We consider the effect of density dependent dark matter on the neutron star mass, radius, and tidal deformability. Nuclear matter (normal matter) as well as the fermionic dark matter sector is considered in a mean field model. We adopt the two fluid formalism to investigate the effect of dark matter on the neutron star properties. In the two fluid picture, there is no direct interaction between the dark matter and the nuclear matter. Rather these two sectors interact only through gravitational interaction. The nuclear matter sector is described by the $σ-ω-ρ$ meson interaction in the "FSU2R" parameterization. In the dark matter sector, we use the Bayesian parameter optimization technique to fix the unknown parameters in the dark matter equation of state. In the two fluid picture, we solve the coupled Tolman-Oppenheimer-Volkoff (TOV) equations to obtain the mass and radius of dark matter admixed neutron stars (DANSs). We also estimate the effect of the density dependent dark matter sector on the tidal deformability of dark matter admixed neutron stars (DANSs).
Motivated by the various theoretical studies regarding the efficient capturing of dark matter by neutron stars, we explore the possible indirect effects of captured dark matter on the cooling mechanism of a neutron star. The equation of states for different configurations of dark matter admixed star at finite temperature is obtained using the relativistic mean-field formalism with the IOPB-I parameter set. We show that the variation in the dark matter momentum vastly modifies the neutrino emissivity through specific neutrino generating processes of the star. The specific heat and the thermal c…
Within the covariant density functional theory of nuclear matter we build equations of state of $Δ$-admixed compact stars. Uncertainties in the interaction of $Δ(1232)$ resonance states with nuclear matter, due to lack of experimental data, are accounted for by varying the coupling constants to scalar and vector mesonic fields. We find that, over a wide range of the parameter space allowed by nuclear physics experiments and astrophysical observations, cold catalyzed star matter exhibits a first order phase transition which persists also at finite temperature and out of $β$-equilibrium in the n…
We put constraints on the secondary component of GW190814 by analyzing the observational data of the event. The relativistic mean-field models are used to calculate the mass-radius profile and tidal deformability of the compact object, considering it as a massive neutron star with the presence of dark matter particles inside it. With the increase of dark matter percentage, the maximum mass, radius, and tidal deformability of the neutron star decreases. We observe that the predicted properties are well consistent with GW190814 observational data, suggesting the possibility of a dark matter admi…
Neutron Stars (NSs) are born as hot, lepton-rich objects that evolve according to the standard paradigm through subsequent stages where they radiate the excess of energy by emitting, first, neutrinos and, later on, photons. Current descriptions based on Standard Model calculations cannot fully explain all the existing cooling data series for the dozens of objects that have been reported. In this work, we consider the intriguing possibility that cooling NSs could be actually admixed with a fraction of light dark matter (LDM), $χ$. We focus on a particular case study assuming a generic light can…
We investigated compact stars consisting of cold quark matter and fermionic dark matter treated as two admixed fluids. We computed the stellar structures and fundamental radial oscillation frequencies for different masses of the dark fermion in the cases of weak and strong self-interacting dark matter. We found that the fundamental frequency can be dramatically modified and, in some cases, stable dark strange planets and dark strangelets with very low masses and radii can be formed.
