In this work we would like to address the problem of the effect of bulk matter on the brane cosmological evolution in a general way. We assume that the spatial part of the brane metric is not maximally symmetric, therefore spatially inhomogeneous. However we retain the conformal flatness property of the standard cosmological model (FRW) i.e. the Weyl tensor of the induced 4D geometry is zero. We refer to it as Spatially Inhomogeneous
Irrotational (SII) brane. It is shown that the model can be regarded as the 5D generalization of the SII spacetimes found recently (Pantelis S. Apostolopoulos, Phys. Rev. D 94 (2016) no.12, 124052 [arXiv:1612.01853 [gr-qc]).

Based on Light speed expansion, modified red shift formula, scaled Hawking’s black hole temperature formula, super gravity of galactic baryon matter and baby Planck ball – in our recent publications, we have clearly established a novel model of quantum cosmology. In this contribution, we appeal the need of reviewing the basics of Lambda cosmology in the context of cosmic quantum spin. We would like to emphasize the point that, spin is a basic property of quantum mechanics and one who is interested in developing quantum models of cosmology, must think about cosmic rotation. It may also be noted that, without a radial in-flow of matter in all directions towards one specific point, one cannot expect a big crunch and without a big crunch, one cannot expect a big bang. Really if there was a “big bang” in the past, with reference to formation of big bang as predicted by GTR and with reference to the cosmic rate of expansion that might have taken place simultaneously in all directions at a “naturally selected rate” about the point of big bang: “point” of big bang can be considered as the characteristic reference point of cosmic expansion in all directions. Thinking in this way, either the point of big bang or baby Planck ball can be considered as a possible center of cosmic evolution.

The line element is unambiguously related to the modeling of the curved spacetime whether an algebraic or a phenomenological or a geometric prescription is applied. Accordingly, the possible quantization of the line element can be suggested. For ds²=g_{mu nu} dx^mu dx^nu, the author derived a quantum-induced revision of the fundamental tensor. To this end, a minimum measurable length was imposed (discretization) and simultaneously the four–dimensional Riemann manifold is extended to the eight–dimensional Finsler manifold (additional curvature), in which the quadratic restriction on the length measure is relaxed, especially in the relativistic regime. The line element measure given by this expression is apparently still precise and accurate. This urges the author to suggest expressing g_{mu nu} and the 1-form dx^mu as quantum operators or suggesting noncommutation relations or imposing probability distribution functions. Alternatively, a full quatization to the local geodesiccharacterizing the additional curvature was also suggested.

Galaxies grow in a hierarchical way, first converting primordial gas into stars, and then accreting new material. Two main processes have been proposed to efficiently supply fresh gas to galaxies, that is, galaxy major mergers and star formation. Although star formation ignited by gas accretion has been considered as the most efficient mechanism for many years, recent works have suggested a possible increase in the fraction of major mergers at early epochs, reviving the debate on which of the two processes dominates over the other. We investigated the importance of major mergers in this scenario by exploiting recent data from the ALPINE survey. This project collected ALMA observations of the rest-frame far-infrared [CII] 158 µm line and the surrounding continuum emission in a hundred of star-forming galaxies one billion years after the Big Bang, when the major phase of galaxy mass-assembly was in place. Along with ancillary multi-wavelength data and spectroscopic observations, ALPINE allowed us to conduct the first panchromatic study of such a large statistical sample of primordial galaxies. We used, for the first time, the morpho-kinematic information provided by [CII] to identify major mergers at z~5. We found that ~40% of normal galaxies at that redshift was undergoing a merging, providing the first constraint on the major merger fraction from [CII] at this epoch. By combining our results with studies at lower redshift, we computed the cosmic evolution of the merger fraction, and compared the processes of merging and star formation as responsible for the growth of galaxies. Our results reveal a significant merging activity in the early Universe, suggesting that major mergers could have an important role in the overall process of galaxy mass-assembly across cosmic time.

Galactic feedback plays a fundamental role in regulating galaxy formation and evolution, and can originate both from star formation processes and active galactic nuclei. Galaxies with low stellar mass are particularly sensitive to feedback (i.e., outflows) and offer a unique opportunity to study these phenomena in great details. Here, we investigate the physical properties of galactic outflows in a sample of 29 local low-metallicity dwarf galaxies drawn from the Dwarf Galaxy Survey. We make use of Herschel/PACS archival data to detect atomic outflows in the broad wings of observed [CII] 158 µm line profiles. We detect outflowing gas in 1/3 of the sample, and in the average galaxy population through line stacking. We find that the outflow rates of our sources are typically comparable to their star-formation rates, implying mass-loading factors (i.e., outflow efficiencies) of the order of unity. Outflow velocities are larger than the velocities required from gas to escape away from all of our targets, suggesting that a large amount of gas and dust is brought out of their halos, enriching their intergalactic medium and shaping their star-formation histories. Our results will be used as input for chemical models, posing new constraints on the processes of dust production/destruction in the interstellar medium of galaxies across cosmic time.

I have shown that the field defined by the Wheeler-DeWitt equation for pure gravity is neither a standard gravitational field nor the field representing a particular universe. The theory offers a unified description of geometry and matter, with geometry being fundamental. The quantum theory possesses gravitational decoherence when the signature of R⁽³⁾ changes. The quantum theory resolves singularities dynamically. Application to the FLRW kappa=0 shows the creation of local geometries during quantum evolution. The 3-metric gets modified near the classical singularity in the case of the Schwarzschild geometry.

