Cosmic Pressure Research Articles

Evaluation of transit cosmological model in f(R,Tϕ) theory of gravity

In this paper, we have explored a transitioning cosmic model, depicting late-time accelerated expansion in the [Formula: see text] theory of gravity for an isotropic and homogeneous universe, where the trace of the energy–momentum tensor [Formula: see text] is the function of the self-interacting scalar field [Formula: see text]. We have proposed an explicit solution to the derived model by utilizing a scale factor of the hybrid form [Formula: see text], where [Formula: see text] and [Formula: see text] are constants. To estimate the best-fit values of model parameters, statistical analysis based on the Markov Chain Monte Carlo (MCMC) method has been employed on 57 [Formula: see text] points in the range [Formula: see text] and Pantheon Sample consisting of a total of 1048 SNe Ia in the range of [Formula: see text]. We have described the dynamical features of the model, like energy density, cosmic pressure, and the equation of state parameter, in the context of the scalar field [Formula: see text]. We have also described the potential and behavior of the scalar field for quintessence and phantom scenarios. For the joint dataset of OHD and Pantheon, the deceleration parameter depicts a transitioning universe with signature flipping at [Formula: see text] with the present value of the deceleration parameter [Formula: see text]. The violation of SEC for the derived model indicates cosmic expansion at a faster rate. We have used state-finders to diagnose the model. The findings for our theoretical model indicate that the derived model agrees with observed findings within a particular range of limitations.

Effects of electron inertia and finite-Larmor radius correction on Jeans instability of quantum plasma with the impact of cosmic pressure

We present a theoretical investigation of the Jeans instability in quantum plasma, taking into consideration cosmic ray (CR) pressure and diffusion effects using a generalized magneto-hydrodynamic (MHD) model. Our analysis incorporates finite electron inertia, finite electrical resistivity, and finite Larmor radius (FLR) correction. By applying the normal mode technique, we derive a unique form of a generalized dispersion relation that describes the behavior of the system. We further discuss this dispersion relation under different limiting cases. Interestingly, we find that all considered parameters have distinct impacts on the growth rate of the system in various scenarios. Additionally, our exploration reveals that both CR-driven acoustic speed as well as quantum parameter influence the conditions for Jeans instability while the remaining parameters do not have any impact on it. Consequently, when combined with the quantum parameter, electron inertia and FLR correction act as stabilizing agents to suppress instability. This research sheds light on the intricate processes involved in structure formation in the universe, highlighting the significance of considering quantum corrections, electron inertia, and FLR to accurately model the dynamics and stability of cosmic plasma systems.

Big Rip in Swiss-cheese brane-worlds with cosmic transit

We study the Big Rip scenario in Swiss-cheese brane-worlds. The results obtained have been found to be independent of the value of the cosmological constant Λ whether it is positive, negative, or zero. Negative tension branes are not allowed in the current model. There is a sign flipping in cosmic pressure corresponding to the sign flipping in the deceleration parameter from positive to negative. The evolution of the equation of state parameter shows the presence of three phases: the matter-dominant decelerating era, the accelerated-Quitessence phase, and the phantom phase. The evolution of the potential and kinetic term also shows a change of sign. The energy conditions and cosmographic parameters have also been investigated.

A NON-SINGULAR CLOSED BOUNCING UNIVERSE WITHOUT VIOLATION OF NULL ENERGY CONDITION

A matter bouncing entropy-corrected cosmological model has been suggested. The model allows only positive curvature with negative pressure and no violation of the null energy condition. The result obtained in this paper is supported by some recent theoretical works where the combination of positive spatial curvature and vacuum energy leads to non-singular bounces with no violation of the null energy condition. An important feature of the current model is that evolutions of the cosmic pressure, energy density and equation of state parameter are independent of the values of the prefactors α and β in the corrected entropy-area relation. The validity of the classical and the new nonlinear energy conditions has been discussed. The cosmographic parameters have been analyzed.

