We review nonsingular static, spherically symmetric solutions of general relativity with
minimally coupled scalar fields. Considered are wormholes and regular black holes (BHs) …

We investigate gravitational lensing by a primary photon sphere which is a sphere filled with
unstable circular light orbits, and by a secondary photon sphere on a wormhole throat in a …

The general parametrization for spacetimes of spherically symmetric Lorentzian, traversable
wormholes in an arbitrary metric theory of gravity is presented. The parametrization is similar …

Observations of gravitational lenses in strong gravitational fields give us a clue to
understanding dark compact objects. In this paper, we extend a method to obtain a …

Echoes are known as modifications of the usual quasinormal ringing of a black hole at late
times because of the deviation of space-time from the initial black hole geometry in a small …

We test the stability of various wormholes and black holes supported by a scalar field with
a<? format?> negative kinetic term. The general axial perturbations and the monopole type …

At the beginning of the 20th century, only two physical fields were known, the
electromagnetic and gravitational ones. Einstein's theory of special relativity (SR), created in …

Morris and Thorne [MS Morris and KS Thorne, Am. J. Phys. 56, 395 (1988)] proposed
geometrical objects called traversable wormholes that act as bridges in connecting two …

Gravitational lensing is a good probe into the topological structure of dark gravitating
celestial objects. In this paper, we investigate the light curve of a light ray that passes …

We study a static, spherically symmetric wormhole model whose metric coincides with that of
the so-called Ellis wormhole but the material source of gravity consists of a perfect fluid with …