scholarly journals Thermodynamics of Modified Cosmic Chaplygin Gas

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
M. Sharif ◽  
Sara Ashraf
Keyword(s):  
Specific Heat ◽  
Chaplygin Gas ◽  
Physical Parameters ◽  
Isotropic Universe ◽  
Thermal Equation ◽  
Third Law Of Thermodynamics ◽  
Homogeneous Isotropic Universe ◽  
Classical Thermodynamics ◽  
The Universe ◽  
Fluid Configuration

We examine the thermodynamic features of an exotic fluid known as modified cosmic Chaplygin gas in the context of homogeneous isotropic universe model. For this purpose, the behavior of physical parameters is discussed that help to analyze nature of the universe. Using specific heat formalism, the validity of third law of thermodynamics is checked. Furthermore, with the help of thermodynamic entities, the thermal equation of state is also discussed. The thermodynamic stability is explored by means of adiabatic, specific heat and isothermal conditions from classical thermodynamics. It is concluded that the considered fluid configuration is thermodynamically stable and expands adiabatically for an appropriate choice of parameters.

Thermodynamics of generalized cosmic Chaplygin gas model

2016 ◽  
Vol 31 (10) ◽  
pp. 1650061 ◽  
Author(s):  
M. Sharif ◽  
Ayesha Sarwar
Keyword(s):  
Isothermal Condition ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Physical Parameters ◽  
Stability Conditions ◽  
Expansion Of The Universe ◽  
The Stability ◽  
Generalized Cosmic Chaplygin Gas ◽  
The Universe ◽  
Thermal Stability Of

In this paper, we study thermal stability of an exotic fluid known as generalized cosmic Chaplygin gas (GCCG). We evaluate different physical parameters and examine how this fluid describes accelerated expansion of the universe. The stability conditions are formulated from thermodynamics which indicate that the respective fluid is stable adiabatically but it cannot be checked under isothermal condition.

THERMODYNAMIC STABILITY OF A FLUID WITH VARIABLE EQUATION OF STATE

2010 ◽  
Vol 25 (27) ◽  
pp. 2333-2348 ◽  
Author(s):  
NAIRWITA MAZUMDER ◽  
RITABRATA BISWAS ◽  
SUBENOY CHAKRABORTY
Keyword(s):  
Equation Of State ◽  
Thermodynamic Stability ◽  
State Parameter ◽  
Expansion Process ◽  
Thermal Equation ◽  
Third Law Of Thermodynamics ◽  
Variable Equation ◽  
Third Law ◽  
The Universe ◽  
General Thermodynamics

This paper deals with general thermodynamics for the universe filled with a perfect fluid, obeying an equation of state p = ω(z)ρ where the varying equation of the state parameter is chosen as two-index parametrization models namely: (a) linear redshift parametrization: ω(z) = ω0 + ω1z or (b) Jassal–Bagla–Padmanabhan (JBP) parametrization: [Formula: see text] where ω0, ω1 are constants. The behavior of temperature and the thermodynamic stability have been discussed. The thermal equation of state depends on both temperature and volume. As the universe evolves the fluid cools down obeying third law of thermodynamics and there will be thermodynamic stability during the expansion process without any phase transition or passing through any critical point.

Cosmological models for an homogeneous, isotropic universe

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Time Evolution ◽  
Space Time ◽  
Scale Factor ◽  
Cosmological Models ◽  
Isotropic Universe ◽  
Friedmann Equations ◽  
Homogeneous Isotropic Universe ◽  
The Universe

The universe is homogeneous and isotropic on sufficiently large scales. The metric which describes such a space-time is derived and it is shown that it is determined by the scale factor a(t) and the parameter k distinguishing between hyperbolic, flat, or spherical 3-spaces. The Friedmann equations, which describe the time evolution of these models, are derived and specific models are discussed.

THE LAWS OF THERMODYNAMICS AND THERMODYNAMIC STABILITY OF THE MODIFIED CHAPLYGIN GAS

2010 ◽  
Vol 25 (32) ◽  
pp. 2779-2793 ◽  
Author(s):  
TANWI BANDYOPADHYAY ◽  
SUBENOY CHAKRABORTY
Keyword(s):  
Equation Of State ◽  
Thermodynamic Stability ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
Expansion Process ◽  
Thermal Equation ◽  
Laws Of Thermodynamics ◽  
Thermodynamic Pressure ◽  
The Universe ◽  
General Thermodynamics

