Nuclear Theory·nucl-th
19 papers—9 primary·10 cross-listed
In this article, we consider the Israel-Stewart equations of relativistic viscous fluid dynamics with bulk viscosity. We investigate the evolution of the equations linearized about solutions that satisfy the physical vacuum boundary condition and establish local well-posedness of the corresponding Cauchy problem.
Antonios Tsokaros🇺🇸 · Jamie Bamber🇺🇸 · Milton Ruiz🇪🇸 · Stuart L. Shapiro🇺🇸
Recent nonmagnetized studies of binary neutron star mergers have indicated the possibility of identifying equation of state features, such as a phase transition or a quark-hadron crossover, based on the frequency shift of the main peak in the postmerger gravitational wave spectrum. By performing a series of general relativistic, magnetohydrodynamic simulations we show that similar frequency shifts can be obtained due to the effect of the magnetic field. The existing degeneracy can either mask or nullify a shift due to a specific equation of state feature, and therefore the interpretation of observational data is more complicated than previously thought, requiring a more complete treatment that would necessarily include the neutron star's magnetic field.
Jamie Bamber🇺🇸 · Antonios Tsokaros🇺🇸 · Milton Ruiz🇪🇸 · Stuart L. Shapiro🇺🇸
The oscillation modes of neutron star (NS) merger remnants, as encoded by the kHz postmerger gravitational wave (GW) signal, hold great potential for constraining the as-yet undetermined equation of state (EOS) of dense nuclear matter. Previous works have used numerical relativity simulations to derive quasi-universal relations for the key oscillation frequencies, but most of them omit the effects of a magnetic field. We conduct full general-relativistic magnetohydrodynamics simulations of NSNS mergers with two different masses and two different EOSs (SLy and ALF2) with three different initial magnetic field topologies (poloidal and toroidal only, confined to the interior, and "pulsar-like": dipolar poloidal extending from the interior to the exterior), with four different magnetic field strengths with maximum values ranging from from to at the time of insertion. We find that magnetic braking and magnetic effective turbulent viscosity drives the merger remnants towards uniform rotation and increases their overall angular momentum loss. As a result, the frequency of the dominant postmerger GW mode shifts upwards over time. The overall shift is up to Hz for the strongest magnetic field we consider and Hz for the median case and is therefore detectable in principle by future GW observatories, which should include the magnetic field in their analyses. We also explore the impact of the magnetic field on the postmerger electromagnetic emission, and demonstrate that an extremely large magnetic field, or alternatively a significant shear viscosity mechanism, can cause a supramassive NS remnant to collapse to a BH in less than 100ms and lead to jet formation, although we do not expect the conditions for such an outcome to be realistic.
Matteo D'Anna🇨🇭 · Marina Krstic Marinkovic🇨🇭 · Joao C. Pinto Barros🇨🇭
Quantum electrodynamics in 1 + 1D (QED2) shares intriguing properties with QCD, including confinement, string breaking, and interesting phase diagram when the non-trivial topological -term is considered. Its lattice regularization is a commonly used toy model for quantum simulations of gauge theories on near-term quantum devices. In this work, we address algorithms for adiabatic state preparation in digital quantum simulations of QED2. We demonstrate that, for specific choices of parameters, the existing adiabatic procedure leads to level crossing between states of different charge sectors, preventing the correct preparation of the ground state. We further propose a new adiabatic Hamiltonian and verify its efficiency in targeting systems with a nonzero topological -term and in studying string breaking phenomena.
Sukhendu Saha · Dipali Basak · Tanmoy Bar · Lalit Kumar Sahoo · Jagannath Datta · Sandipan Dasgupta · Norikazu Kinoshita · Chinmay Basu
The proton capture cross-section of the least abundant proton-rich stable isotope of cadmium, Cd (abundance 0.89\%), has been measured near the Gamow window corresponding to a temperature range of 3-4 GK. The measurement of the Cd(p,)In reaction was carried out using the activation technique. The cross-section at the lowest energy point of 3T, E= 2.28 MeV, has been reported for the first time. The astrophysical S-factor was measured in the energy range relevant to the astrophysical p-process, between E= 2.29 and 6.79 MeV. The experimental results have been compared with theoretical predictions of Hauser-Feshbach statistical model calculations using TALYS-1.96. A calculated proton-optical potential was implemented to achieve better fitting, with different combinations of available nuclear level densities (NLDs) and -ray strength functions in TALYS-1.96. The calculations provided satisfactory agreement with the experimental results. The reaction rate was calculated using the calculated potential in TALYS-1.96 and compared with the values provided in the REACLIB database.
