Cosmic Entropy Research Articles

Ecology under the falling sky: Nature, ecology and entropy in Yanomami cosmology

This article is a theoretical engagement with the book The Falling Sky, written by anthropologist Bruce Albert and Yanomami shaman Davi Kopenawa. It presents how the concepts of nature and ecology in Yanomami cosmology, as developed by Kopenawa, break with stereotypes of indigenous people living in harmonic and stable relationships with nature. Instead, this ecology is a way of dealing with an unstable nature that can derail into chaos, disarranging the cosmic arrangement of humans, non-humans and spirits that shamans should work to keep in place. Kopenawa named this cosmic entropy the fall of the sky, which now is an imminent risk caused by the destruction of the forests. His conception of ecology shows that maintaining forests in indigenous land is not merely a spontaneous fact. Rather, it is also a consequence of the intellectual engagement of indigenous people and their collaboration with other living beings.

Flat Space Cosmology as a Model of Light Speed Cosmic Expansion—Implications for the Vacuum Energy Density

Cosmologists have long ignored a stipulation by quantum field theorists that the vacuum pressure p corresponding to the zero-state vacuum energy must always be equal in magnitude to the vacuum energy density ρ (i.e., p=ρ). Although general relativity stipulates the additional condition of proportionality between the vacuum gravitational field and (ρ+3p), the equation of state for the cosmic vacuum must fulfill both relativistic and quantum stipulations. This paper fully integrates Flat Space Cosmology (FSC) into the Friedmann equations containing a cosmological term, with interesting implications for the nature of dark energy, cosmic entropy and the entropic arrow of time. The FSC vacuum energy density is shown to be equal to the cosmic fluid bulk modulus at all times, thus meeting the quantum theory stipulation of (p=ρ). To date, FSC is the only viable dark energy cosmological model which has fully-integrated general relativity and quantum features.

Clues to the Fundamental Nature of Gravity, Dark Energy and Dark Matter

This paper integrates the Flat Space Cosmology (FSC) model into the Friedmann equations containing a cosmological term. The Lambda term within this model scales according to 3H2t/c2 and 3/R2t. Use of the Bekenstein-Hawking definition of closed gravitational system total entropy provides for FSC cosmic parameter definitions in terms of . Cosmic time, radius, total matter mass-energy and vacuum energy in this model scale in exactly the same way as . This analysis opens the way for understanding gravity, dark energy and dark matter as being deeply connected with cosmic entropy. The recent theoretical work of Roger Penrose and Erik Verlinde is discussed in this context. The results of this FSC model analysis dovetail nicely with Verlinde’s work suggesting gravity as being fundamentally an emergent property of cosmic entropy. This emergent-property-of-entropy definition of gravity, if true, would also indicate that gravitational inertia, dark matter and dark energy are simply manifestations of cosmic entropy. Thus, they would likely have no identifiable connection to quantum physics, including the standard particle model.

Calculating Radiation Temperature Anisotropy in Flat Space Cosmology

The purpose of this paper is to show how one can use the FSC model of gravitational entropy to calculate cosmic radiation temperature anisotropy for any past cosmic time t since the Planck scale. Cosmic entropy follows the Bekenstein-Hawking definition, although in the correct-scaling form of, which scales 60.63 logs of 10 from the Planck scale. In the FSC model, cosmic radiation temperature anisotropy At = (t/to). The derived past anisotropy value can be compared to current co-moving anisotropy defined as unity (to/to). Calculated in this way, current gravitational entropy and temperature anisotropy have maximum values, and the earliest universe has the lowest entropy and temperature anisotropy values. This approach comports with the second law of thermodynamics and the theoretical basis of the Sachs-Wolfe effect, gravitational entropy as defined by Roger Penrose, and Erik Verlinde’s “emergent gravity” theory.

Cosmic Time as an Emergent Property of Cosmic Thermodynamics

This paper, in conjunction with recent Flat Space Cosmology (FSC) publications, provides theoretical support for cosmic time being an emergent property of cosmic entropy and temperature. Therefore, if Verlinde’s “emergent gravity” theory is correct, both time and gravity are most fundamentally emergent properties of cosmic thermodynamics. Since emergent properties within complex systems with a huge number of degrees of freedom are often not definable at the smallest scales, these results suggest that quantum time and quantum gravity may be no more definable than consciousness within two connecting neurons. String theorists now struggling to define quantum space-time and quantum gravity should bear this in mind.