The distribution of the dark matter (DM) in DM-admixed-neutron stars (DANSs) is supposed to be either a dense dark core or an extended dark halo, which is subject to the DM fraction of DANS ($f_χ$) and the DM properties, such as the mass ($m_χ$) and the strength of the self-interaction ($y$). In this paper, we perform an in-depth analysis of the formation criterion for dark core/dark halo and point out that the relative distribution of these two components is essentially determined by the ratio of the central enthalpy of the DM component to that of the baryonic matter component inside DANSs. F…
In this work, we study the effects of nuclear symmetry energy slope on neutron star dense matter equation of state and its impact on neutron star observables (mass-radius, tidal response). We construct the equation of state within the framework of covariant density functional theory implementing coupling schemes of non-linear and density-dependent models with viability of heavier non-nucleonic degrees of freedom. The slope of symmetry energy parameter ($L_{\text{sym}}$) is adjusted following density-dependence of isovector meson coupling to baryons. We find that smaller values of $L_{\text{sym…
We investigate the possible presence of dark matter (DM) in massive and rotating neutron stars (NSs). For the purpose we extend our previous work [1] to introduce a light new physics vector mediator besides a scalar one in order to ensure feeble interaction between fermionic DM and $β$ stable hadronic matter in NSs. The masses of DM fermion, the mediators and the couplings are chosen consistent with the self-interaction constraint from Bullet cluster and from present day relic abundance. Assuming that both the scalar and vector mediators contribute equally to the relic abundance, we compute th…
Two-fluid $f$-mode oscillations of dark-matter-admixed neutron stars
Institute of Astrophysics, Central China Normal University（华中师范大学天文物理研究所）；School of Optoelectronic Information Engineering, Institute of Astronomy and High Energy Physics, Hubei University of Education（湖北教育学院光电信息工程学院、天体与高能物理研究所）；School of Mathematics and Physics, China University of Geosciences（中国地质大学数学与物理学院）；School of Physics, Huazhong University of Science and Technology（华中科技大学物理学院）；INFN Sezione di Catania, Dipartimento di Fisica, Universitá di Catania（意大利国家核物理研究院卡塔尼亚分部、卡塔尼亚大学物理系）
Density-induced dark-baryon conversion in $Δ-$admixed hypernuclear neutron stars
Birangana Sati Sadhani Rajyik Vishwavidyalaya（比朗加纳·萨蒂·萨达尼·皇家大学）；Indian Institute of Science Education and Research, Tirupati（印度科学教育与研究学院提鲁帕提分校）；Wroclaw University of Science and Technology（弗罗茨瓦夫科技大学）；Institute of Theoretical Physics, Wroclaw University of Science and Technology（弗罗茨瓦夫科技大学理论物理研究所）；Physical Research Laboratory（物理研究实验室）
Finite-Temperature Axion-Admixed Neutron Stars in a Quarkyonic Crossover Framework
Institute of Physics, Sachivalaya Marg, Bhubaneswar-751005, India（印度布巴内斯瓦尔物理研究所）；Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India（印度孟买霍米巴巴哈国立研究所）；Department of Physics, Indira Gandhi Institute of Technology, Sarang, Dhenkanal, Odisha-759146, India（印度奥迪沙邦德赫卡纳尔萨拉格英迪拉甘地理工学院物理系）
Yanshan University（燕山大学）；Tsinghua University（清华大学）；Lanzhou University（兰州大学）；China University of Petroleum (East China)（中国石油大学（华东））；Nankai University（南开大学）
The concept of boson stars (BSs) was first introduced by Kaup and Ruffini-Bonazzola in the 1960s. Following this idea, we investigate an effect of self-interacting asymmetric bosonic dark matter (DM) according to Colpi et al. model for BSs (1986) on different observable properties of neutron stars (NSs). In this paper, the bosonic DM and baryonic matter (BM) are mixed together and interact only through gravitational force. The presence of DM as a core of a compact star or as an extended halo around it is examined by applying different boson masses and DM fractions for a fixed coupling constant…
We use a set of hadronic equations of state derived from covariant density functional theory to study the impact of their high-density behavior on the properties of rapidly rotating $Δ$-resonance-admixed hyperonic compact stars. In particular, we explore systematically the effects of variations of the bulk energy isoscalar skewness, $Q_{\mathrm{sat}}$, and the symmetry energy slope, $L_{\mathrm{sym}}$, on the masses of rapidly rotating compact stars. With models for equation of state satisfying all the modern astrophysical constraints, excessively large gravitational masses of around $2.5 \, M…
We study the composition of nuclear matter at sub-saturation densities, non-zero temperatures, and isospin asymmetry, under the conditions characteristic of binary neutron star mergers, stellar collapse, and low-energy heavy-ion collisions. The composition includes light clusters with mass number $A\le 4$, a heavy nucleus ($\isotope[56]{Fe}$), the $Δ$-resonances, the isotriplet of pions, as well as the $Λ$ hyperon. The nucleonic mean-fields are computed from a zero-range density functional, whereas the pion-nucleon interactions are treated to leading order in chiral perturbation theory. We sho…
