The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
P Haensel - One of the best experts on this subject based on the ideXlab platform.
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Hyperons in neutron star cores and a 2 m pulsar
Astronomy and Astrophysics, 2012Co-Authors: I Bednarek, P Haensel, J L Zdunik, M Bejger, R MankaAbstract:Context. A recent measurement of the mass of PSR J1614-2230 rules out most existing models of the equation of state (EOS) of dense matter that is subjected to the high-density softening caused by either hyperonization or a phase transition to either quark matter or a boson condensate. Aims. We attempt to resolve the apparent differences between the predictions derived from up-to-date hypernuclear data, which in- clude the appearance of Hyperons at about three nuclear densities and the existence of a M = 2.0 Mneutron star. Methods. We consider a non-linear relativistic mean field (RMF) model involving the baryon octet coupled to meson fields. An effective Lagrangian includes quartic terms in the meson fields. The values of the model parameters are obtained by fitting the semi- empirical parameters of nuclear matter at the saturation point, as well as potential wells for Hyperons in nuclear matter and the strength of the Λ − Λ attraction in double-Λ hypernuclei. Results. We propose a non-linear RMF model that is consistent with up-to-date semi-empirical nuclear and hypernuclear data and allows for neutron stars with hyperon cores and M > 2 M� . The model involves hidden-strangeness scalar and vector mesons, coupled only to Hyperons, and quartic terms involving vector meson fields. Conclusions. Our EOS involving Hyperons is stiffer than the corresponding nucleonic EOS (in which Hyperons are artificially sup- pressed) above five nuclear densities. The required stiffening is generated by the quartic terms involving the hidden-strangeness vector meson.
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Hyperons in neutron star cores and two solar mass pulsar
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: I Bednarek, P Haensel, J L Zdunik, M Bejger, R MankaAbstract:Recent measurement of mass of PSR J1614-2230 rules out most of existing models of equation of state (EOS) of dense matter with high-density softening due to hyperonization or a phase transition to quark matter or a boson condensate. We look for a solution of an apparent contradiction between the consequences stemming from up-to-date hypernuclear data, indicating appearance of Hyperons at 3 nuclear densities and existence of a two-solar-mass neutron star. We consider a non-linear relativistic mean field (RMF) model involving baryon octet coupled to meson fields. An effective lagrangian includes quartic terms in the meson fields. The values of the parameters of the model are obtained by fitting semi-empirical parameters of nuclear matter at the saturation point, as well as potential wells for Hyperons in nuclear matter and the strength of the Lambda-Lambda attraction in double-Lambda hypernuclei. We propose a non-linear RMF model which is consistent with up-to-date semiempirical nuclear and hypernuclear data and allows for neutron stars with hyperon cores and M larger than 2 solar masses. The model involves hidden-strangenes scalar and vector mesons, coupled to Hyperons only, and quartic terms involving vector meson fields. Our EOS involving Hyperons is stiffer than the corresponding nucleonic EOS (with Hyperons artificially suppressed) above five nuclear densities. Required stiffening is generated by the quartic terms involving hidden-strangeness vector meson.
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bulk viscosity in superfluid neutron star cores iii effects of mathsf sigma Hyperons
Astronomy and Astrophysics, 2002Co-Authors: P Haensel, K P Levenfish, D G YakovlevAbstract:The bulk viscosity of neutron star cores containing Hyperons is studied taking into account non-equilibrium weak process $\rm n+n \rightleftharpoons p+\Sigma^-$. The rapid growth of the bulk viscosity within the neutron star core associated with switching on new reactions (modified Urca process, direct Urca process, hyperon reactions) is analyzed. The suppression of the bulk viscosity by superfluidity of baryons is considered and found out to be very important.
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bulk viscosity in superfluid neutron star cores iii effects of sigma Hyperons
arXiv: Astrophysics, 2001Co-Authors: P Haensel, K P Levenfish, D G YakovlevAbstract:Bulk viscosity of neutron star cores containing Hyperons is studied taking into account non-equilibrium weak process $n+n \rightleftharpoons p+\Sigma^-$. Rapid growth of the bulk viscosity within the neutron star core associated with switching on new reactions (modified Urca process, direct Urca process, hyperon reactions) is analyzed. The suppression of the bulk viscosity by superfluidity of baryons is considered and found out to be very important.
D G Yakovlev - One of the best experts on this subject based on the ideXlab platform.
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bulk viscosity in superfluid neutron star cores iii effects of mathsf sigma Hyperons
Astronomy and Astrophysics, 2002Co-Authors: P Haensel, K P Levenfish, D G YakovlevAbstract:The bulk viscosity of neutron star cores containing Hyperons is studied taking into account non-equilibrium weak process $\rm n+n \rightleftharpoons p+\Sigma^-$. The rapid growth of the bulk viscosity within the neutron star core associated with switching on new reactions (modified Urca process, direct Urca process, hyperon reactions) is analyzed. The suppression of the bulk viscosity by superfluidity of baryons is considered and found out to be very important.
