Linearized stability analysis of gravastars in noncommutative geometry

In this work, we find exact gravastar solutions in the context of noncommutative geometry, and explore their physical properties and characteristics. The energy density of these geometries is a smeared and particle-like gravitational source, where the mass is diffused throughout a region of linear dimension $\sqrt{(\alpha)}$ due to the intrinsic uncertainty encoded in the coordinate commutator. These solutions are then matched to an exterior Schwarzschild spacetime. We further explore the dynamical stability of the transition layer of these gravastars, for the specific case of $\beta=M^2/\alpha<1.9$, where M is the black hole mass, to linearized spherically symmetric radial perturbations about static equilibrium solutions. It is found that large stability regions exist and, in particular, located sufficiently close to where the event horizon is expected to form.Comment: 6 pages, 3 figure

Smoothed one-core and core-multi-shell regular black holes

We discuss the generic properties of a general, smoothly varying, spherically symmetric mass distribution D(r,theta), with no cosmological term (. is a length scale parameter). Observing these constraints, we show that (1.) the de Sitter behavior of spacetime at the origin is generic and depends only on D(0,theta), (2.) the geometry may posses up to 2(k + 1) horizons depending solely on the total mass M if the cumulative distribution of D(r,theta) has 2k + 1 inflection points, and (3.) no scalar invariant nor a thermodynamic entity diverges. We define new two-parameter mathematical distributions mimicking Gaussian and step-like functions and reduce to the Dirac distribution in the limit of vanishing parameter.. We use these distributions to derive in closed forms asymptotically flat, spherically symmetric, solutions that describe and model a variety of physical and geometric entities ranging from noncommutative black holes, quantumcorrected black holes to stars and dark matter halos for various scaling values of.. We show that the mass-to-radius ratio pi c(2)/G is an upper limit for regular-black-hole formation. Core-multi-shell and multi-shell regular black holes are also derived