Nuclear Theory·nucl-th
13 papers—6 primary·7 cross-listed
Semyon Potesnov🇩🇪 · David Wagner🇮🇹
Employing a kinetic framework, we calculate all transport coefficients for relativistic dissipative (second-order) hydrodynamics for arbitrary particle masses in the 14-moment approximation. Taking the non-relativistic limit, it is shown that the relativistic theory reduces to the Grad equations computed in the 'order-of-magnitude' approach.
Jing Ye🇨🇳 · Wei-Zhou Jiang🇨🇳
The zero-sound modes at finite temperature are investigated with the relativistic random phase approximation to signal the uncertainty of the equation of state (EOS) of asymmetric nuclear matter. It is observed that in typically selected stiff and soft relativistic mean-field (RMF) models, zero-sound modes arise at low temperature, whereas increasing the temperature gradually breaks the zero sound in soft models, with a smaller density range compared to stiff models. At high density, the presence or absence of zero sound turns out to be correspondingly the character of the stiff or soft RMF EOS. More strikingly, we find by analyzing the dispersion relation and sound velocity that at finite temperature the zero-sound modes in RMF models with the stiff EOS undergo a thermal bifurcation, resulting in the transform of zero sound into the first sound at some momentum . The thermally bifurcated sound branch in the stiff models and the zero-sound branch in the soft models are both highly sensitive to the slope of the symmetry energy, providing promising signals for the pending high-density symmetry energies. In addition, it is found that there exists a nonlinear dispersion relation for both the stiff and soft models that supports the zero sound in the relatively lower density region.
Muhammad Majid · Jameel-Un Nabi · Gul Daraz
The allowed charge-changing transitions are the most common weak interaction processes of spin-isospin form that play a crucial role in several nuclear/astrophysical processes. The first-forbidden (FF) transition becomes important, in the circumstances where allowed Gamow-Teller (GT) transitions are unfavored, specifically for neutron-rich nuclei due to phase space considerations. In this paper deformed proton-neutron quasi-particle random phase approximation (pn-QRPA) model is applied, for the first time, for the estimation of allowed GT and unique first-forbidden (U1F) transitions (J = 2) of neutron rich copper isotopes in mass range 72 A 82 under stellar conditions. We compared our computed terrestrial -decay half-life values with previous calculations and experimental results. It was concluded that the pn-QRPA calculation is in good accordance with measured data. Our study suggests that the addition of rank (0 and 1) operators in FF transitions can further improve the comparison which remain unattended at this stage. The deformed pn-QRPA model was employed for the estimation of GT and U1F stellar electron emission (-decay) rates over wide range of stellar temperature (0.01 GK -- 30 GK) and density (10 -- 10 g/cm) domains for astrophysical applications. Our study shows that, in high density and low temperature regions, the contribution of U1F rates to total electron emission rates of neutron-rich copper nuclei is negligible.
Jameel-Un Nabi · Muhammad Majid
Charge-changing transitions play a significant role in stellar weak-decay processes. The fate of the massive stars is decided by these weak-decay rates including lepton (positron and electron) captures rates, which play a consequential role in the dynamics of core collapse. As per previous simulation results, weak interaction rates on nickel isotopes have significant influence on the stellar core vis--vis controlling the lepton content of stellar matter throughout the silicon shell burning phases of high mass stars up to the presupernova stages. In this paper we perform a microscopic calculation of Gamow-Teller charge-changing transitions, in the -decay and electron capture directions, for neutron-rich nickel isotopes (Ni). We further compute the associated weak-decay rates for these selected nickel isotopes in stellar environment. The computations are accomplished by employing the deformed proton-neutron quasiparticle random phase approximation (pn-QRPA) model. A recent study showed that the deformed pn-QRPA theory is well suited for the estimation of Gamow-Teller transitions. The astral weak-decay rates are determined over densities in the range of 10 -- 10g/cm and temperatures in the range of 0.0110 -- 3010K. The calculated lepton capture rates are compared with the previous calculation of Pruet and Fuller. The overall comparison demonstrates that, at low stellar densities and high temperatures, our electron captures rates are bigger by as much as two orders of magnitude. Our results show that, at higher temperatures, the lepton capture rates are the dominant mode for the stellar weak rates and the corresponding lepton emission rates may be neglected.
