Dynamics of false vacuum bubbles: beyond the thin shell approximation

Charged black holes in string-inspired gravity. I. Causal structures and responses of the Brans-Dicke field

“…Of course, we know that if we consider the limit ω < −3/2, then the Brans-Dicke field becomes a ghost and hence it can allow a wormhole or a baby universe [65]. However, what we show is that such objects can be obtained just by gravitational collapse of a charged matter field, i.e., in an extremely simple way while previously, complicated initial conditions were needed to obtain such a state [66]. Case β = 1: the causal structure of this case, shown in figure 8, shares many qualitative properties with the β = 0.5 case.…”

Cusp singularities in f(R) gravity:prosandcons

“…We use the same integration method that was used in previous papers [11,14,16,18]. We use the second order Runge-Kutta method [28].…”

“…For numerical integration, it is convenient to change all equations by a set of first order differential equations. For this purpose, we introduce the following notations [11,14,16,18]: the metric function α, the radial function r, the Brans-Dicke field Φ, and a scalar field s ≡ √ 4πφ, and define…”

“…Especially we use double-null formalism [13] to study the formation of charged black holes [14,15] where this can be applied for cosmology [16] as well as scalar-tensor models [17,18]. We first show that we can cure the cusp singularity problem by adding a ∼ R 2 term; in addition, we show that there can be a higher curvature region.…”

Moduli destabilization via gravitational collapse

“…Secondly, we need to study the causal structure during the gravitational collapses to understand whether the destabilized effect can affect the future infinity or if it is inside of the event horizon and hence there is no hope to see any effects of the destabilization; whether the destabilized field is maintained eternally and form a kind of hair around the event horizon or if such destabilized region disappears eventually, etc. We aim to answer these questions by using the more advanced double null formalism [13][14][15][16][17][18][19][20].…”