Matter Creation Process Research Articles

Energy-Momentum Squared Gravity: A Brief Overview

In this work, we present a review of Energy-Momentum Squared Gravity (EMSG)—more specifically, f(R,TμνTμν) gravity, where R represents the Ricci scalar and Tμν denotes the energy-momentum tensor. The inclusion of quadratic contributions from the energy-momentum components has intriguing cosmological implications, particularly during the Universe’s early epochs. These effects dominate under high-energy conditions, enabling EMSG to potentially address unresolved issues in General Relativity (GR), such as the initial singularity and aspects of big-bang nucleosynthesis in certain models. The theory’s explicit non-minimal coupling between matter and geometry leads to the non-conservation of the energy-momentum tensor, which prompts the investigation of cosmological scenarios through the framework of irreversible thermodynamics of open systems. By employing this formalism, we interpret the energy-balance equations within EMSG from a thermodynamic perspective, viewing them as descriptions of irreversible matter creation processes. Since EMSG converges to GR in a vacuum and differences emerge only in the presence of an energy-momentum distribution, these distinctions become significant in high-curvature regions. Therefore, deviations from GR are expected to be pronounced in the dense cores of compact objects. This review delves into these facets of EMSG, highlighting its potential to shed light on some of the fundamental questions in modern cosmology and gravitational theory.

Modified Gravity in the Presence of Matter Creation: Scenario for the Late Universe.

We consider a dynamic scenario for characterizing the late Universe evolution, aiming to mitigate the Hubble tension. Specifically, we consider a metric f(R) gravity in the Jordan frame which is implemented to the dynamics of a flat isotropic Universe. This cosmological model incorporates a matter creation process, due to the time variation of the cosmological gravitational field. We model particle creation by representing the isotropic Universe (specifically, a given fiducial volume) as an open thermodynamic system. The resulting dynamical model involves four unknowns: the Hubble parameter, the non-minimally coupled scalar field, its potential, and the energy density of the matter component. We impose suitable conditions to derive a closed system for these functions of the redshift. In this model, the vacuum energy density of the present Universe is determined by the scalar field potential, in line with the modified gravity scenario. Hence, we construct a viable model, determining the form of the f(R) theory a posteriori and appropriately constraining the phenomenological parameters of the matter creation process to eliminate tachyon modes. Finally, by analyzing the allowed parameter space, we demonstrate that the Planck evolution of the Hubble parameter can be reconciled with the late Universe dynamics, thus alleviating the Hubble tension.

Evolution of holographic dark energy model with adiabatic matter creation

We study the holographic dark energy (HDE) with adiabatic matter creation process to explain the present-day accelerated expansion of the Universe. The field equations are discussed and solved analytically for various cosmological parameters such as the Hubble parameter, deceleration parameter and effective equation of state parameter in terms of redshift by considering a more general form of the matter creation rate. The viability of such model is checked using the recent data of Type Ia supernovae Pantheon sample, Hubble function [Formula: see text] data, joined data of baryon acoustic oscillations/cosmic microwave background and latest local [Formula: see text] by SH0ES. We achieve the most fitting values of model parameters by performing the statistical analysis of our model with the three different combination of data sets. The HDE model, with IR cutoff as Hubble horizon, in the absence of matter creation does not show phase transition. While the induction of matter creation to the same model shows the recent transition from a decelerating to an accelerated phase. Our outcomes show that the model with matter creation is compatible with the data sets used. We find that the HDE model with matter creation provides the Hubble function which matches sufficiently well with the observed Hubble data. Finally, we perform geometrical and cosmographic analyses to explicate our model and compare it with the other dark energy models like [Formula: see text]CDM model. It is found that the evolution of model starts from Chaplygin gas region in early times, enters into quintessence region in medieval time and finally approaches to [Formula: see text]CDM model.

