Nuclear Theory·nucl-th

Tuesday·December 8, 2020

16 papers—7 primary·9 cross-listed

01
Equivalence of generator coordinate Brink cluster model and nonlocalized cluster model and supersolidity of $α$ cluster structure in nuclei
S. Ohkubo
It is found that $α$ cluster structure has the apparently opposing dual property of crystallinity and condensation simultaneously. The mathematical equivalence of the spatially localized Brink $α$ cluster model in the generator coordinate method (GCM) and the nonlocalized cluster model (NCM), which is also called the THSR (Tohsaki-Horiuchi-Schuck-R $o ¨$ pke) wave function based on the condensation of $α$ clusters, is shown. The latter is found to be an equivalent representation of the localized cluster model and it is a natural consequence that the many NCM (THSR) calculations reproduce the proceeding cluster model calculations using the GCM and the resonating group method (RGM). Localized cluster models, which have been successfully used for more than half a century, will continue to be very powerful. The equivalence is a manifestation of the duality of incompatible aspects: crystallinity and coherent wave nature due to condensation of $α$ clusters, i.e. the dual properties of a supersolid. The Pauli principle causes the duality. The evidence for supersolidity, the emergence of a Nambu-Goldstone mode caused by the spontaneous symmetry breaking of the global phase, is discussed
nucl-th0 citations
02
Nonequilibrium kinetic freeze-out properties in relativistic heavy ion collisions from energies employed at the RHIC beam energy scan to those available at the LHC
Jia Chen🇨🇳 · Jian Deng🇨🇳 · Zebo Tang🇨🇳 · Zhangbu Xu🇺🇸 · Li Yi🇨🇳
In this paper, we investigate the kinetic freeze-out properties in relativistic heavy ion collisions at different collision energies. We present a study of standard Boltzmann-Gibbs Blast-Wave (BGBW) fits and Tsallis Blast-Wave (TBW) fits performed on the transverse momentum spectra of identified hadrons produced in Au + Au collisions at collision energies of $s_{NN} =$ 7.7 - 200 GeV at the Relativistic Heavy Ion Collider (RHIC), and in Pb + Pb collisions at collision energies of $s_{NN} =$ 2.76 and 5.02 TeV at the Large Hadron Collider (LHC). The behavior of strange and multi-strange particles is also investigated. We found that the TBW model describes data better than the BGBW one overall, and the contrast is more prominent as the collision energy increases as the degree of non-equilibrium of the produced system is found to increase. From TBW fits, the kinetic freeze-out temperature at the same centrality shows a weak dependence of collision energy between 7.7 and 39 GeV, while it decreases as collision energy continues to increase up to 5.02 TeV. The radial flow is found to be consistent with zero in peripheral collisions at RHIC energies but sizable at LHC energies and central collisions at all RHIC energies. We also observed that the strange hadrons, with higher temperature and similar radial flow, approach equilibrium more quickly from peripheral to central collisions than light hadrons. The dependence of temperature and flow velocity on non-equilibrium parameter ( $q - 1$ ) is characterized by two second-order polynomials. Both $a$ and $d ξ$ from the polynomials fit, related to the influence of the system bulk viscosity, increase toward lower RHIC energies.
