scholarly journals Anisotropic Strange Star in 5D Einstein-Gauss-Bonnet Gravity

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 1015
Author(s):  
Mahmood Khalid Jasim ◽  
Sunil Kumar Maurya ◽  
Ksh. Newton Singh ◽  
Riju Nag
Keyword(s):  
Gravitational Potential ◽  
Stellar System ◽  
Critical Value ◽  
Radial Component ◽  
Strange Star ◽  
Coupling Constant ◽  
Star Model ◽  
Anisotropic Solution ◽  
Surface Redshift ◽  
Tov Equation

In this paper, we investigated a new anisotropic solution for the strange star model in the context of 5D Einstein-Gauss-Bonnet (EGB) gravity. For this purpose, we used a linear equation of state (EOS), in particular pr=βρ+γ, (where β and γ are constants) together with a well-behaved ansatz for gravitational potential, corresponding to a radial component of spacetime. In this way, we found the other gravitational potential as well as main thermodynamical variables, such as pressures (both radial and tangential) with energy density. The constant parameters of the anisotropic solution were obtained by matching a well-known Boulware-Deser solution at the boundary. The physical viability of the strange star model was also tested in order to describe the realistic models. Moreover, we studied the hydrostatic equilibrium of the stellar system by using a modified TOV equation and the dynamical stability through the critical value of the radial adiabatic index. The mass-radius relationship was also established for determining the compactness and surface redshift of the model, which increases with the Gauss-Bonnet coupling constant α but does not cross the Buchdahal limit.

Self-gravitating anisotropic star using gravitational decoupling

2021 ◽  
Author(s):  
Baiju Dayanandan ◽  
T. T. Smitha ◽  
Sunil Maurya
Keyword(s):  
Compact Star ◽  
Radial Component ◽  
Energy Conditions ◽  
Regularity Conditions ◽  
Star Model ◽  
Anisotropic Solution ◽  
Seed System ◽  
The Stability ◽  
Metric Function ◽  
Anisotropic Star

Abstract This paper addresses a new gravitationally decoupled anisotropic solution for the compact star model via the minimal geometric deformation (MGD) approach. We consider a non-singular well-behaved gravitational potential corresponding to the radial component of the seed spacetime and embedding class I condition that determines the temporal metric function to solve the seed system completely. However, two different well-known mimic approaches such as pr = Θ1 1 and ρ = Θ0 0 have been employed to determine the deformation function which gives the solution of the second system corresponding to the extra source. In order to test the physical viability of the solution, we have checked several conditions such as regularity conditions, energy conditions, causality conditions, hydrostatic equilibrium, etc. Moreover, the stability of the solutions has been also discussed by the adiabatic index and its critical value. We find that the solutions set seems viable as far as observational data are concerned.

scholarly journals Constraining values of bag constant for strange star candidates

2019 ◽  
Vol 28 (13) ◽  
pp. 1941006 ◽  
Author(s):  
Abdul Aziz ◽  
Saibal Ray ◽  
Farook Rahaman ◽  
M. Khlopov ◽  
B. K. Guha
Keyword(s):  
Compact Star ◽  
A Priori ◽  
Stellar System ◽  
Mass Function ◽  
Strange Star ◽  
Compact Stars ◽  
Stellar Structure ◽  
Star Model ◽  
Field Equations ◽  
Bag Constant

We provide a strange star model under the framework of general relativity by using a general linear equation of state (EOS). The solution set thus obtained is employed on altogether 20 compact star candidates to constraint values of MIT bag model. No specific value of the bag constant ([Formula: see text]) a priori is assumed, rather possible range of values for bag constant is determined from observational data of the said set of compact stars. To do so, the Tolman–Oppenheimer–Volkoff (TOV) equation is solved by homotopy perturbation method (HPM) and hence we get a mass function for the stellar system. The solution to the Einstein field equations represents a nonsingular, causal and stable stellar structure which can be related to strange stars. Eventually, we get an interesting result on the range of the bag constant as [Formula: see text]. We have found the maximum surface redshift [Formula: see text] and shown that the central redshift ([Formula: see text]) cannot have value larger than [Formula: see text], where [Formula: see text]. Also, we provide a possible value of bag constant for neutron star with quark core using hadronic as well as quark EOS.

scholarly journals Asymptotic Behavior and Critical Coupling in Scalar Yukawa Model

2018 ◽  
Vol 47 ◽  
pp. 1860095
Author(s):  
V. E. Rochev
Keyword(s):  
Asymptotic Behavior ◽  
Matrix Model ◽  
Critical Value ◽  
Leading Order ◽  
Coupling Constant ◽  
Critical Coupling ◽  
Yukawa Model ◽  
Four Dimensions ◽  
Euclidean Region ◽  
Vector Matrix

The solution of the equation for the pion propagator in the leading order of the [Formula: see text] – expansion for a vector-matrix model with interaction [Formula: see text] in four dimensions shows a change of the asymptotic behavior in the deep Euclidean region in a vicinity of a certain critical value of the coupling constant.

scholarly journals A Solvable Twisted One-Plaquette Model

1997 ◽  
Vol 12 (15) ◽  
pp. 2741-2762 ◽  
Author(s):  
M. Billó ◽  
A. D'Adda
Keyword(s):  
Phase Transition ◽  
Heat Kernel ◽  
Quantum Fluctuations ◽  
Critical Value ◽  
Classical Solutions ◽  
Coupling Constant ◽  
Time Direction ◽  
Distribution Of Eigenvalues ◽  
Kernel Model ◽  
Link Variable