Remark on creation and dis-creation processes related to origination of charge and matter

The ubiquitous creation process of the electron-positron pairs is brought out as being due to resonant von Karman vortex streets caused by local aether flows, as related to the Kelvin-Helmholtz vortex model of the electron and positron from fluid dynamics. The origination of electric charge is discussed as being caused by the bending and slowing of infinite velocity vortex lines, where electrons and positrons exhibit continuous charge because vortex lines are captured, always bent away from a perfectly straight line, and constantly circulate internal to these particles. The ubiquitous dis-creation (dissociation) of atomic matter due to gamma ray resonance with the given atom, can be controlled, and can produce any manner of force desired, arising from the vicinity of the atomic dissociation site. Both processes, creation and dis-creation, can produce excess electrical energy, so we think these investigations are valuable, in this regard. As these useful matter creation processes are more deeply investigated and new technologies arise from these studies, we will be able to make any amount of any kinds of atoms we like. We will also will be able to make designer atoms which will have physical properties, as desired by us, perfectly suited for the selected application

Particle creation from thermodynamics point of view in f(𝒢,T) gravity

This paper aims to discuss the gravitationally induced particle creation in the framework of [Formula: see text] theory, which involves the non-minimal coupling (NMC) between Gauss–Bonnet (GB) invariant, [Formula: see text] and trace of the energy–momentum tensor (EMT), [Formula: see text]. Here, NMC between matter and gravitational sector results in non-divergence of EMT. We discuss the generalized conservation equation for the irreversible process of matter creation with the help of generalized second law of thermodynamics (GSLT). Particle creation rate, creation pressure, entropy production rate and temperature are obtained for this theory using flat FRW geometry. We work on three particular [Formula: see text] models and study cosmological implications of open irreversible thermodynamics. Furthermore, the impact of NMC on cosmological evolution and entropy production is briefly discussed.

Holographic dark energy, matter creation, and cosmic acceleration

In this paper, we study the adiabatic matter creation process in holographic dark energy (HDE) with the motivation of considering it as an alternative choice to explain the recent accelerating phase of the Universe. In the background, we consider a homogeneous and isotropic flat Friedmann-Robertson-Walker geometry. It has been observed that the HDE with Hubble horizon as an IR cutoff does not show an accelerating Universe. Instead of assuming other IR cutoffs in order to have a transition at low redshifts, we consider the HDE model with the gravitationally induced matter creation processes. The matter creation rate is phenomenologically parametrized by a linear combination in terms of Hubble parameter, that is, $\mathrm{\ensuremath{\Gamma}}=3\ensuremath{\alpha}{H}_{0}+3\ensuremath{\beta}H$, where $\ensuremath{\alpha}$ and $\ensuremath{\beta}$ are positive constants. Some particular cases like HDE with $\mathrm{\ensuremath{\Gamma}}=0$ and $\mathrm{\ensuremath{\Gamma}}\ensuremath{\propto}H$ are also studied. The evolution of such models are tested by the latest observational data of a type Ia supernova, observational Hubble data, and latest local ${H}_{0}$ by SH0ES. We discuss the evolution of the Universe by plotting the trajectory of cosmological parameters using best-fit values. We find that the HDE model $\mathrm{\ensuremath{\Gamma}}=3\ensuremath{\alpha}{H}_{0}+3\ensuremath{\beta}H$ corresponds to early deceleration and then a smooth transition into an accelerated epoch. We discuss the cosmographic parameters and $Om$ to distinguish models with other standard dark energy models. By using the Akaike information criterion and the Bayesian information criterion, we also assess the viability of models corresponding to the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. Finally, we discuss the thermodynamics of HDE model with matter creation and find that the model satisfies the generalized second law of thermodynamic under certain conditions.

Beyond Einstein’s General Relativity: Hybrid metric-Palatini gravity and curvature-matter couplings

Einstein’s General Relativity (GR) is possibly one of the greatest intellectual achievements ever conceived by the human mind. In fact, over the last century, GR has proven to be an extremely successful theory, with a well established experimental footing, at least for weak gravitational fields. Its predictions range from the existence of black holes and gravitational radiation (now confirmed) to the cosmological models. Indeed, a central theme in modern Cosmology is the perplexing fact that the Universe is undergoing an accelerating expansion, which represents a new imbalance in the governing gravitational equations. The cause of the late-time cosmic acceleration remains an open and tantalizing question, and has forced theorists and experimentalists to question whether GR is the correct relativistic theory of gravitation. This has spurred much research in modified theories of gravity, where extensions of the Hilbert–Einstein action describe the gravitational field, in particular, [Formula: see text] gravity, where [Formula: see text] is the curvature scalar. In this review, we perform a detailed theoretical and phenomenological analysis of specific modified theories of gravity and investigate their astrophysical and cosmological applications. We present essentially two largely explored extensions of [Formula: see text] gravity, namely: (i) the hybrid metric-Palatini theory; (ii) and modified gravity with curvature-matter couplings. Relative to the former, it has been established that both metric and Palatini versions of [Formula: see text] gravity possess interesting features but also manifest severe drawbacks. A hybrid combination, containing elements from both of these formalisms, turns out to be very successful in accounting for the observed phenomenology and avoids some drawbacks of the original approaches. Relative to the curvature-matter coupling theories, these offer interesting extensions of [Formula: see text] gravity, where the explicit nonminimal couplings between an arbitrary function of the scalar curvature [Formula: see text] and the Lagrangian density of matter, induces a nonvanishing covariant derivative of the energy-momentum tensor, which implies nongeodesic motion and consequently leads to the appearance of an extra force. We extensively explore both theories in a plethora of applications, namely, the weak-field limit, galactic and extragalactic dynamics, cosmology, stellar-type compact objects, irreversible matter creation processes and the quantum cosmology of a specific curvature-matter coupling theory.

