Related papers: Wormholes, Void Bubbles and Vacuum Energy Suppress…
Despite the many efforts, our theoretical understanding of the ultimate nature of the dark energy component of the universe still lags well behind the astounding experimental evidence achieved from the increasingly sophisticated…
We re-examine the problem of vacuum decay in the presence of spherically symmetric black holes. Within the semiclassical approximation, we study configurations describing a bubble of true vacuum propagating outside a black hole formed from…
The effects of asymptotically anti-de Sitter wormholes in low-energy field theory are calculated in full detail for three different matter contents: a conformal scalar field, an electromagnetic field and gravitons. There exists a close…
Properties of $n(\ge 5)$-dimensional static wormhole solutions are investigated in Einstein-Gauss-Bonnet gravity with or without a cosmological constant $\Lambda$. We assume that the spacetime has symmetries corresponding to the isometries…
Within the $\Lambda$CDM cosmological model, the absolute value of Einstein's cosmological constant $\Lambda$, sometimes expressed as the gravitating mass-energy density $\rho_\Lambda$ of the physical vacuum, is a fundamental constant of…
We extend the notion of phantom energy--which is generally accepted for homogeneously distributed matter with $w<-1$ in the universe--on inhomogeneous spherically symmetric spacetime configurations. A spherically symmetric distribution of…
We obtain a large class of Lorentzian wormhole spacetimes in scalar-tensor gravity, for which the matter stress energy does satisfy the weak energy condition. Our constructions have zero Ricci scalar and an everywhere finite, non-zero…
Recently a bound on negative energy densities in four-dimensional Minkowski spacetime was derived for a minimally coupled, quantized, massless, scalar field in an arbitrary quantum state. The bound has the form of an uncertainty…
We generalize the fractal bubble model (FB), recently proposed in the literature as an alternative to the standard $\Lambda$CDM cosmology, to include a non-zero cosmological constant. We retain the same volume partition of voids and walls…
The cosmological constant problem can be understood as the failure of the decoupling principle behind effective field theory, so that some quantities in the low-energy theory are extremely sensitive to the high-energy properties. While this…
We present a new wormhole solution connecting two points of the same universe separated by finite distance. Virtually all the existing solutions connect two disconnected universes, or two points of the same universe that are infinitely far…
We investigate the role of a specifically warped extra dimension in constructing examples of higher dimensional spacetimes representing Lorentzian wormholes. The warping chosen is largely inspired by the well-known non-static Witten bubble…
The energy density of the vacuum, Lambda, is at least 60 orders of magnitude smaller than several known contributions to it. Approaches to this problem are tightly constrained by data ranging from elementary observations to precision…
In this letter, we investigate the changes in the quantum vacuum energy density of a massless scalar field inside a Casimir cavity that orbits a wormhole, by considering the cosmological model with an isotropic form of the Morris-Thorne…
A possible cause of the late-time cosmic acceleration is an exotic fluid with an equation of state lying within the phantom regime, i.e., $w=p/\rho <-1$. The latter violates the null energy condition, which is a fundamental ingredient in…
We review the cosmological evidence for a low matter density universe and a cosmological constant or dynamical vacuum energy and address the cosmolog$ coincidence problem: why is the matter density about one-half the vacuum energy {\em…
A mechanism for suppressing the cosmological constant is described, using a superconducting analogy in which fermions coupled to gravitons are in an unstable false vauum. The coupling of the fermions to gravitons and a screened attractive…
The properties of an hyperbolically-expanding wormhole are studied. Using a particular equation of state for the fluid on the wormhole throat, we reached an equation of motion for the throat that leads to a constant surface energy density…
In present paper the gravitational effect of spontaneous symmetry breaking vacuum energy density is investigated by subtracting the flat space-time contribution from the energy in the curved space-time. We found that the remain effective…
Gauss-Bonnet formula is used to derive a new and simple theorem of nonexistence of vacuum static nonsingular lorentzian wormholes. We also derive simple proofs for the nonexistence of lorentzian wormhole solutions for some classes of static…