Stress-energy connection: Degravitating the vacuum energy

13th Regional Conference on Mathematical Physics; Antalya; Turkey; 27 October 2010 through 31 October 2010This talk summarizes recent studies on the gravitational properties of vacuum energy in a non-Riemannian geometry formed by the stress-energy tensor of vacuum, matter and radiation. Postulating that the gravitational effects of matter and radiation can be formulated by an appropriate modification of the spacetime connection, we obtain varied geometro-dynamical equations which properly comprise the usual gravitational field equations with, however, Planck-suppressed, non-local, higher-dimensional additional terms. The prime novelty brought about by the formalism is that, the vacuum energy does act not as the cosmological constant but as the source of the gravitational constant. The formalism thus deafens the cosmological constant problem by channeling vacuum energy to gravitational constant. Nevertheless, quantum gravitational effects, if any, restore the problem via the graviton and graviton-matter loops, and the mechanism proposed here falls short of taming such contributions to cosmological constant

Design of Experiment Study of the Parameters that Affect Performance of a Thermoplastic Elastomer Spring of a Hybrid Vehicle Torque Limiter

Due to the C02 emission ratio restrictions, hybrid vehicles become more popular nowadays. Because of that reason, research studies on hybrid vehicles and their powertrain systems have been increased recently. There are several types of hybrid vehicle powertrain structures in use by the car manufacturers; they depend on both the drive modes and the design of conventional and electrical engine layout designed by the car manufacturers. The most known of these structures is the power split hybrid structure. In this study, a thermoplastic elastomer spring was mechanically investigated, which has been designed for torque limiter of a power split type hybrid powertrain. The function of the elastomer spring is to damp the abnormal contact between damper inner metallic components during limiting function. The result of finite element analyses and stiffness measurement result of real parts were compared

Optimization of electro-blown PVDF nanofibrous mats for Air filter applications

Particles with diameters smaller than 2.5 µm (PM2.5) have the capability to penetrate into respiratory system, thereby exerting adverse effects on human health. High-efficiency nanofiber mats present a viable and efficient solution for the purification of ambient air contaminated with such particulate matter. In this study, PVDF based electret nanofiber mats were optimized via electro-blowing technique. The experimental parameters were systematically devised utilizing a Taguchi three-level L9 orthogonal design, and the results were subsequently analyzed using ANOVA. In this context, among the examined parameters (solution concentration, air pressure, and electrical field), the most significant factors influencing fiber diameters were identified as solution concentration and electric field strength. While an increase in air pressure exhibited a negligible influence on fiber diameters, it was observed to mitigate undesired droplet density. The optimal parameters yielding the thinnest fiber (124 ± 71 nm) were determined as 9 wt.% solution concentration, 2 bar air pressure, and 30 kV electrical voltage. Furthermore, the application of corona discharge treatment to the specimens resulted in a remarkable enhancement of quality factors by over 70%

The opinions of hotel managers about halal hotel concept: A research in Cappadocia

The number of halal business hotel concept in Turkey in recent years, especially in regions where intensive maritime tourism has been increasing. However, there are no such hotels in the Cappadocia destination. The main purpose of this study is to determine the thoughts of hotel managers in the Cappadocia tourist region on halal tourism and the concept of halal hotels. Using the semi-structured interview technique, open-ended questions were asked by the researchers to the managers of 17 four and five-star hotels with tourism management certificates in the region. The obtained data were subjected to content analysis and interpreted. The main findings obtained from the research are that hotel managers in Cappadocia see "halal tourism" as a rapidly developing market in the world that will become even more important in the future, and there is no need for a halal hotel concept to promote the demand for the region; they did not intend to make arrangements in accordance with the halal hotel concept and obtain halal hotel certification in their businesses. They kept prayer rugs in their hotel upon the requests of the guests, they turned their meeting rooms into masjids when requested; and hotel rooms have a sign showing qibla on nightstand drawers

An Analysis of Service Failures and Recovery Strategies in the Turkish Third Party Logistics Service Industry

