*}} / m_{π} = 3.808 (18)$ and $g_{K^{*} K π}^{BW} = 5.33 (20)$ which are insensitive to the inclusion of $d$ -wave mixing and variation of the $s$ -wave parametrization. An effective range description of the near-threshold $s$ -wave amplitude yields $m_{π} a_{0} = - 0.353 (25)$ .
↳ hep-lathep-phnucl-thNPB(2018)·82 citations
09
Correspondence between the physics of extremal black holes and that of stable heavy atomic nuclei
B. P. Kosyakov🇷🇺 · E. Yu. Popov🇷🇺 · M. A. Vronsky🇷🇺
Extremal black holes are immune of Hawking evaporation. On the other hand, some heavy atomic nuclei feature extraordinary stability to spontaneous transmutations changing their mass numbers. The fact that extremal black holes and stable nuclei share a common trait, that of defying spontaneous ejection of their constituents, suggests that a good part of nuclear physics is modelled on physics of extremal black holes through a simple version of gauge/gravity duality. A general criterion for discriminating between stable and unstable microscopic systems can be formulated to gain a new insight into some imperfectly understood phenomena, such as instability of truly neutral spinless particles (Higgs bosons, $π_{0}$ , quarkonia, glueballs).
↳ hep-thgr-qchep-phnucl-thClass.Quant.Grav.(2019)·4 citations
10
Radial Distributions of Power and Isotopic Concentrations in Candidate Accident Tolerant Fuel U3Si2 and UO2/U3Si2 Fuel Pins with FeCrAl Cladding
Shengli Chen🇨🇳 · Cenxi Yuan🇨🇳 · Daxi Guo🇨🇳
Monte Carlo simulations show similarity on radial distributions of power and isotopic concentrations at any effective full power depletion time among five kinds of fuel-cladding combinations with the same cycle length, including the normal UO2-zircaloy combination, the candidate Accident Tolerant Fuel (ATF) UO2/U3Si2-FeCrAl combination, and three kinds of candidate ATF U3Si2-FeCrAl combinations. An analytical formula f(x,s) including the fuel exposure (s) and the relative radial (x) is proposed to describe the radial properties for all five kinds of fuel-cladding combinations. f(x,s) has the form of the second order polynomial term of s with the exponential type of coefficients depending on x. It is shown that the suggested function f(x,s) gives a nice description on the simulation data with rather small deviations and can immediately provide radial distribution of power, burnup, and isotopic concentrations of 235U, 238U, 239Pu, and 241Pu at any fuel exposure and relative radius. It is useful to discuss the fuel temperature through the present analytical formula. The realistic radial power distribution gives flatter radial temperature distribution compared with the uniform power distribution. Because of the different thermal conductivities of fuels and claddings and the different thicknesses of claddings, the present discussed five kinds of fuel-cladding combinations have different radial temperature distributions, although their radial power distributions are quite similar. The present work provides an analytical formula to describe the radial properties of the ATF which is expected to be helpful for further neutronic and multi-physics coupling studies.
↳ physics.app-phnucl-thAnnals Nucl.Energy(2019)·2 citations
11
The $B = 5$ Skyrmion as a two-cluster system
Sven Bjarke Gudnason🇨🇳 · Chris Halcrow🇨🇳
The classical $B = 5$ Skyrmion can be approximated by a two-cluster system where a $B = 1$ Skyrmion is attached to a core $B = 4$ Skyrmion. We quantise this system, allowing the $B = 1$ to freely orbit the core. The configuration space is 11-dimensional but simplifies significantly after factoring out the overall spin and isospin degrees of freedom. We exactly solve the free quantum problem and then include an interaction potential between the Skyrmions numerically. The resulting energy spectrum is compared to the corresponding nuclei -- the Helium-5/Lithium-5 isodoublet. We find approximate parity doubling not seen in the experimental data. In addition, we fail to obtain the correct ground state spin. The framework laid out for this two-cluster system can readily be modified for other clusters and in particular for other $B = 4 n + 1$ nuclei, of which the $B = 5$ is the simplest example.
↳ hep-thnucl-thPRD(2018)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE