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cosmology with Noether symmetry
This paper is devoted to explore modified [Formula omitted] theories of gravity using Noether symmetry approach. For this purpose, Friedmann-Robertson-Walker spacetime is chosen to investigate the cosmic evolution. The study is mainly divided into two parts: Firstly Noether symmetries of metric [Formula omitted] gravity are revisited and some new class of solutions with the help of conserved quantities are reported. It is shown that different scenarios of cosmic evolution can be discussed using Noether symmetries and one of the case indicates the chances for the existence of Big Rip singularity. Secondly, [Formula omitted] theory coupled with scalar field has been discussed in detail. The Noether equations of modified gravity are reported with three subcases for flat Friedmann-Robertson-Walker universe. It is concluded that conserved quantities are quite helpful to find some important exact solutions in the cosmological contexts. Moreover, the scalar field involved in the modified gravity plays a vital role in the cosmic evolution and an accelerated expansion phase can be observed for some suitable choices of [Formula omitted] gravity models.
Journal Article
Running vacuum in QFT in FLRW spacetime: the dynamics of Formula omitted from the quantized matter fields
Phenomenological work in the last few years has provided significant support to the idea that the vacuum energy density (VED) is a running quantity with the cosmological evolution and that this running helps to alleviate the cosmological tensions afflicting the [Formula omitted]CDM. On the theoretical side, recent devoted studies have shown that the properly renormalized [Formula omitted] in QFT in FLRW spacetime adopts the 'running vacuum model' (RVM) form. While in three previous studies by two of us (CMP and JSP) such computations focused solely on scalar fields non-minimally coupled to gravity, in the present work we compute the spin-1/2 fermionic contributions and combine them both. The calculation is performed using a new version of the adiabatic renormalization procedure based on subtracting the UV divergences at an off-shell renormalization point M. The quantum scaling of [Formula omitted] with M turns into cosmic evolution with the Hubble rate, H. As a result the 'cosmological constant' [Formula omitted] appears in our framework as the nearly sustained value of [Formula omitted] around (any) given epoch H, where G(H) is the gravitational coupling, which is also running, although very mildly (logarithmically). We find that the VED evolution at present reads [Formula omitted]. The coefficient [Formula omitted] receives contributions from all the quantized fields, bosons and fermions, which we compute here for an arbitrary number of matter fields. Remarkably, there also exist higher powers [Formula omitted] which can trigger inflation in the early universe. Finally, the equation of state (EoS) of the vacuum receives also quantum corrections from bosons and fermion fields, shifting its value from - 1. The striking consequence is that the EoS of the quantum vacuum may nowadays effectively appears as quintessence.
Journal Article
When the gods were born : Greek cosmogonies and the Near East
\"Ancient Greece has for too long been studied in isolation from its Near Eastern neighbors. And the Ancient Near East itself has for too long been seen as an undifferentiated cultural monolith. Classics and Near Eastern studies, in our modern universities, continue to be separated by various disciplinary, linguistic, and ideological walls. Yet there is growing trend to dismantle these divides and look at the Greek world within its fullest geographical and cultural contexts. This book aims to bring the comparative study of Greek and Near Eastern cosmogonies to a new level. It analyzes themes such as succession myths, expressions of poetic inspiration, and claims to cosmic knowledge, as well as the role of itinerant specialists in the transmission of cosmogonies. Rather than compiling literary parallels from different periods and languages and treating the Near East as a monolithic matrix, the author focuses on the motifs specific to the Northwest Semitic tradition with which the Greeks had direct contact in the Archaic period. Focusing on Hesiod's Theogony, the Orphic texts, and their Ugaritic, Phoenician and Hebrew counterparts, Carolina López-Ruiz avoids traditional diffusionist assumptions and proposes instead that dynamic cultural interaction led to the oral and intimate transmission of stories and beliefs.\"-From jacket.
Book
Theoretical insights and implications of bouncing cosmology in Formula omitted theory
In this paper, we explore cosmological bouncing solutions to investigate the cosmic evolution in the framework of energy-momentum squared gravity. We consider flat Friedmann-Robertson-Walker spacetime with a perfect matter distribution. We assume two different functional forms of [Formula omitted] gravity model to examine the impact of this modified framework in the evolution of the universe. Furthermore, we consider a specific scale factor to investigate different cosmological parameters, analyzing the evolutionary behavior of the universe in this gravity. We also perform stability analysis using the perturbation technique. Our findings indicate that the null energy condition violates at the bounce point and equation of state parameter exhibits characteristics of a quintessence era or phantom regimes. These aspects highlight the complex interplay between energy conditions and stability in bouncing cosmological model. We conclude that the [Formula omitted] theory successfully provides viable alternatives to the standard cosmological scenarios, offering insights into the early universe and the nature of gravity.
Journal Article
The Cooperative Spirit of Nature in the IKalevala/I Creation Myth: An Argument for Modern Animism
The Finnish Kalevala epic contains a world-creation myth that exemplifies the essential cooperation between humans and the nature spirits that inhabit the land. These stories not only reflect the culture’s animistic worldview, they also contain a remarkable awareness of how humans depend on the wisdom of nature to survive and illustrate how that coexistence benefits both humans and nature—a perspective that can be increasingly valuable in the modern era.
Journal Article