Výsledky vyhľadávania
Názov NICER data and a sigma-field-dependent stiffness of the hadronic equation of state Aut.údaje Evgeni Kolomeitsev, Dmitri Voskresensky Autor Kolomeitsev Evgeni E. 1970- ( 50%) UMBFP06 - Katedra fyziky
Spoluautori Voskresensky Dmitri (50%)
Zdroj.dok. Physical Review C. Vol. 110, no. 2 (2024), pp. 1-10. - Maryland : American Physical Society, 2024 Kľúč.slová neutrónové hviezdy nukleárna fyzika astrofyzika - astrophysics stavová rovnica Form.deskr. články - journal articles Jazyk dok. angličtina Krajina Spojené štáty Anotácia Analyses for the NICER data indicate that there is no significant variation of compact star radii within the mass range of 1.4 to 2.0 solar masses. Yamamoto et al. [Phys. Rev. C 108, 035811 (2023)] concluded recently that “this feature cannot be reproduced by the hadronic matter due to the softening of the equation of state (EoS) by hyperon mixing, suggesting the possible existence of quark phases in neutron-star interiors.” Using a collection of 162 purely nucleonic, hyperonic, and quarkish EoSs from the CompOSE database and some other works, we verify that hyperons indeed lead to a significant difference in radii of stars of 1.4 and 2.0 solar masses, which diminishes in the presence of quarks. We compare the shapes of the mass-radius curves and show that hyperons and quarks in the neutron star cores prefer a particular curve shape with backbending. It is argued that the shape is controlled by the density dependence of the nuclear symmetry energy. We draw attention to the existence of a class of purely hadronic relativistic mean-field EoSs with scalar-field dependent hadron masses and coupling constants that satisfy the known constraints on the EoSs including the analyses of the new NICER data and the above requirement of insignificant variation of the neutron star radii. URL Link na zdrojový dokument Kategória publikačnej činnosti ADC Číslo archívnej kópie 54690 Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika Názov Hyperon puzzle and the RMF model with scaled hadron masses and coupling constants Aut.údaje E. E. Kolomeitsev, K. A. Maslov, D. N. Voskresensky Autor Kolomeitsev Evgeni E. 1970- (96%) UMBFP06 - Katedra fyziky
Spoluautori Maslov K. A. (2%)
Voskresensky Dmitri (2%)
Zdroj.dok. Journal of Physics: Conference Series. Vol. 668 (2016), pp. 1-6. - Bristol : IOP Publishing, 2016 ; SQM 2015 medzinárodná konferencia Kľúč.slová stavová rovnica relativistický model stredného poľa neutrónové hviezdy equation of state relativistic mean-field models neutron stars Jazyk dok. angličtina Krajina Veľká Británia Systematika 533 Anotácia The equation of state of cold baryonic matter is studied within a relativistic mean-field model with hadron masses and coupling constants depending on a scalar field. We demonstrate that if the effective nucleon mass stops to decrease with a density increase at densities n > n > n0, where n0 is the nuclear saturation density, the equation of state stiffens for these densities and the limiting neutron star mass increases. The stabilization of the nucleon mass can be realised if in the equation of motion for the scalar mean-field there appear a term sharply varying in a narrow vicinity of the field value corresponding to the density n . We show several possible realizations of this mechanism getting sufficiently stiff equations of state. The appearance of hyperons in dense neutron star interiors is accounted for. The obtained equations of state remain sufficiently stiff if the reduction of the ϕ meson mass is incorporated. Thereby, the hyperon puzzle can be resolved Kategória publikačnej činnosti AFC Číslo archívnej kópie 35029 Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika Názov Relativistic mean-field models with scaled hadron masses and couplings Podnázov hyperons and maximum neutron star mass Aut.údaje K. A. Maslov, E. E. Kolomeitsev, D. N. Voskresensky Autor Maslov K. A. (1%)
Spoluautori Kolomeitsev Evgeni E. 1970- (98%) UMBFP06 - Katedra fyziky
Voskresensky Dmitri (1%)
Zdroj.dok. Nuclear Physics A. Vol. 950 (2016), pp. 64-109. - Amsterdam : Elsevier B.V., 2016 Kľúč.slová stavová rovnica equation of state neutrónové hviezdy neutron stars fyzika - physics Jazyk dok. angličtina Krajina Holandsko Systematika 53 Kategória publikačnej činnosti ADC Číslo archívnej kópie 36997 Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika Názov Viscosity of neutron star matter and r-modes in rotating pulsars Aut.údaje E. E. Kolomeitsev, D. N. Voskresensky Autor Kolomeitsev Evgeni E. 1970- (80%) UMBFP06 - Katedra fyziky
Spoluautori Voskresensky Dmitri (20%)
