Charge Neutral Matter Research Articles

QCD phase transition and equation of state of stellar strong interaction matter via Dyson\u2013Schwinger equation approach

We study the phase structure and phase transition of cold dense QCD matter via the Dyson–Schwinger equation approach. We take the rainbow approximation and the Gaussian-type gluon model. In order to guarantee that the quark number density begins to appear at the nuclear liquid-gas phase transition chemical potential, we propose a chemical potential dependent modification factor for the gluon model. We find that for the iso-symmetric quark matter, the modification reduces the chemical potential of the phase coexistence region of the first-order phase transition. We also implement the relativistic mean field theory to describe the hadron matter, and make use of the Maxwell and Gibbs construction method to study the phase transition of beta -equilibrium and charge neutral matter in compact stars. The results show that the phase transition will not happen in case of the Gaussian-type gluon model without any modification. The results also indicate that the upper boundary of the coexistence region should be larger than the current Nambu solution existing region. We also calculate the mass-radius relation of the compact stars, and find that the hadron-quark phase transition happens at too high chemical potential so that the maximum mass of the compact star is hardly affected by the hadron-quark phase transition.

Possibility of $ \rho$ meson condensation in neutron stars: Unified approach of chiral SU(3) model and QCD sum rules

In the present work the conjunction of chiral SU(3) model with QCD sum rules is employed to explore the possibility of $ \rho$ meson condensation in neutron stars. The quark and gluon condensates in terms of which the in-medium masses of $ \rho$ mesons can be expressed are calculated using the chiral SU(3) model in the charge neutral matter which is relevant for neutron stars. We observe that the condition of $ \rho$ meson condensation is satisfied for the density of about 7$ \rho_{{0}}^{}$ , where $ \rho_{{0}}^{}$ is the nuclear saturation density. We also observe that the medium modified mass of $ \rho$ meson is found to have a considerable effect on the mass-radius relationship of neutron star. In the end, a brief qualitative discussion of the magnetic field is also involved to search for further possibilities of $ \rho$ meson condensation.

Thermodynamic instabilities in compact stars

We investigate the presence of thermodynamic instabilities in the high density nuclear matter reached in the central core of compact stars. In the framework of a relativistic mean-field theory, we study the cold hadronic equation of state in beta-equilibrium and charge neutral matter, including hyperons and Δ-isobar degrees of freedom. By considering fluctuations of the electric charge concentration of strongly interacting matter, we analyze a finite density phase transition characterized by pure hadronic matter with both mechanical instability that by chemical-diffusive instability. It turns out that in this situation hadronic phases with different values of electric charge content may coexist, with several implications in the bulk properties of compact stars.

Appearance of hyperons in neutron stars within LOCV method

Chemical potentials of nucleons in asymmetric nuclear matter are calculated in a completely self-consistent manner, using the lowest order constrained variational (LOCV) method. Employing different nucleon–nucleon potentials, threshold density of free hyperons formation and the maximum mass of hypernuclear star are determined. Furthermore, the particles fraction in beta stable and charge neutral matter is calculated as well. The effects of three-body force (TBF) on the onset of hyperons, particle composition and maximum mass of the star are discussed. The results show that, for all different nucleon–nucleon interactions considered, onset of hyperons formation sets in at about 2–3 times of the nuclear saturation density. In particular, it is shown that by considering the TBF, the density of appearance of hyperons shifts to a lower value. The maximum masses of hypernuclear star are obtained about 1.3068M⊙ and 1.1032M⊙ with and without TBF respectively. Although these results are much below the ones required by observations of astrophysics, they are in agreement with the previous works based on Brueckner–Hartree–Fock (BHF) approach as well as other non-relativistic potential models.

Anisotropy in the equation of state of strongly magnetized quark matter within the Nambu–Jona-Lasinio model

In this article, we calculate the magnetization and other thermodynamical quantities for strongly magnetized quark matter within the Nambu-Jona-Lasinio model at zero temperature. We assume two scenarios, chemically equilibrated charge neutral matter present in the interior of compact stars and zero-strangeness isospin-symmetric matter created in nuclear experiments. We show that the magnetization oscillates with density but in a much more smooth form than what was previously shown in the literature. As a consequence, we do not see the unphysical behavior in the pressure in the direction perpendicular to the magnetic field that was previously found. Finally, we also analyze the effects of a vector interaction on our results.

Dielectrophoretic Separation of Airborne Microbes and Dust Particles Using a Microfluidic Channel for Real-Time Bioaerosol Monitoring

Airborne microbes such as fungi, bacteria, and viruses are a threat to public health. Robust and real-time detection systems are necessary to prevent and control such dangerous biological particles in public places and dwellings. For direct and real-time detection of airborne microbes, samples must be collected and typically resuspended in liquid prior to detection; however, environmental particles such as dust are also trapped in such samples. Therefore, the isolation of target bacteria or a selective collection of microbes from unwanted nonbiological particles prior to detection is of great importance. Dielectrophoresis (DEP), the translational motion of charge neutral matter in nonuniform electric fields, is an emerging technique that can rapidly separate biological particles in microfluidics because low voltages produce significant and contactless forces on particles without any modification or labeling. In this paper, we propose a new method for the separation of airborne microbes using DEP with a simple and novel curved electrode design for separating bacteria in a solution containing beads or dust that are taken from an airborne environmental sample. Using this method, we successfully isolated 90% of the airborne bacterium Micrococcus luteus from a mixture of bacteria and dust using a microfluidic device, consisting of novel curved electrodes that attract bacteria and repel or leave dust particles. As there has been little research on analyzing environmental samples using microfluidics and DEP, this work describes a novel strategy for a rapid and direct bioaerosol monitoring system.

Hadrons in compact stars

We discuss $\beta$-equilibrated and charge neutral matter involving hyperons and $\bar K$ condensates within relativistic models. It is observed that populations of baryons are strongly affected by the presence of antikaon condensates. Also, the equation of state including $\bar K$ condensates becomes softer resulting in a smaller maximum mass neutron star.

Novel phases and transitions in color flavor locked matter

We analyze the phases of dense quark matter at nonzero quark masses. We map out the phase diagrams for charged quark matter as well as charge neutral matter containing leptons. We find that in Color Flavor Locked (CFL) quark matter, the symmetric phase with equal numbers of $u$, $d$ and $s$ quarks is unlikely to occur in nature. Various less symmetric phases with additional meson condensates may play a role in neutron star cores, however, in agreement with the analysis of Bedaque and Sch\"afer. We discuss the implications of these novel color superconducting quark matter phases and their transitions for neutron stars.

Onset of hyperon formation in neutron star matter from Brueckner theory

We determine fully self-consistent single-particle potentials and chemical potentials of nucleons and hyperons in asymmetric nuclear matter, using an extended Brueckner-Hartree-Fock formalism. We carefully analyze the onset of ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ and $\ensuremath{\Lambda}$ formation in $\ensuremath{\beta}$ stable and charge neutral matter. The role played by the three-body nucleon interaction is widely discussed. The results indicate that formation of hyperons sets in at about (2--3) times normal nuclear matter density, for all the different nucleonic equations of state that are considered.