Browsing by Author "Dr. Abdul Jawad"

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Cosmic Acceleration in Modified Horava- Lifshitz Gravity
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Sameen Ashraf; CIIT/FA19-RMT-094/LHR; Dr. Abdul Jawad; LHR TP 7395
We discuss the cosmological implications of the interacting Barrow holo- graphic dark energy model in the context of ﬂat deformed Hoˇrava-Lifshitz gravity by assuming the interaction (Γ) between dark energy and pressure- less dark matter. To understand the mechanism of recent accelerated ex- pansion of the universe, we consider Hubble and event horizons as infrared cutoﬀ. We investigate the evolutionary history of cosmological parame- ters especially the equation of state, Hubble, deceleration, squared speed of sound and ﬁnd results that favor observational data of Planck 2018. It is found that the Hubble parameter lies in the range 72+2 −2 (for event horizon) and 74.004+0.004 −0.004 (for Hubble horizon). The equation of state parameter pro- vides the phantom phase of the universe, while the deceleration parameter illustrates the accelerated phase of the universe. On the other hand, we plot the squared speed of sound and ﬁnd the positive behavior which ensures the stability of underlying model. Moreover, we examine the generalized second law of thermodynamics of this cosmological system with barrow entropy as horizon entropy and observe that this law holds for both horizons.
Cosmic Implications of Tsallis Holographic Dark Energy with Various IR Cutoffs in Horava- Lifshitz Gravity
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Mehwish Shad; CIIT/SP20-RMT-024/LHR; Dr. Abdul Jawad; LHR TP 7653
Horava-Lifshitz gravity is a very fascinating proposal of modiﬁed gravity for explaining the current acceleration and other cosmic issues. In contin- uation of this discussion, we study the consequences of Tsallis dark energy with Hubble and particle horizons in the framework of deformed Horava- Lifshitz gravity by taking into account ﬂat FRW universe. The interaction between Tsallis holographic dark energy and dark matter are also taken into account to discuss the underlying scenario. It is found that fractional dark energy density (ΩD) approaches to 0.70+0.03 −0.03 as redshift goes to zero (present epoch) for both cases of horizons. The cosmic parameter (ωD) shows phantom crossing behavior in both models, i.e., it evolutes the uni- verse from quintessence phase to phantom phase by crossing the vacuum horizon. In both cases of horizons, the deceleration support the cosmic ac- celeration by exhibiting the negative values. The perturbation sound speed also favors the viability of our models through positive behavior. The co- incidence parameter support the exchange of dark matter to dark energy phenomenon through positivity. We also discuss the behavior of growth rate and growth index in the growth of matter density perturbations for both horizons. These parameters mimic the ΛCDM behavior of the universe.
Cosmic Inflation Evading Swampland Conjectures
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Kashaf Embreen; CIIT/FA19-RMT-022/LHR; Dr. Abdul Jawad; LHR TP 7440
In this thesis, we study the inﬂationary scenario in the realm of k-essence model and swampland conjecture. Taking into account three models of Chaplygin gas, that is, generalized, modiﬁed and generalized cosmic Chap- lygin gas models, we discuss the slow roll parameters (²(φ), η(φ)), curvature perturbation (Ps), tensor to scaler ratio (r) and scaler spectral index (ns). In reference to k-essence model, the coupling function as a function of scaler ﬁeld L(φ) is used. We investigate the swampland conjecture and then ﬁnd the value of ζ(φ) i.e bound of second conjecture for the above three models by unifying swampland conjecture and k-essence. We plot the inﬂationary parameters and bound of swampland conjecture r −ns, ζ(φ) − φ, and check their values according to Planck data 2018.
