Strange Matter Research Articles

Magnetized strange quark matter solutions in f(R, T) gravity with cosmological constant

In this research, we have studied magnetized strange quark matter (SQM) solutions for Friedmann-Robertson-Walker (FRW) universe in f(R, T) gravity. To obtain exact solutions of modified field equations we have used f(R,T)=R+2f(T) and f(R,T)=f1(R)+f2(T) models given by Harko et al. (Harko et al. in Phys. Rev. D 84:024020, 2011) and f(R,T)=R+f3(T) model (here f3 is an arbitrary function) with cosmological constant Λ. For t → ∞ we obtain p=−ρ dark energy situation with small constant values of cosmological constant in three different f(R, T) gravitation models. In our solutions magnetic field does not observe also we have transformed our solutions from FRW universe to Static Einstein Universe (SEU) and we get f(R, T) gravity results for SEU universe. Finally we discussed our physical solutions.

Prospects for strangelet detection with large-scale cosmic ray observatories

Quark matter which contains [Formula: see text]-quarks in addition to [Formula: see text]- and [Formula: see text]- could be stable or metastable. In this case, lumps made of this strange matter, called strangelets, could occasionally hit the Earth. When travelling through the atmosphere they would behave not dissimilar to usual high-velocity meteors with only exception that, eventually, strangelets reach the surface. As these encounters are expected to be extremely rare events, very large exposure is needed for their observation. Fluorescence detectors utilized in large ultra-high energy cosmic ray observatories, such as the Pierre Auger observatory and the Telescope Array are well suited for a task of the detection of these events. The flux limits that can be obtained with the Telescope Array fluorescence detectors could be as low as 2.5 × 10−22 cm−2s−1sr−1 which would improve by two orders of magnitude of the strongest present limits obtained from ancient mica crystals.

Strange quark matter solutions for Marder’s universe in f ( R , T ) $f(R,T)$ gravity with Λ $\varLambda$

In this paper, we investigate homogeneous cylindrically symmetric Marder’s universe in the presence of strange quark matter (SQM) source in \(f(R,T)\) gravity with cosmological constant \(\varLambda\). For this aim we have used the anisotropy feature \((\frac{\sigma_{x}^{x}}{\theta})\) of Marder type universe and equation of state (EoS) strange quark matter to obtain solutions in two classes \(f(R,T)\) gravity (Harko et al. in Phys. Rev. D 84:024020, 2011). Finally, some physical and kinematical properties are discussed.

Radial stability of anisotropic strange quark stars

The influence of the anisotropy in the equilibrium and stability of strange stars is investigated through the numerical solution of the hydrostatic equilibrium equation and the radial oscillation equation, both modified from their original version to include this effect. The strange matter inside the quark stars is described by the MIT bag model equation of state. For the anisotropy two different kinds of local anisotropic σ = pt−pr are considered, where pt and pr are respectively the tangential and the radial pressure: one that is null at the star's surface defined by pr(R) = 0, and one that is nonnull at the surface, namely, σs = 0 and σs ≠ 0. In the case σs = 0, the maximum mass value and the zero frequency of oscillation are found at the same central energy density, indicating that the maximum mass marks the onset of the instability. For the case σs ≠ 0, we show that the maximum mass point and the zero frequency of oscillation coincide in the same central energy density value only in a sequence of equilibrium configurations with the same value of σs. Thus, the stability star regions are determined always by the condition dM/dρc > 0 only when the tangential pressure is maintained fixed at the star surface's pt(R). These results are also quite important to analyze the stability of other anisotropic compact objects such as neutron stars, boson stars and gravastars.

CHARACTERISTICS OF FREE SURFACE OF HOT STRANGE QUARK MATTER

Within the framework of MIT bag model, properties of hot strange quark matter at zero pressure are investigated. It is shown that the self-boundness property of strange quark matter has a temperature dependent character. With increasing temperature, the strange quark matter which is self-bound at zero temperature, starting with a certain critical temperature becomes not self-bound.

Holes in reality

Start playing with particles that don't exist and you'll see just how strange matter's building blocks are, says Andrea Taroni

Strange quark matter and quark stars with the Dyson-Schwinger quark model

We calculate the equation of state of strange quark matter and the interior structure of strange quark stars in a Dyson-Schwinger quark model within rainbow or Ball-Chiu vertex approximation. We emphasize constraints on the parameter space of the model due to stability conditions of ordinary nuclear matter. Respecting these constraints, we find that the maximum mass of strange quark stars is about 1.9 solar masses, and typical radii are 9 --11 km. We obtain an energy release as large as $3.6 \times 10^{53}\,\text{erg}$ from conversion of neutron stars into strange quark stars.

