Let （V, U） be the vertex-partition of tree T as a bipartite graph. T is called an （m, n）-tree if ｜V｜ = m and ｜U｜ = n. For given positive integers m, n and d, the maximum spectral radius of all （m, n）-trees o...Let （V, U） be the vertex-partition of tree T as a bipartite graph. T is called an （m, n）-tree if ｜V｜ = m and ｜U｜ = n. For given positive integers m, n and d, the maximum spectral radius of all （m, n）-trees on diameter d are obtained, and all extreme graphs are determined.展开更多
A two-dimensional Brans-Dicke star model with exotic matter and dark energy is studied in this paper,the field equation and balance equation are derived at finite temperature,the analytic solutions of these equations ...A two-dimensional Brans-Dicke star model with exotic matter and dark energy is studied in this paper,the field equation and balance equation are derived at finite temperature,the analytic solutions of these equations canbe used to calculate the mass of star.In addition,we find that star's mass has a minimum when matter state parameterγ→0.展开更多
In order to study the structure of neutralino star and dark galaxy, we consider dynamical interactions due to boson-exchange in the neutralino matter. Taking into account interactions of neutralinos with bosons, we de...In order to study the structure of neutralino star and dark galaxy, we consider dynamical interactions due to boson-exchange in the neutralino matter. Taking into account interactions of neutralinos with bosons, we derive the equation of state （EOS） of neutralino stars in terms of the relativistic mean-field approach. Then we apply the resulting EOS to investigate properties of the neutralino star such as its density profile and mass limit. For example, if the neutralino mass is around 1 TeV, the Oppenheimer mass limit of the neutralino star is obtained as 6.06 ×10^-7 M⊙, and the corresponding radius is about 7.8 mm. Actually, due to an increasing annihilation rate as indicated by our calculation, this dense state can never be realized in practice. Our results also show that the low-density neutralino star may be a possible aggregation of the cold dark matter.展开更多
We have investigated the possibility of the presence of the deltas in neutron star matter and their effects on neutron stars. Δ-meson couplings of the theoretical predictions are only restricted in a region where the...We have investigated the possibility of the presence of the deltas in neutron star matter and their effects on neutron stars. Δ-meson couplings of the theoretical predictions are only restricted in a region where the deltas can be present and even a first-order phase transition may take place, making the EOS sorer and the maximum mass of neutron stars smaller. The presence of the deltas leads to the rapid decrease of neutrino mean free paths.展开更多
The influence of trapped neutrinos on the proto-neutron star is studied in the framework of relativistic mean-field theory. The results show that trapped neutrinos increase proton fraction and make the equation of sta...The influence of trapped neutrinos on the proto-neutron star is studied in the framework of relativistic mean-field theory. The results show that trapped neutrinos increase proton fraction and make the equation of state of neutron star matter softer when neglecting hyperonic freedom, while suppress the appearance of hyperons and make the equation of state stiffer when including hyperons in the protoneutron star. The maximum mass, compared with cold neutron star which is in beta equilibrium, decreases by 0.06M⊙ for non-strange protoneutron star while increases by 0.21M ⊙ for protoneutron star with hyperons when the relative number of trapped neutrino is 0.4.展开更多
基金Supported by the Department Fund of Science and Technology in Tianjin Higher Education Institutions(20050404)
文摘Let （V, U） be the vertex-partition of tree T as a bipartite graph. T is called an （m, n）-tree if ｜V｜ = m and ｜U｜ = n. For given positive integers m, n and d, the maximum spectral radius of all （m, n）-trees on diameter d are obtained, and all extreme graphs are determined.
基金Supported by the Natural Science Foundation of Sichuan Education Committee under Grant No.08ZA038
文摘A two-dimensional Brans-Dicke star model with exotic matter and dark energy is studied in this paper,the field equation and balance equation are derived at finite temperature,the analytic solutions of these equations canbe used to calculate the mass of star.In addition,we find that star's mass has a minimum when matter state parameterγ→0.
基金The project partly supported by National Natural Science Foundation of China
文摘In order to study the structure of neutralino star and dark galaxy, we consider dynamical interactions due to boson-exchange in the neutralino matter. Taking into account interactions of neutralinos with bosons, we derive the equation of state （EOS） of neutralino stars in terms of the relativistic mean-field approach. Then we apply the resulting EOS to investigate properties of the neutralino star such as its density profile and mass limit. For example, if the neutralino mass is around 1 TeV, the Oppenheimer mass limit of the neutralino star is obtained as 6.06 ×10^-7 M⊙, and the corresponding radius is about 7.8 mm. Actually, due to an increasing annihilation rate as indicated by our calculation, this dense state can never be realized in practice. Our results also show that the low-density neutralino star may be a possible aggregation of the cold dark matter.
基金The project supported by National Natural Science Foundation of China under Grant Nos.10575005 and 10435080the Key Grant Project of the Ministry of Education under Grant No.305001
文摘We have investigated the possibility of the presence of the deltas in neutron star matter and their effects on neutron stars. Δ-meson couplings of the theoretical predictions are only restricted in a region where the deltas can be present and even a first-order phase transition may take place, making the EOS sorer and the maximum mass of neutron stars smaller. The presence of the deltas leads to the rapid decrease of neutrino mean free paths.
基金The project supported by National Natural Science Foundation of China
文摘The influence of trapped neutrinos on the proto-neutron star is studied in the framework of relativistic mean-field theory. The results show that trapped neutrinos increase proton fraction and make the equation of state of neutron star matter softer when neglecting hyperonic freedom, while suppress the appearance of hyperons and make the equation of state stiffer when including hyperons in the protoneutron star. The maximum mass, compared with cold neutron star which is in beta equilibrium, decreases by 0.06M⊙ for non-strange protoneutron star while increases by 0.21M ⊙ for protoneutron star with hyperons when the relative number of trapped neutrino is 0.4.