I analyze the Wheeler-DeWitt equation for pure gravity in the light of standard quantum field theories. Because the field is defined only over the space of 3-metric can be re-interpreted without the issue discussed above. The field defined satisfies ADM constraints for pure gravity. Therefore, one would interpret that the field Φ is a pure gravitational field. But I observe that even gauge fields obey ADM constraints for pure gravity. I also observe that these fields have non-trivial stress tensors. Whereas the stress tensor for pure gravitational field is R_µν −1/2 g_µνR = 0. The quadratic coupling always remains non-negative regardless of the signature of R⁽³⁾. I also observe that the higher order couplings with Φ ∼ e^{i q_abP_ab} allow us to interpret it as a matter-like term. The other interpretation is that the field Φ describes a particular Universe. I observe that such interpretation faces problems due to the interaction between different fields. It shows that neither of the interpretation is true. The field Φ is a unified description of the gravity and scalar matter.

The re-interpretation partly modifies both the theories, the quantum theory as well as the classical gravity. On the quantization of the field, we get the geometric quantum corresponding to the field but no graviton.

In a recent paper (A. Strumia and N. Tetradis, JHEP 09 (2022) 203) a new conformally flat metric was introduced, describing an expanding scalar field in a spherically symmetric geometry. The spacetime can be interpreted as a Schwarzschild-like model with an apparent horizon surrounding the curvature singularity. For the above metric, we present the complete conformal Lie algebra consists of a six-dimensional subalgebra of isometries (Killing Vector Fields or KVFs) and nine proper conformal vector fields (CVFs). An interesting aspect of our findings is that there exist a gradient (proper) conformal symmetry (i.e. its bivector F_{ab} vanishes) which verifies the importance of gradient symmetries in constructing viable cocmological models with sound physical interest. In addition, the 9-dimensional conformal algebra imply the existence of constants of motion along null geodesics that allow us to determine the complete solution of null geodesic equation.

It is generally expected that quantum gravity effects can produce a repulsive force of gravity causing a bounce which resolves the singularity. Loop quantum cosmology is one arena in which a non-singular bounce resulting from holonomy modifications has been shown to be generic feature of various spacetimes. Due to the presence of bounce, the effective minisuperspace potential in a quantum cosmology setting resulting from such models is step-like or infinite near the classical big bang. Absence of a barrier potential, as in Wheeler-DeWitt theory, suggests that the Vilenkin's tunneling wavefunction proposal is incompatible since the universe can not tunnel from nothing at the zero scale factor. We examine this issue in the case of LQC for a spatially closed FLRW model sourced with a positive cosmological constant and show that if one includes inverse volume effects as suggested by underlying quantum geometry then the step-like potential is modified to a barrier potential with height higher than that of the Wheeler-DeWitt case. Then, we realized that generally the universe can tunnel to inflationary universe or cyclic universe depending on the value of cosmological constant.

Advances in cosmology and astronomical observations over the last two decades have revealed significant tensions and many ambiguities within the standard model of cosmology of a spatially flat Universe, the lambda cold dark matter model. Moreover, the recent Planck Legacy 2018 (PL18) release has confirmed the presence of an enhanced lensing amplitude in the cosmic microwave background (CMB) power spectra, which prefers a positively curved early Universe with a confidence level higher than 99%. This paper addresses the study of a quantum mechanism that could replace the concept of dark matter and energy by considering a primordial curvature as preferred by the PL18 release while yielding the present-day spatial flatness. The implied primordial curvature is incorporated as the background curvature to extend the field equations in terms of the brane-world modified gravity. The Universe evolution is modeled by utilizing a new wavefunction of the Universe that propagates in the bulk with reference to the scale factor of the early Universe and its radius of curvature upon the emission of the CMB, which revealed both positive and negative solutions. This characteristic implies that a pair of entangled wavefunctions was created and evolved in opposite directions as a manifestation of distinct matter and antimatter sides of the Universe. The wavefunction indicates a nascent hyperbolic expansion away from early plasma is followed by a first phase of decelerating expansion during the first 10 Gyr, and then, a second phase of accelerating expansion in reverse directions, whereby both sides free-fall towards each other under gravitational acceleration. The predicted conformal curvature evolution demonstrates the fast orbital speed of outer stars owing to external fields exerted on galaxies as they traveled through earlier conformally curved spacetime. Finally, the wavefunction predicts an eventual phase of rapid spatial contraction that culminates in a Big Crunch, signaling a cyclic Universe. These findings reveal that early plasma could be separated and evolved into distinct sides of the Universe that collectively and geometrically inducing its evolution, physically explaining the effects attributed to dark matter and dark energy.

Large inconsistencies in the outcome of precise measurements of the Newtonian gravitational ‘constant’ were identified throughout more than three hundred experiments conducted up to date. This paper illustrates the dependency of the Newtonian gravitational parameter on the curvature of the background and the associated field strength of vacuum energy. Experimental conditions are recommended to verify the presented theoretical predictions and achieve consistent measurement outcomes under the defined settings.