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bulk viscosity in superfluid neutron star cores iii effects of sigma Hyperons
arXiv: Astrophysics, 2001Co-Authors: P Haensel, K P Levenfish, D G YakovlevAbstract:Bulk viscosity of neutron star cores containing Hyperons is studied taking into account non-equilibrium weak process $n+n \rightleftharpoons p+\Sigma^-$. Rapid growth of the bulk viscosity within the neutron star core associated with switching on new reactions (modified Urca process, direct Urca process, hyperon reactions) is analyzed. The suppression of the bulk viscosity by superfluidity of baryons is considered and found out to be very important.
W Weise - One of the best experts on this subject based on the ideXlab platform.
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hyperon nucleon three body forces and strangeness in neutron stars
European Physical Journal A, 2020Co-Authors: Dominik Gerstung, Norbert Kaiser, W WeiseAbstract:Three-body forces acting on a $$\varLambda $$ hyperon in a nuclear medium are investigated, with special focus on the so-called hyperon puzzle in neutron stars. The hyperon–nucleon two-body interaction deduced from SU(3) chiral effective field theory is employed at next-to-leading order. Hyperon–nucleon three-body forces are approximated using saturation by decuplet baryons and are transcribed to density-dependent effective two-body interactions. These together are taken as input in a Brueckner–Bethe–Goldstone equation with explicit treatment of the $$\varLambda N\leftrightarrow \varSigma N$$ and $$\varLambda NN\leftrightarrow \varSigma NN$$ coupled channels. Single-particle potentials of a $$\varLambda $$ hyperon in symmetric nuclear matter and neutron matter are calculated. With parameters of the $$\varLambda NN$$ three-body force constrained by hypernuclear phenomenology, extrapolations to high baryon density are performed. By comparison of the $$\varLambda $$ and neutron chemical potentials at densities characteristic of the core of neutron stars it is found that the combined repulsive effects of two- and three-body correlations can make the appearance of $$\varLambda $$ Hyperons in neutron stars energetically unfavourable, thus potentially offering a possible answer to a longstanding query.
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hyperon nucleon three body forces and strangeness in neutron stars
arXiv: Nuclear Theory, 2020Co-Authors: Dominik Gerstung, Norbert Kaiser, W WeiseAbstract:Three-body forces acting on a $\Lambda$ hyperon in a nuclear medium are investigated, with special focus on the so-called hyperon puzzle in neutron stars. The hyperon-nucleon two-body interaction deduced from SU(3) chiral effective field theory is employed at next-to-leading order. Hyperon-nucleon three-body forces are approximated using saturation by decuplet baryons and are transcribed to density-dependent effective two-body interactions. These together are taken as input in a Brueckner-Bethe-Goldstone equation with explicit treatment of the $\Lambda N\leftrightarrow\Sigma N$ and $\Lambda NN\leftrightarrow\Sigma NN$ coupled channels. Single-particle potentials of a $\Lambda$ hyperon in symmetric nuclear matter and neutron matter are calculated. With parameters of the $\Lambda NN$ three-body force constrained by hypernuclear phenomenology, extrapolations to high baryon density are performed. By comparison of the $\Lambda$ and neutron chemical potentials at densities characteristic of the core of neutron stars it is found that the combined repulsive effects of two- and three-body correlations makes the appearance of $\Lambda$ Hyperons in neutron stars energetically unfavourable, thus offering a possible solution to a longstanding question.
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Hyperons in nuclear matter from su 3 chiral effective field theory
European Physical Journal A, 2016Co-Authors: Stefan Petschauer, J Haidenbauer, N Kaiser, Ulfg Meisner, W WeiseAbstract:Brueckner theory is used to investigate the properties of Hyperons in nuclear matter. The hyperon-nucleon interaction is taken from chiral effective field theory at next-to-leading order with SU(3) symmetric low-energy constants. Furthermore, the underlying nucleon-nucleon interaction is also derived within chiral effective field theory. We present the single-particle potentials of \( \Lambda\) and \( \Sigma\) Hyperons in symmetric and asymmetric nuclear matter computed with the continuous choice for intermediate spectra. The results are in good agreement with the empirical information. In particular, our calculation gives a repulsive \( \Sigma\) -nuclear potential and a weak \( \Lambda\) -nuclear spin-orbit force.
R Manka - One of the best experts on this subject based on the ideXlab platform.