Effects of cosmic radiation pressure on the gravitational instability of rotating plasmas

Effects of cosmic radiation pressure on the gravitational instability of rotating plasmas

Cosmological models in R2 gravity with hybrid expansion law

In this paper, evolution of a Friedmann–Robertson–Walker universe is studied in a higher derivative theory of gravity. The relativistic solutions admitting hybrid expansion law of the universe are explored here. Hybrid expansion law is a general form of scale factor from which one can recover both the power-law expansion and exponential expansion as a special case. The hybrid expansion law is interesting as it addresses the early deceleration phase and presents accelerating phase satisfactorily. It is found that an inflationary scenario with hybrid expansion law is permitted in the [Formula: see text] gravity fairly well. We consider universe filled with cosmic fluid that describes by an equation of state (EoS) parameter which varies with time. Consequently, we analyze the time variation of energy density parameter, cosmic pressure, equation of state parameter, deceleration parameter and jerk parameter in the cosmological model. The constraints of the model parameters imposed by the cosmological observational data set are determined. The present value of the deceleration parameter [Formula: see text], EoS parameter and the epoch at which the transition of decelerated phase to accelerated phase are estimated. In the higher derivative theory, we obtain some new and interesting cosmological solutions relevant for building cosmological models.

The possibility of a stable flat dark energy-dominated Swiss-cheese brane-world universe

In this paper, we study the possibility of obtaining a stable flat dark energy-dominated universe in a good agreement with observations in the framework of Swiss-cheese brane-world cosmology. Two different brane-world cosmologies with black strings have been introduced for any cosmological constant [Formula: see text] using two empirical forms of the scale factor. In both models, we have performed a fine-tuning between the brane tension and the cosmological constant so that the Equation of state (EoS) parameter [Formula: see text] for the current epoch, where the redshift [Formula: see text]. We then used these fine–tuned values to calculate and plot all parameters and energy conditions. The deceleration–acceleration cosmic transition is allowed in both models, and the jerk parameter [Formula: see text] at late-times. Both solutions predict a future dark energy-dominated universe in which [Formula: see text] with no crossing to the phantom divide line. While the pressure in the first solution is always negative, the second solution predicts a better behavior of cosmic pressure where the pressure is negative only in the late-time accelerating era but positive in the early-time decelerating era. Such a positive-to-negative transition in the evolution of pressure helps to explain the cosmic deceleration–acceleration transition. Since black strings have been proved to be unstable by some authors, this instability can actually reflect doubts on the stability of cosmological models with black strings (Swiss-cheese type brane-worlds cosmological models). For this reason, we have carefully investigated the stability through energy conditions and sound speed. Because of the presence of quadratic energy terms in Swiss-cheese type brane-world cosmology, we have tested the new nonlinear energy conditions in addition to the classical energy conditions. We have also found that a negative tension brane is not allowed in both models of the current work as the energy density will no longer be well defined.

Dark Future for Dark Matter

The prevailing cosmological constant and cold dark matter (ΛCDM) cosmic concordance model accounts for the radial expansion of the universe after the Big Bang. The model appears to be authoritative because it is based on the Einstein gravitational field equation. However, a thorough scrutiny of the underlying theory calls into question the suitability of the field equation, which states that the Einstein tensor Gμv is a constant multiple of the stress-energy tensor Tμv when they both are evaluated at the same 4D space-time point: Gμv = 8πkTμv, where k is the gravitational constant. Notwithstanding its venerable provenance, this equation is incorrect unless the cosmic pressure is p = 0; but then all that remains of the Einstein equation is the Poisson equation which models the Newtonian gravity field. This shortcoming is not resolved by adding the cosmological constant term to the field equation, Gμv +Λ gμv =8πkTμv, as in the ΛCDM model, because then p = Λ, so the pressure is a universal constant, not a variable. Numerous studies support the concept of a linearly expanding universe in which gravitational forces and accelerations are negligible because the baryonic mass density of the universe is far below its critical density. We show that such a coasting universe model agrees with SNe Ia luminosity vs. redshift distances just as well or even better than the ΛCDM model, and that it does so without having to invoke dark matter or dark energy. Occam’s razor favors a coasting universe over the ΛCDM model.

Ricci–Gauss–Bonnet holographic dark energy in Chern–Simons modified gravity: A flat FLRW quintessence-dominated universe

We discuss the recently suggested Ricci–Gauss–Bonnet holographic dark energy in Chern–Simons modified gravity. We have tested some general forms of the scale factor [Formula: see text], and used two physically reasonable forms which have been proved to be consistent with observations. Both solutions predict a sign flipping in the evolution of cosmic pressure which is positive during the early-time deceleration and negative during the late-time acceleration. This sign flipping in the evolution of cosmic pressure helps in explaining the cosmic deceleration–acceleration transition, and it has appeared in other cosmological models in different contexts. However, this work shows a pressure singularity which needs to be explained. The evolution of the equation of state parameter [Formula: see text] shows the same asymptotic behavior for both solutions indicating a quintessence-dominated universe in the far future. We also note that [Formula: see text] goes to negative values (leaving the decelerating dust-dominated era at [Formula: see text]) at exactly the same time the pressure becomes negative. Again, there is another singularity in the behavior of [Formula: see text] which happens at the same cosmic time of the pressure singularity.

