scholarly journals Extreme compression behaviour of higher derivative properties of solids based on the generalized Rydberg equation of state

2009 ◽  
Vol 12 (2) ◽  
pp. 205-213 ◽  
Author(s):  
Shanker ◽  
Singh ◽  
Jitendra
Keyword(s):  
Equation Of State ◽  
Compression Behaviour ◽  
Higher Derivative

Cosmological models in R2 gravity with hybrid expansion law

2021 ◽  
pp. 2150143
Author(s):  
Partha Sarathi Debnath ◽  
Bikash Chandra Paul
Keyword(s):  
Equation Of State ◽  
Deceleration Parameter ◽  
State Parameter ◽  
Cosmological Models ◽  
Model Parameters ◽  
Density Parameter ◽  
Eos Parameter ◽  
Data Set ◽  
Deceleration Phase ◽  
Higher Derivative

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.

scholarly journals Holographic colour superconductors at finite coupling with NJL Interactions

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Kazem Bitaghsir Fadafan ◽  
Jesús Cruz Rojas
Keyword(s):  
Equation Of State ◽  
Cooper Pair ◽  
Chemical Potential ◽  
Coupling Parameter ◽  
Einstein Gravity ◽  
Superconducting Phase ◽  
Holographic Model ◽  
Higher Derivative ◽  
Holographic Qcd ◽  
Holographic Description

AbstractWe study a bottom-up holographic description of the QCD colour superconducting phase in the presence of higher derivative corrections. We expand this holographic model in the context of Gauss–Bonnet (GB) gravity. The Cooper pair condensate has been investigated in the deconfinement phase for different values of the GB coupling parameter $$\lambda _{G B}$$ λ GB , we observe a change in the value of the critical chemical potential $$\mu _c$$ μ c in comparison to Einstein gravity. We find that $$\mu _c$$ μ c grows as $$\lambda _{G B}$$ λ GB increases. We add four fermion interactions and show that in the presence of these corrections the main interesting features of the model are still present and that the intrinsic attractive interaction can not be switched off. This study suggests to find GB corrections to equation of state of holographic QCD matter.

Holographic dark energy models in higher derivative torsion corrected modified teleparallel gravity

2018 ◽  
Vol 15 (04) ◽  
pp. 1850067 ◽  
Author(s):  
Shamaila Rani ◽  
Abdul Jawad
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Holographic Dark Energy ◽  
Teleparallel Gravity ◽  
Eos Parameter ◽  
Phantom Divide ◽  
Energy Models ◽  
Higher Derivative ◽  
Phantom Divide Line ◽  
The Universe

We consider the recently proposed higher derivative torsion corrected modified teleparallel gravity and holographic dark energy (HDE) models. We apply the correspondence scheme to construct models in underlying scenario using various scale factor forms. We investigate the reconstructed functions through equation of state (EoS) parameter. It is demonstrated that the EoS parameter provides quintom-like nature of the Universe in most of the cases, i.e. it drives the Universe from vacuum dark energy era toward phantom era of the Universe by crossing the phantom divide line. We also demonstrate that the consistency with the observational data can be achieved.

scholarly journals Higher derivative corrections of f(R) gravity with varying equation of state in the case of variable G and Λ

2015 ◽  
Vol 93 (4) ◽  
pp. 449-455 ◽  
Author(s):  
M. Khurshudyan ◽  
B. Pourhassan ◽  
A. Pasqua
Keyword(s):  
Numerical Analysis ◽  
Equation Of State ◽  
Modified Gravity ◽  
Deceleration Parameter ◽  
Cosmological Parameters ◽  
Variable G And Λ ◽  
Hubble Expansion ◽  
Higher Derivative ◽  
Higher Order Terms ◽  
Variable G

In this paper, we study three models of f(R) modified gravity including higher order terms based on different equation of state parameters. We also assume variable G and Λ. Using numerical analysis, we obtain the behavior of some important cosmological parameters, like the Hubble expansion H parameter and the deceleration parameter q. Statefinder diagnostics are also performed for all models.