Laws of thermodynamics have been examined for the universe filled with a perfect fluid, obeying an adiabatic equation of state p = γρ-A/ρα (called modified Chaplygin gas), where γ, A and α are positive constants and ρ and p are energy density and thermodynamic pressure respectively. Using general thermodynamics, the behavior of temperature and the thermodynamic stability has been discussed for modified Chaplygin gas. A scenario is obtained such that the thermal equation of state depends on both temperature and volume and there will be thermodynamic stability during the expansion process so that the fluid cools down through the expansion without any phase transition (or passing through any critical point).

scholarly journals Dynamical system analysis of FLRW models with Modified Chaplygin gas

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ali Osman Yılmaz ◽  
Ertan Güdekli
Keyword(s):  
Dynamical System ◽  
Equation Of State ◽  
Energy Density ◽  
System Analysis ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
State Spaces ◽  
The Universe ◽  
Matter Energy ◽  
Far Future

AbstractWe investigate Friedmann–Lamaitre–Robertson–Walker (FLRW) models with modified Chaplygin gas and cosmological constant, using dynamical system methods. We assume $$p=(\gamma -1)\mu -\dfrac{A}{\mu ^\alpha }$$ p = ( γ - 1 ) μ - A μ α as equation of state where $$\mu$$ μ is the matter-energy density, p is the pressure, $$\alpha$$ α is a parameter which can take on values $$0<\alpha \le 1$$ 0 < α ≤ 1 as well as A and $$\gamma$$ γ are positive constants. We draw the state spaces and analyze the nature of the singularity at the beginning, as well as the fate of the universe in the far future. In particular, we address the question whether there is a solution which is stable for all the cases.

State finder and Om diagnostics in modified and generalised Chaplygin gas from recent data

2021 ◽  
Author(s):  
P. Thakur
Keyword(s):  
Chaplygin Gas ◽  
Red Shift ◽  
Recent Past ◽  
Eos Parameter ◽  
Deceleration Phase ◽  
Om Diagnostic ◽  
Expected Values ◽  
Best Fit ◽  
The Universe ◽  
Jerk Parameter

A modified and generalised Chaplygin gas (MCG, [Formula: see text] and GCG, [Formula: see text]) has been separately chosen here as a constituent of the universe. Concept of state finder and Om diagnostics are introduced to track the dark energy in the models. Here, observed Hubble data (OHD) and binned Pantheon data of supernovae are used to determine the best-fit equation-of-state (EoS) parameters of these models and these are compared with the [Formula: see text]CDM model. The best-fit value and expected values of cosmological jerk parameter [Formula: see text], snap parameter [Formula: see text] are determined, which are close to each other. A plot of [Formula: see text] with red-shift, with themselves, as well as with deceleration parameter [Formula: see text], shows the evolution of the universe and its possible future. Variations of [Formula: see text] and EoS parameter [Formula: see text] with red-shift show acceleration–deceleration phase transition in the recent past. Lastly, the state finder pair [Formula: see text] and Om diagnostic have been utilized to discriminate the models.

scholarly journals Opening PANDORA’s box: APEX observations of CO in PNe

2018 ◽  
Vol 618 ◽  
pp. A91 ◽  
Author(s):  
L. Guzman-Ramirez ◽  
A. I. Gómez-Ruíz ◽  
H. M. J. Boffin ◽  
D. Jones ◽  
R. Wesson ◽  
...  
Keyword(s):  
Column Density ◽  
Planetary Nebulae ◽  
Close Binaries ◽  
Physical Parameters ◽  
Molecular Gas ◽  
Intermediate Mass Stars ◽  
Circumstellar Shells ◽  
Large Survey ◽  
Late Stages ◽  
The Universe

Context. Observations of molecular gas have played a key role in developing the current understanding of the late stages of stellar evolution. Aims. The survey Planetary nebulae AND their cO Reservoir with APEX (PANDORA) was designed to study the circumstellar shells of evolved stars with the aim to estimate their physical parameters. Methods. Millimetre carbon monoxide (CO) emission is the most useful probe of the warm molecular component ejected by low- to intermediate-mass stars. CO is the second-most abundant molecule in the Universe, and the millimetre transitions are easily excited, thus making it particularly useful to study the mass, structure, and kinematics of the molecular gas. We present a large survey of the CO (J = 3−2) line using the Atacama Pathfinder EXperiment (APEX) telescope in a sample of 93 proto-planetary nebulae and planetary nebulae. Results. CO (J = 3−2) was detected in 21 of the 93 objects. Only two objects (IRC+10216 and PN M2-9) had previous CO (J = 3−2) detections, therefore we present the first detection of CO (J = 3−2) in the following 19 objects: Frosty Leo, HD 101584, IRAS 19475+3119, PN M1-11, V* V852 Cen, IC 4406, Hen 2-113, Hen 2-133, PN Fg 3, PN Cn 3-1, PN M2-43, PN M1-63, PN M1-65, BD+30 3639, Hen 2-447, Hen 2-459, PN M3-35, NGC 3132, and NGC 6326. Conclusions. CO (J = 3−2) was detected in all 4 observed pPNe (100%), 15 of the 75 PNe (20%), one of the 4 wide binaries (25%), and in 1 of the 10 close binaries (10%). Using the CO (J = 3−2) line, we estimated the column density and mass of each source. The H2 column density ranges from 1.7 × 1018 to 4.2 × 1021 cm−2 and the molecular mass ranges from 2.7 × 10−4 to 1.7 × 10−1 M⊙.