Cosmographic Analysis of Holographic Non-Zero Torsion Framework
(Library Information Services, CUI Lahore, 2023) Aitazaz Ahsan; FA21-RMT-018; Dr. Abdul Jawad
In this thesis, we use the cosmographic approach to discuss Friedmann-like space-time in the presence of torsion. For this, we explore equations of motion that explain creation in an isotropic and homogeneous cosmic backdrop with non-zero torsion. Here, we consider the energy density of p L¡2. We examine this DE model with both constant and variable holographic length-scale in terms of Hubble parameter to determine the best ¯t scale. The interaction between dark sector components is taken to evaluate cosmographic parameters, like Hubble, equation of state, deceleration, jerk, snap, lerk the state¯nder pa- rameters. We consider four c(z) parameterizations, which are Chevalier- Polarski-Linder, Jassal-Bagla-Padmanabhan, Wetterich and Ma-Zhang for both cases. We obtain consistent results for speci¯c choices of constant parameters in the underlying scenario.
Dynamical Properties of Specific Black Holes
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) Muhammad Umair Shahzad; FA13-PMATH-005; LHR TP 5606; Dr. Abdul Jawad
The present thesis comprises the study of three dynamical phenomenon such as thermal fluctuations, accretion and tidal forces of black holes/regular black holes. We consider the logarithmic corrected entropy in order to analyze the thermal fluctuations. We examine the effects of thermal fluctuations on a regular black hole of the non-minimal Einstein-Yang-Mill theory with gauge field of magnetic Wu-Yang type and a cosmological constant. We investigate the first law of thermodynamics in the presence of logarithmic corrected entropy and non-minimal regular black hole. Furthermore, we discuss the thermal fluctuation problem by utilizing the higher order corrected entropy. We examine the thermodynamical behavior of two well-known black holes such as Reissner-Nordström Anti de Sitter black hole with global monopole and f(R) black hole in the presence of higher order corrected entropy. We also discuss the accretion problem in two phases. In first phase, we analyze the accretion onto static spherically symmetric regular black holes for specific choices of the equation of state parameter. The underlying regular black holes are charged regular black holes using the Fermi-Dirac distribution, logistic distribution, non-linear electrodynamics, respectively, and Kehagias-Sftesos asymptotically flat regular black holes. In second phase, we develop the Hamiltonian dynamical system to tackle the accretion problem. We investigate the accretion of test fluids onto regular black holes such as Kehagias-Sftesos black hole and regular black holes with Dagum distribution function. We analyze the accretion process when different test fluids are falling onto these regular black holes. The behavior of fluid flow and the existence of sonic points is being checked for these regular black holes. Finally, we investigate the tidal forces occurring in a Kiselev black hole surrounded by radiation and dust fluids. We also solve the geodesic deviation equation for radially free-falling bodies toward Kiselev black hole. We explain the geodesic deviation vector graphically and point out the location of the event and Cauchy horizons for specific values of the radiation and dust parameters.
Dynamical Properties of Specific Black Holes
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) Muhammad Umair Shahzad; CIIT/FA13-PMATH-005/LHR; Dr. Abdul Jawad; LHR TP 5606
The present thesis comprises the study of three dynamical phenomenon such as thermal fluctuations, accretion and tidal forces of black holes/regular black holes. We consider the logarithmic corrected entropy in order to analyze the thermal fluctuations. We examine the effects of thermal fluctuations on a regular black hole of the non-minimal Einstein-Yang-Mill theory with gauge field of magnetic Wu-Yang type and a cosmological constant. We investigate the first law of thermodynamics in the presence of logarithmic corrected entropy and non-minimal regular black hole. Furthermore, we discuss the thermal fluctuation problem by utilizing the higher order corrected entropy. We examine the thermodynamical behavior of two well-known black holes such as Reissner-Nordström Anti de Sitter black hole with global monopole and f(R) black hole in the presence of higher order corrected entropy. We also discuss the accretion problem in two phases. In first phase, we analyze the accretion onto static spherically symmetric regular black holes for specific choices of the equation of state parameter. The underlying regular black holes are charged regular black holes using the Fermi-Dirac distribution, logistic distribution, non-linear electrodynamics, respectively, and Kehagias-Sftesos asymptotically flat regular black holes. In second phase, we develop the Hamiltonian dynamical system to tackle the accretion problem. We investigate the accretion of test fluids onto regular black holes such as Kehagias-Sftesos black hole and regular black holes with Dagum distribution function. We analyze the accretion process when different test fluids are falling onto these regular black holes. The behavior of fluid flow and the existence of sonic points is being checked for these regular black holes. Finally, we investigate the tidal forces occurring in a Kiselev black hole surrounded by radiation and dust fluids. We also solve the geodesic deviation equation for radially free-falling bodies toward Kiselev black hole. We explain the geodesic deviation vector graphically and point out the location of the event and Cauchy horizons for specific values of the radiation and dust parameters.