Apparent horizon and gravitational thermodynamics of the Universe: Solutions to the temperature and entropy confusions and extensions to modified gravity

The thermodynamics of the Universe is restudied by requiring its compatibility with the holographic-style gravitational equations which govern the dynamics of both the cosmological apparent horizon and the entire Universe, and possible solutions are proposed to the existent confusions regarding the apparent-horizon temperature and the cosmic entropy evolution. We start from the generic Lambda Cold Dark Matter ($\Lambda$CDM) cosmology of general relativity (GR) to establish a framework for the gravitational thermodynamics. The Cai-Kim Clausius equation for the isochoric process of an instantaneous apparent horizon indicates that, the Universe and its horizon entropies encode the \emph{positive heat out} thermodynamic sign convention, which encourages us to adjust the traditional positive-heat-in Gibbs equation into the positive-heat-out version $dE_m=-T_mdS_m-P_mdV$. It turns out that the standard and the generalized second laws (GSLs) of nondecreasing entropies are always respected by the event-horizon system as long as the expanding Universe is dominated by nonexotic matter $-1\leq w_m\leq 1$, while for the apparent-horizon simple open system the two second laws hold if $-1\leq w_m<-1/3$; also, the artificial local equilibrium assumption is abandoned in the GSL. All constraints regarding entropy evolution are expressed by the equation of state parameter, which show that from a thermodynamic perspective the phantom dark energy is less favored than the cosmological constant and the quintessence. Finally, the whole framework is extended from GR and $\Lambda$CDM to modified gravities with field equations $R_{\mu\nu}-Rg_{\mu\nu}/2=8\pi G_{\text{eff}} T_{\mu\nu}^{\text{(eff)}}$. Furthermore, this paper argues that the Cai-Kim temperature is more suitable than Hayward, and the Bekenstein-Hawking and Wald entropies cannot unconditionally apply to the event and particle horizons.

On the right side of Einstein's equation

Every story has two sides and so does any good equation. Recent developments in observational cosmology have led to attempts to make modifications on both sides of the Einstein equation to explain some of the puzzling new findings. The work described here is concerned with an examination of the source of gravity that we usually find on the right-hand side of Einstein's equation. My aim is to describe a modified version of the stress-energy tensor that is the source of the gravitational field. The derivation is based on the kinetic theory of a gas of identical particles with no internal structure. The presentation here is in two parts. In Part I, I describe the stress tensor that Xinzhong Chen and I have proposed for the matter tensor for a nonrelativistic gas with input from Hongling Rao and Jean-Luc Thiffeault. Our derivation of the equations of fluid dynamics is based on kinetic theory and without recourse to the standard Chapman–Enskog approximation. The nonrelativistic treatment reveals the underlying physics clearly and it facilitates comparison with experimental results on acoustic propagation. Further, it provides a setting for a Newtonian cosmology, which remains a topic of some interest. I regret though that there is room only for the relativistic version of cosmology here. In Part II, I derive the stress-energy tensor in the relativistic case in a similar manner and exhibit its application to the usual isotropic cosmological model. The surprising result of that discussion is that, in addition to the Friedmann solution, we find a second solution that arises from terms that the usual Chapman–Enskog approximation discards. The new solution is a temporal analogue of a spatial shock wave. Just as the usual shock waves make transitions in properties within a mean free path, the new solution can change its properties in a mean flight time. Whereas the Friedmann solution is not dissipative, the new solution produces entropy at a rate that may be of cosmological interest. For the calculation of cosmic entropy production I work in the ultrarelativistic limit in which particle masses are negligible. A stability calculation to decide whether and when the new solution may be realized has yet to be done since the microphysics seems so uncertain.

Szoa – nowe stworzenie. Metafizyka zła

Wiele czynników kulturowych w Europie służy współcześnie temu, by sprawę Zagłady zamknąć, by stała się ona elementem przeszłości, czymś, co nie ma już wpływu na nasze pogodne i szczęśliwe „dziś”. Formami zapomnienia są między innymi przebaczenie i pojednanie. Dlatego pamięć o złu Zagłady wymaga nieprzebaczenia i niepojednania. Nośnikiem pamięci może być jedynie nienawiść. Jednakże w kulturze chrześcijańskiej – opartej na stwarzaniu pozorów, udawaniu własnej dobroci – jest to kwestia wstydliwa. Ofiary Zagłady, które nie chcą wyrzec się nienawiści, raz jeszcze zostają oskarżone i skazane, tym razem przez własną zakłamaną kulturę

Entropy and Gravity

The effect of gravity upon changes of the entropy of a gravity-dominated system is discussed. In a universe dominated by vacuum energy, gravity is repulsive, and there is accelerated expansion. Furthermore, inhomogeneities are inflated and the universe approaches a state of thermal equilibrium. The difference between the evolution of the cosmic entropy in a co-moving volume in an inflationary era with repulsive gravity and a matter-dominated era with attractive gravity is discussed. The significance of conversion of gravitational energy to thermal energy in a process with gravitational clumping, in order that the entropy of the universe shall increase, is made clear. Entropy of black holes and cosmic horizons are considered. The contribution to the gravitational entropy according to the Weyl curvature hypothesis is discussed. The entropy history of the Universe is reviewed.