We solve a hot twisted Eguchi-Kawai model with only timelike plaquettes in the deconfined phase, by computing the quadratic quantum fluctuations around the classical vacuum. The solution of the model has some novel features: the eigenvalues of the timelike link variable are separated in L bunches, if L is the number of links of the original lattice in the time direction, and each bunch obeys a Wigner semicircular distribution of eigenvalues. This solution becomes unstable at a critical value of the coupling constant, where it is argued that a condensation of classical solutions takes place. This can be inferred by comparison with the heat-kernel model in the Hamiltonian limit, and the related Douglas–Kazakov phase transition in QCD2. As a byproduct of our solution, we can reproduce the dependence of the coupling constant from the parameter describing the asymmetry of the lattice, and compare it to previous results by Karsch.

scholarly journals MATRIX MODEL APPROACH TO d>2 NONCRITICAL SUPERSTRINGS

1995 ◽  
Vol 10 (34) ◽  
pp. 2639-2649 ◽  
Author(s):  
AKIKAZU HASHIMOTO ◽  
IGOR R. KLEBANOV
Keyword(s):  
Field Theory ◽  
Matrix Model ◽  
Light Cone ◽  
Critical Value ◽  
Coupling Constant ◽  
Numerical Evidence ◽  
Large N ◽  
Light Cone Quantization ◽  
Model Approach

We apply light-cone quantization to a (1+1)-dimensional supersymmetric field theory of large-N matrices. We provide some preliminary numerical evidence that when the coupling constant is tuned to a critical value, this model describes a (2+1)-dimensional noncritical superstring.

Finite-size effects in exponential random graphs

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
A Gorsky ◽  
O Valba
Keyword(s):  
Random Graphs ◽  
Ground State ◽  
Size Effects ◽  
Chemical Potential ◽  
Network Flows ◽  
Finite Size ◽  
Critical Value ◽  
Star Model ◽  
Finite Size Effects ◽  
Exponential Random Graphs

Abstract In this article, we show numerically the strong finite-size effects in exponential random graphs. Particularly, for the two-star model above the critical value of the chemical potential for triplets a ground state is a star-like graph with the finite set of hubs at network density $p<0.5$ or as the single cluster at $p>0.5$. We find that there exists the critical value of number of nodes $N^{*}(p)$ when the ground state undergoes clear-cut crossover. At $N>N^{*}(p),$ the network flows via a cluster evaporation to the state involving the small star in the Erdős–Rényi environment. The similar evaporation of the cluster takes place at $N>N^{*}(p)$ in the Strauss model. We suggest that the entropic trap mechanism is relevant for microscopic mechanism behind the crossover regime.

EFFECTIVE POTENTIALS FOR ϕ4-THEORY IN 2+1 DIMENSIONS

1994 ◽  
Vol 09 (28) ◽  
pp. 2623-2635 ◽  
Author(s):  
R.A. OLSEN ◽  
F. RAVNDAL
Keyword(s):  
Transition Temperature ◽  
Symmetry Breaking ◽  
Effective Potential ◽  
Gaussian Approximation ◽  
Critical Value ◽  
Zero Temperature ◽  
Coupling Constant ◽  
Effective Potentials ◽  
Bare Coupling Constant ◽  
Symmetric Phase

Spontaneous symmetry breaking in ϕ4-theory in 2+1 dimensions is investigated using the Gaussian approximation. The theory stays in the symmetric phase at zero temperature as long as the bare coupling constant is below a critical value λc. When λ>λc the symmetric phase is again stable when the temperature is above a transition temperature T(λ). The obtained results are compared with the predictions of the standard one-loop effective potential.

scholarly journals THERMODYNAMICAL PHASES OF A REGULAR SAdS BH

2013 ◽  
Vol 22 (03) ◽  
pp. 1350010 ◽  
Author(s):  
ANAIS SMAILAGIC ◽  
EURO SPALLUCCI
Keyword(s):  
Ground State ◽  
Weak Coupling ◽  
Critical Value ◽  
Minimal Length ◽  
Coupling Constant ◽  
Weak Coupling Regime ◽  
Pure Radiation ◽  
First Order ◽  
Different Temperatures ◽  
First Order Phase

This paper studies the thermodynamical stability of regular BHs in AdS5 background. We investigate off-shell free energy of the system as a function of temperature for different values of a "coupling constant" [Formula: see text], where the cosmological constant is Λ = -3/l2 and [Formula: see text] is "minimal length." The parameter [Formula: see text] admits a critical value, [Formula: see text], corresponding to the appearance of an inflexion point in the Hawking temperature. In the weak-coupling regime [Formula: see text], there are first-order phase transitions at different temperatures. Unlike the Hawking–Page case, at temperature 0 ≤ T ≤ T min the ground state is populated by "cold" near-extremal BHs instead of a pure radiation. On the other hand, for [Formula: see text], only large, thermodynamically stable BHs exist.

Stability of the two-dimensional Brown–Ravenhall operator

2002 ◽  
Vol 132 (5) ◽  
pp. 1133-1144 ◽  
Author(s):  
A. Bouzouina
Keyword(s):  
Critical Value ◽  
Two Dimensional ◽  
Coupling Constant ◽  
Kato Inequality

We prove that the two-dimensional Brown–Ravenhall operator is bounded from below when the coupling constant is below a specified critical value—a property also referred to as stability. As a consequence, the operator is then self-adjoint. The proof is based on the strategy followed by Evans et al. and Lieb and Yau, with some relevant changes characteristic of the dimension. Our analysis also yields a sharp Kato inequality.

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