Effects of Modified Entropy on Black Hole Thermodynamics in Bumblebee Gravity
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2025) Zainab Nazish; CIIT/SP24-RMT-019/LHR; Dr. Abdul Jawad; LHR TP 10080
This thesis explores the thermodynamic behavior and stability of anti-de Sitter (AdS) black holes within the framework of bumblebee gravity, a theory in which Lorentz symmetry is spontaneously broken by a vector field. The study examines how the Lorentz-violating bumblebee parameter influences the event horizon structure and various thermodynamic properties in both standard and extended phase spaces. Thermal stability is analyzed through heat capacity and Helmholtz free energy. The results show that large bumblebee AdS black holes can simultaneously satisfy local and global stability conditions, with the stable regions strongly depending on the Lorentz-violating parameter. The research also investigates heat capacity at constant pressure in the extended phase space, where the cosmological constant is interpreted as thermodynamic pressure. In this case, the stability criteria are found not to be fulfilled, highlighting the significant role of Lorentz symmetry violation in black hole thermodynamics. In addition, the thesis studies the sparsity parameter and Hawking radiation emission rates for black hole solutions in bumblebee gravity using generalized entropy models, including Sharma–Mittal entropy and three-parameter entropy indices. The findings reveal that changing the sign of the cosmological constant significantly affects thermodynamic sparsity and entropy behavior. A negative cosmological constant reduces sparsity while increasing entropy, indicating a denser thermodynamic system. Conversely, a positive cosmological constant preserves higher thermodynamic sparsity. Furthermore, the emission spectrum becomes sharper for negative cosmological constant values, indicating enhanced low-energy emission within a confining AdS background, while a positive cosmological constant generally suppresses the emission rate.
Effects of Well-Known Potentials on Cosmic Inflation in f(T) Gravity
(Library Information Services, CUI Lahore, 2023) Ayesha Aslam; FA21-RMT-064; Dr. Abdul Jawad
In this thesis, we investigate a canonical scalar ¯eld in°ationary scenarioby considering an exponential model in the context of f (T ) theory. We take some well-known potentials as general hilltop in°ation potential (GHI), valley hybrid in°ation potential (VHI), shaft potential and minimal in°ation potential to evaluate some in°ationary parameters. We evaluate number of e-folds N , the slow-roll parameter ²1, ratio of tensor-scalar r, scalar-spectral index (ns) and its running ®. For a comparison of our results with Planck data, we draw ns - r and ns - ®s planes for the di®erent well known potentials. Our outcomes for three potentials depict a consist and compatible in°ationary scenario with the recent observational data (Planck data 2018).
