Null and Timelike Geodesics Near the Throats of Phantom Scalar Field Wormholes

TL;DR

This paper investigates the unique properties of geodesic motion near the throats of traversable wormholes supported by phantom scalar fields, highlighting differences from black hole horizons and potential astrophysical implications.

Contribution

It provides a detailed analysis of bound orbits and photon trajectories near wormhole throats, distinguishing between two types based on the metric function behavior, and discusses observational prospects.

Findings

Orbits near wormhole centers exhibit retrograde precession.

First-type wormholes have the innermost stable circular orbit at the throat.

Second-type wormholes have a stable resting-state orbit at the throat.

Abstract

We study geodesic motion near the throats of asymptotically flat, static, spherically~symmetric traversable wormholes supported by a self-gravitating minimally coupled phantom scalar field with an arbitrary self-interaction potential. We assume that any such wormhole possesses the reflection symmetry with respect to the throat, and consider only its observable "right~half". It turns out that the main features of bound orbits and photon trajectories close to the throats of such wormholes are very different from those near the horizons of black holes. We~distinguish between wormholes of two types, the first and second ones, depending on whether the redshift metric function has a minimum or maximum at the throat. First, it turns out that orbits located near the centre of a wormhole of any type exhibit retrograde precession, that is, the angle of pericentre precession is negative. Second, in the case of high accretion activity, wormholes of the first type have the innermost stable circular orbit at the throat while those of the second type have the resting-state stable circular orbit in which test particles are at rest at all times. In our study, we have in mind the possibility that the strongly gravitating objects in the centres of galaxies are wormholes, which can be regarded as an alternative to black holes, and the scalar field can be regarded as a realistic model of dark matter surrounding galactic centres. In this connection, we~discuss qualitatively some observational aspects of results obtained in this article.