RENORMALIZATION EFFECTS IN THE SUPERSTRING MODULI FROM THE HIGHER-DERIVATIVE TERMS

2001 ◽  
Vol 16 (19) ◽  
pp. 3217-3235 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Equation Of State ◽  
Kinetic Energy ◽  
Canonical Form ◽  
Dimensional Reduction ◽  
Scalar Fields ◽  
Adiabatic Index ◽  
Einstein Metric ◽  
Tree Level ◽  
Superstring Theory ◽  
Higher Derivative

The dimensional reduction of the effective ten-action [Formula: see text] of the heterotic superstring theory to the physical four-action S[gij] results in the appearance of three moduli B(a), whose real parts [Formula: see text], set equal for simplicity, define the radius and shape of the compact internal six-space [Formula: see text], in addition to the dilaton [Formula: see text], the ten-interval being [Formula: see text]. These scalar fields are massless at tree level and can be put into canonical form with coefficients [Formula: see text] for the positive kinetic-energy terms, when higher-derivative terms are ignored, as found by Witten, so that [Formula: see text]. Previously, we have shown that σA and σB acquire a potential from the higher-derivative terms [Formula: see text] and [Formula: see text], which becomes large close to the Planck era. Here, we discuss the renormalization of the kinetic-energy terms due to [Formula: see text] which, after diagonalization, results in a mixing of ∇σB with ∇σA, while the remaining coefficient of (∇σB)2 vanishes at t c ≈ t P /12 in a radiation-dominated Universe, corresponding to a temperature T c ≈ 5 × 1017 GeV , where the four-theory is still classical. At earlier times, the energy is unbounded from below, signalling that the four-theory has become unphysical, and that the string must still be in its uncompactified form with one dilaton ϕ, whose canonical kinetic energy is positive in the Einstein metric. This mechanism depends upon the equation of state of the source for the Friedmann expansion assumed, and is only effective for values of the adiabatic index in the range 1.14 < γ < 2.63, which thus includes radiation (γ = 4/3) and the Zel'dovich equation of state (γ = 2).

EXTREME COMPRESSION BEHAVIOUR OF SOLIDS BASED ON THE ROY-ROY INVERTED EQUATION OF STATE

2008 ◽  
Vol 22 (07) ◽  
pp. 909-915
Author(s):  
R. S. CHAUHAN ◽  
K. LAL
Keyword(s):  
Equation Of State ◽  
Bulk Modulus ◽  
Organic Solids ◽  
Inorganic Solids ◽  
The Core ◽  
The Earth ◽  
Compression Behaviour ◽  
Seismological Data ◽  
Murnaghan Equation ◽  
Data Modifications

An analysis has been presented using the Roy-Roy equation of state (EOS), which represents an extended and modified version of the Murnaghan EOS. It is found that the value of [Formula: see text] for various types of solids remain between 5/3 and 2. The Roy-Roy EOS has been found to become applicable for the core of the Earth, predicting the values of the pressure and bulk modulus in the range of seismological data. Modifications suggested recently to remove the shortcomings of the Murnaghan equation have been discussed. The maximum values of [Formula: see text] obtained from the Roy-Roy EOS for different inorganic solids and organic solids are also discussed.

Compression Behaviour and Equation of State of Zr 44.4 Nb 7 Cu 13.5 Ni 10.8 Be 24.3 Bulk Metallic Glass up to 39 GPa

2004 ◽  
Vol 21 (5) ◽  
pp. 898-900 ◽  
Author(s):  
Li Gong ◽  
Zhan Zai-Ji ◽  
Wang Li-Min ◽  
Sun Li-Ling ◽  
Liu Jing ◽  
...  
Keyword(s):  
Equation Of State ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Compression Behaviour
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