arXiv subjects

Rishi Pokhrel

Publications and source records attributed to Rishi Pokhrel.

6 recordsLinked to original sources

arXiv2026

Bouncing shellworld embedded in charged AdS spacetime

We investigate the cosmological evolution of a spherical brane within the shellworld (dark bubble) scenario embedded in a five-dimensional charged AdS bulk spacetime. For zero or small value of the brane cosmological constant, the shellworld universe has a nonsingular bouncing and cyclic nature with the bounce induced by the charge parameter of the bulk spacetime. On large value of the brane cosmological constant, the shellworld undergoes a nonsingular bounce and expands eternally. Under certain conditions, the brane bounces outside the bulk horizons, leading to a geometrical resolution of the Cauchy horizon instability present in standard braneworld models. Furthermore, analysis of linear scalar perturbations reveals that test scalar field modes remain regular and non-divergent across the bounce. Finally, we incorporate uniformly distributed long strings in the bulk and demonstrate that the bounce still persists while avoiding the horizon instability.

hep-th↗

arXiv2026

Non-singular Brane/Bubble Cosmologies in the Presence of String Cloud

We investigate the cosmological evolution of a four-dimensional brane/bubble universe embedded in a five-dimensional Anti-de Sitter bulk containing a uniformly distributed cloud of strings. The endpoints of the strings attached to the brane induce an effective matter component in the four-dimensional universe. We derive the Friedmann equations for both the Randall-Sundrum braneworld and the shellworld (dark bubble) scenarios and show that one can obtain a nonsingular bounce in both the brane and bubble universes under certain conditions of the black hole mass and the four-dimensional cosmological constant. Though the bounce due to the spatial curvature occurs outside the black hole horizon, however, the bounce obtained due to the presence of string cloud in the braneworld scenario suffers from the Cauchy horizon instability as the bounce occurs inside the Cauchy horizon of the black hole. In contrast, for the shellworld scenario, the bounce can be made to occur outside the black hole horizon, thereby avoiding the horizon instability. We also analyze the field fluctuations on the brane/bubble and show that the fluctuations remain finite and well-behaved at the bounce point.

hep-th↗

arXiv2026

Transport properties of baryon rich back-reacted thermal plasma with finite 't Hooft coupling correction

In this work, holographic approach has been used to analyse the transport properties of baryon rich back-reacted thermal plasma with finite 't Hooft coupling correction. The dual bulk geometry is charged AdS black hole with higher derivative Gauss-Bonnet (GB) correction and string cloud. Specially, we have studied the nature of drag force, jet quenching parameter, screening length, radial profile and energy loss with respect to different parameters. The drag force and jet quenching parameter are enhanced with GB coupling, baryon and flavor density whereas the screening length reduces with these parameters. The radial profile and energy loss of the rotating quark has also been studied and it is observed that the radial profile decreases with increase in baryon potential and flavor density, temperature and angular frequency, whereas it is enhanced with conjugate momenta and GB coupling. Further, the energy loss of the quark grows with potential and flavor density, velocity and angular frequency and it is suppressed with GB coupling.

hep-th↗

arXiv2025

Hydrodynamical properties of back reacted thermal plasma with finite 't Hooft coupling correction

In this work, holographic approach has been used to analyse the hydrodynamical properties of $\mathcal{N}=4$ Super Yang-Mills thermal plasma with subleading 't Hooft coupling correction and flavour quarks dual to the AdS Gauss-Bonnet gravity in the presence of string cloud. The drag exerted on an external probe quark while translating through the thermal plasma enhances with probe velocity, flavour quark density, temperature and finite coupling correction. The jet quenching parameter gets enhanced on increase of flavour quark density, temperature and finite coupling correction. Quark-antiquark screening length is observed to reduce with rapidity parameter, flavour quark density, finite coupling correction and temperature which suggests an early transition to the thermal plasma phase of QGP. The screening length is found to be larger for the parallel orientation compared to the perpendicular configuration. Finally, the rotational dynamics of the heavy probe quark is studied. The rotational and drag energy loss increases with angular frequency and quark density, but is almost independent of the 't Hooft coupling.

hep-th↗

arXiv2024

Hydrodynamical properties of baryon rich thermal plasma with flavour quarks

In this work, we holographically study the hydrodynamical properties of strongly coupled $\mathcal{N} = 4$ SYM baryon rich thermal plasma with large number of flavour quarks. Specifically, we study the drag force acting on the moving heavy probe quark and corresponding energy loss. We also study the jet quenching parameter, screening length and binding energy of the quark-antiquark pair. Due to the presence of finite baryon density and flavour quarks the drag force, energy loss, jet quenching parameter and binding energy of the quark-antiquark pair are enhanced for the increase in temperature. However, the screening length of the quark-antiquark pair is reduced, leading to the thermal plasma phase being achieved at a lower temperature, which is consistent with the thermal phase diagram of the quark-gluon plasma. We observed that the perpendicular orientation of quark-antiquark pair with respect to the direction of motion deconfined early compare to the parallel orientation once temperature raises.

hep-th↗

arXiv2024

Charged AdS Black Holes in Presence of String Cloud and Cardy-Verlinde Formula

In this study, charged AdS black holes with a string cloud are taken into consideration. We identify three distinct black hole solutions within a specific temperature range, which subsequently merge into a single black hole beyond this range in the case of spherical space with low chemical potential and string density. However, in the case of large chemical potential and string density, only one black hole solution exists for all temperatures. Notably, we observe that for flat and hyperbolic space, there is only one black hole solution irrespective of the chemical potential and string density. By subtracting the contribution of the extremal black hole from the on-shell Euclidean action, the thermodynamical quantities associated with these black holes are calculated. We also investigate the stability of these black holes and find that medium-sized black hole is unstable. In the dual boundary theory side we verify the existence of bound state of quark-antiquark pair. Finally, we establish the Cardy-Verlinde formula for the boundary theory and we observed an additional energy term arising because of the presence of string cloud.

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