nucl-thPRC(2021)·42 citations
03
Quasinormal modes of scalar field coupled to Einstein's tensor in the non-commutative geometry inspired black hole
Zening Yan🇨🇳 · Chen Wu🇨🇳 · Wenjun Guo🇨🇳
We investigate the quasinormal modes (QNMs) of the scalar field coupled to the Einstein's tensor in the non-commutative geometry inspired black hole spacetime. It is found that the lapse function of the non-commutative black hole metric can be represented by a Kummer's confluent hypergeometric function, which can effectively solve the problem that the numerical results of the QNMs are sensitive to the model parameters and make the QNMs values more reliable. We make a careful analysis of the scalar QNM frequencies by using several numerical methods, and find that the numerical results obtained by the new WKB method (the Padé approximants) and the Mashhoon method (P $o ¨$ schl-Teller potential method) are quite different from those obtained by the asymptotic iterative method (AIM) and time-domain integration method when the non-commutative parameter $θ$ and coupling parameter $η$ are large. The most obvious difference is that the numerical results obtained by the AIM and the time-domain integration method appear a critical value $η_{c}$ with an increase of $η$ , which leads to the dynamical instability. After carefully analyzing the numeral results, we conclude that the numerical results obtained by the AIM and the time-domain integration method are closer to the theoretical values than those obtained by the WKB method and the Mashhoon method, when the $θ$ and $η$ are large. Moreover, through a numerical fitting, we obtain that the functional relationship between the threshold $η_{c}$ and the non-commutative parameter $θ$ satisfies $η_{c} = a θ^{b} + c$ for a fixed $l$ approximately. We find that the stability of dynamics can be ensured in the $η < η_{c} (θ, l)$ region.
nucl-thgr-qcNPB(2021)·17 citations
04
Demonstration of the Universality of Molecular Structures in Prolate Deformed Nuclei
R Canavan · M Freer
The relationship between the deformed harmonic oscillator and the formation of molecular cluster structures, whereby valence neutrons are exchanged between cluster cores, is examined. It is found that there is a strong connection between the properties of the valence orbitals associated with deformed structures in the deformed harmonic oscillator and the molecular orbitals created by linear combinations of single-centre orbitals around nuclear clusters. The conclusion is that in addition to the appearance of clustering in the deformed harmonic oscillator that \emph{every} prolate deformed cluster structure should have molecular orbitals built on that structure. This is demonstrated through a series of examples that range from $^{13}$ C to $^{57}$ Ni.
nucl-thJ.Phys.G(2020)·5 citations
05
Interpretation of the quasiparticle plus triaxial rotor model
Q. B. Chen · S. Frauendorf
We discuss in depth the application of the classical concepts for interpreting the quantal results from the triaxial rotor core without and with odd-particle. The corresponding limitations caused by the discreteness and finiteness of the angular momentum Hilbert space and the extraction of the relevant features from the complex wave function and distributions of various angular momentum components are discussed in detail. New methods based on spin coherent states and spin squeezed states are introduced. It is demonstrated that the spin coherent state map is a powerful tool to visualize the angular momentum geometry of rotating nuclei. The topological nature of the concepts of transverse and longitudinal wobbling is clarified and the transitional axis-flipregime is analysed for the first time.
nucl-thnucl-ex2 citations
06
Microscopic equation of state of hot nuclear matter for numerical relativity simulations
Domenico Logoteta · Albino Perego · Ignazio Bombaci
A precise understanding of the equation of state (EOS) of dense and hot matter is key to modeling relativistic astrophysical environments, including core-collapse supernovae (CCSNe), protoneutron star (PNSs) evolution, and compact binary mergers. In this paper, we extend the microscopic zero-temperature BL (Bombaci and Logoteta) %nuclear equation of state nuclear EOS %derived by Bombaci and Logoteta to finite temperature and arbitrary nuclear composition. We employ this new EOS to describe hot $β$ -stable nuclear matter and to compute various structural properties of nonrotating PNS. %protoneutron stars. We also apply the EOS to perform dynamical simulations of a spherically symmetric CCSN. The EOS is derived using the finite temperature extension of the Brueckner--Bethe--Goldstone quantum many-body theory in the Brueckner--Hartree--Fock approximation. Neutron star properties are computed by solving the Tolman--Oppenheimer--Volkoff structure equations numerically. The sperically symmetric CCSN simulations are performed using the AGILE-IDSA code. Our EOS models are able to reproduce typical features of both PNS and spherically symmetric CCSN simulations. In addition, our EOS model is consistent with present measured neutron star masses and particularly with the masses: $M = 2.01 \pm 0.04 M_{⊙}$ and $M = 2.1 4_{- 0.18}^{+ 0.20} M_{⊙}$ of the neutron stars in PSR~J0348+0432 and PSR J0740+6620 respectively. Finally, we suggest a feasible mechanism to produce low-mass black holes ( $M \sim 2 M_{⊙}$ ) that could have far-reaching consequences for interpreting the gravitational wave event GW190814 as a BH--BH merger.
