scholarly journals Ricci cosmology in light of astronomical data

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Roberto Caroli ◽  
Mariusz P. Da̧browski ◽  
Vincenzo Salzano
Keyword(s):  
Transport Coefficients ◽  
Second Law Of Thermodynamics ◽  
Momentum Tensor ◽  
Second Order ◽  
Main Concern ◽  
Equilibrium Pressure ◽  
Spacetime Curvature ◽  
Cosmological Data ◽  
Standard Set ◽  
The Universe

AbstractRecently, a new cosmological framework, dubbed Ricci cosmology, has been proposed. Such a framework has emerged from the study of relativistic dynamics of fluids out of equilibrium in a curved background and is characterised by the presence of deviations from the equilibrium pressure in the energy–momentum tensor which are due to linear terms in the Ricci scalar and the Ricci tensor. The coefficients in front of such terms are called the second order transport coefficients and they parametrise the fluid response to the pressure terms arising from the spacetime curvature. Under the preliminary assumption that the second order transport coefficients are constant, we find the simplest solution of Ricci cosmology in which the presence of pressure terms causes a departure from the perfect fluid redshift scaling for matter components filling the Universe. In order to test the viability of this solution, we make four different ansätze on the transport coefficients, giving rise to four different cases of our model. On the physical ground of the second law of thermodynamics for fluids with non-equilibrium pressure, we find some theoretical bounds (priors) on the parameters of the models. Our main concern is then the check of each of the case against the standard set of cosmological data in order to obtain the observational bounds on the second order transport coefficients. We find those bounds also realising that Ricci cosmology model is compatible with $$\Lambda $$ Λ CDM cosmology for all the ansätze.

scholarly journals THE DARK MAGNETISM OF THE UNIVERSE

2011 ◽  
Vol 26 (40) ◽  
pp. 3025-3039 ◽  
Author(s):  
JOSE BELTRÁN JIMÉNEZ ◽  
ANTONIO L. MAROTO
Keyword(s):  
Magnetic Fields ◽  
Cosmological Constant ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Electromagnetic Interactions ◽  
Effective Current ◽  
Spacetime Curvature ◽  
Effective Cosmological Constant ◽  
Hubble Horizon ◽  
The Universe

Despite the success of Maxwell's electromagnetism in the description of the electromagnetic interactions on small scales, we know very little about the behavior of electromagnetic fields on cosmological distances. Thus, it has been suggested recently that the problems of dark energy and the origin of cosmic magnetic fields could be pointing to a modification of Maxwell's theory on large scales. Here, we review such a proposal in which the scalar state which is usually eliminated by means of the Lorenz condition is allowed to propagate. On super-Hubble scales, the new mode is essentially given by the temporal component of the electromagnetic potential and contributes as an effective cosmological constant to the energy–momentum tensor. The new state can be generated from quantum fluctuations during inflation and it is shown that the predicted value for the cosmological constant agrees with observations, provided inflation took place at the electroweak scale. We also consider more general theories including non-minimal couplings to the spacetime curvature in the presence of the temporal electromagnetic background. We show that both in the minimal and non-minimal cases, the modified Maxwell's equations include new effective current terms which can generate magnetic fields from sub-galactic scales up to the present Hubble horizon. The corresponding amplitudes could be enough to seed a galactic dynamo or even to account for observations just by collapse and differential rotation in the protogalactic cloud.

Imaginings

2017 ◽  
Vol 9 (3) ◽  
pp. 17-30
Author(s):  
Kelly James Clark
Keyword(s):  
Religious Tradition ◽  
Second Order ◽  
Fine Tuning ◽  
Intellectual Humility ◽  
First Order ◽  
Natural Processes ◽  
Empirically Supported ◽  
Group Violence ◽  
The World ◽  
The Universe

In Branden Thornhill-Miller and Peter Millican’s challenging and provocative essay, we hear a considerably longer, more scholarly and less melodic rendition of John Lennon’s catchy tune—without religion, or at least without first-order supernaturalisms (the kinds of religion we find in the world), there’d be significantly less intra-group violence. First-order supernaturalist beliefs, as defined by Thornhill-Miller and Peter Millican (hereafter M&M), are “beliefs that claim unique authority for some particular religious tradition in preference to all others” (3). According to M&M, first-order supernaturalist beliefs are exclusivist, dogmatic, empirically unsupported, and irrational. Moreover, again according to M&M, we have perfectly natural explanations of the causes that underlie such beliefs (they seem to conceive of such natural explanations as debunking explanations). They then make a case for second-order supernaturalism, “which maintains that the universe in general, and the religious sensitivities of humanity in particular, have been formed by supernatural powers working through natural processes” (3). Second-order supernaturalism is a kind of theism, more closely akin to deism than, say, Christianity or Buddhism. It is, as such, universal (according to contemporary psychology of religion), empirically supported (according to philosophy in the form of the Fine-Tuning Argument), and beneficial (and so justified pragmatically). With respect to its pragmatic value, second-order supernaturalism, according to M&M, gets the good(s) of religion (cooperation, trust, etc) without its bad(s) (conflict and violence). Second-order supernaturalism is thus rational (and possibly true) and inconducive to violence. In this paper, I will examine just one small but important part of M&M’s argument: the claim that (first-order) religion is a primary motivator of violence and that its elimination would eliminate or curtail a great deal of violence in the world. Imagine, they say, no religion, too.Janusz Salamon offers a friendly extension or clarification of M&M’s second-order theism, one that I think, with emendations, has promise. He argues that the core of first-order religions, the belief that Ultimate Reality is the Ultimate Good (agatheism), is rational (agreeing that their particular claims are not) and, if widely conceded and endorsed by adherents of first-order religions, would reduce conflict in the world.While I favor the virtue of intellectual humility endorsed in both papers, I will argue contra M&M that (a) belief in first-order religion is not a primary motivator of conflict and violence (and so eliminating first-order religion won’t reduce violence). Second, partly contra Salamon, who I think is half right (but not half wrong), I will argue that (b) the religious resources for compassion can and should come from within both the particular (often exclusivist) and the universal (agatheistic) aspects of religious beliefs. Finally, I will argue that (c) both are guilty, as I am, of the philosopher’s obsession with belief. 