Entropy Corrected Thermodynamic Geometries of Regular Black Holes
(Library Information Services COMSATS University Lahore Campus, 2023-03-13) Hamza Tariq; SP22-RMT-001; Dr. Abdul Jawad; LHR TP 8710
In this thesis, we explore the thermodynamic characteristics of a Bardeen black hole that interacts with a string cloud and is minimally connected to nonlinear electrodynamics. We present a entropy function with five parame ters, demonstrating its singularity-free behavior throughout the entire cos mic evolution of the universe. Moreover, this function serves to extend the Tsallis, R´enyi, and Sharma-Mittal entropies for appropriate parameter limit conditions.For instance the Tsallis entropy is expressed as ST = S δ , where δ represents the Tsallis exponent and S denotes the Bekenstein-Hawking entropy. This formula is particularly applicable to systems with long-range interactions where the Boltzmann-Gibbs entropy is not suitable. It’s evident that when δ = 1, the Tsallis entropy converges to the BekensteinHawking limit, but for values of δ other than 1, it does not exhibit additivity. On the contrary, the R´enyi entropy it converges to the Bekenstein-Hawking limit as a approaches zero. While the Tsallis and R´enyi entropies might be combined to generate the Sharma-Mittal entropy, the R´enyi entropy was first offered as a way to assess information content. We analyze a variety of parameters, including mass, temperature, pressure, and Gibbs free en ergy, using the Tsallis, R´enyi, and Sharma-Mittal entropies. In our study, we derive stable behavior and find physical solutions by taking particular values for the parameters a and q.
Exploring Patterns and Relations in Knot Theory by Using Machine Learning
(Library Information Services, CUI Lahore, 2023) Muhammad Umer; CIIT/FA21-RMT-105/LHR; Dr. Abdul Jawad
. Machine learning is a sub-domain of AI which has manifested impressive applicability in various scientific domains, and provides different techniques that could be used to identify relations or patterns in the data. Machine learning could be used in multiple ways in analyzing and exploring knot theory. In this thesis, we will discuss how machine learning techniques could be used to find relations in knot theory, particularly, how it could be used to discover relations in different knot invariants. Briefly, given a training set {x
Generalized Chaplygin Gas Traversable Wormhole Solutions by Using GUP Corrected Casimir Energy
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2020) Ubaid Ur Rehman; SP19-RMT-019; LHR TP 6477; Dr. Abdul Jawad
In this thesis, we explore the wormhole solutions (which are initially pro- sed by Garattoni (Eur. Phys. J. C 79(2019)951) who take generalized certainty principle (GUP) with Casimir energy) in the framework of two ll-known dark energy models, generalized Chaplygin gas and polytropic s. We consider the GUP corrected pressure (force per unit surface area) the equation of state of these dark energy models to construct the gener- zed Chaplygin gas corrected energy density and polytropic gas corrected ergy density. Three models of redshift function are taken into account construct shape function as well as wormhole geometry for both cases corrected energy densities. We ﬁnd the behavior of some parameters ough equation of state, energy conditions (null, weak and strong) at the oat of the wormhole with radius r0.
Geometric Thermodynamics of Well-Known Black Holes
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Syeda Rabab Fatima; CIIT/FA19-RMT-111/LHR; Dr. Abdul Jawad; LHR TP 7532
We study the phase transition and thermodynamic geometries of a charged AdS black hole with a global monopole. For this purpose, we develop the thermodynamic quantities such as Hawking temperature, spe- ciﬁc heat and pressure on horizon radius in the presence of Barrow entropy. The stability of this black hole is being observed through speciﬁc heat. Also, we investigate the thermodynamic curvatures behavior of black hole by applying Weinhold and Ruppiner formulations. It is found that ther- modynamic curvatures exhibit the attractive and repulsive nature of black hole for speciﬁc constants. We also study the thermodynamic curvature of charged BTZ black hole by ﬁxing phase space of entropy, pressure and volume on curvature, i.e., entropy-pressure corrected curvature (RSP ) and entropy-volume corrected curvature (RSV ). It is found that there present a repulsive force by the charged BTZ black hole for its molecules, qual- itatively or phenomenologically. However, RSV shows negative behavior initially which exhibits the attractive nature of charged BTZ black hole.
