Narrow Results

Properties of baryonic matter made of nucleons and $\alpha$-particles are studied within a relativistic mean-field (RMF) model. The Lagrangian describing the relativistic field $\varphi$ of $\alpha$-particles is allowed to contain also self-interaction terms. Various types of RMF parametrizations are employed to calculate the energy of $\alpha$-particles embedded in the baryonic matter. We first consider baryonic systems with small admixtures of $\alpha$-particles and calculate the energy spectrum as a function of baryon density. Then we turn to the case of pure $\alpha$-matter and derive once again the energy spectrum, this time as a function of $\alpha$-particle density, with and without quartic self-interaction. In the second part of the paper, we focus on the ground-state properties (energy per particle, radii of the spherical lumps made of $\alpha$-particles) of charge neutralized Q-balls formed of baryonic $\alpha$-particles for the case of linear $\sigma$ and $\omega$ fields and nonlinear (quartic+sextic) self-interactions of the $\varphi$ field.

We consider a dark matter halo (DMH) of a spherical galaxy as a Bose–Einstein condensate (BEC) of the ultra-light axions (ULA) interacting with the baryonic matter. In the mean-field (MF) limit, we have derived the integro-differential equation of the Hartree–Fock type for the spherically symmetrical wave function of the DMH component. This equation includes two independent dimensionless parameters: (i) $\beta$ is the ratio of baryon and axion total mases and (ii) $\xi$ is the ratio of characteristic baryon and axion spatial parameters. We extended our “dissipation algorithm” for studying numerically the ground state of the axion halo in the gravitational field produced by the baryonic component. We calculated the characteristic size, $x_c$ of DMH as a function of $\beta$ and $\xi$ and obtained an analytical approximation for $x_c$.

Modified dark matter (MDM) is a phenomenological model of dark matter, inspired by gravitational thermodynamics. For an accelerating universe with positive cosmological constant ($\mathrm{\Lambda }$), such phenomenological considerations lead to the emergence of a critical acceleration parameter related to $\mathrm{\Lambda }$. Such a critical acceleration is an effective phenomenological manifestation of MDM, and it is found in correlations between dark matter and baryonic matter in galaxy rotation curves. The resulting MDM mass profiles, which are sensitive to $\mathrm{\Lambda }$, are consistent with observational data at both the galactic and cluster scales. In particular, the same critical acceleration appears both in the galactic and cluster data fits based on MDM. Furthermore, using some robust qualitative arguments, MDM appears to work well on cosmological scales, even though quantitative studies are still lacking. Finally, we comment on certain nonlocal aspects of the quanta of modified dark matter, which may lead to novel nonparticle phenomenology and which may explain why, so far, dark matter detection experiments have failed to detect dark matter particles.

Neutron Stars (NSs) are compact stellar objects that are stable solutions in General Relativity. Their internal structure is usually described using an equation of state that involves the presence of ordinary matter and its interactions. However there is now a large consensus that an elusive sector of matter in the universe, described as dark matter, remains as yet undiscovered. In such a case, NSs should contain both, baryonic and dark matter. We argue that depending on the nature of the dark matter and in certain circumstances, the two matter components would form a mixture inside NSs that could trigger further changes, some of them observable. The very existence of NSs constrains the nature and interactions of dark matter in the universe.

The purpose of our work is to investigate some new features of a static anisotropic relativistic hybrid compact star composed of strange quark matter (SQM) in the inner core and normal baryonic matter distribution in the crust. Here we apply the simplest form of the phenomenological MIT bag model equation of state $p_q=\frac{1}{3}({\rho }_q-4B_g)$ to correlate the density and pressure of strange quark matter within the stellar interior, whereas radial pressure and matter density due to baryonic matter are connected by the simple linear equation of state $p_r=\alpha \rho -\beta$. In order to obtain the solution of the Einstein field equations, we have used the Tolman–Kuchowicz ansatz [R. C. Tolman, Static solutions of Einstein’s field equations for spheres of fluid, Phys. Rev.55 (1939) 364–373; B. Kuchowicz, Acta Phys. Pol.33 (1968) 541] and further derivation of the arbitrary constants from some physical conditions. Here, we examine our proposed model graphically and analytically in detail for physically plausible conditions. In particular, for this investigation, we have reported on the compact object Her $X-1$ [$\mathrm{\text{Mass}}=(0.98\pm 0.12)M_{\odot }$; $\mathrm{\text{Radius}}=8.1_{-0.41}^{+0.41}$ km] in our paper as a strange quark star candidate. In order to check the physical validity and stability of our suggested model, we have performed various physical tests both analytically and graphically, namely, dynamical equilibrium of applied forces, energy conditions, compactness factor and surface redshift. Finally, we have found that our present model meets all the necessary physical requirements for a realistic model and can be studied for strange quark stars (SQS).

We discuss the role of dilaton, which is supposed to be representing a special feature of scale symmetry of QCD, trace anomaly, in dense baryonic matter. The idea that the scale symmetry breaking of QCD is responsible for the spontaneous breaking of chiral symmetry is presented along the similar spirit of Freund-Nambu model. The incorporation of dilaton field in the hidden local symmetric parity doublet model is briefly sketched with the possible role of dilaton at high density baryonic matter, the emergence of linear sigma model in dilaton limit.

Baryonic matter is studied in the Skyrme model by taking into account the roles of π, ρ and ω mesons through the hidden local symmetry up to terms including the homogeneous Wess-Zumino (hWZ) terms. Using the master formulas for the low energy constants derived from holographic QCD models the skyrmion matter properties can be quantitatively calculated with the input values of the pion decay constant f_π and the vector meson mass m_ρ. We find that the hWZ terms are responsible for the repulsive interactions of the ω meson. In addition, the self-consistently included terms with the hWZ terms is found to increase the half skyrmion phase transition point above the normal nucleon density.