اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدPossibility of s-wave pion condensates in neutron stars revisited
52
0
0.0
(
0
)
تأليف
A. Ohnishi
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We examine possibilities of pion condensation with zero momentum (s-wave condensation) in neutron stars by using the pion-nucleus optical potential U and the relativistic mean field (RMF) models. We use low-density phenomenological optical potentials parameterized to fit deeply bound pionic atoms or pion-nucleus elastic scatterings. Proton fraction (Y_p) and electron chemical potential (mu_e) in neutron star matter are evaluated in RMF models. We find that the s-wave pion condensation hardly takes place in neutron stars and especially has no chance if hyperons appear in neutron star matter and/or b_1 parameter in U has density dependence.
قيم البحث
اقرأ أيضاً
Neutrino emission in processes of breaking and formation of neutron and proton Cooper pairs is calculated within the Larkin-Migdal-Leggett approach for a superfluid Fermi liquid. We demonstrate explicitly that the Fermi-liquid renormalization respect
s the Ward identity and assures the weak vector current conservation. The systematic expansion of the emissivities for small temperatures and nucleon Fermi velocity, v_{F,i}, i=n,p, is performed. Both neutron and proton processes are mainly controlled by the axial-vector current contributions, which are not strongly changed in the superfluid matter. Thus, compared to earlier calculations the total emissivity of processes on neutrons paired in the 1S_0 state is suppressed by a factor ~(0.9-1.2) v_{F,n}^2. A similar suppression factor (~v_{F,p}^2) arises for processes on protons.
Motivated by the recent gravitational wave detection by the LIGO-VIRGO observatories, we study the Love number and dimensionless tidal polarizability of highly magnetized stars. We also investigate the fundamental quasi-normal mode of neutron stars s
ubject to high magnetic fields. To perform our calculations we use the chaotic field approximation and consider both nucleonic and hyperonic stars. As far as the fundamental mode is concerned, we conclude that the role played by the constitution of the stars is far more relevant than the intensity of the magnetic field and if massive stars are considered, the ones constituted by nucleons only present frequencies somewhat lower than the ones with hyperonic cores, a feature that can be used to point out the real internal structure of neutron stars. Moreover, our studies clearly indicate that strong magnetic fields play a crucial role in the deformability of low mass neutron stars, with possible consequences on the interpretation of the detected gravitational waves signatures.
In this review we highlight a few physical properties of neutron stars and their theoretical treatment inasmuch as they can be useful for nuclear and particle physicists concerned with matter at finite density (and newly, temperature). Conversely, we
lay out some of the hadron physics necessary to test General Relativity with binary mergers including at least one neutron star, in view of the event GW170817: neutron stars and their mergers reach the highest matter densities known, offering access to the matter side of Einsteins equations. In addition to minimum introductory material for those interested in starting research in the field of neutron stars, we dedicate quite some effort to a discussion of the Equation of State of hadron matter in view of gravitational wave developments; we address phase transitions and how the new data may help; we show why transport is expected to be dominated by turbulence instead of diffusion through most if not all of the star, in view of the transport coefficients that have been calculated from microscopic hadron physics; and we relate many of the interesting physics topics in neutron stars to the radius and tidal deformability.
An $omega$-meson in motion with respect to a nuclear medium can couple to a $sigma$-meson through a particle-hole excitation. This coupling is large. We investigate its consequences for the width of $omega$-mesons in matter and for the s-wave annihil
ation of pions into lepton pairs which can take place in relativistic heavy ion collisions. We find that the two pion decay of $omega$-mesons, resulting from the $omega-sigma$ transition and the subsequent $2pi$ decay of the $sigma$-meson, leads to a substantial broadening of $omega$-mesons in matter and possibly to an observable effect in experiments measuring the $e^+e^-$ decay of vector mesons produced in nuclei and in relativistic heavy-ion collisions. The inverse process, the s-wave annihilation of pions into $omega$-mesons decaying into $e^+e^-$ pairs, has in general a much smaller cross section than the corresponding p-wave annihilation through $rho$-mesons and is expected to contribute rather little to the total $e^+e^-$ pair production in relativistic heavy ion collisions.
The total cross section for the $pp to pp pi^0$ reaction at energies close to threshold is calculated within the frame of a chiral perturbation theory, taking into account tree and one loop diagrams up to chiral order D=2. Two-pion loop contributions
dominate $pi^0$ production at threshold. The calculated cross section reproduces data, both scale and energy dependence, fairly well.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