Observational constraints on holographic dark energy model with matter creation

In this paper, we consider a holographic dark energy model driven by the gravitationally induced adiabatic matter creation with constant creation rate. It is assumed that the present accelerating stage is a consequence of the negative pressure describing the irreversible process of gravitational matter creation. Exact solutions are obtained to discuss the evolution of the universe. We obtain the best-fit values of the model parameters through MCMC method by the use of EMCEE python package on latest observational data. With the best-fit values, it is found that the universe shows transition from decelerated phase to accelerated phase. We carry out the diagnostic analysis to distinguish our model with other standard dark energy models. We also discuss the cosmography analysis of our model. We analyse the model by applying Akaike information criterion (AIC) and Bayesian information criterion (BIC) based on the penalization associated to the number of parameters. The results show that the model behaves quintessence like and approaches to $\Lambda $ CDM model in late time.

Three Possible Applications of Neutrosophic Logic in Fundamental and Applied Sciences

In Neutrosophic Logic, a basic assertion is that there are variations of about everything that we can measure; the variations surround three parameters called T,I,F (truth, indeterminacy, falsehood) which can take a range of values. This paper shortly reviews the links among aether and matter creation from the perspective of Neutrosophic Logic. Once we accept the existence of aether as physical medium, then we can start to ask on what causes matter ejection, as observed in various findings related to quasars etc. One particular cosmology model known as VMH (variable mass hypothesis) has been suggested by notable astrophysicists like Halton Arp and Narlikar, and the essence of VMH model is matter creation processes in various physical phenomena. Nonetheless, matter creation process in Nature remains a big mystery for physicists, biologists and other science researchers. To this problem Neutrosophic Logic offers a solution. We also discuss two other possible applications of Neutrosophic Logic. In short, Neutrosophic Logic may prove useful in offering resolution to long standing conflicts.

An Expanded Model of Unmatter from Neutrosophic Logic perspective: Towards Matter-Spirit Unity View

In Neutrosophic Logic, a basic assertion is that there are variations of about everything that we can measure; the variations surround three parameters called T, I, F (truth, indeterminacy, falsehood) which can take a range of values. A previous paper in IJNS, 2020 shortly reviews the links among aether and matter creation from the perspective of Neutrosophic Logic. In any case, matter creation process in nature stays a major puzzle for physicists, scientists and other science analysts. To this issue neutrosophic logic offers an answer: unmatter. This paper examines an extended model of unmatter, to incorporate issue soul solidarity. So, neutrosophic logic may demonstrate helpful in offering goal to long standing clashes.

Irreversible thermodynamic perception of particle creation in generalized non-minimally coupled gravity

In this article we are interested to deal with non-minimally coupled F(R, T, Q) theory of gravity where R, T, Q=RμνTμν are Ricci scalar, trace of energy momentum tensor and interaction of Ricci tensor and energy momentum tensor, respectively. Such theories preserve the property that divergence of energy momentum tensor is non-zero. Here, we interpret the generic conservation equation of F(R, T, Q) theory from thermodynamic point of view, as describing irreversible matter creation processes. We formulate some explicit results of particle creation rate, pressure of created particle and entropy with respect to time variation in the context of FRW space-time. We presented our results for three different models of F(R, T, Q) gravity in the background of power law cosmology. It is concluded that non-minimal coupling of matter and geometry can provide a phenomenological description for the role of particle creation or decay on cosmic evolution of matter contents.

