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Jaydeep Goswami

Publications and source records attributed to Jaydeep Goswami.

3 recordsLinked to original sources

Five-Dimensional Traversable Wormholes in Einstein-Gauss-Bonnet Gravity with a Cloud of Strings

We present an exact static and spherically symmetric traversable wormhole solution in 5D Einstein-Gauss-Bonnet (EGB) gravity supported by a Letelier cloud of strings. The physically admissible parameter space is determined by imposing the flare-out condition together with the positivity of the string-cloud density, and the resulting spacetime is shown to be asymptotically flat. An analysis of the Ricci scalar, Ricci tensor squared, and Kretschmann scalar confirms that the geometry is free from curvature singularities. The effective null, weak, strong and dominant energy conditions are either satisfied or saturated at the throat. The generalized TOV equation demonstrates that the wormhole remains in mechanical equilibrium. We further investigate its traversability by studying the proper radial distance, embedding diagrams, traversal time, proper acceleration, and tidal accelerations, showing that the solution satisfies the Morris-Thorne criteria for traversable wormholes. The optical properties of the spacetime are explored through null geodesics, unstable photon circular orbits, and the corresponding shadow, revealing the influence of both the Gauss-Bonnet coupling and the string-cloud density. Finally, scalar perturbations are analyzed using the sixth-order WKB approximation method together with time-domain evolution. The quasinormal mode spectra exhibit negative imaginary frequencies throughout the considered parameter space, indicating linear stability, while the close agreement between the WKB, time-domain, and eikonal results provides additional consistency for the analysis. These results demonstrate that higher-curvature effects in 5D EGB gravity can support a regular, traversable and dynamically stable wormhole sustained by a physically motivated string-cloud matter source.

gr-qc

Traversable wormholes in $\boldsymbol{f(Q)}$ gravity: Energy conditions, stability and quasinormal modes

We investigate static and spherically symmetric traversable wormhole solutions in the framework of $f(Q)$ gravity by considering a power-law model of the form $f(Q)=\gamma(-Q)^m$. By adopting an anisotropic matter distribution and imposing an equation of state relating the radial pressure and energy density, we obtain an analytic shape function that satisfies the geometric requirements for a traversable wormhole. The model parameter is constrained to $0<m<1/2$, corresponding to a quintessence-like regime with $-1<\omega<-1/3$. The energy conditions are analyzed in detail, showing that violations of the null and weak energy conditions are unavoidable but remain localized near the wormhole throat. The anisotropy parameter is positive throughout the spacetime, indicating that repulsive anisotropic stresses play a key role in sustaining the wormhole. The equilibrium configuration is examined using the generalized Tolman-Oppenheimer-Volkoff (TOV) equation for both zero and logarithmic redshift functions, where a consistent force balance is achieved with anisotropic effects providing the dominant outward support. Dynamical stability is studied through scalar perturbations, leading to a Schr\"odinger-like wave equation with a single-peak effective potential. The quasinormal modes are computed using the sixth-order WKB method with Pad\'e approximation. The resulting frequencies possess negative imaginary parts, indicating stable damping of perturbations. Time-domain simulations further confirm the stability of the solutions and show good agreement with the WKB results, with small deviations in the damping rates. Thus, these results establish that $f(Q)$ gravity admits traversable wormhole solutions that are geometrically consistent and dynamically stable, with $f(Q)$ gravity effects effectively regulating the required matter content.

gr-qc

Morris-Thorne-type wormhole with global monopole charge and the energy conditions

In this paper, we investigate Morris-Thorne-type wormholes with global monopole charge using various shape function forms known in the literature. We solve the Einstein field equations incorporating an anisotropic energy-momentum tensor and obtain different physical quantities associated with the matter-content. A crucial aspect of this study is the non-exotic matter distribution, examined through the evaluation of energy conditions, and exploring how different shape functions impact these conditions. Additionally, the anisotropy parameter is calculated to quantify the extent of attractive or repulsive behavior. Our study demonstrates that for different types of shape function forms, the energy conditions are influenced by the global monopole parameter. Our findings provide valuable insights for further theoretical explorations of these fascinating hypothetical structures in the realm of general relativity and beyond.

gr-qc