Holographic Inflation in Modified Theories of Gravity
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2020) Manzar Abbas; SP19-RMT-013; LHR TP 6472; Dr. Abdul Jawad
In this thesis, we investigate the holographic inflation in the framework of two gravitational theories like f(T) gravity where T corresponds to the torsion scalar and DGP braneworld model which is based on the idea that our four dimensional FRW universe located on five dimensional manifold. TheGranda-Oliveros cutoff is used to explore all the inflationary parameters as slow roll parameters ( 1, 2, 3), number of e−folds N, scalar spectral index ns, tensor-to-scalar ratio r and running of the scalar spectral index αs. Also, we investigate the behavior of inflationary parameters ns−N, αs− N, r−N, αs−ns and r−ns through graphical presentation. The behavior of these parameters show the consistency with Planck data 2018.
Inflationary Dynamics and Thermodynamics of Chaplygin Gas Models
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2018) Muhammad Adeel Sultan; CIIT/SP17-RMT-006/LHR; Dr. Abdul Jawad; LHR TP 5441
In this thesis, we study the reconstruction of warm inﬂation model with the help of tensor to scalar ratio (r) and scalar spectral index (ns) in terms of number of e-folds (N). In this regards, we take ﬂat FRW metric and discuss the general forms of dissipative coeﬃcient Γ(φ, T ) as well as eﬀec- tive potential V (φ, T ) for two dissipative regimes i.e., the weak and strong. We use inﬂationary parameters like slow roll parameters, power spectrum of the curvature perturbation, tensor spectrum, spectral index, scalar to tensor ratio and Hubble parameter to ﬁnd the generalized form of dissi- pative coeﬃcient and eﬀective potential. Further, we discuss generalized cosmic Chaplygin gas in the scenario of particle creation. We examine energy density (ρ), Hubble parameter (H), declaration parameter (q), tem- perature (T ) and particle number density (n) under three diﬀerent models of particle creation rate. We also analyze the production of entropy and Bekenstein entropy in the scenario of ﬁrst law of thermodynamics. We dis- cuss the validity of generalized second law of thermodynamics and thermal equilibrium under three models of Γ and discuss the graphical behavior of above mentioned terms.
Modified Entropy Inspired Scalar Field Cosmic Inflation with Well-known Potentials
(Library Information Services COMSATS University Lahore Campus, 2024-03-17) Hafiza Iqra Nadeem; FA22-RMT-022; Dr. Abdul Jawad; LHR TP 9377
This thesis is dedicated to discuss the inflationary setup with the help of modified Barrow entropy with f(R) gravity framework. We derive the Friedmann equations by using the first law of thermodynamics. With the help of these equations, we reconstruct f(R) gravity model to establish the relationships governing scalar and tensor perturbation power spectra and interestingly this model mimics thermodynamically under the slow-roll approximation. Two different types of potentials like the β potential and the exponential potential are used to explore the insights of inflationary parameters in the underlying scenario. Thus, the inflation-related quantities like scalar spectral index and tensor-to-scalar ratio are discussed graphically in our scenario by developing contour plots. It is worthwhile mention here that our results are consistent with Planck 2018 data.
Phase Space Analysis and Cosmic Parameters of Dynamical Dark Energy Model
(Library Information Services COMSATS University Lahore Campus, 2024-03-18) Ruqia Arif; SP23-RMT-027; Dr. Abdul Jawad; LHR TP 9581
This thesis explores the stability analysis of Friedmann-like spacetimes using dynamical system methods. For this purpose, we begin by considering a modified cosmological sce nario based on Tsallis entropy corrections. These entropic formulations modify the cosmo logical field equations that govern the universe’s dynamics. We incorporate these modified Friedmann equations and convert them into a first-order autonomous system of differential equations. To identify the system’s equilibrium points, we consider the interaction between cosmological fluids. Various linear and non-linear forms of interaction models are exam ined. For each model, we calculate the critical points and discuss their behavior associated with eigenvalues. We investigate the different stages in the universe’s evolution including dust and radiation dominated era of the universe as well as quintessence, ΛCDM and phan tom regimes. In addition, we develop the phase space portraits of all the interaction models revealing the stable, unstable and saddle behavior of critical points. In most of the cases, the system supports stable critical points.