Jameel-Un Nabi🇵🇰 · Mahmut Boyukata🇨🇭
The structure and the weak interaction mediated rates of the heavy waiting point (WP) nuclei Zr, Mo, Ru, Pd and Cd along line were studied within the interacting boson model-1 (\mbox{IBM-1}) and the proton-neutron quasi-particle random phase approximation (\mbox{pn-QRPA}). The energy levels of the = WP nuclei were calculated by fitting the essential parameters of \mbox{IBM-1} Hamiltonian and their geometric shapes were predicted by plotting potential energy surfaces (PESs). Half-lives, continuum electron capture rates, positron decay rates, electron capture cross sections of WP nuclei, energy rates of -delayed protons and their emission probabilities were later calculated using the \mbox{pn-QRPA}. The calculated Gamow-Teller strength distributions were compared with previous calculation. We present positron decay continuum electron capture rates on these WP nuclei under -process conditions using the same model. For the -process conditions, the calculated total weak rates are twice the Skyrme HF+BCS+QRPA rates for Zr. For remaining nuclei the two calculations compare well. The electron capture rates are significant and compete well with the corresponding positron decay rates under -process conditions. The finding of the present study supports that electron capture rates form an integral part of the weak rates under -process conditions and has an important role for the nuclear model calculations.
Ashutosh Dwibedi · Dushmanta Sahu · Jayanta Dey · Kangkan Goswami · Sabyasachi Ghosh · Raghunath Sahoo
The Lagrangian for strongly interacting and rotating quark matter is modified with the inclusion of the spinorial connections, which in turn affect the thermodynamic equation of state and transport properties of the medium. In this work, we investigate the transport properties of quark matter under finite rotation, focusing specifically on electrical conductivity and shear viscosity by using a two-flavor Nambu--Jona-Lasinio (NJL) model. The chiral condensate in the NJL model decreases under rotation, leading to enhanced transport properties. Moreover, rotation induces anisotropy in the transport coefficients, which are calculated within the kinetic theory framework using the Boltzmann transport equation. The Coriolis force is introduced in the force term of the Boltzmann transport equation, like the Lorentz force, which is considered for finite magnetic fields. By using a phenomenological temperature-dependent angular velocity, we observe that the variation of anisotropic components with temperature preserves the traditional valley-shaped pattern. However, the magnitude of the anisotropic components is suppressed compared to the usual component one finds in the absence of rotation. Interestingly, at zero net quark density, Hall-like transport phenomena emerge as significant non-dissipative contributions under rotation, which is not expected under finite magnetic fields due to the cancellation of quark and anti-quark Hall currents.
The nature of confinement is connected with color charge. Unfortunately, the color charge densities in QCD, the Noether charge densities associated with the global color invariance, are not invariant under local color rotations. This implies that the expectation values of the net color charge in any region of any physical state in QCD, states that satisfy the color Gauss law, are automatically zero for all components of color. In this paper it is shown that the expectation value of the square of the net color charge in a region, a measure of the color charge fluctuations, is necessarily nonzero when evaluated in physical states and the result, while depending on the scheme and scale by which the theory is regulated, is gauge invariant. This holds despite the formal lack of gauge invariance of the operator. Moreover, there is a particular combination of the color charge fluctuations for the vacuum and for a system describable by a non-trivial density matrix that is independent that has a well-defined continuum limit
Wren Yamada🇯🇵 · Osamu Morimatsu🇯🇵 · Toru Sato🇯🇵 · Koichi Yazaki🇯🇵
We analyze the pole expansion of the two-hadron imaginary-time correlation function. We first explain the general idea that the imaginary-time correlation function is expressed as a sum of the pole terms, the Mittag-Leffler expansion, in terms of the uniformization variable, which makes the S-matrix single-valued. We then derive explicit expressions of the pole expansion for the single-channel ( meson) and two-channel () examples and demonstrate that the pole expansion actually holds employing phenomenological models, the vector-dominance model for the meson and the chiral unitary model for . From this observation we propose the pole expansion as a method to extract information of unstable states such as masses and widths from the two-hadron imaginary-time correlation functions obtained by lattice QCD simulations.
We investigate how the stabilizer formalism, in particular highly-entangled stabilizer states, can be used to describe the emergence of many-body shape collectivity from individual constituents, in a symmetry-preserving and classically efficient way. The method that we adopt is based on determining an optimal separation of the Hamiltonian into a stabilizer component and a residual part inducing non-stabilizerness. The corresponding stabilizer ground state is efficiently prepared using techniques of graph states and stabilizer tableaux. We demonstrate this technique in context of the Lipkin-Meshkov-Glick model, a fully-connected spin system presenting a second order phase transition from spherical to deformed state. The resulting stabilizer ground state is found to capture to a large extent both bi-partite and collective multi-partite entanglement features of the exact solution in the region of large deformation. We also explore several methods for injecting non-stabilizerness into the system, including ADAPT-VQE, and imaginary-time evolution (ITE) techniques. Stabilizer ground states are found to accelerate ITE convergence due to a larger overlap with the exact ground state. While further investigations are required, the present work suggests that collective features may be associated with high but simple large-scale entanglement which can be captured by stabilizer states, while the interplay with single-particle motion may be responsible for inducing non-stabilizerness. This study motivates applications of the proposed approach to more realistic quantum many-body systems, whose stabilizer ground states can be used in combinations with powerful classical many-body techniques and/or quantum methods.
