【摘要】：中子星由于其極端的物理?xiàng)l件,一直是核物理和天體物理學(xué)的研究熱點(diǎn)。在關(guān)于中子星問題的研究中,尋找合適的狀態(tài)方程(EOS)一直是長期的目標(biāo)與中心的任務(wù)。中子星物質(zhì)的狀態(tài)方程很大程度上決定了中子星的質(zhì)量半徑關(guān)系。然而,對(duì)于高密下的狀態(tài)方程仍然存在相當(dāng)大的理論不確定性,不同理論模型給出的結(jié)果也存在很大的分歧。并且,最新研究表明目前許多理論模型給出的質(zhì)量-半徑關(guān)系都不符合天文觀測(cè),尤其是理論給出的中子星半徑都普遍偏大。近幾十年來,相對(duì)論平均場(RMF)理論在原子核結(jié)構(gòu)、原子核反應(yīng)和核天體物理等領(lǐng)域取得了很大的成功。被廣泛使用的RMF理論忽略了同位旋矢量標(biāo)量δ介子自由度。最近,有人利用擬合大量微觀從頭計(jì)算的結(jié)果將同位旋矢量矢量道和同位旋矢量標(biāo)量道分離擬合出了一組包含δ介子的高精度參數(shù)DD-MEδ.本論文的主要工作是基于密度依賴的相對(duì)論平均場(DDRMF)理論,利用包含δ介子自由度的參數(shù)DD-MEδ與另三組廣泛使用的不含δ介子的DDRMF模型參數(shù)DD.ME2,TW99,和PKDD,計(jì)算了一些核物質(zhì)和中子星的性質(zhì),并詳細(xì)討論了δ介子對(duì)于非對(duì)稱核物質(zhì)高密區(qū)域狀態(tài)方程的影響。結(jié)果表明同位旋矢量標(biāo)量道會(huì)影響核子的有效質(zhì)量和同位旋標(biāo)量標(biāo)量σ場從而軟化非對(duì)稱核物質(zhì)的狀態(tài)方程,并且會(huì)影響核物質(zhì)對(duì)稱能在高密區(qū)域的密度依賴行為。由于δ介子對(duì)核物質(zhì)對(duì)稱能的影響,DD-MEδ給出了較高的中子星內(nèi)部質(zhì)子比例,得到的質(zhì)子比例足以支持質(zhì)量大于1.86M⊙的中子星發(fā)生直接Urca過程。DD-MEδ參數(shù)給出的中子星的最大質(zhì)量極限為1.97M⊙,這一結(jié)果與目前觀測(cè)到的最重的中子星PSR J1614-2230(1.97±0.04 M⊙)和PSR J0348+0432'(2.01 ±0.04 M⊙)的質(zhì)量恰好一致。在所選的幾組參數(shù)中,DD-MEδ給出的中子星半徑最小,1.4M⊙中子星的半徑與目前的天文觀測(cè)也十分相符。這一符合天文觀測(cè)的結(jié)果證實(shí)了在相對(duì)論平均場模型框架下引入6介子的必要性。
[Abstract]:Neutron stars have been a hot research area in nuclear physics and astrophysics because of their extreme physical conditions. In the study of neutron stars, finding a suitable equation of state (EOS) has always been a long-term goal and central task. The equation of state of neutron star matter largely determines the mass radius relation of neutron star. However, there is still considerable theoretical uncertainty for the equation of state under high density, and the results given by different theoretical models are also very different. Moreover, recent studies show that the mass-radius relationship given by many theoretical models does not accord with astronomical observations, especially that the neutron star radius is generally larger. In recent decades, the relativistic mean field (RMF) theory has achieved great success in the fields of nuclear structure, nuclear reaction and nuclear astrophysics. The widely used RMF theory ignores the isospin vector scalar 未 meson degree of freedom. Recently, a group of high-precision parameters, DD-ME 未, containing 未 mesons, have been fitted separately from the isospin vector channel and the isospin vector scalar channel by using a large number of microcosmic ab initio calculations. The main work of this thesis is based on the density dependent relativistic mean field (DDRMF) theory, using the parameter DD-ME 未 which includes the degree of freedom of 未 mesons and the other three widely used DDRMF model parameters DD.ME2,TW99, and PKDD, without 未 mesons. The properties of some nuclear matter and neutron star are calculated, and the effect of 未 meson on the equation of state in the high density region of asymmetric nuclear matter is discussed in detail. The results show that the isospin vector scalar channel will affect the effective mass of the nucleon and the 蟽 field of the isospin scalar, thus softening the equation of state of the asymmetric nuclear matter, and will also affect the density dependent behavior of the symmetric energy of the nuclear matter in the high density region. Due to the effect of 未 mesons on the symmetric energy of nuclear matter, DD-ME 未 gives a higher proton ratio in neutron stars. The proton ratio obtained is sufficient to support the direct Urca process of neutron stars with a mass greater than 1.86m. The maximum mass limit of the neutron stars given by the DD-ME 未 parameter is 1.97m 298. The results are in good agreement with the mass of the heaviest neutron star PSR J1614-2230 (1.97 鹵0.04M) and PSR J0348 0432'( 2.01 鹵0.04M). Among the selected parameters, the radius of the neutron star given by DD-ME 未 is the smallest, and the radius of the 1.4 m ~ (-) ~ (*) neutron star is in good agreement with the present astronomical observations. The results obtained in accordance with astronomical observations confirm the necessity of introducing 6 mesons in the framework of the relativistic mean field model.
【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P145.6;O571

【共引文獻(xiàn)】

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