How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem

We analyze cosmology assuming unitary quantum mechanics, using a tripartite partition into system, observer and environment degrees of freedom. This generalizes the second law of thermodynamics to "The system's entropy can't decrease unless it interacts with the observer, and it can't increase unless it interacts with the environment." The former follows from the quantum Bayes Theorem we derive. We show that because of the long-range entanglement created by cosmological inflation, the cosmic entropy decreases exponentially rather than linearly with the number of bits of information observed, so that a given observer can reduce entropy by much more than the amount of information her brain can store. Indeed, we argue that as long as inflation has occurred in a non-negligible fraction of the volume, almost all sentient observers will find themselves in a post-inflationary low-entropy Hubble volume, and we humans have no reason to be surprised that we do so as well, which solves the so-called inflationary entropy problem. An arguably worse problem for unitary cosmology involves gamma-ray-burst constraints on the "Big Snap", a fourth cosmic doomsday scenario alongside the "Big Crunch", "Big Chill" and "Big Rip", where an increasingly granular nature of expanding space modifies our life-supporting laws of physics. Our tripartite framework also clarifies when it is valid to make the popular quantum gravity approximation that the Einstein tensor equals the quantum expectation value of the stress-energy tensor, and how problems with recent attempts to explain dark energy as gravitational backreaction from super-horizon scale fluctuations can be understood as a failure of this approximation.

Singularities and Entropy in Bulk Viscosity Dark Energy Model

In this paper bulk viscosity is introduced to describe the effects of cosmic non-perfect fluid on the cosmos evolution and to build the unified dark energy (DE) with (dark) matter models. Also we derive a general relation between the bulk viscosity form and Hubble parameter that can provide a procedure for the viscosity DE model building. Especially, a redshift dependent viscosity parameter ζ ∝ λ0 + λ1(1 + z)n proposed in the previous work [X.H. Meng and X. Dou, Commun. Theor. Phys. 52 (2009) 377] is investigated extensively in this present work. Further more we use the recently released supernova dataset (the Constitution dataset) to constrain the model parameters. In order to differentiate the proposed concrete dark energy models from the well known ΛCDM model, statefinder diagnostic method is applied to this bulk viscosity model, as a complementary to the Om parameter diagnostic and the deceleration parameter analysis performed by us before. The DE model evolution behavior and tendency are shown in the plane of the statefinder diagnostic parameter pair {r, s} as axes where the fixed point represents the ΛCDM model. The possible singularity property in this bulk viscosity cosmology is also discussed to which we can conclude that in the different parameter regions chosen properly, this concrete viscosity DE model can have various late evolution behaviors and the late time singularity could be avoided. We also calculate the cosmic entropy in the bulk viscosity dark energy frame, and find that the total entropy in the viscosity DE model increases monotonously with respect to the scale factor evolution, thus this monotonous increasing property can indicate an arrow of time in the universe evolution, though the quantum version of the arrow of time is still very puzzling.

From spacetime foam to holographic foam cosmology

Due to quantum fluctuations, spacetime is foamy on small scales. For maximum spatial resolution of the geometry of spacetime, the holographic model of spacetime foam stipulates that the uncertainty or fluctuation of distance l is given, on the average, by (llP2)1/3 where lP is the Planck length. Applied to cosmology, it predicts that the cosmic energy is of critical density and the cosmic entropy is the maximum allowed by the holographic principle. In addition, it requires the existence of unconventional (dark) energy/matter and accelerating cosmic expansion in the present era. We will argue that a holographic foam cosmology of this type has the potential to become a full fledged competitor (with distinct testable consequences) for scalar driven inflation.

Energy Composition of the Universe: Time-Independent Internal Symmetry

The energy composition of the Universe, as emerged from the Type Ia supernova observations and the WMAP data, looks preposterously complex, -- but only at the first glance. In fact, its structure proves to be simple and regular. An analysis in terms of the Friedmann integral enables to recognize a remarkably simple time-independent covariant robust recipe of the cosmic mix: the numerical values of the Friedmann integral for vacuum, dark matter, baryons and radiation are approximately identical. The identity may be treated as a symmetry relation that unifies cosmic energies into a regular set, a quartet, with the Friedmann integral as its common genuine time-independent physical parameter. Such cosmic internal (non-geometrical) symmetry exists whenever cosmic energies themselves exist in nature. It is most natural for a finite Universe suggested by the WMAP data. A link to fundamental theory may be found under the assumption about a special significance of the electroweak energy scale in both particle physics and cosmology. A freeze-out model developed on this basis demonstrates that the physical nature of new symmetry might be due to the interplay between electroweak physics and gravity at the cosmic age of a few picoseconds. The big `hierarchy number' of particle physics represents the interplay in the model. This number quantifies the Friedmann integral and gives also a measure to some other basic cosmological figures and phenomena associated with new symmetry. In this way, cosmic internal symmetry provides a common ground for better understanding of old and recent problems that otherwise seem unrelated; the coincidence of the observed cosmic densities, the flatness of the co-moving space, the initial perturbations and their amplitude, the cosmic entropy are among them.