Higher dimensional FRW universe solutions with quark and strange quark matter in creation field cosmology

In this study, firstly we have studied the behavior of quark and strange quark matter for a (n+2)-dimensional Friedmann–Robertson–Walker (FRW) universe which is homogeneous and isotropic in creation field (C-field) cosmology. Using the deceleration parameter two different exact solutions of the modified Einstein equations in C-field cosmology are obtained. In addition, we obtain exact solutions of the quark and strange quark matter for a (n+2)-dimensional homogeneous and isotropic static Einstein universe (SEU) and a maximally symmetric de Sitter vacuum universe in four dimensions. Also, using C˙=0 in C-field theory, we get the SEU and de Sitter vacuum universes in Riemann geometry. Finally, some physical and kinematical quantities are discussed.

Magnetized strange quark matter in the equivparticle model with both confinement and perturbative interactions

We investigated the properties of strange quark matter in an external strong magnetic field with both confinement and leading-order perturbative interactions considered. It was found that the leading-order perturbative interaction can stiffen the equation of state of magnetized quark matter, while the magnetic field lowers the minimum energy per baryon. By solving the Tolman–Oppenheimer–Volkoff equations, we obtain the internal structure of strange stars. The maximum mass of strange stars can be as large as 2 times the solar mass.

Landau levels of cold dense quark matter in a strong magnetic field

The occupied Landau levels of strange quark matter are investigated in the framework of the SU(3) NJL model with a conventional coupling and a magnetic-field dependent coupling respectively. At lower density, the Landau levels are mainly dominated by u and d quarks. Threshold values of the chemical potential for the s quark onset are shown in the $\mu$-$B$ plane. The magnetic-field-dependent running coupling can broaden the region of three-flavor matter by decreasing the dynamical masses of $s$ quarks. Before the onset of $s$ quarks, the Landau level number of light quarks is directly dependent on the magnetic field strength $B$ by a simple inverse proportional relation $k_{i,\mathrm{max}}\approx B_i^0/B$ with $B_d^0=5\times 10^{19}$ G, which is approximately 2 times $B_u^0$ of $u$ quarks at a common chemical potential. When the magnetic field increases up to $B^0_d$, almost all three flavors are lying in the lowest Landau level.

The Mini-EUSO telescope on the ISS

The Mini-EUSO project aims to perform observations of the UV-light night emission from Earth. The UV background produced in atmosphere is a key measurement for any experiment aiming at the observation of Extreme Energy Cosmic Rays (EECR) from space, the most energetic component of the cosmic radiation. The Mini-EUSO instrument will be placed within the International Space Station (ISS) in the Russian Module and measures through a UV transparent window. The instrument comprises a compact telescope with a large field of view, based on an optical system employing two Fresnel lenses for increased light collection. The light is focused onto an array of photo-multipliers and the resulting signal is converted into digital, processed and stored via the electronics subsystems on-board. The instrument is designed and built by the members of the JEM-EUSO collaboration. JEM-EUSO is a wide-angle refractive UV telescope being proposed for attachment to the ISS, which has been designed to address basic problems of fundamental physics and high-energy astrophysics investigating the nature of cosmic rays with energies above 1020eV. Mini-EUSO will be able to study beside EECRs a wide range of scientific phenomena including atmospheric physics, strange quark matter and bioluminescence. The mission is approved by the Italian Space Agency and the Russian Space Agency. Scientific, technical and programmatic aspects of this project will be described.

Non-existence of Brans-Dicke theory in higher dimensional FRW universe

In this paper, we have studied exact solutions of Brans-Dicke (BD) theory for higher dimensional generalized Friedmann-Robertson-Walker (FRW) universe in the presence of strange quark matter (SQM) attached to the string cloud and domain walls. We have obtained that string tension density does not survive in this model. This result agrees with Kiran and Reddy, Krori et al., Sahoo and Mishra and Reddy. Also we have obtained constant scalar field in the presence of string cloud and domain walls. Then BD theory does not observe for higher dimensional FRW universe with SQM attached to the string cloud and domain walls. Our BD solutions turn into general relativity (GR). Finally, some physical properties are discussed.

Quark matter in an SU(3) Nambu–Jona-Lasinio model with two types of vector interactions

We investigate the properties of asymmetric quark matter and strange quark matter in the framework of the SU(3) Nambu--Jona-Lasinio (NJL) model with two types of vector interactions: (1) the flavor-dependent repulsion among different flavors of quarks with the coupling constant ${G}_{V}$, and (2) the universal repulsion and the vector-isovector interaction among different flavors of quarks with the coupling constants ${g}_{V}$ and ${G}_{IV}$. Using these two types of vector interactions in the NJL model, we study the quark symmetry energy in asymmetric quark matter, the constituent quark mass, the quark fraction, the equation of state in strange quark matter, the maximum mass of a quark star, and the properties of the QCD phase diagram. We find that including the two types of vector interactions in the SU(3) NJL model can significantly influence the quark matter symmetry energy as well as the properties of strange quark matter and quark stars. In particular, our results indicate that we can describe PSR $\mathrm{J}1614\ensuremath{-}2230$ and PSR $\mathrm{J}0348+0432$ as quark stars by considering the universal repulsion and the vector-isovector interaction among quark matter in the SU(3) NJL model.