Fakeha Farooq · Jameel-Un Nabi · Ramoona Shehzadi
Key nuclear inputs for the astrophysical r process simulations are the weak interaction rates. Consequently, the accuracy of these inputs directly affects the reliability of nucleosynthesis modeling. Majority of the stellar rates, used in simulation studies, are calculated invoking the Brink Axel (BA) hypothesis. The BA hypothesis assumes that the strength functions of all parent excited states are the same as for the ground state, only shifted in energies. However, BA hypothesis has to be tested against microscopically calculated state by state rates. In this project we study the impact of the BA hypothesis on calculated stellar \b{eta} decay and electron capture rates. Our investigation include both Unique First Forbidden (U1F) and allowed transitions for 106 neutron rich trans iron nuclei ([27, 77] less than equal to [Z, A] less than equal to [82, 208]). The calculations were performed using the deformed proton-neutron quasiparticle randomphase approximation (pn QRPA) model with a simple plus quadrupole separable and schematic interaction. Waiting-point and several key r process nuclei lie within the considered mass region of the nuclear chart.
B.F. Irgaziev · Abdul Kabir · Jameel-Un Nabi
The CNO cycle is the main source of energy in stars more massive than our Sun. It defines the energy production and the duration contributes in determining the lifetime of massive stars. The cycle is an important tool for the determination of the age of globular clusters. Radiative capture p plus 14N 15O plus {\gamma}, at energies of astrophysical interest, is one of the important processes in the CNO cycle. In this project, we apply a potential model to describe both non resonant and resonant reactions in the channels where radiative capture occurs through electric E1 transitions. We employed the R matrix method to describe the reactions going via M1 resonant transitions, when it was not possible to correctly reproduce the experimental data by a potential model. The partial components of the astrophysical S factor are calculated for all possible electric and magnetic dipole transitions in 15O. The linear extrapolated S factor at zero energy (S(0)) is in good agreement with earlier reported values for all types of transitions considered in this work. Based on the value of the total astrophysical S factor, depending on the collision energy, we calculate the nuclear reaction rates for p plus 14N 15O plus {\gamma}. The computed rates are in good agreement with the results of the NACRE II Collaboration and the most recent existing measurements.
Maxim Virta🇫🇮 · Jasper Parkkila🇵🇱 · Dong Jo Kim🇫🇮
Improved constraints on current model parameters in a heavy-ion collision model are established using the latest measurements from three distinct collision systems. Various observables are utilized from Au--Au collisions at ~GeV and Pb--Pb collisions at ~TeV and ~TeV. Additionally, the calibration of centrality is now carried out separately for all parametrizations. The inclusion of an Au--Au collision system with an order of magnitude lower beam energy, along with separate centrality calibration, suggests a preference for smaller values of nucleon width, minimum volume per nucleon, and free-streaming time. The results with the acquired \textit{maximum a posteriori} parameters show improved agreement with the data for the second-order flow coefficient, identified particle yields, and mean transverse momenta. This work contributes to a more comprehensive understanding of heavy-ion collision dynamics and sets the stage for future improvements in theoretical modeling and experimental measurements.
Angel S. Miramontes🇪🇸 · K. Raya🇪🇸 · A. Bashir🇲🇽 · P. Roig🇪🇸 · G. Paredes-Torres🇲🇽
We investigate the properties of the radially excited charged pion, with a specific focus on its electromagnetic form factor (EFF) and its box contribution to the hadronic light-by-light (HLbL) component of the muon's anomalous magnetic moment, . Utilizing a coupled non-perturbative framework combining Schwinger-Dyson and Bethe-Salpeter equations, we first compute the mass and weak decay constant of the pion's first radial excitation. Initial results are provided for the Rainbow-Ladder (RL) approximation, followed by an extended beyond RL (BRL) analysis that incorporates meson cloud effects. Building on our previous work, this analysis demonstrates that an accurate description of the first radial excitation can be achieved without the need for a reparametrization of the interaction kernels. Having demonstrated the effectiveness of the truncation scheme, we proceed to calculate the corresponding EFF, from which we derive the contribution of the pion's first radial excitation to the HLbL component of the muon's anomalous magnetic moment, producing , . Our computation also sets the groundwork for calculating related pole contributions of excited pseudoscalar mesons to .
Theo F. Motta🇩🇪 · Julian Bernhardt🇩🇪 · Michael Buballa🇩🇪 · Christian S. Fischer🇩🇪
In this letter, we discuss a novel method to search for inhomogeneous chiral symmetry breaking in theories with fermions. The prime application we have in mind is QCD, but the method is also applicable for other theories, including solid-state applications. It is based on an extension of the chiral susceptibility to inhomogeneous phases and it works as a stability analysis. Our method allows us to determine when homogeneous solutions have the tendency to create spatially modulated condensates. As proof of principle, we apply this technique to a rainbow-ladder QCD model and find that its phase diagram contains an inhomogeneous region.
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