Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSupercritically charged objects and electron-positron pair creation
112
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We investigate the stability and $e^+e^-$ pair creation of supercritically charged superheavy nuclei, $ud$QM nuggets, strangelets, and strangeon nuggets based on Thomas-Fermi approximation. The model parameters are fixed by reproducing their masses and charge properties reported in earlier publications. It is found that $ud$QM nuggets, strangelets, and strangeon nuggets may be more stable than ${}^{56}$Fe at $Agtrsim 315$, $5times10^4$, and $1.2times10^8$, respectively. For those stable against neutron emission, the most massive superheavy element has a baryon number $sim$965, while $ud$QM nuggets, strangelets, and strangeon nuggets need to have baryon numbers larger than $39$, 433, and $2.7times10^5$. The $e^+e^-$ pair creation will inevitably start for superheavy nuclei with charge numbers $Zgeq177$, $ud$QM nuggets with $Zgeq163$, strangelets with $Zgeq 192$, and strangeon nuggets with $Zgeq 212$. A universal relation $Q/R_e = left(m_e - bar{mu}_eright)/alpha$ is obtained at a given electron chemical potential $bar{mu}_e$, where $Q$ is the total charge and $R_e$ the radius of electron cloud. This predicts the maximum charge number by taking $bar{mu}_e=-m_e$. For supercritically charged objects with $bar{mu}_e<-m_e$, the decay rate for $e^+e^-$ pair production is estimated based on the JWKB approximation. It is found that most positrons are emitted at $tlesssim 10^{-15}$ s, while a long lasting positron emission is observed for large objects with $Rgtrsim 1000$ fm. The emission and annihilation of positrons from supercritically charged objects may be partially responsible for the short $gamma$-ray burst during the merger of binary compact stars, the 511 keV continuum emission, as well as the narrow faint emission lines in X-ray spectra from galaxies and galaxy clusters.
rate research
Read More
Droplets of absolutely stable strange quark matter (strangelets) immersed in a lepton background may be the energetically preferred composition of strange star crusts and of the interior of a new class of stars known as strangelet dwarfs. In this work we calculate the surface tension $sigma$ and the curvature coefficient $gamma$ of charged strangelets as a function of the baryon number density, the temperature, the chemical potential of trapped neutrinos, the strangelet size, the electric potential and the electric charge at their boundary. Strange quark matter in chemical equilibrium and with global electric charge neutrality is described within the MIT bag model. We focus on three different astrophysical scenarios, namely cold strange stars, proto strange stars and post merger strange stars. Finite size effects are implemented within the multiple reflection expansion framework. We find that $sigma$ decreases significantly as the strangelets boundary becomes more positively charged. This occurs because $sigma$ is dominated by the contribution of $s$ quarks which are the most massive particles in the system. Negatively charged $s$-quarks are suppressed in strangelets with a large positive electric charge, diminishing their contribution to $sigma$ and resulting in smaller values of the total $sigma$. We verify that the more extreme astrophysical scenarios, with higher temperatures and higher neutrino chemical potentials, allow higher positive values of the strangelets electric charge at the boundary and consequently smaller values of $sigma$. In contrast, $gamma$ is strongly dominated by the density of light ($u$ and $d$) quarks and is quite independent of the charge-per-baryon ratio, the temperature and neutrino trapping. We discuss the relative importance of surface and curvature effects as well as some astrophysical consequences of these results.
Particles in quantum vortex states (QVS) carrying definite orbital angular momenta (OAM) brings new perspectives in various fundamental interaction processes. When unique properties arise in the QVS, understanding how OAM manifest itself between initial particles and the outcome in vortex particle collisions becomes essential. This is made possible by applying the complete vortex description for all involved particles such that angular momenta (AM) are represented by explicit quantum numbers and their connections are naturally retrieved. We demonstrate the full-vortex quantum-electrodynamics (QED) results for the Breit-Wheeler pair creation process and derive the AM-dependent selection rule. The numerically resolved cross-sections show anti-symmetric spin polarization and most importantly, the first OAM spectra in vortex collision processes. The latter reveals efficient conversion of OAM to created pairs, leading to featured hollow and ring-shaped structure in the density distribution. These results demonstrate a clear picture in understanding the OAM physics in the scattering processes of high energy particles.
A new method for calculations of electron-positron pair-creation probabilities in low-energy heavy-ion collisions is developed. The approach is based on the propagation of all one-electron states via the numerical solving of the time-dependent Dirac equation in the monopole approximation. The electron wave functions are represented as finite sums of basis functions constructed from B-splines using the dual-kinetic-balance technique. The calculations of the created particle numbers and the positron energy spectra are performed for the collisions of bare nuclei at the energies near the Coulomb barrier with the Rutherford trajectory and for different values of the nuclear charge and the impact parameter. To examine the role of the spontaneous pair creation the collisions with a modified velocity and with a time delay are also considered. The obtained results are compared with the previous calculations and the possibility of observation of the spontaneous pair creation is discussed.
An exact and regular solution, describing a couple of charged and spinning black holes, is generated in an external electromagnetic field, via Ernst technique, in Einstein-Maxwell gravity. A wormhole instantonic solution interpolating between the two black holes is constructed to discuss, at the semi-classical level, the quantum process of creation rate, in an external magnetic field, of this charged and spinning black hole pair.
Creation of electrons and positrons from light alone is a basic prediction of quantum electrodynamics, but yet to be observed. Here we show that it is possible to create ${>}10^8$ positrons by dual laser irradiation of a structured plasma target, at intensities of $2 times 10^{22} mathrm{W}mathrm{cm}^{-2}$. In contrast to previous work, the pair creation is primarily driven by the linear Breit-Wheeler process ($gammagamma to e^+ e^-$), not the nonlinear process assumed to be dominant at high intensity, because of the high density of $gamma$ rays emitted inside the target. The favorable scaling with laser intensity of the linear process prompts reconsideration of its neglect in simulation studies, but also permits positron jet formation at intensities that are already experimentally feasible. Simulations show that the positrons, confined by a quasistatic plasma magnetic field, may be accelerated by the lasers to energies $> 200$ MeV.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