GRAVITY CAN BE OBSERVED IN THE ABSENCE OF CURVED SPACETIME, THUS CURVED SPACETIME IS NOT RESPONCIBLE FOR GRAVITY

2015 ◽  
Vol 8 (1) ◽  
pp. 1976-1981
Author(s):  
Casey McMahon
Keyword(s):  
General Relativity ◽  
Special Relativity ◽  
Relative Position ◽  
Gravitational Force ◽  
Curved Spacetime ◽  
Relative Time ◽  
Curved Space ◽  
Spacetime Curvature ◽  
Equivalence Model ◽  
The Universe

The principle postulate of general relativity appears to be that curved space or curved spacetime is gravitational, in that mass curves the spacetime around it, and that this curved spacetime acts on mass in a manner we call gravity. Here, I use the theory of special relativity to show that curved spacetime can be non-gravitational, by showing that curve-linear space or curved spacetime can be observed without exerting a gravitational force on mass to induce motion- as well as showing gravity can be observed without spacetime curvature. This is done using the principles of special relativity in accordance with Einstein to satisfy the reader, using a gravitational equivalence model. Curved spacetime may appear to affect the apparent relative position and dimensions of a mass, as well as the relative time experienced by a mass, but it does not exert gravitational force (gravity) on mass. Thus, this paper explains why there appears to be more gravity in the universe than mass to account for it, because gravity is not the resultant of the curvature of spacetime on mass, thus the “dark matter” and “dark energy” we are looking for to explain this excess gravity doesn’t exist.

Evolution of the universe from the perspective of entropy and information

2021 ◽  
pp. 2150111
Author(s):  
Fei-Quan Tu ◽  
Bin Sun ◽  
Meng Wan ◽  
Qi-Hong Huang
Keyword(s):  
Information Entropy ◽  
Second Law Of Thermodynamics ◽  
Boltzmann Entropy ◽  
Evolution Of The Universe ◽  
Thermodynamic Entropy ◽  
Entire Universe ◽  
Low Entropy ◽  
The Relationship ◽  
The Universe ◽  
Entropy Of The Universe

Entropy is a key concept widely used in physics and other fields. At the same time, the meaning of entropy with different names and the relationship among them are confusing. In this paper, we discuss the relationship among the Clausius entropy, Boltzmann entropy and information entropy and further show that the three kinds of entropy are equivalent to each other to some extent. Moreover, we point out that the evolution of the universe is a process of entropy increment and life originates from the original low entropy of the universe. Finally, we discuss the evolution of the entire universe composed of the cosmological horizon and the space surrounded by it and interpret the entropy as a measure of information of all microstates corresponding to a certain macrostate. Under this explanation, the thermodynamic entropy and information entropy are unified and we can conclude that the sum of the entropy of horizon and the entropy of matter in the space surrounded by the horizon does not decrease with time if the second law of thermodynamics holds for the entire universe.

scholarly journals CLASSICAL TRACE ANOMALY

2005 ◽  
Vol 14 (07) ◽  
pp. 1233-1250 ◽  
Author(s):  
M. FARHOUDI
Keyword(s):  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Second Order ◽  
Alternative Form ◽  
Mathematical Form ◽  
Einstein’S Field Equations ◽  
Einstein’S Equations ◽  
Field Equations ◽  
Einstein's Equations ◽  
Trace Anomaly

We seek an analogy of the mathematical form of the alternative form of Einstein's field equations for Lovelock's field equations. We find that the price for this analogy is to accept the existence of the trace anomaly of the energy–momentum tensor even in classical treatments. As an example, we take this analogy to any generic second order Lagrangian and exactly derive the trace anomaly relation suggested by Duff. This indicates that an intrinsic reason for the existence of such a relation should perhaps be, classically, somehow related to the covariance of the form of Einstein's equations.

scholarly journals Self-organizing Systems in the Light of the Arrows of Orderedness, Symmetry, and Entropy

