Nuclear Theory·nucl-th

Thursday·November 2, 2017

6 papers—5 primary·1 cross-listed

01
[Submitted on 1 Nov 2017]
Why does the sign problem occur in evaluating the overlap of HFB wave functions?
Takahiro Mizusaki · Makito Oi · Noritaka Shimizu
For the overlap matrix element between Hartree-Fock-Bogoliubov states, there are two analytically different formulae: one with the square root of the determinant (the Onishi formula) and the other with the Pfaffian (Robledo's Pfaffian formula). The former formula is two-valued as a complex function, hence it leaves the sign of the norm overlap undetermined (i.e., the so-called sign problem of the Onishi formula). On the other hand, the latter formula does not suffer from the sign problem. The derivations for these two formulae are so different that the reasons are obscured why the resultant formulae possess different analytical properties. In this paper, we discuss the reason why the difference occurs by means of the consistent framework, which is based on the linked cluster theorem and the product-sum identity for the Pfaffian. Through this discussion, we elucidate the source of the sign problem in the Onishi formula. We also point out that different summation methods of series expansions may result in analytically different formulae.
Comments:
7 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1711.00369 [pdf]
PLB(2018)·19 citations
02
[Submitted on 31 Oct 2017]
Transport coefficients in neutron star cores in BHF approach. Comparison of different nucleon potentials
P S Shternin (1) · M Baldo (2) · H-J Schulze (2) ((1) Ioffe Institute · (2) INFN Sez. di Catania)
Thermal conductivity and shear viscosity of npe $μ$ matter in non-superfluid neutron star cores are considered in the framework of Brueckner-Hartree-Fock many-body theory. We extend our previous work (Shternin, Baldo and Haensel, 2013) by analysing different nucleon-nucleon potentials and different three-body forces. We find that the use of different potentials leads up to one order of magnitude variations in the values of the nucleon contribution to transport coefficients. The nucleon contribution dominates the thermal conductivity, but for all considered models the shear viscosity is dominated by leptons.
Comments:
4 pages, 2 figures; in v.2 misprints in eqs. (5)-(9) corrected
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1711.00371 [pdf]
J.Phys.Conf.Ser.(2017)·12 citations
03
[Submitted on 31 Oct 2017]
Heavy quarkonia in a contact interaction and an algebraic model: mass spectrum, decay constants, charge radii and elastic and transition form factors
K. Raya🇲🇽 · M.A. Bedolla🇮🇹 · J.J. Cobos-Martínez🇲🇽 · A. Bashir🇲🇽
For the flavor-singlet heavy quark system of bottomonia, we compute the masses of the ground state mesons in four different channels, namely, pseudo-scalar ( $η_{b} (1 S)$ ), vector ( $Υ (1 S)$ ), scalar ( $χ_{b_{0}} (1 P)$ ) and axial vector ( $χ_{b_{1}} (1 P)$ ). We also calculate the weak decay constants of the $η_{b} (1 S)$ and $Υ (1 S)$ as well as the charge radius of $η_{b} (1 S)$ . It complements our previous study of the corresponding charmonia systems: $η_{c} (1 S)$ , $J /Ψ (1 S)$ , $χ_{c_{0}} (1 P)$ ) and ( $χ_{c_{1}} (1 P)$ ). The unified formalism for this analysis is provided by a symmetry-preserving Schwinger-Dyson equations treatment of a vector $\times$ vector contact interaction. Whenever a comparison is possible, our results are in fairly good agreement with experimental data and model calculations based upon Schwinger-Dyson and Bethe-Salpeter equations involving sophisticated interaction kernels. Within the same framework, we also report the elastic and transition form factors to two photons for the pseudo-scalar channels $η_{c} (1 S)$ and $η_{b} (1 S)$ in addition to the elastic form factors for the vector mesons $J /Ψ$ and $Υ$ for a wide range of photon momentum transfer squared ( $Q^{2}$ ). For $η_{c} (1 S)$ and $η_{b} (1 S)$ , we also provide predictions of an algebraic model which correlates remarkably well between the known infrared and ultraviolet limits of these form factors.