W. C. Haxton🇺🇸 · Xing Liu🇺🇸 · Annie McCutcheon🇺🇸 · Anupam Ray🇺🇸
We argue that Na is a potentially significant source of galactic axions. For temperatures K -- characteristic of carbon burning in the massive progenitors of supernovae and ONeMg white dwarfs -- the 440 keV first excited state of Na is thermally populated, with its repeated decays pumping stellar energy into escaping axions. Odd-A nuclear abundances are typically very low in high-temperature stellar environments (or absent entirely due to burn-up). Na is an exception: of the isotope is synthesized during carbon burning then maintained at K for times ranging up to y. Using MESA simulations, a galactic model, and sampling over progenitor masses, locations, and evolutionary stages, we find a continuous flux at earth of /cms for . Some fraction of these axions convert to photons as they propagate through the galactic magnetic field, producing a distinctive 440 keV line ray detectable by all-sky detectors like the Compton Spectrometer and Imager (COSI). Assuming a 1G galactic magnetic field and a sufficiently light axion mass, we find that COSI will be able to probe GeV at after two years of surveying.
Saraswati Pandey🇮🇳 · B.K. Singh🇮🇳
In this letter, we present the study of the role of octupole deformation in non-spherical nuclei in most-central Pb--Pb collisions at the LHC energy regime. The sensitivity of octupole deformation to the QGP observables is presented by employing the Monte Carlo HYDJET++ model. Motivated by the discrepancies in the -to- puzzle found in Pb--Pb collisions and the low-energy nuclear structure calculations of nuclear deformation, we studied the first basic observables necessary for any study in heavy-ion collisions. Using the HYDJET++ framework, we calculate the pseudorapidity distribution, transverse momentum () spectra, and average anisotropic flow ( and ) of primary charged hadrons with different parameters in two geometrical configurations: body-body and tip-tip types of Pb--Pb collisions. The kinematic ranges and are considered. We observe that the charged hadron multiplicity and transverse momentum spectra are dependent on the strength of the octupole deformation parameter. The and in body-body collisions show a weak positive correlation with , while the average anisotropic flow in tip-tip collisions is weakly correlated with in the most-central collision region.
Roland C. Farrell🇺🇸 · Nikita A. Zemlevskiy🇺🇸 · Marc Illa🇺🇸 · John Preskill🇺🇸
High-energy particle collisions can convert energy into matter through the inelastic production of new particles. Quantum computers are an ideal platform for simulating the out-of-equilibrium dynamics of collisions and the formation of subsequent many-particle states. In this work, evidence for inelastic particle production is observed in one-dimensional Ising field theory using IBM's quantum computers. The scattering experiment is performed on 104 qubits of ibm_marrakesh and uses up to 5,589 two-qubit gates to access the post-collision dynamics. An outgoing heavy particle produced in the collision is identified from the skewness of the measured energy density. Integral to this computation is a new quantum algorithm for preparing the initial state (wavepackets) of a quantum field theory scattering simulation. This method efficiently prepares wavepackets by extending recent protocols for creating W states with mid-circuit measurement and feedforward. The required circuit depth is independent of wavepacket size and spatial dimension, representing a superexponential improvement over previous methods. Our wavepacket preparation algorithm can be applied to a wide range of lattice models and is demonstrated in one-dimensional Ising field theory, scalar field theory, the Schwinger model and two-dimensional Ising field theory.
Zhaohui Wang🇨🇳 · Xiaofeng Luo🇨🇳
We propose a novel centrality definition-independent method for analyzing higher-order cumulants, specifically addressing the challenge of volume fluctuations that dominate in low-energy heavy-ion collisions. This method reconstructs particle number distributions using the Edgeworth expansion, with parameters optimized via a combination of differential evolution algorithm and Bayesian inference. Its effectiveness is validated using UrQMD model simulations and benchmarked against traditional approaches, including centrality definitions based on particle multiplicity. Our results show that the proposed framework yields cumulant patterns consistent with those obtained using number of participant nucleon () based centrality observables, while eliminating the conventional reliance on centrality determination. This consistency confirms the method's ability to extract genuine physical signals, thereby paving the way for probing the intrinsic thermodynamic properties of the produced medium through event-by-event fluctuations.
first authorsco-authorsvia INSPIRE