nucl-thastro-ph.HEAstron.Astrophys.(2021)·61 citations
07
Transverse expansion of (1 + 2) dimensional magneto-hydrodynamics flow with longitudinal boost invariance
R.Emamian🇮🇷 · A. F. Kord🇮🇷 · A. Ghaani🇮🇷 · B.Azadegan🇮🇷
In the present work, we investigate the effects of magnetic field on expanding hot and dense nuclear matter as an ideal fluid. We consider QGP, on the particular case of a (1 + 2) dimensional longitudinally boost-invariant fluid expansion, in the background of an inhomogeneous magnetic field that is generated by external sources. We assume the magnetic field points in the direction perpendicular to the reaction plane, follows the power-law decay in proper time, and has two components on the transverse plane. To simplify the calculation, we suppose the investigated fluid has azimuthal symmetry, and magneto-hydrodynamic equations are described in a polar coordinate system on the transverse plane of reaction. Our results depict the space-time evolution of the transverse expansion of the fluid in the presence of an inhomogeneous external magnetic field. Ultimately, we utilize transverse velocity and correction of energy density to estimate the transverse momentum spectrum of final particles that emerge from heavy-ion collisions based on experimental data.
nucl-thhep-phhep-thPLB(2022)·2 citations
08
Retarded Green's Function from Rotating AdS Black Holes: Emergent CFT $_{2}$ and Viscosity
Jun Nian🇺🇸 · Leopoldo A. Pando Zayas🇺🇸
Using the AdS/CFT correspondence we consider the retarded Green's function in the background of rotating near-extremal AdS $_{4}$ black holes. Following the canonical AdS/CFT dictionary into the asymptotic boundary we get a CFT $_{3}$ result. We also take a new route and zoom in on the near-horizon region, blow up this region and show that it yields a CFT $_{2}$ result. We argue that the decoupling of the near-horizon region is akin to the decoupling of the near-throat region of a D3-brane, which led to the original formulation of the AdS/CFT correspondence, thus implying that the Kerr/CFT correspondence follows as a decoupling of the standard AdS/CFT correspondence applied to rotating black holes. As a byproduct, we compute the shear viscosity to entropy density ratio for the strongly coupled boundary CFT $_{3}$ , and find that it violates the $1/ (4 π)$ bound.
↳ hep-thgr-qcnucl-thPRD(2021)·4 citations
09
Left-right symmetry and electric dipole moments. A global analysis
Michael J. Ramsey-Musolf🇨🇳 · Juan Carlos Vasquez🇺🇸
We perform a global fit using results of searches for electric dipole moments (EDM) of diamagnetic systems within the context of the minimal left-right symmetric model. In this way, we disentangle the new "left-right" electroweak and $θ ˉ$ contributions that cannot be separated using a single EDM system. Although the fit is done for a specific model, the approach can be applied to any particle physics model. Finally, we revisit the constraint on the $D$ coefficient in $β$ -decay and find that current EDM bounds do not preclude observation of this T-violating effect in a possible next generation $β$ -decay experiment.