Comments:
11 pages, 6 figures. arXiv admin note: text overlap with arXiv:1606.03760
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1711.00383 [pdf]
Few Body Syst.(2018)·50 citations
04
[Submitted on 1 Nov 2017]
Revisiting the Gluon Spectrum in the Boost-Invariant Glasma from a Semi-Analytic Approach
Ming Li🇺🇸
In high energy heavy-ion collisions, the degrees of freedom at the very early stage can be effectively represented by strong classical gluonic fields within the Color Glass Condensate framework. As the system expands, the strong gluonic fields eventually become weak such that an equivalent description using the gluonic particle degrees of freedom starts to become valid. We revisit the spectrum of these gluonic particles by solving the classical Yang-Mills equations semi-analytically with the solutions having the form of power series expansions in the proper time. We propose a different formula for the gluon spectrum which is consistent with energy density during the whole time evolution. We find that the chromo-electric fields have larger contributions to the gluon spectrum than the chromo-magnetic fields do. Furthermore, the large momentum modes take less time to reach the weak-field regime while smaller momentum modes take more time. The resulting functional form of the gluon spectrum is exponential in nature and the spectrum is close to a thermal distrubtion with effective temperatures around $0.6$ to $0.9 Q_{s}$ late in the Glasma evolution. The sensitiveness of the gluon spectrum to the infrared and the ultraviolet cut-offs are discussed.
Comments:
14 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1711.00409 [pdf]
PRC(2017)·6 citations
05
[Submitted on 1 Nov 2017]
Signatures of $α$ clustering in ultra-relativistic collisions with light nuclei
Maciej Rybczyński🇵🇱 · Milena Piotrowska🇵🇱 · Wojciech Broniowski🇵🇱
We explore possible observable signatures of $α$ clustering of light nuclei in ultra-relativistic nuclear collisions involving $^{7, 9}$ Be, $^{12}$ C, and $^{16}$ O. The clustering leads to specific spatial correlations of the nucleon distributions in the ground state, which are manifest in the earliest stage of the ultra-high energy reaction. The formed initial state of the fireball is sensitive to these correlations, and the effect influences, after the collective evolution of the system, the hadron production in the final stage. Specifically, we study effects on the harmonic flow in collisions of light clustered nuclei with a heavy target ( $^{208}$ Pb), showing that measures of the elliptic flow are sensitive to clusterization in $^{7, 9}$ Be, whereas triangular flow is sensitive to clusterization in $^{12}$ C and $^{16}$ O. Specific predictions are made for model collisions at the CERN SPS energies. In another exploratory development we also examine the proton-beryllium collisions, where the $3/ 2^{-}$ ground state of $^{7, 9}$ Be nucleus is polarized by an external magnetic field. Clusterization leads to multiplicity distributions of participant nucleons which depend on the orientation of the polarization with respect to the collision axis, as well as on the magnetic number of the state. The obtained effects on multiplicities reach a factor of a few for collisions with a large number of participant nucleons.
Comments:
10 pages, 12 figures, references added
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1711.00438 [pdf]
PRC(2018)·47 citations

Affiliations

first authorsco-authorsvia INSPIRE

Why does the sign problem occur in evaluating the overlap of HFB wave functions?

Transport coefficients in neutron star cores in BHF approach. Comparison of different nucleon potentials

Heavy quarkonia in a contact interaction and an algebraic model: mass spectrum, decay constants, charge radii and elastic and transition form factors

Revisiting the Gluon Spectrum in the Boost-Invariant Glasma from a Semi-Analytic Approach

Signatures of α clustering in ultra-relativistic collisions with light nuclei

Affiliations

Signatures of $α$ clustering in ultra-relativistic collisions with light nuclei