118411783
Brownian motion in strongly coupled, anisotropic Yang-Mills plasma: A holographic approach
We employ methods of gauge/string duality to analyze the Brownian motion and the concomitant Langevin equation of a heavy quark in a strongly coupled, thermal, anisotropic Yang-Mills plasma. We consider fluctuations both along and perpendicular to the direction of anisotropy and study the effects of anisotropy on the drag coefficient, the diffusion constant and the Langevin coefficient for both the directions. We also verify the fluctuation-dissipation theorem for Brownian motion in an anisotropic medium.
55676024
Holographic quark-antiquark potential in hot, anisotropic Yang-Mills plasma
Abstract Using the gauge/gravity duality we calculate the heavy quark–antiquark potential in a hot, anisotropic and strongly coupled Yang–Mills plasma in ( 3 + 1 )-dimensions. As the anisotropic medium we take a deformed version of N = 4 super Yang–Mills theory at finite temperature following a recent work where the dual type IIB supergravity solution is also proposed. We turn on a small value of the anisotropy parameter, for which the gravity dual is known analytically (perturbatively), and compute the velocity-dependent quark–antiquark interaction potential when the pair is moving through the plasma with a velocity v . By setting v = 0 we recover the static quark–antiquark potential. We numerically study how the potential is modified in the presence of anisotropy. We further show numerically how the quark–antiquark separation (both in the static and the velocity-dependent case) and hence, the screening length gets modified by anisotropy. We discuss various cases depending upon the direction of the dipole and the direction of its propagation and make a comparative study of these cases. We are also able to obtain an analytical expression for the screening length of the dipole moving in a hot, anisotropic plasma in a special case.
118454700
Wilson loops in (p+1)-dimensional Yang–Mills theories using gravity/gauge theory correspondence
Abstract We compute the expectation values of both the time-like and the light-like Wilson loops in a strongly coupled plasma of ( p + 1 ) -dimensional Yang–Mills theories using gravity/gauge theory correspondence. From the time-like Wilson loop we obtain the velocity dependent quark–antiquark potential where the dipole is moving through the plasma with an arbitrary velocity 0 v 1 and also obtain expressions for the screening lengths. When the velocity v → 1 , the Wilson loop becomes light-like and we obtain the form of the jet quenching parameter in those strongly coupled plasma.
117015116
Letter: A Study of Asymptotic Behavior of Homogeneous Cosmological Models with a Varying Cosmological Constant in Einstein-Cartan Theory: Cosmic No-Hair Theorem
We have investigated cosmic no-hair theorem with varying cosmological constant Λ in homogeneous anisotropic Bianchi-models for Einstein-Cartan theory. We have taken the variation of Λ to be as the square of the extrinsic curvature scalar and asymptotic behavior has been studied.
119975967
Solutions of the Wheeler-DeWitt equation
This paper deals with the solution of the Wheeler-DeWitt equation with a massive scalar field for a Kantowski-Sachs metric using the Born-Oppenheimer approximation. Also, solutions under different assumptions are determined to indicate different stages of evolution of the universe. Finally, these wave functions in the asymptotic regions are compared with the Hartle-Hawking wave functions (including second-order corrections) evaluated using the concept of microsuperspace.
118758806
Gravitational Field of Spherical Domain Walls
In this paper we have considered a spherically symmetric domain wall with non vanishing stress component in the direction perpendicular to the plane of the wall. The exact solutions are obtained using functional separability of metric coefficients. Also we have studied the motion of the test particles in different situations.
122802796
THERMODYNAMIC STABILITY OF A FLUID WITH VARIABLE EQUATION OF STATE
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: $\omega(z)=\omega_{0}+\frac{\omega_{1}z}{(1+z)^{2}}$ 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.
118400878
A redefinition of Hawking temperature on the event horizon: Thermodynamical equilibrium
Abstract In this Letter we have used the recently introduced redefined Hawking temperature on the event horizon and investigated whether the generalized second law of thermodynamics (GSLT) and thermodynamic equilibrium holds for both the event and the apparent horizons. Here we have considered FRW universe and examined the GSLT and thermodynamic equilibrium with three examples. Finally, we have concluded that from the thermodynamic viewpoint, the universe bounded by the event horizon is more realistic than that by the apparent horizon at least for some examples.