Zdroj.dok. Physical Review C : Nuclear Physics. Vol. 91, no. 2 (2015), pp. [1-35]. - Maryland : American Physical Society, 2015 Kľúč.slová neutrónové hviezdy neutron stars r-modes shear viscosity bulk viscosity superconductivity superfluidity Jazyk dok. angličtina Krajina Spojené štáty Systematika 539.1 Anotácia We study viscosity of the neutron star matter and $r$-mode instability in rotating neutron stars. Contributions to the shear and bulk viscosities from various processes are calculated accounting for in-medium modifications of the nucleon-nucleon interaction. A softening of the pion mode at densities larger than the nuclear saturation density $n_0$ and a possibility of the pion condensation at densities above $3/,n_0$ are included. The neutron-neutron and proton-proton pairings are incorporated, where necessary. In the shear viscosity we include the lepton contribution calculated taking into account the Landau damping in the photon exchange, the nucleon contribution described by the medium-modified one pion exchange, and some other terms, such as the novel phonon contribution in the 1S$_0$ superfluid neutron phase, and the neutrino term in the neutrino opacity region. The nucleon shear viscosity depends on the density rather moderately and proves to be much less than the lepton term. On the contrary, among the terms contributing to the bulk viscosity, induced by the delay of the relaxation of lepton concentrations in the star matter perturbed by the $r$-modes, the term from the two-nucleon medium modified Urca reactions possesses strongest density dependence (rising by several orders of magnitude for massive stars) because of the pion softening. Also, contributions to the bulk viscosity arising from other reactions induced by charged weak currents, e.g., in the Urca processes on a pion condensate and in direct Urca processes, are included. The radiative bulk viscosity induced by charged and neutral weak currents in the region of the neutrino transparency of the star is also calculated accounting for in-medium effects. We exploit the equation of state, which is similar to the Akmal-Pandharipande-Ravenhall equation of state up to $4/,n_0$, but is stiffer at higher densities, producing the maximum neutron star mass compatible with observations. The direct Urca processes do not appear up to $5/,n_0$ (corresponding to the star mass $M/simeq 1.9 M_{/odot}$). Computed with account of in-medium effects, the frequency boundary of the $r$-mode stability for the stars with the mass $/gsim 1.8 M_{/odot}$ proves to be above the frequencies of all rotating young pulsars. However, none of the conventional contributions to the viscosity are able to explain the stability of rapid rotation of old recycled pulsars in X-ray binaries. To solve this problem we propose a novel efficient mechanism associated with the appearance of condensates of low-lying modes of bosonic excitations with finite momentum and/or with an enhancement of the inhomogeneous pion/kaon condensates in some parts of the star, if the angular velocity exceeds a critical value Kategória publikačnej činnosti ADC Číslo archívnej kópie 32975 Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika Názov Making a soft relativistic mean-field equation of state stiffer at high density Aut.údaje K. A. Maslov, E. E. Kolomeitsev, D. N. Voskresensky Autor Maslov K. A. (25%)
Spoluautori Kolomeitsev Evgeni E. 1970- (50%) UMBFP06 - Katedra fyziky
Voskresensky Dmitri (25%)
Zdroj.dok. Physical Review C : Nuclear Physics. Vol. 92, no. 5 (2015), pp. [1-5]. - Maryland : American Physical Society, 2015 Kľúč.slová neutrónové hviezdy stavová rovnica relativistický model stredného poľa neutron stars equation of state relativistic mean-field models Jazyk dok. angličtina Krajina Spojené štáty Systematika 531 Kategória publikačnej činnosti ADC Číslo archívnej kópie 34334 Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika Názov Solution of the hyperon puzzle within a relativistic mean-field model Aut.údaje K. A. Maslov, Evgeni E. Kolomeitsev, D. N. Voskresensky Autor Maslov K. A. (34%)
Spoluautori Kolomeitsev Evgeni E. 1970- (33%) UMBFP06 - Katedra fyziky
Voskresensky Dmitri (33%)
Zdroj.dok. Physics Letters B. Vol. 748 (2015), pp. 369-375. - Amsterdam : Elsevier B.V., 2015 Kľúč.slová neutrónové hviezdy neutron stars relativistic mean-field models hyperons Jazyk dok. angličtina Krajina Holandsko Kategória publikačnej činnosti ADC Číslo archívnej kópie 33613 Katal.org. BB301 - Univerzitná knižnica Univerzity Mateja Bela v Banskej Bystrici Báza dát xpca - PUBLIKAČNÁ ČINNOSŤ Odkazy PERIODIKÁ-Súborný záznam periodika