Physical Analysis of Black Holes Through Well- Known Approaches
(Library Information Services COMSATS University Lahore Campus, 2022-03-13) Shahid Chaudhary; FA17-PMT-015; Dr. Abdul Jawad; LHR TP 6837
This thesis includes the study of thermodynamic geometry, thermal corrections, Joule Thomson expansion, shadow images, quasinormal modes, greybody factors, evaporation of various black holes in non-massive and massive gravities. Ruppeiner approach is investigated for anti de Sitter black hole in Einstein-Maxwell-scalars theory by developing particular forms of the line element of thermodynamic geometry in different phase spaces. It is found that the curvatures in different phase spaces are identical and positive which lead to the repulsive interacting information between black hole molecules. We investigate the thermal stability of anti de Sitter black hole in Einstein-Maxwell-scalar theory and regularized Lovelock theory in the presence of thermal fluctuations. It is observed that momentum relaxation parameter and coupling constants of Lovelock theory increase the thermal stability of black holes. For black hole in regularized Lovelock theory, Joule Thomson expansion is also investigated to obtain some interesting outcomes. The influence of the first-order correction of entropy caused by thermal quantum fluctuations on the thermodynamics of logarithmic corrected charged black hole in massive gravity is discussed. For this purpose, the thermodynamic quantities such as entropy, Helmholtz free energy, internal energy, enthalpy, Gibbs free energy and specific heat are explored. We discuss the influence of the topology of the event horizon, dimensions and non-linearity parameter on the local and global stability of black hole. The higher order generalized uncertainty principle on the thermodynamics of 5- dimensional black hole in Einstein-Gauss-Bonnet gravity coupled to nonlinear electrodynamics is analyzed and compare our results with usual thermodynamic relations. In this framework, we detect the relationship of shadow radius and quasinormal modes. We also verify the inverse relation between the quasinormal modes frequencies and shadow radius, i.e., quasinormal modes should increase with the increasing values of Gauss-Bonnet parameter and electric charge. xi The new effective approach is adopted to analyze the thermodynamic phase transitions onto non-minimal magnetic charged regular back hole and regular black hole with cosmological constant. We find out the phase transitions points and horizon radii of non-physical range for black holes. The new thermodynamically relations are used to briefly study Joule Thomson affects on regular black holes. The study of greybody factor helps us to understand the quantum nature of black hole. Gravitational potentials and bounds on the greybody factors for some well-known black holes are developed to investigate the influence of Born-Infeld and massive gravity parameters on them. We also discuss the relationship of transmission probability and reflection probability. Finally, we study the Hawking evaporation process, thermodynamics and shadow images in the presence of deflection images of the exact black hole with nonlinear electrodynamics for positive and negative coupling constant  . We observe that evaporation rate depends on  and black hole evaporates more quickly for positive  as compared to negative  . For the case  = −1 , the black hole's lifetime becomes infinite which makes the black hole a remnant and the third law of black hole thermodynamics holds in this scenario. For this black hole, we discuss the thermodynamic quantities and shadow images in the presence of deflection angle. Moreover, we consider the Gibbs energy optical dependence to investigate the Hawking-Page transition. Our findings show that the large and small phase transitions of black hole occur at a specific value of the deflection angle.