1970 ◽  
Vol 2 (2) ◽  
pp. 63-73
Author(s):  
György Darvas
Keyword(s):  
Second Law Of Thermodynamics ◽  
Local Symmetry ◽  
Evolution Of The Universe ◽  
Global Evolution ◽  
New Material ◽  
New Interpretation ◽  
The One ◽  
Global And Local ◽  
The Universe ◽  
Matter Energy

The paper makes an attempt to resolve two conceptual mingling: (a) the mingling of the two interpretations of the concept of orderedness applied in statistical thermodynamics and in symmetrology, and (b) the mingling of two interpretations of evolution applied in global and local processes. In conclusion, it formulates a new interpretation on the relation of the emergence of new material qualities in selforganizing processes on the one hand, and the evolution of the universe, on the other. The process of evolution is a sequence of emergence of new material qualities by self-organization processes, which happen in negligible small segments of the universe. Although thermodynamics looks at the universe as a closed (isolated) system, this holds for its outside boundaries only, while the universe has many subsystems inside, which are not isolated (closed), since they are in a permanent exchange of matter, energy, etc. with their environment (with the rest of the universe) through their open boundaries. Any ";;emergence";; takes place, i.e., all new qualities come into being just in these small open segments of the universe. The conditions to apply the second law of thermodynamics are not present here. Therefore, global evolution of the universe is the consequence of local symmetry decreases, local decreases of orderedness, and possible local decreases of entropy.

scholarly journals Lattice study of transport coefficients in second order dissipative hydrodynamics

2011 ◽  
Author(s):  
Y. Kohno ◽  
Masayuki Asakawa ◽  
Masakiyo Kitazawa ◽  
Chiho Nonaka
Keyword(s):  
Transport Coefficients ◽  
Second Order

Time’s Arrow and Statistical Uncertainty in Physics and Philosophy

2020 ◽  
pp. 204-241
Author(s):  
Theodore M. Porter
Keyword(s):  
Free Will ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Statistical Uncertainty ◽  
Newtonian Mechanics ◽  
Historical School ◽  
James Clerk Maxwell ◽  
Objective Chance ◽  
The Universe ◽  
Time’S Arrow

This chapter explores how German economists and statisticians of the historical school viewed the idea of social or statistical law as the product of confusion between spirit and matter or, equivalently, between history and nature. That the laws of Newtonian mechanics are fully time-symmetric and hence can be equally run backwards or forwards could not easily be reconciled with the commonplace observation that heat always flows from warmer to cooler bodies. James Clerk Maxwell, responding to the apparent threat to the doctrine of free will posed by thermodynamics and statistics, pointed out that the second law of thermodynamics was only probable, and that heat could be made to flow from a cold body to a warm one by a being sufficiently quick and perceptive. Ludwig Boltzmann resisted this incursion of probabilism into physics but in the end he was obliged, largely as a result of difficulties presented by the issue of mechanical reversibility, to admit at least the theoretical possibility of chance effects in thermodynamics. Meanwhile, the American philosopher and physicist C. S. Pierce determined that progress—the production of heterogeneity and homogeneity—could never flow from rigid mechanical laws, but demanded the existence of objective chance throughout the universe.

Category theory, introduction to

2018 ◽  
Author(s):  
Colin McLarty
Keyword(s):  
Number Theory ◽  
Set Theory ◽  
Category Theory ◽  
Standard Set ◽  
Universe Of Sets ◽  
The Universe

A ‘category’, in the mathematical sense, is a universe of structures and transformations. Category theory treats such a universe simply in terms of the network of transformations. For example, categorical set theory deals with the universe of sets and functions without saying what is in any set, or what any function ‘does to’ anything in its domain; it only talks about the patterns of functions that occur between sets. This stress on patterns of functions originally served to clarify certain working techniques in topology. Grothendieck extended those techniques to number theory, in part by defining a kind of category which could itself represent a space. He called such a category a ‘topos’. It turned out that a topos could also be seen as a category rich enough to do all the usual constructions of set-theoretic mathematics, but that may get very different results from standard set theory.

The wormhole thermodynamics in f (R ) gravity

2019 ◽  
Vol 35 (04) ◽  
pp. 1950360 ◽  
Author(s):  
A. S. Sefiedgar ◽  
M. Mirzazadeh
Keyword(s):  
Continuity Equation ◽  
Energy Momentum Tensor ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Momentum Tensor ◽  
Second Law ◽  
Standard Entropy ◽  
Field Equations ◽  
First Law Of Thermodynamics ◽  
Generalized Second Law

Thermodynamics of the evolving Lorentzian wormhole at the apparent horizon is investigated in [Formula: see text] gravity. Redefining the energy density and the pressure, the continuity equation is satisfied and the field equations in [Formula: see text] gravity reduce to the ones in general relativity. However, the energy–momentum tensor includes all the corrections from [Formula: see text] gravity. Therefore, one can apply the standard entropy-area relation within [Formula: see text] gravity. It is shown that there may be an equivalency between the field equations and the first law of thermodynamics. It seems that an equilibrium thermodynamics may be held on the apparent horizon. The validity of the generalized second law of thermodynamics (GSL) is also investigated in the wormholes.

Sign in / Sign up

Export Citation Format

Share Document