Nuclear Theory·nucl-th

Thursday·January 29, 2015

8 papers—5 primary·3 cross-listed

01
Nuclear equation of state and finite nucleon volumes
Jacek Rożynek🇵🇱
It is shown how the Equation of State (EoS) depends on nucleon properties inside Nuclear Matter (NM). We propose to benefit from the concept of enthalpy in order to include volume corrections to the nucleon rest energy, which are proportional to pressure and absent in a standard Relativistic Mean Field (RMF) with point-like nucleons. As a result, the nucleon mass can decrease inside NM, making the model nonlinear and the EoS softer. The course of the EoS in our RMF model agrees with a semi-empirical estimate and is close to the results obtained from extensive DBHF calculations with a Bonn A potential, which produce an EoS stiff enough to describe neutron star properties (mass--radius constraint), especially the masses of PSR J1614_2230 and PSR J0348_0432, known as the most massive ( $\sim 2 M_{⊙}$ ) neutron stars. The presented model has proper saturation properties, including a good value of compressibility.
nucl-thhep-phJ.Phys.G(2015)·4 citations
02
Present Status of Fission Research Based on TDDFT
Yoritaka Iwata
Fission resulting from collision of atomic nuclei is systematically investigated based on time-dependent density functional calculations. Time-dependent density functional theory (TDDFT) is a framework, which enables us to treat quantum many-body dynamics with nucleon degrees of freedom. In this article a theoretical framework called Composite-Nucleus Constrained TDDFT is introduced, and charge equilibrium hypothesis for collision fission dynamics is examined.
nucl-thnucl-exJAEA-Conf 2015-003, INDC(JPN)-201, 93 (20…·0 citations
03
Complex-energy approach to sum rules within nuclear density functional theory
Nobuo Hinohara · Markus Kortelainen · Witold Nazarewicz · Erik Olsen
The linear response of the nucleus to an external field contains unique information about the effective interaction, correlations, and properties of its excited states. To characterize the response, it is useful to use its energy-weighted moments, or sum rules. By comparing computed sum rules with experimental values, the information content of the response can be utilized in the optimization process of the nuclear Hamiltonian or EDF. But the additional information comes at a price: compared to the ground state, computation of excited states is more demanding. To establish an efficient framework to compute sum rules of the response that is adaptable to the optimization of the nuclear EDF and large-scale surveys of collective strength, we have developed a new technique within the complex-energy FAM based on the QRPA. To compute sum rules, we carry out contour integration of the response function in the complex-energy plane. We benchmark our results against the conventional matrix formulation of the QRPA theory, the Thouless theorem for the energy-weighted sum rule, and the dielectric theorem for the inverse energy-weighted sum rule. We demonstrate that calculated sum-rule values agree with those obtained from the matrix formulation of the QRPA. We also discuss the applicability of both the Thouless theorem about the energy-weighted sum rule and the dielectric theorem for the inverse energy-weighted sum rule to nuclear density functional theory in cases when the EDF is not based on a Hamiltonian. The proposed sum-rule technique based on the complex-energy FAM is a tool of choice when optimizing effective interactions or energy functionals. The method is very efficient and well-adaptable to parallel computing. The FAM formulation is especially useful when standard theorems based on commutation relations involving the nuclear Hamiltonian and external field cannot be used.
nucl-thPRC(2015)·27 citations
04
2p-2h excitations in neutrino scattering: angular distribution and frozen approximation
I. Ruiz Simo🇪🇸 · C. Albertus🇪🇸 · J.E. Amaro🇪🇸 · M.B. Barbaro🇮🇹 · J.A. Caballero🇪🇸 · T.W. Donnelly🇺🇸
We study the phase-space dependence of 2p-2h excitations in neutrino scattering using the relativistic Fermi gas model. We follow a similar approach to other authors, but focusing in the phase-space properties, comparing with the non-relativistic model. A careful mathematical analysis of the angular distribution function for the outgoing nucleons is performed. Our goals are to optimize the CPU time of the 7D integral to compute the hadron tensor in neutrino scattering, and to conciliate the different relativistic and non relativistic models by describing general properties independently of the two-body current. For some emission angles the angular distribution becomes infinite in the Lab system, and we derive a method to integrate analytically around the divergence. Our results show that the frozen approximation, obtained by neglecting the momenta of the two initial nucleons inside the integral of the hadron tensor, reproduces fairly the exact response functions for constant current matrix elements.
nucl-thPoS(2015)·1 citation
05
On the accuracy of using Fokker Planck equation in heavy ion collision
Nirupam Dutta🇮🇳 · Trambak Bhattacharyya🇮🇳
Application of Fokker-Planck equation to heavy quark transport in the evolving medium created in heavy ion collision is critically scrutinised. We realise that the approach introduces a moderate uncertainty in drag and diffusion coefficients culminating in huge ambiguity in the theoretical prediction of nuclear modification factor $R_{AA}$ . Quantitative estimation of the error is presented by considering recent developments in this field.
nucl-thhep-phnucl-ex0 citations
06
Quantum decoherence in the entanglement entropy of a composite particle and its relationship to coarse graining in the Husimi function
Yoshiko Kanada-En'yo
I investigate quantum decoherence in a one-body density matrix of a composite particle consisting of two correlated particles. Because of a two-body correlation in the composite particle, quantum decoherence occurs in the one-body density matrix that has been reduced from the two-body density matrix. As the delocalization of the distribution of the composite particle grows, the entanglement entropy increases, and the system can be well-described by a semi-classical approximation, wherein the center position of the composite particle can be regarded as a classical coordinate. I connect the quantum decoherence in the one-body density matrix of a composite particle to the coarse graining in a phase space distribution function of a single particle and associate it with the Husimi function.
↳ quant-phcond-mat.str-elmath-phmath.MP+1PTEP(2015)·9 citations
07
On the question of current conservation for the Two-Body Dirac equations of constraint theory
Matthias Lienert🇩🇪
The Two-Body Dirac equations of constraint theory are of special interest not only in view of applications for phenomenological calculations of mesonic spectra but also because they avoid no-go theorems about relativistic interactions. Furthermore, they provide a quantum mechanical description in a manifestly Lorentz invariant way using the concept of a multi-time wave function. In this paper, we place them into the context of the multi-time formalism of Dirac, Tomonaga and Schwinger for the first time. A general physical and mathematical framework is outlined and the mechanism which permits relativistic interaction is identified. The main requirement derived from the general framework is the existence of conserved tensor currents with a positive component which can play the role of a probability density. We analyze this question for a general class of Two-Body Dirac equations thoroughly and comprehensively. While the free Dirac current is not conserved, it is possible to find replacements. Improving on previous research, we achieve definite conclusions whether restrictions of the function space or of the interaction terms can guarantee the positive definiteness of the currents -- and whether such restrictions are physically adequate. The consequences of the results are drawn, with respect to both applied and foundational perspectives.
↳ quant-phhep-thnucl-thJ.Phys.A(2015)·10 citations
08
The Tsallis Distribution at Large Transverse Momenta
M.D. Azmi🇮🇳 · J. Cleymans🇿🇦
Fits to the transverse momentum distributions of charged particles produced in p - p collisions at LHC energies based on the Tsallis distribution have been shown to work over 14 orders of magnitude. Two versions of the Tsallis distribution are compared and discussed, the thermodynamically consistent version leads to a temperature of T = 74 +/- 13 MeV at the highest beam energy, a result which is in agreement with previous analyses done with lower transverse momentum data.
↳ hep-phnucl-thEPJC(2015)·73 citations

Affiliations

first authorsco-authorsvia INSPIRE