Maximum mass of hybrid star formed via shock induced phase transition in cold neutron stars

This article studies the maximum mass limit of the hybrid star formed after the shock-induced phase transition of a cold neutron star. By employing hadronic and quark equation of state that satisfies the current mass bound, we use combustion adiabat conditions to find such a limit. The combustion adiabat condition results in a local or a global maximum pressure at an intermediate density range. The maximum pressure corresponds to a local or global maximum mass for the phase transformed hybrid star. The phase transition is usually exothermic if we have a local maximum mass. The criteria for exothermic or endothermic phase transition depend on whether the quark pressure/energy ratios to nuclear pressure/energy are smaller or greater than 1. We find that exothermic phase transition in a cold neutron star usually results in hybrid stars whose mass is smaller than a parent neutron star. The phase transition is endothermic for a global maximum pressure; thereby, one gets a global maximum mass. Hybrid stars much massive than phase transformed local maximum mass can be formed, provided there is some external energy source during the phase transition process. However, for some cases, even massive hybrid stars can form with exothermic phase transition for equations of state having global maximum pressure.

Performance evaluation of WLAN in enterprise WAN with real-time applications based on OPNET modeler

<p><span>Wireless local area networks (WLAN) has been used recently due to their benefits which exhibits outstanding mobility with easier and faster configurations. The wireless local area network performance is much influenced by both network topology and hardware specifications and thus will impact the quality of service (QoS) parameters which are delay, load, and response time. This works estimated the performance of WLAN in enterprise WAN based on the OPNET modeler. Three scenarios have been suggested which are FDDI scenario, FDDI Hybrid Star scenario, and FDDI hybrid ring scenario involving web browsing (HTTP) and file transfer protocol (FTP). Hardware objects and software configurations kept the same for all proposed scenarios. Different types of links and topologies have been applied among WLAN subnets as well as the involved gateway has been changed to measure parameters of quality of services (QoS) for all scenarios used. The findings confirmed that the FDDI Hybrid Ring scenario presents better performance than the FDDI Hybrid Star Scenario and FDDI scenario in terms of WLAN delay, WLAN load, FTP download response time, and HTTP object response time.</span></p>

Constraint on Hybrid Stars with Gravitational Wave Events

Motivated by the recent discoveries of compact objects from LIGO/Virgo observations, we study the possibility of identifying some of these objects as compact stars made of dark matter called dark stars, or the mix of dark and nuclear matters called hybrid stars. In particular, in GW190814, a new compact object with 2.6 M⊙ is reported. This could be the lightest black hole, the heaviest neutron star, and a dark or hybrid star. In this work, we extend the discussion on the interpretations of the recent LIGO/Virgo events as hybrid stars made of various self-interacting dark matter (SIDM) in the isotropic limit. We pay particular attention to the saddle instability of the hybrid stars which will constrain the possible SIDM models.

Impact of quark deconfinement in neutron star mergers and hybrid star mergers

We describe an unambiguous gravitational-wave signature to identify the occurrence of a strong phase transition from hadronic matter to deconfined quark matter in neutron star mergers. Such a phase transition leads to a strong softening of the equation of state and hence to more compact merger remnants compared to purely hadronic models. If a phase transition takes place during merging, this results in a characteristic increase of the dominant postmerger gravitational-wave frequency relative to the tidal deformability characterizing the inspiral phase. By comparing results from different purely hadronic and hybrid models we show that a strong phase transition can be identified from a single, simultaneous measurement of pre- and postmerger gravitational waves. Furthermore, we present new results for hybrid star mergers, which contain quark matter already during the inspiral stage. Also for these systems we find that the postmerger GW frequency is increased compared to purely hadronic models. We thus conclude that also hybrid star mergers with an onset of the hadron-quark phase transition at relatively low densities may lead to the very same characteristic signature of quark deconfinement in the postmerger GW signal as systems undergoing the phase transition during merging.