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Hyperons in neutron star cores and a 2 m pulsar
Astronomy and Astrophysics, 2012Co-Authors: I Bednarek, P Haensel, J L Zdunik, M Bejger, R MankaAbstract:Context. A recent measurement of the mass of PSR J1614-2230 rules out most existing models of the equation of state (EOS) of dense matter that is subjected to the high-density softening caused by either hyperonization or a phase transition to either quark matter or a boson condensate. Aims. We attempt to resolve the apparent differences between the predictions derived from up-to-date hypernuclear data, which in- clude the appearance of Hyperons at about three nuclear densities and the existence of a M = 2.0 Mneutron star. Methods. We consider a non-linear relativistic mean field (RMF) model involving the baryon octet coupled to meson fields. An effective Lagrangian includes quartic terms in the meson fields. The values of the model parameters are obtained by fitting the semi- empirical parameters of nuclear matter at the saturation point, as well as potential wells for Hyperons in nuclear matter and the strength of the Λ − Λ attraction in double-Λ hypernuclei. Results. We propose a non-linear RMF model that is consistent with up-to-date semi-empirical nuclear and hypernuclear data and allows for neutron stars with hyperon cores and M > 2 M� . The model involves hidden-strangeness scalar and vector mesons, coupled only to Hyperons, and quartic terms involving vector meson fields. Conclusions. Our EOS involving Hyperons is stiffer than the corresponding nucleonic EOS (in which Hyperons are artificially sup- pressed) above five nuclear densities. The required stiffening is generated by the quartic terms involving the hidden-strangeness vector meson.
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Hyperons in neutron star cores and two solar mass pulsar
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: I Bednarek, P Haensel, J L Zdunik, M Bejger, R MankaAbstract:Recent measurement of mass of PSR J1614-2230 rules out most of existing models of equation of state (EOS) of dense matter with high-density softening due to hyperonization or a phase transition to quark matter or a boson condensate. We look for a solution of an apparent contradiction between the consequences stemming from up-to-date hypernuclear data, indicating appearance of Hyperons at 3 nuclear densities and existence of a two-solar-mass neutron star. We consider a non-linear relativistic mean field (RMF) model involving baryon octet coupled to meson fields. An effective lagrangian includes quartic terms in the meson fields. The values of the parameters of the model are obtained by fitting semi-empirical parameters of nuclear matter at the saturation point, as well as potential wells for Hyperons in nuclear matter and the strength of the Lambda-Lambda attraction in double-Lambda hypernuclei. We propose a non-linear RMF model which is consistent with up-to-date semiempirical nuclear and hypernuclear data and allows for neutron stars with hyperon cores and M larger than 2 solar masses. The model involves hidden-strangenes scalar and vector mesons, coupled to Hyperons only, and quartic terms involving vector meson fields. Our EOS involving Hyperons is stiffer than the corresponding nucleonic EOS (with Hyperons artificially suppressed) above five nuclear densities. Required stiffening is generated by the quartic terms involving hidden-strangeness vector meson.
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The influence of the strength of hyperon-hyperon interactions on neutron star properties
Journal of Physics G: Nuclear and Particle Physics, 2005Co-Authors: I Bednarek, R MankaAbstract:An equation of state of neutron star matter with strange baryons has been obtained. The effects of the strength of hyperon–hyperon interactions on the equations of state constructed for the chosen parameter sets have been analysed. Numerous neutron star models show that the appearance of Hyperons is connected with the increasing density in neutron star interiors. The performed calculations have indicated that a change of the hyperon–hyperon coupling constants affects the chemical composition of a neutron star. The obtained numerical hyperon star models exclude a large population of strange baryons in the star interior.
K P Levenfish - One of the best experts on this subject based on the ideXlab platform.
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bulk viscosity in superfluid neutron star cores iii effects of mathsf sigma Hyperons
Astronomy and Astrophysics, 2002Co-Authors: P Haensel, K P Levenfish, D G YakovlevAbstract:The bulk viscosity of neutron star cores containing Hyperons is studied taking into account non-equilibrium weak process $\rm n+n \rightleftharpoons p+\Sigma^-$. The rapid growth of the bulk viscosity within the neutron star core associated with switching on new reactions (modified Urca process, direct Urca process, hyperon reactions) is analyzed. The suppression of the bulk viscosity by superfluidity of baryons is considered and found out to be very important.
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bulk viscosity in superfluid neutron star cores iii effects of sigma Hyperons
arXiv: Astrophysics, 2001Co-Authors: P Haensel, K P Levenfish, D G YakovlevAbstract:Bulk viscosity of neutron star cores containing Hyperons is studied taking into account non-equilibrium weak process $n+n \rightleftharpoons p+\Sigma^-$. Rapid growth of the bulk viscosity within the neutron star core associated with switching on new reactions (modified Urca process, direct Urca process, hyperon reactions) is analyzed. The suppression of the bulk viscosity by superfluidity of baryons is considered and found out to be very important.