Irreversible Thermodynamic Description of Dark Matter and Radiation Creation during Inflationary Reheating

We investigate matter creation processes during the reheating period of the early Universe, by using the thermodynamic of open systems. The Universe is assumed to consist of the inflationary scalar field, which, through its decay, generates relativistic matter and pressureless dark matter. The inflationary scalar field transfers its energy to the newly created matter particles, with the field energy decreasing to near zero. The equations governing the irreversible matter creation are obtained by combining the thermodynamics description of the matter creation and the gravitational field equations. The role of the different inflationary scalar field potentials is analyzed by using analytical and numerical methods. The values of the energy densities of relativistic matter and dark matter reach their maximum when the Universe is reheated up to the reheating temperature, which is obtained as a function of the scalar field decay width, the scalar field particle mass, and the cosmological parameters. Particle production leads to the acceleration of the Universe during the reheating phase, with the deceleration parameter showing complex dynamics. Once the energy density of the scalar field becomes negligible with respect to the matter densities, the expansion of the Universe decelerates, and inflation has a graceful exit.

Cosmological implications of modified gravity induced by quantum metric fluctuations

We investigate the cosmological implications of modified gravities induced by the quantum fluctuations of the gravitational metric. If the metric can be decomposed as the sum of the classical and of a fluctuating part, of quantum origin, then the corresponding Einstein quantum gravity generates at the classical level modified gravity models with a nonminimal coupling between geometry and matter. As a first step in our study, after assuming that the expectation value of the quantum correction can be generally expressed in terms of an arbitrary second order tensor constructed from the metric and from the thermodynamic quantities characterizing the matter content of the Universe, we derive the (classical) gravitational field equations in their general form. We analyze in detail the cosmological models obtained by assuming that the quantum correction tensor is given by the coupling of a scalar field and of a scalar function to the metric tensor, and by a term proportional to the matter energy-momentum tensor. For each considered model we obtain the gravitational field equations, and the generalized Friedmann equations for the case of a flat homogeneous and isotropic geometry. In some of these models the divergence of the matter energy-momentum tensor is non-zero, indicating a process of matter creation, which corresponds to an irreversible energy flow from the gravitational field to the matter fluid, and which is direct consequence of the nonminimal curvature-matter coupling. The cosmological evolution equations of these modified gravity models induced by the quantum fluctuations of the metric are investigated in detail by using both analytical and numerical methods, and it is shown that a large variety of cosmological models can be constructed, which, depending on the numerical values of the model parameters, can exhibit both accelerating and decelerating behaviors.

Cosmological consequences of an adiabatic matter creation process

In this paper we investigate the cosmological consequences of a continuous matter creation associated with the production of particles by the gravitational field acting on the quantum vacuum. To illustrate this, three phenomenological models are considered. An equivalent scalar field description is presented for each models. The effects on the cosmic microwave background power spectrum are analyzed for the first time in the context of adiabatic matter creation cosmology. Further, we introduce a model independent treatment, $Om$, which depends only on the Hubble expansion rate and the cosmological redshift to distinguish any cosmological model from $\Lambda$CDM by providing a null test for the cosmological constant, meaning that, for any two redshifts $z_1$, $z_2$, $Om (z)$ is same, i.e. $Om (z_1)- Om (z_2)= 0$. Also, this diagnostic can differentiate between several cosmological models by indicating their quintessential/ phantom behavior without knowing the accurate value of the matter density, and the present value of the Hubble parameter. For our models, we find that particle production rate is inversely proportional to $Om$. Finally, the validity of the generalized second law of thermodynamics bounded by the apparent horizon has been examined.

Gravitational induced particle production through a nonminimal curvature–matter coupling

We consider the possibility of a gravitationally induced particle production through the mechanism of a nonminimal curvature-matter coupling. An interesting feature of this gravitational theory is that the divergence of the energy-momentum tensor is nonzero. As a first step in our study we reformulate the model in terms of an equivalent scalar-tensor theory, with two arbitrary potentials. By using the formalism of open thermodynamic systems, we interpret the energy balance equations in this gravitational theory from a thermodynamic point of view, as describing irreversible matter creation processes. The particle number creation rates, the creation pressure, and the entropy production rates are explicitly obtained as functions of the scalar field and its potentials, as well as of the matter Lagrangian. The temperature evolution laws of the newly created particles are also obtained. The cosmological implications of the model are briefly investigated, and it is shown that the late-time cosmic acceleration may be due to particle creation processes. Furthermore, it is also shown that due to the curvature--matter coupling, during the cosmological evolution a large amount of comoving entropy is also produced.