Specific Heat of Tribological Wear Debris Material

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Maria Maciąg
Keyword(s):  
Specific Heat ◽  
Thermodynamic Model ◽  
Wear Debris ◽  
Friction And Wear ◽  
Mass Conservation ◽  
Phenomenological Approach ◽  
Wear Testing ◽  
Physical Parameters ◽  
Friction Process ◽  
Solid Friction

Stationary processes of solid friction, heating and wear are analyzed in this paper on the basis of the first principle of thermodynamics. Analytical dependences between physical parameters of a tribological system have been determined. Densities of extensive quantity fluxes are referred to elementary surface and elementary time, which has permitted to include intensive quantities, especially temperature, in the model presented here. Although the discussion is restricted to the phenomenological approach, conclusions regarding some microscopic properties of the matter in the process of fragmentation are drawn directly from the laws of energy and mass conservation. Differences between specific heat of the starting material cp and of the debris produced cp′ are emphasized. The model of the friction process described by Maciąg, M. (2010, “Thermodynamic Model of the Metallic Friction Process,” ASME J. Tribol., 132(3), pp. 1–7) has been modified and a new method of evaluating cp′ is proposed. Results of standard friction and wear testing are used to describe selected tribological systems in quantitative terms based on the thermodynamic model discussed here (Sadowski, J., and Żurowski, W., 1992, “Thermodynamic Aspects of Metals' Wear-Resistance,” Tribol. Lubr. Eng., 3, pp. 152–159). Very high specific heat of tribological wear debris material is found at the moment of the material's production. To conclude, results of theoretical and experimental analysis are discussed and their interpretation is proposed. Applicability of the system magnitudes C and D to modeling of friction and wear is highlighted.

The evolutionary pictures for phantom field in loop quantum cosmology

2019 ◽  
Vol 28 (15) ◽  
pp. 1950170
Author(s):  
Kui Xiao
Keyword(s):  
Dark Matter ◽  
Quantum Cosmology ◽  
Scalar Fields ◽  
Chaplygin Gas ◽  
Loop Quantum Cosmology ◽  
Phantom Field ◽  
Dynamical Behaviors ◽  
Slow Roll ◽  
The Universe ◽  
Slow Roll Inflation

The evolutionary pictures for phantom field in loop quantum cosmology are discussed in this paper. Comparing the dynamical behaviors of the phantom field with one of the canonical scalar fields in loop quantum cosmology scenario, we found that the [Formula: see text] phase trajectories are the same, but the [Formula: see text] phase-spaces are very different, and the phantom field with considering potentials can drive neither super inflation nor slow-roll inflation in loop quantum cosmology (LQC) scenario. While the universe is filled with multiple dark fluids, to ensure that the condition [Formula: see text] does not violate, the energy density of dark matter [Formula: see text] and the equation-of-state of phantom field [Formula: see text] should satisfy the condition [Formula: see text] at the bounce point. If this constraint condition holds, the universe can enter an inflationary stage, and it is possible to unify the description of phantom field, dark matter and inflation. We introduced a toy model which has the same form of the general Chaplygin gas to unify the dark energy, dark matter and slow-roll inflation, and the slow-roll inflation of the toy model has also been discussed.

scholarly journals The Scaling of Solar Flare Hard X-ray Emission to Other Flaring Objects in the Universe

2000 ◽  
Vol 195 ◽  
pp. 133-134
Author(s):  
P. C. H. Martens
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Galactic Nuclei ◽  
Physical Parameters ◽  
X Ray ◽  
Transport Code ◽  
Type Particle ◽  
Fokker Planck Equations ◽  
The Universe ◽  
Fokker Planck

Fletcher & Martens have successfully modeled solar hard X-ray sources observed at the top and footpoints of flaring magnetic loops with a Fokker-Planck type particle transport code. I show here that there are invariances in the Fokker-Planck equations that make these results applicable to environments with vastly different physical parameters, such as hard X-ray flares in accretion disks in active galactic nuclei, and in RS CVn and ALGOL type binaries.

Sign in / Sign up

Export Citation Format

Share Document