Properties of strange quark matter objects with two types of surface treatments

We study strange quark matter (SQM) objects ranging from strangelets to strange stars based on our recently proposed unified description. The important interface effects are investigated by adopting a constant surface tension as well as the multiple reflection expansion (MRE) method. It is shown that the properties of SQM objects are strongly affected by the different surface treatments. In the former case, strangelets are more compact, an electric dipole is predicted on the surface of the quark part, and a local minimum of the energy per baryon appears for unusually small values of the surface tension. In the latter case, on the other hand, an electric potential well is formed, and the energy per baryon decreases monotonically with the SQM object's size. It is found that the MRE scenario coincides with the constant-surface-tension one if realistic values are considered. However, the effects of quark depletion on the quark-vacuum interface cannot be solely described by a constant surface tension. Thus we conclude that the MRE scenario is more reasonable.

Properties of quark matter in a new quasiparticle model with QCD running coupling

The running of the QCD coupling in the effective mass causes thermodynamic inconsistency problem in the conventional quasiparticle model. We provide a novel treatment which removes the inconsistency by an effective bag constant. The chemical potential dependence of the renormalization subtraction point is constrained by the Cauchy condition in the chemical potential space. The stability and microscopic properties of strange quark matter are then studied within the completely self-consistent quasiparticle model, and the obtained equation of state of quark matter is applied to the investigation of strange stars. It is found that our improved model can describe well compact stars with mass about two times the solar mass, which indicates that such massive compact stars could be strange stars.

String cloud and domain walls with quark matter for a higher dimensional FRW universe in self creation cosmology

In this study, we research a higher dimensional flat Friedmann-Robertson-Walker (FRW) universe in Barber–s second theory when strange quark matter (SQM) and normal matter (NM) are attached to the string cloud and domain walls. We obtain zero string tension density for this model. We obtain dust quark matter solutions. This result agrees with Kiran and Reddy, Krori et al, Sahoo and Mishra and Reddy. In our solutions the quark matter transforms to other particles over time. We also obtain two different solutions for domain walls with quark and normal matters by using a deceleration parameter. Also, the features of the obtained solutions are discussed and some physical and kinematical quantities are generalized and discussed. Our results are consistent with Yılmaz, Adcox et al and Back et al in four and five dimensions.

R-mode Instability of Low-mass Bare Strange Stars

The r-mode instability window of low-mass strange stars is studied using the modified bag model of strange quark matter and reasonable sets of parameters. The results show that the ultimate spin frequency of strange stars increases with the decreasing stellar mass, and the highest spin frequency (716Hz) of pulsars observed sofar can be explained by the bare strange stars with a mass lower than about 0.1∼0.2M⊙, depending on the selected parameters.

Density dependent B parameter of relativistic stars with anisotropy in pseudo-spheroidal space-time

We present a class of relativistic solutions for compact cold stars with strange matter in a pseudo-spheroidal space-time. Considering strange matter equation of state namely, $p = \frac{1}{3}(\rho -4B)$ , where $\rho $ , $p$ and $B$ are energy density, pressure and MIT Bag parameter respectively, stellar models are obtained. In the presence of anisotropy with a pseudo-spheroidal geometry described by Vaidya-Tikekar, metric stellar models are explored where the Bag parameter varies with the energy density ( $\rho $ ) inside the compact object. We determine the density dependence of $B$ at different anisotropy. It is noted that although $B$ varies with anisotropy inside the star, finally at the surface it attains a value which is independent of the anisotropy. The Bag parameter $B$ is found to increase with an increase in anisotropy for a given compactness factor $(M/b)$ and spheroidicity $\lambda $ . It is also noted that for a star with given mass and radius, the parameter $B$ increases with the increase in $\lambda $ and finally at large $\lambda $ , it attains a constant. The equation of state (EoS) obtained here from geometrical consideration with allowed ‘B’ value is found same to that one obtains from micro-physics. The stability of the stellar models for compact stars with anisotropy in hydrostatic equilibrium obtained here is also studied.

Magnetized quark matter with a magnetic-field dependent coupling

It was recently derived that the QCD running coupling is a function of the magnetic field strength under the strong magnetic field approximation. Inspired by this progress and based on the self-consistent solutions of gap equations, the properties of two-flavor and three-flavor quark matter are studied in the framework of the Nambu--Jona-Lasinio model with a magnetic-field-dependent running coupling. We find that the dynamical quark masses as functions of the magnetic field strength are not monotonous in the fully chirally broken phase. Furthermore, the stability of magnetized quark matter with the running coupling is enhanced by lowering the free energy per baryon, which is expected to be more stable than that of the conventional constant coupling case. It is concluded that the magnetized strange quark matter described by running coupling can be absolutely stable.

Gravitational Radiation of Compact Stars

Some mechanisms for gravitational radiation from neutron and quark stars are examined. The amplitudes of gravitational waves from a deformed star as it rotates and from an oscillating star during irregular changes in its rotation dynamics are calculated. The feasibility of detecting gravitational waves with existing detectors is discussed. Depending on the character of the signals, when gravitational waves are detected it can be established whether strange quark matter is present in compact gravitational wave sources.