Thermodynamic interpretation of the generalized gravity models with geometry-matter coupling

Modified gravity theories with geometry - matter coupling, in which the action is an arbitrary function of the Ricci scalar and the matter Lagrangian ($f\left(R,L_m\right)$ gravity), and of the Ricci scalar and of the trace of the matter energy-momentum tensor ($f(R,T)$ gravity), respectively, have the intriguing property that the divergence of the matter energy - momentum tensor is nonzero. In the present paper, by using the formalism of open thermodynamic systems, we interpret the generalized conservation equations in these gravitational theories from a thermodynamic point of view as describing irreversible matter creation processes, which could be validated by fundamental particle physics. Thus particle creation corresponds to an irreversible energy flow from the gravitational field to the created matter constituents, with the second law of thermodynamics requiring that space-time transforms into matter. The equivalent particle number creation rates, the creation pressure and the entropy production rates are obtained for both $f\left(R,L_m\right)$ and $f(R,T)$ gravity theories. The temperature evolution laws of the newly created particles are also obtained. In the case of the $f(R,T)$ gravity theory the open irreversible thermodynamic interpretation of a simple cosmological model is presented in detail. It is also shown that due to the geometry--matter coupling, during the cosmological evolution a large amount of comoving entropy could be produced.

CCDM model from quantum particle creation: constraints on dark matter mass

In this work the results from the quantum process of matter creation have been used in order to constrain the mass of the dark matter particles in an accelerated Cold Dark Matter model (Creation Cold Dark Matter, CCDM). In order to take into account a back reaction effect due to the particle creation phenomenon, it has been assumed a small deviation ε for the scale factor in the matter dominated era of the form t2/3+ε. Based on recent H(z) data, the best fit values for the mass of dark matter created particles and the ε parameter have been found as m = 1.6× 103 GeV, restricted to a 68.3% c.l. interval of 1.5 < m < 6.3× 107) GeV and ε = -0.250+0.15-0.096 at 68.3% c.l. For these best fit values the model correctly recovers a transition from decelerated to accelerated expansion and admits a positive creation rate near the present era. Contrary to recent works in CCDM models where the creation rate was phenomenologically derived, here we have used a quantum mechanical result for the creation rate of real massive scalar particles, given a self consistent justification for the physical process. This method also indicates a possible solution to the so called ``dark degeneracy'', where one can not distinguish if it is the quantum vacuum contribution or quantum particle creation which accelerates the Universe expansion.

Studies on Bone-mass Formation within a Theoretical Model

Bone-mass formation in human is looked at to understand the underlying dynamics with an eye on healing of bone-fracture and non-unions in non-invasive pathways. Three biological cells osteoblasts, osteoclasts and osteocytes are important players in creating new bone or osseous matter in which quite a few hormones, proteins and minerals have indispensable supportive role. Assuming populations of the three mentioned cells as variables, we frame a theoretical model which is represented as a set of time differential equations. These equations imitate the dynamic process of bone matter creation. High value of osteocytes with moderate level values of osteoblast and osteoclast, all at asymptotic scale, imply creation of new bone-matter in our model. The model is studied both analytically and numerically. Some important results are highlighted and relevant predictions are made which could be put to future experimental test.

Self-similar chameleon Jordan-Brans-Dicke cosmological models

In this paper we study the chameleon Jordan-Brans-Dicke (JBD) cosmological models under the hypothesis of self-similarity. Since there are several ways to define the matter Lagrangian for a perfect fluid: L m =−ρ and L m =γρ, we show that they bring us to obtain two completely different cosmological models. In the first approach, L m =−ρ, there is ordinary matter conservation, while in the second approach, L m =γρ, we get matter creation processes. We deduce for each approach the behaviour of each physical quantity, under the self-similar hypothesis, by employing the Lie group method. The results are quite general and valid for any homogeneous geometry (FRW, Bianchi types, etc.). As example, we calculate exact solutions for each approach by considering the case of a Bianchi II geometry. In this way we can determine the exact behaviour of each physical quantity and in particular of G eff and U (the potential that mimics the cosmological constant).We compare the solutions with the obtained ones in the framework of the usual JBD models.

Classical-quantum correspondence in electron-positron pair creation

We examine the creation of electron-positron pairs in a very strong force field. Using numerical solutions to quantum field theory we calculate the spatial and momentum probability distributions for the created particles. A comparison with classical mechanical phase space calculations suggests that despite the fully relativistic and quantum mechanical nature of the matter creation process, most aspects can be reproduced accurately in terms of classical mechanics.