Entropy of Reissner–Nordstrom–De Sitter Black Hole in Nonthermal Equilibrium**The project supported by Natural Science Foundation of Shanxi Province of China and by Foundation for the Returned Scholar from the Education Commission of Shanxi Province of China

By making use of the method of quantum statistics, we directly derive the partition function of bosonic and fermionic fields in Reissner–Nordstrom–De Sitter black hole and obtain the integral expression of black hole's entropy and the entropy to which the cosmic horizon surface corresponds. It avoids the difficulty in solving the wave equation of various particles. Then via the improved brick-wall method, i.e. the membrane model, we calculate black hole's entropy and cosmic entropy and find out that if we let the integral upper limit and lower limit both tend to the horizon, the entropy of black hole is proportional to the area of horizon and the entropy to which cosmic horizon surface corresponds is proportional to the area of cosmic horizon. In our result, the stripped term and the divergent logarithmic term in the original brick-wall method no longer exist. In the whole process, the physical idea is clear and the calculation is simple. We offer a new simple and direct way for calculating the entropy of different complicated black holes.

ENTROPY OF SCHWARZSCHILD–de SITTER BLACK HOLE IN NON-THERMAL-EQUILIBRIUM

Starting from the Klein–Gordon equation, we calculate the entropy of Schwarzschild–de Sitter black hole in non-thermal-equilibrium by using the improved brick-wall method-membrane model. When taking the proper cutoff in the obtained result, we obtain that both black hole's entropy and cosmic entropy are proportional to the areas of event horizon. We avoid the logarithmic term and stripped term in the original brick-wall method. It offers a new way of studying the entropy of the black hole in non-thermal-equilibrium.

Black Hole and Cosmic Entropy for Schwarzschild–de Sitter Space–Time

We calculate the free energy and the entropy of a scalar field in terms of the brick-wall method in the background of the Schwarzschild–de Sitter space–time. We obtain the entropy of a black hole and the cosmic entropy at nonasymptotic flat space. When the cut-off satisfies the proper condition, the entropy of a black hole is proportional to the area of a black hole horizon, and the cosmic entropy is proportional to the cosmic horizon area.

Causal Statistical Mechanics Calculation of Initial Cosmic Entropy and Quantum Gravity Prospects

We report on the consequences of applying thecausal laws to the statistical mechanical calculation ofthe initial cosmic entropy. It can be deduced that theentropy density tends to zero as one approaches the initial singularity. This result along withsome quantum gravity considerations lead us to theconclusion that the initial data of the physical fieldsare asymptotically homogeneous in that limit.

On the origin of the light elements (Z&lt;6)

The author reviews the status of our understanding of nucleosynthesis of the light nuclei ($Zl6$). The standard view today is that these elements are, for the most part, generated by two different processes: first, thermonuclear reactions in the early universe (big-bang nucleosynthesis or (BBN), and second, galactic cosmic-ray-induced spallation reactions (GCR) in cold interstellar atoms. A third contribution comes from stellar processes. The arguments in favor of this view are presented. Numerous astrophysical and cosmological implications are discussed, such as the baryonic density, the possible existence of baryonic dark matter and of nonbaryonic (exotic) matter, the constraints imposed on new particle physics, the leptonic number of the universe, the increase in cosmic entropy since primordial nucleosynthesis, and the constancy of the constants of physics.

An attempt toward string cosmology

We explore the possibility of constructing a string model of the early Universe. Our model assumes an intuitive picture of the string era of the Universe, the dominance of a single long string, as suggested by string thermodynamics. We argue that, irrespectively of the precise initial condition, the system evolves such that it approaches the scaling era in which the long string, the loops, and the radiation coexist with roughly equal weight. The scenario is based on the notion of the scaling solution obtained in the study of the evolution of a cosmic-string network. Unlike the cosmic-string case, however, there exist self-consistency conditions one of which relates the motion of the string in a classical background geometry to the structure of space-time itself. The other determines the effective number of light degrees of freedom for given fundamental constants in string theory. Interestingly, our scenario offers an explanation of the origin of cosmic entropy: it has been stored in the complex structure of the cosmic fundamental string.

The exact present parameters of the Universe

On the basis of the model properties of the expansive nondecelerative universe, present temperature of cosmic microwave background and specific entropy in the era of matter, the present parameters of our Universe may be exactly determined.