Physical Aspects of Black Hole Thermodynamics Through Modified Entropy
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2025) Maham Muzaffar; FA23-RMT-018; Dr. Abdul Jawad; LHR TP 9765
In this thesis, we study the thermodynamics and stability of five-dimensional Schwarzschild AdS black hole by using the modified entropy. We analyze the stability and phase tran sitions with the help of modified entropy and calculate thermodynamic quantities such as mass, temperature, Gibbs free energy, chemical potential, and heat capacities. As modified entropy, we use a three parameter entropy which straightforwardly meets all the conditions like the monotonically increasing function, the generalized third law, and Bekenstein-Hawking limit. Using this three parameter entropy along with five-dimensional Schwarzschild AdS black hole, we examine the thermodynamical geometries like Wein hold, Ruppineir and Quevedo geometries through their curvature scalars. Finally, we also f ind the sparsity index to check the unusual nature of Hawking radiation emission from black holes.
Study of Cosmic Acceleration and Thermodynamic Consequences in Alternative Theories of Gravity
(Library Information Services COMSATS University Islamabad Lahore Campus, 2021) Ayesha Iqbal; FA14-PMATH-002; LHR TP 7450; Dr. Abdul Jawad
In this thesis, we discuss two interesting issues: the accelerated expansion of the universe and thermodynamics. We consider flat Friedmann-Robertson-Walker universe model in alternative theories of gravity like loop quantum cosmology, Dvali- Gabadaze-Porrati brane world and fractal universe. We use different models of dark energy like Ricci Gauss-Bonnet dark energy and some latest holographic dark energy models namely Tsallis, Renyi and Sharma-Mittal holographic dark energy models for the analysis of both issues. For accelerated expansion of the universe, we examine the cosmological parameters like effective equation of state parameter, deceleration parameter, statefinder parameters, Om-diagnostic, plane of effective equation of state parameter with its evolutionary parameter and squared speed of sound parameter. We investigate the validity of the generalized second law of thermodynamics and thermodynamical equilibrium for the case of thermodynamic analysis. Firstly, we consider loop quantum cosmology and fractal universe in flat FRW universe with an interacting scenario between a non-canonical scalar field model of dark energy and dark matter. We make the analysis by using constant and variable (CPL parametrization) forms of equation of state parameters. We discuss the deceleration parameter for expansion rate along with squared speed of sound for stability analysis. Taking Bekenstein, logarithmic and power law entropies as the horizon entropy, we examine generalized second law of thermodynamics and thermal equilibrium. Secondly, we study the cosmological implications using Tsallis, Renyi and Sharma- Mittal holographic dark energy models in the interacting framework. We take into account two theories, fractal and Dvali-Gabadaze-Porrati brane world. We discuss the cosmological parameters and planes in both theories for the evolving universe. Finally, we examine the validity of generalized second law of thermodynamics of a physical system enveloped by apparent as well as event horizons. The system is comprised of Ricci Gauss-Bonnet dark energy and dark matter. We use various forms of entropy namely Bekenstein, Renyi, logarithmic and power law entropy corrections. We also examine the thermodynamic equilibrium in case of each entropy.
Study of Entropy Corrected Cosmic Scalar Field Inflation
(Library Information Services COMSATS University Lahore Campus, 2023-03-13) Rimsha; SP22-RMT-020; Dr. Abdul Jawad; LHR TP 8726
In this thesis, inflationary phase of the universe in the framework of generalized Chaplygin gas is studied. We consider modified cosmological scenarios based on two entropy corrections known as Tsallis and Barrow entropy which lead to the modification of Friedmann equations. Using these correction and modified equations, we discuss the slow roll parame ters, number of e-folds, curvature perturbation, tensor to scalar ratio and spectral index. To analyze the effects of these entropy corrections on infla tionary dynamics, we plot the graphs of tensor to scalar ratio and spectral index for two different scalar potentials. We observe the variations in the values of these inflationary parameters with respect to Tsallis and Barrow parameters. The graphical analysis demonstrates the compatibility of our models with the Planck data from 2020. Moreover, in view of these correc tions to entropy, we also find out the bounds of swampland conjecture for generalized Chaplygin gas. In all the cases, this bound remains less than one which is according to observational data