↳ hep-phnucl-thPLB(2021)·21 citations
10
Real-time dynamics of Chern-Simons fluctuations near a critical point
Kazuki Ikeda🇯🇵 · Dmitri E. Kharzeev🇺🇸 · Yuta Kikuchi🇺🇸
The real-time topological susceptibility is studied in $(1 + 1)$ -dimensional massive Schwinger model with a $θ$ -term. We evaluate the real-time correlation function of electric field that represents the topological Chern-Pontryagin number density in $(1 + 1)$ dimensions. Near the parity-breaking critical point located at $θ = π$ and fermion mass $m$ to coupling $g$ ratio of $m / g \approx 0.33$ , we observe a sharp maximum in the topological susceptibility. We interpret this maximum in terms of the growth of critical fluctuations near the critical point, and draw analogies between the massive Schwinger model, QCD near the critical point, and ferroelectrics near the Curie point.
↳ hep-phhep-latnucl-thquant-phPRD(2021)·37 citations
11
The energy-momentum tensor at the earliest stage of relativistic heavy ion collisions
Margaret E. Carrington🇨🇦 · Alina Czajka🇵🇱 · Stanislaw Mrowczynski🇵🇱
Nuclear collisions at high energies produce a gluon field that can be described using the Colour Glass Condensate (CGC) effective theory at proper times $τ ≲ 1$ fm/c. The theory can be used to calculate the gluon energy-momentum tensor, which provides information about the early time evolution of the chromo-electric and chromo-magnetic fields, energy density, longitudinal and transverse pressures, and other quantities. We obtain an analytic expression for the energy-momentum tensor using an expansion in the proper time, and working to sixth order. The calculation is technically difficult, in part because the number of terms involved grows rapidly with the order of the $τ$ expansion, but also because of several subtle issues related to the definition of event-averaged correlators, the method chosen to regulate these correlators, and the dependence of results on the parameters introduced by the regularization and nuclear density profile functions. All of these issues are crucially related to the important question of the extent to which we expect a CGC approach to be able to accurately describe the early stages of a heavy ion collision. We present some results for the evolution of the energy density and the longitudinal and transverse pressures. We show that our calculation gives physically meaningful results up to values of the proper time which are close to the regime at which hydrodynamic simulations are initialized. In a companion paper [1] we give a detailed analysis of several other experimentally relevant quantities that can be calculated from the energy-momentum tensor.
↳ hep-phnucl-thEPJA(2022)·32 citations
12
Unpolarized Quark and Gluon TMD PDFs and FFs at N $^{3}$ LO
Ming-xing Luo🇨🇳 · Tong-Zhi Yang🇨🇭 · Hua Xing Zhu🇨🇳 · Yu Jiao Zhu🇨🇳
In this paper we calculate analytically the perturbative matching coefficients for unpolarized quark and gluon Transverse-Momentum-Dependent (TMD) Parton Distribution Functions (PDFs) and Fragmentation Functions (FFs) through Next-to-Next-to-Next-to-Leading Order (N $^{3}$ LO) in QCD. The N $^{3}$ LO TMD PDFs are calculated by solving a system of differential equation of Feynman and phase space integrals. The TMD FFs are obtained by analytic continuation from space-like quantities to time-like quantities, taking into account the probability interpretation of TMD PDFs and FFs properly. The coefficient functions for TMD FFs exhibit double logarithmic enhancement at small momentum fraction $z$ . We resum such logarithmic terms to the third order in the expansion of $α_{s}$ . Our results constitute important ingredients for precision determination of TMD PDFs and FFs in current and future experiments.
↳ hep-phnucl-thJHEP(2021)·127 citations
13
Parton energy loss in a hard-soft factorized approach
Tianyu Dai🇺🇸 · Jean-François Paquet🇺🇸 · Derek Teaney🇺🇸 · Steffen A. Bass🇺🇸
An energetic parton travelling through a quark-gluon plasma loses energy via occasional hard scatterings and frequent softer interactions. Whether or not these interactions admit a perturbative description, the effect of the soft interactions can be factorized and encoded in a small number of transport coefficients. In this work, we present a hard-soft factorized parton energy loss model which combines a stochastic description of soft interactions and rate-based modelling of hard scatterings. We introduce a scale to estimate the regime of validity of the stochastic description, allowing for a better understanding of the model's applicability at small and large coupling. We study the energy and fermion-number cascade of energetic partons as an application of the model.