Study of Entropy-Corrected Models Using Dark Energy in the Framework of a Complementary Gravitational Field

The dark energy (DE) model of a complementary gravitational field is used to address the entropy-corrected cosmological model. The dominant DE universe can originate from an indirect coupling between vacuum energy and another complementary gravitational field. This idea is used together with entropy-corrected models to study the evolution of DE in the universe. The zero point energy is calculated from one-loop corrections and used to reconstruct the scale factor and the Hubble parameter. It is then used to evaluate the equation of state (EoS) parameter for both interacting and non-interacting DE and the cosmic pressure. The square of sound speed, used to assess the stability of DE models, and the deceleration parameter are obtained. Further, the geometrical statefinder parameters s and r and a new diagnostic statefinder parameter, om(z), are evaluated and used to distinguish between the energy densities of various DE models. It is found that the studied cosmological functions show strong variation with cosmic time, and numerical results show a good agreement with observations.

Cosmological determination to the values of the pre-factors in the logarithmic corrected entropy-area relation

In this paper, we continue investigating the possible values of the pre-factors $\alpha$ and $\beta$ in the logarithmic corrected entropy-area relation based on cosmological stability arguments. In a previous study, we have investigated the stability of the entropy-corrected cosmology using an empirical hyperbolic form of the scale factor. We found that the zero values of the two pre-factors are necessary to obtain a stable flat universe with a deceleration-acceleration transition and no causality violation. The necessity of the zero values of the two pre-factors has also been reached in the current work using a hybrid scale factor Ansatz in the entropy-corrected cosmological equations. Investigating the corrected entropy-area relation in different gravitational and cosmological contexts can provide an accurate estimation to the correct values of the pre-factors. The current work opens a discussion on the validity of the correction terms in the logarithmic corrected entropy-area relation on the cosmological scale. The evolution of the cosmic pressure, energy density, equation of state parameter, jerk parameter and the nonlinear energy conditions has been analyzed.

A cyclic universe with varying cosmological constant in f(R, T) gravity

A new kind of evolution for cyclic models in which the Hubble parameter oscillates and remains positive has been explored in a specific f(R, T) gravity reconstruction. A singularity-free cyclic universe with negative varying cosmological constant has been obtained, which supports the role suggested for negative Λ in stopping the eternal acceleration. The cosmological solutions have been obtained for the case of a flat universe, supported by observations. The cosmic pressure grows without singular values; it is positive during the early-time decelerated expansion and negative during the late-time accelerating epoch. The time-varying equation of state parameter ω(t) shows quintom behavior and is restricted to the range –2.25 ≤ ω(t) ≲ 1/3. The validity of the classical linear energy conditions and the sound speed causality condition has been studied. The non-conventional mechanism of negative cosmological constant that are expected to address the late-time acceleration has been discussed.

STAGES OF DEVELOPMENT OF THE PLANET EARTH IN THE FRAMEWORK OF ANALYTICAL GEOLOGY

Based on the known geophysical data on the structure of the inner and outer core, mantle, oceanic and continental crust, within the framework of the concept of self-development and self-organization of protoplanetary matter underthe influence of the cosmic pressure, against the background of a pulsating reduction in the earth's radius, a possible mechanism for the formation of the planet's geospheres and its surface shell. Attention is drawn to the morphology of geo-textures and morphostructures of the ocean floor - as an information system that gives an idea of the course of deep processes. The prism blocks of increased stiffness (BCG) of the primary oceanic crust are located in deep-water basins, marginal and inland seas of the continents and their lowered areas. The assumption is that the BPZ ensembles, moving in expansion-contraction regimes under the influence of radial and rotational dynamics forces, formed sigmoid structures of the planet's surface and formed Procrustean beds for the development of icebergs of continents. The symmetry and antipodality of the surface structures of the Earth is explained by the superposition of two energy sources - external and internal: the internal energy substance, according to the rule of the borer, is more dynamic in the southern hemisphere, and the waves of the external energy of the universe are rolling on the Pacific Ocean.Key words: globule of the right-hand plane, high-energy substance, cosmic pressure, the wave field of the universe, sources-ooids, rheons, pulsation, expansion-contraction regimes.