We investigate the effects of dark matter (DM) on the nuclear equation of state (EoS) and neutron star structure, in the relativistic mean field theory, both in the absence and presence of a crust. The $σ-ω$ model is modified by adding a WIMP-DM component, which interacts with nucleonic matter through the Higgs portal. This model agrees well with previous studies which utilized either a more complicated nuclear model or higher-order terms of the Higgs potential, in that DM softens the EoS, resulting in stars with lower maximum masses. However, instabilities corresponding to negative pressure v…
We use covariant density functional theory to obtain the equation of state (EoS) of matter in compact stars at non-zero temperature, including the full baryon octet as well as the $Δ(1232)$ resonance states. Global properties of hot $Δ$-admixed hypernuclear stars are computed for fixed values of entropy per baryon ($S/A$) and lepton fraction ($Y_L$). Universal relations between the moment of inertia, quadrupole moment, tidal deformability, and compactness of compact stars are established for fixed values of $S/A$ and $Y_L$ that are analogous to those known for cold catalyzed compact stars. We …
Fudan University（复旦大学）；INFN Sezione di Catania, Dipartimento di Fisica, Universitá di Catania（意大利国家核物理研究所卡塔尼亚分部、物理学系、卡塔尼亚大学）；University of Geosciences, Wuhan（武汉地球科学学院）；Shanghai Research Center for Theoretical Nuclear Physics, NSFC, Fudan University（国家自然科学基金委上海理论核物理研究中心，复旦大学）
Explosive astrophysical systems - such as supernovae or compact star binary mergers - provide conditions where exotic degrees of freedom can be populated. Within the covariant density functional theory of nuclear matter we build several general purpose equations of state which, in addition to the baryonic octet, account for $Δ(1232)$ resonance states. The thermodynamic stability of $Δ$-admixed nuclear matter is investigated in the limiting case of vanishing temperature for charge fractions $Y_Q=0.01$ and $Y_Q=0.5$ and wide ranges of the coupling constants to the scalar and vector mesonic field…
We calculate the baryon-meson coupling constants for the spin-1/2 baryonic octet and spin-3/2 decuplet in a unified approach relying on symmetry arguments such as the fact that the Yukawa couplings, present in the Lagrangian density of the Walecka-type models, must be an invariant under SU(3) and SU(6) group transformations. The coupling constants of the baryon with the scalar $σ$ meson are fixed to reproduce the known potential depths for the hyperons and $Δ$ resonances, in an approach that can be extended to all particles. We then apply the calculated coupling constants to study neutron star…
Dark matter effects on the properties of hybrid neutron stars
School of Mathematics and Physics, China University of Geosciences（中国地质大学数学与物理学院）；INFN, Sezione di Catania, Dipartimento di Fisica, Universitá di Catania（意大利国家核物理研究所卡塔尼亚分部卡塔尼亚大学物理系）
In this paper, we studied the ``hyperon puzzle", a problem that nevertheless the large number of studies is still an open problem. The solution of this issue requires one or more mechanisms that could eventually provide the additional repulsion needed to make the EoS stiffer and, therefore, the value of $M_{\rm{max}, T}$ compatible with the current observational limits. In this paper we proposed that including dark matter (DM) admixed with ordinary matter in neutron stars (NSs), change the hydrostatic equilibrium and may explain the observed discrepancies, regardless to hyperon multi-body inte…
We investigate compact objects formed by dark matter admixed with ordinary matter made of neutron star matter and white dwarf material. We consider non-self annihilating dark matter with an equation-of-state given by an interacting Fermi gas. We find new stable solutions, dark compact planets, with Earth-like masses or lower and radii about one meter for weakly interacting dark matter. For the strongly interacting dark matter case, we obtain dark compact planets with Jupiter-like masses or lower and radii of a kilometer. These objects could be formed primordially and accrete white dwarf materi…
We investigate the slowly rotating general relativistic superfluid neutron stars including the entrainment effect in a two-fluid model, where one fluid represents the superfluid neutrons and the other is the charge-neutral fluid called the proton fluid, made of protons and electrons. The equation of state and the entrainment effect between the superfluid neutrons and the proton fluid are computed using a relativistic mean field (RMF) model where baryon-baryon interaction is mediated by the exchange of $σ$, $ω$, and $ρ$ mesons and scalar self interactions are also included. The equations govern…