Service literature indicates that both service failure and service recovery have a strong impact on the business relationships between service providers and their customers. The purpose of this research is twofold: to explore and analyze the most common service failures and implemented recovery strategies in Turkish third party logistics service industry and examine their impact on business relationships. Critical Incident Technique (CIT) was used. Thus, information on critical incidents were collected from both third party logistics service providers (3PLs) and their customers, failures and recovery strategies were categorized and the impact of service failures and recovery strategies on future relationships between customers and 3PLs examined. The findings indicate that service failures are most frequently encountered in customer services and port operations and that symbolic service recovery is the most common recovery strategy implemented by third party logistics service providers. The findings also show that third party logistics service providers and carriers are the most common sources of failure in third party logistics services

Testing Symmergent gravity through the shadow image and weak field photon deflection by a rotating black hole using the M87∗^* and Sgr. A∗^* results

In this paper, we study rotating black holes in symmergent gravity, and use deviations from the Kerr black hole to constrain the parameters of the symmergent gravity. Symmergent gravity induces the gravitational constant $G$ and quadratic curvature coefficient $c_{\rm O}$ from the flat spacetime matter loops. In the limit in which all fields are degenerate in mass, the vacuum energy $V_{\rm O}$ can be wholly expressed in terms of $G$ and $c_{\rm O}$. We parametrize deviation from this degenerate limit by a parameter ${\hat \alpha}$ such that the black hole spacetime is dS for ${\hat \alpha} < 1$ and AdS for ${\hat \alpha} > 1$. In constraining the symmergent parameters $c_{\rm O}$ and ${\hat \alpha}$, we utilize the EHT observations on the M87* and Sgr. A* black holes. We investigate first the modifications in the photon sphere and shadow size, and find significant deviations in the photonsphere radius and the shadow radius with respect to the Kerr solution. We also find that the geodesics of time-like particles are more sensitive to symmergent gravity effects than the null geodesics. Finally, we analyze the weak field limit of the deflection angle, where we use the Gauss-Bonnet theorem for taking into account the finite distance of the source and the receiver to the lensing object. Remarkably, the distance of the receiver (or source) from the lensing object greatly influences the deflection angle. Moreover, $c_{\rm O}$ needs be negative for a consistent solution. In our analysis, the rotating black hole acts as a particle accelerator and possesses the sensitivity to probe the symmergent gravity.Comment: 22 pages, 9 figures, 2 tables. Accepted for publication in the European Physical Journal C (https://link.springer.com/article/10.1140/epjc/s10052-023-11400-6

Thin accretion disk images of the black hole in symmergent gravity

In this paper, we study circular orbits, effective potential, and thin-accretion disk of a black hole in symmergent gravity within the Novikov-Thorne model in a way including the energy flux and temperature distribution. We determine bounds on symmergent gravity parameters and conclude that the accretion disk could be used as an astrophysical tool to probe symmergent gravity.Comment: 30 pages. Accepted for publication in Classical and Quantum Gravity, "Special Issue: Focus on Quantum Gravity Phenomenology in the Multi-Messenger Era: Challenges and Perspectives" (https://iopscience.iop.org/article/10.1088/1361-6382/aceb45). arXiv admin note: text overlap with arXiv:1901.05762, arXiv:2002.00589 by other author

Quasinormal modes and greybody factors of symmergent black hole

Symmergent gravity is an emergent gravity framework in which gravity emerges guided by gauge invariance, accompanied by new particles, and reconciled with quantum fields. In this paper, we perform a detailed study of the quasinormal modes and greybody factors of the black holes in symmergent gravity. Its relevant parameters are the quadratic curvature term $c_{\rm O}$ and the vacuum energy parameter $\alpha$. In our analyses, effects of the both parameters are investigated. Our findings suggest that, in both positive and negative direction, large $|c_{\rm O}|$ values of the parameter on the quasinormal modes parallel the Schwarzschild black hole. Moreover, the quasinormal model spectrum is found to be sensitive to the symmergent parameter $\alpha$. We contrast the asymptotic iteration and WKB methods in regard to their predictions for the quasinormal frequencies, and find that they differ (agree) slightly at small (large) multipole moments. We analyze time-domain profiles of the perturbations, and determine the greybody factor of the symmergent black hole in the WKB regime. The symmergent parameter $\alpha$ and the quadratic curvature term $c_{\rm O}$ are shown to impact the greybody factors significantly. We provide also rigorous limits on greybody factors for scalar perturbations, and reaffirm the impact of model parameters.Comment: 23 pages, 16 figures. Published versio