Response of Haloalkaliphilic Archaeon Natronococcus Jeotgali RR17 to Hypergravity

The survival of archaeabacteria in extreme inhabitable environments on earth that challenge organismic survival is ubiquitously known. However, the studies related to the effect of hypergravity on the growth and proliferation of archaea are unprecedented. The survival of organisms in hypergravity and rocks in addition to resistance to cosmic radiations, pressure and other extremities is imperative to study the possibilities of microbial travel between planets and endurance in hyperaccelerative forces faced during ejection of rocks from planets. The current investigation highlights the growth of an extremophilic archaeon isolated from a rocky substrate in hypergravity environment. The haloalkaliphilic archaeon, Natronococcus jeotgali RR17 was isolated from an Indian laterite rock, submerged in the Arabian sea lining Coastal Maharashtra, India. The endolithic haloarchaeon was subjected to hypergravity from 56 – 893 X gusing acceleration generated by centrifugal rotation. The cells of N. jeotgali RR17 proliferated and demonstrated good growth in hypergravity (223 X g). This is the first report on isolation of endolithic haloarchaeon N. jeotgali RR17 from an Indian laterite rock and its ability to proliferate in hypergravity. The present study demonstrates the ability of microbial life to survive and proliferate in hypergravity. Thus the inability of organismic growth in hypergravity may no longer be a limitation for astrobiology studies related to habitability of substellar objects, brown dwarfs and other planetary bodies in the universe besides planet earth.

Gravity from refraction of CMB photons using the optical-mechanical analogy in general relativity

Relativistic light bending and gravitational lensing have traditionally been viewed purely as effects of spacetime curvature. Yet for many years they have also been treated as a quasi-refraction of light in a special optical medium, wherein the refractive index is considered proportional to the gravitational potential. We now propose that this ‘optical-mechanical analogy’ in general relativity can also account for gravity. Using classical optics we show that a photon moving through the refractive medium about a mass transfers momentum first to the medium and then to the mass itself. Due to transfer of momentum primarily from ultra-remote CMB photons, masses are then subject to a cosmic pressure on all sides. Where two masses occur, mutual screening by their respective envelopes of refractive medium is shown to result in an attractive force of the Le Sage or ‘pushing gravity’ type. We suggest that the gravito-optical medium is comprised of gravitons, which may be modeled as a quasi-Einstein-Bose conjugate interconnecting all the masses of the visible universe.

AN ORGANIC COSMO-BAROMETER: DISTINCT PRESSURE AND TEMPERATURE EFFECTS FOR METHYL SUBSTITUTED POLYCYCLIC AROMATIC HYDROCARBONS

There are a number of key structures that can be used to reveal the formation and modification history of organic matter in the cosmos. For instance, the susceptibility of organic matter to heat is well documented and the relative thermal stabilities of different isomers can be used as cosmothermometers. Yet despite being an important variable, no previously recognized organic marker of pressure exists. The absence of a pressure marker is unfortunate considering our ability to effectively recognize extraterrestrial organic structures both remotely and in the laboratory. There are a wide variety of pressures in cosmic settings that could potentially be reflected by organic structures. Therefore, to develop an organic cosmic pressure marker, we have used state-of-the-art diamond anvil cell (DAC) and synchrotron-source Fourier transform infrared (FTIR) spectroscopy to reveal the effects of pressure on the substitution patterns for representatives of the commonly encountered methyl substituted naphthalenes, specifically the dimethylnaphthalenes. Interestingly, although temperature and pressure effects are concordant for many isomers, pressure appears to have the opposite effect to heat on the final molecular architecture of the 1,5-dimethylnaphthalene isomer. Our data suggest the possibility of the first pressure parameter or "cosmo-barometer" (1,5-dimethylnaphthalene/total dimethylnaphthalenes) that can distinguish pressure from thermal effects. Information can be obtained from the new pressure marker either remotely by instrumentation on landers or rovers or directly by laboratory measurement, and its use has relevance for all cases where organic matter, temperature, and pressure interplay in the cosmos.

The Thermodynamic Evolution of the Cosmological Event Horizon

By manipulating the integral expression for the proper radius R e of the cosmological event horizon (CEH) in a Friedmann-Robertson-Walker (FRW) universe we obtain an analytical expression for the change δR e in response to a uniform fluctuation δρ in the average cosmic background density ρ. We stipulate that the fluctuation arises within a vanishing interval of proper time, during which the CEH is approximately stationary, and evolves subsequently such that δρ/ρ is constant. The respective variations 2πR e δR e and δE e in the horizon entropy S e and enclosed energy E e should be therefore related through the cosmological Clausius relation. In that manner we find that the temperature T e of the CEH at an arbitrary time in a flat FRW universe is E e /S e , which recovers asymptotically the usual static de Sitter temperature. Furthermore it is proven that during radiation-dominance and in late times the CEH conforms to the fully dynamical First Law T e dS e =PdV e −dE e , where V e is the enclosed volume and P is the average cosmic pressure.