↳ hep-phnucl-thPRC(2022)·18 citations
14
Cooper Triples in Attractive Three-Component Fermions: Implication for Hadron-Quark Crossover
Hiroyuki Tajima🇯🇵 · Shoichiro Tsutsui🇯🇵 · Takahiro M. Doi🇯🇵 · Kei Iida🇯🇵
We investigate many-body properties of equally populated three-component fermions with attractive three-body contact interaction in one dimension. A diagrammatic approach suggests the possible occurrence of Cooper triples at low temperature, which are three-body counterparts of Cooper pairs with a two-body attraction. We develop a minimal framework that bridges the crossover from tightly-bound trimers to Cooper triples with increasing chemical potential and show how the formation of Cooper triples occurs in the grand-canonical phase diagram. Moreover, we argue that this non-trivial crossover is similar to the hadron-quark crossover proposed in dense matter. A coexistence of medium-induced triples and the underlying Fermi sea at positive chemical potential is analogous to quarkyonic matter consisting of baryonic excitations and the underlying quark Fermi sea. The comparison with the existing quantum Monte Carlo results implies that the emergence of these kinds of three-body states can be a microscopic origin of the peak of the sound velocity along the crossover.
↳ cond-mat.quant-gascond-mat.str-elhep-phnucl-thPRResearch(2022)·27 citations
15
Probes of the quark-gluon plasma and plasma instabilities
Sigtryggur Hauksson🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
Penetrating probes in heavy-ion collisions, like jets and photons, are sensitive to the transport coefficients of the produced quark-gluon plasma, such as shear and bulk viscosity. Quantifying this sensitivity requires a detailed understanding of photon emission and jet-medium interaction in a non-equilibrium plasma. Up to now, such an understanding has been hindered by plasma instabilities which arise out of equilibrium and lead to spurious divergences when evaluating the rate of interaction of hard probes with the plasma. In this paper, we show that taking into account the time evolution of an unstable plasma cures these divergences. We calculate the time evolution of gluon two-point correlators in a setup with small initial momentum anisotropy and show that the gluon occupation density grows exponentially at early times. Based on this calculation, we argue for a phenomenological prescription where instability poles are subtracted. Finally, we show that in the Abelian case instability fields do not affect medium-induced photon emission to our order of approximation.
↳ hep-phnucl-thPRC(2021)·17 citations
16
Emergence of N-body tunable interactions in universal few-atom system
Marcelo T. Yamashita · Tobias Frederico · Lauro Tomio
A three-atom molecule AAB, formed by two identical bosons A and a distinct one B, is studied by considering coupled channels close to a Feshbach resonance. It is assumed that the subsystems AB and AA have, respectively, one and two channels, where, in this case, AA has open and closed channels separated by an energy gap. The induced three-body interaction appearing in the single channel description is derived using the Feshbach projection operators for the open and closed channels. An effective three-body interaction is revealed in the limit where the trap setup is tuned to vanishing scattering lengths . The corresponding homogeneous coupled Faddeev integral equations are derived in the unitarity limit. The s-wave transition matrix for the AA subsystem is obtained with a zero-range potential by a subtractive renormalization scheme with the introduction of two finite parameters, besides the energy gap. The effect of the coupling between the channels in the coupled equations is identified with the energy gap, which essentially provides an ultraviolet scale that competes with the van der Waals radius - this sets the short-range physics of the system in the open channel. The competition occurring at short distances exemplifies the violation of the ``van der Waals universality" for narrow Feshbach resonances in cold atomic setups. In this sense, the active role of the energy gap drives the short-range three-body physics.
↳ physics.atom-phcond-mat.quant-gasnucl-thBraz.J.Phys.(2021)·2 citations

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