ESTIMATION OF SEASONAL VARIATIONS OF HARD COSMIC RAY FLUX AND ATMOSPHERIC PRESSURE IN 2004–2005

This paper focuses on the analysis of connection between changes in hard cosmic ray flux (HCRF) and atmospheric pressure. To analyse connection between HCRF and atmospheric pressure change, the data of HCRF were obtained using a gamma spectrometer. The statistical data of measurements have been analysed. Detailed information on atmospheric pressure was presented by the Lithuanian Hydrometeorological Service. Correlation coefficients were calculated by performing a simple linear regression analysis between HCRF and atmospheric pressure in the same day. A strong inverse correlation during simultaneous measurements was determined. The correlation coefficients were defined for different seasons of the year. An empirical criterion of –20 imp/h was chosen in analysis of HCRF. Connection between HCRF decrease at 1.2–1.6 MeV energy interval and the minimum atmospheric pressure in 3–6 days at individual time intervals is defined in Vilnius. The efficiency of prognosis was 59–73% for the period 2004–2005. Santrauka Straipsnyje analizuojamas kietosios kosmines spinduliuotes srauto (KKSS) ir atmosferos slegio pokyčiu saryšis. KKSS buvo matuojamas gama spektrometru su scintiliaciniu jutikliu. Išsamia meteorologine informacija pateike Lietuvos hidrometeorologijos tarnyba. Koreliacijos koeficientai apskaičiuoti taikant tiesine regresija tarp KKSS ir atmosferos slegio pokyčiu. Nustatyta stipri atvirkštine koreliacija, kai matavimai atlikti ta pačia diena. Gauti skirtingi ivairiu metu sezonu koreliacijos koeficientai. Atliekant KKSS mažejimo analize buvo parinktas empirinis kriterijus –20 imp./h. Nustatytas saryšis tarp KKSS mažejimo 1,2–1,6 MeV energetiniame intervale ir atmosferos slegio mažejimo po 3–6 paru Vilniuje. KKSS mažejimas buvo analizuojamas per 8–9, 9–10, 11–12, 12–13 val. laiko intervalus. 2004–2005 m. atmosferos slegio mažejimo prognozes efektyvumas Vilniuje pagal KKSS mažejima buvo 59–73 %. Резюме Анализируется связь между изменениями потока жёсткого космического излучения (ПЖКИ) и атмосферного давления. ПЖКИ определялся с помощью гамма-спектрометра со сцинтилляционным детектором. Подробная метеорологическая информация была прегoставлена гидрометеорологической службой Литвы. Коэффициенты корреляции между колебаниями ПЖКИ и атмосферного давления были рассчитаны методом прямой регрессии. Установлена сильная обратная корреляция для тех случаев, когда измерения проводились одновременно. Значения коэффициентов корреляции оказались различными для разных сезонов года. При проведении анализа уменьшения ПЖКИ был выбран эмпирический критерий – 20 имп/час. Установлена прогностическая связь между уменьшением ПЖКИ в энергическом интервале 1,2–1,6 МэВ и уменьшением атмосферного давления через 3–6 суток в г. Вильнюсе. Уменьшение ПЖКИ рассматривалось в следующих временных интервалах: 8–9, 9–10, 11–12, 12–13 час. Эффективность прогноза уменьшения атмосферного давления в г. Вильнюсе по уменьшению ПЖКИ составила 59–73% в 2004–2005 гг.

Amplification of gravitational waves in scalar-tensor accelerating lambda-Universes

After reviewing the scalar-tensor lambda-accelerating power-law solutions by Berman (Astrophys. Space Sci. 323:103, 2009a), we obtain solutions for the amplification of gravitational waves in the models. The solutions consider a perfect gas equation of state, with cosmic pressure proportional to the energy density, the proportionality constant being smaller than −2/3.

Amplification of Gravitational Waves in Scalar-Tensor Inflationary Lambda-Model

After reviewing the scalar-tensor inflationary solutions by Berman and Trevisan (Int. J. Theor. Phys. 29, 1411–1414, 2009), we obtain solutions for the amplification of gravitational waves in the models. The solutions consider a perfect gas equation of state, with cosmic pressure proportional to the energy density, the proportionality constant being smaller than −2/3, and a cosmological term.