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APS/1: Thin-shell-wormhole 

# Thin-shell wormholes from charged black holes in generalized dilaton-axion gravity 

A. A. Usmani ∗ and Z. Hasan ∗ 

Department of Physics, Aligarh Muslim University, Aligarh 202 002, Uttar Pradesh, India. 

F. Rahaman † and Sk. A. Rakib † 

Department of Mathematics, Jadavpur University, Kolkata 700 032, West Bengal, India 

Saibal Ray ‡ 

Department of Physics, Government College of Engineering & Ceramic Technology, Kolkata 700 010, West Bengal, India 

Peter K. F. Kuhfittig § 

Department of Mathematics, Milwaukee School of Engineering, Milwaukee, Wisconsin 53202-3109, USA 

(Dated: November 12, 2018) 

This paper discusses a new type of thin-shell wormhole constructed by applying the cut-and-paste technique to two copies of a charged black hole in generalized dilaton-axion gravity, which was inspired by low-energy string theory. After analyzing various aspects of this thin-shell wormhole, we discuss its stability to linearized spherically symmetric perturbations. 

The study of traversable wormholes has received con- siderable attention from researchers for the past two decades. Although lacking observational evidence, worm- holes are just as good a prediction of the general the- ory of relativity as black holes. In particular, we re- fer to the pioneering work of Visser [1], who proposed a theoretical method for constructing a new class of traversable Lorentzian wormholes from black-hole space- times. This construction proceeds by surgically graft- ing two Schwarzschild spacetimes together in such a way that no event horizon is permitted to form. The resulting structure is a wormhole spacetime in which the throat is a three-dimensional thin shell. In recent years, Visser’s approach was adopted by various authors for construct- ing thin-shell wormholes by similar methods, generally requiring spherical symmetry [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]. The approach is of special interest because it minimizes the amount of ex- otic matter required. All the exotic matter is confined to the shell. 

More recently, Sur, Das, and SenGupta [21] discovered a new black-hole solution for Einstein-Maxwell scalar field systems inspired by low-energy string theory. They considered a generalized action in which two scalar fields are minimally coupled to an Einstein-Hilbert-Maxwell 

PACS numbers: 95.30.Sf, 95.36.+x, 04.20.Jb 

## I. INTRODUCTION 

field in four dimensions, 

where 

<img src='content_image/382697.jpg'>

κ = 8 πG , R is the curvature scalar, F$_{µν}$ is the Maxwell field tensor, while ϕ and ζ are two massless scalar or pseudo scalar fields, which are coupled to the Maxwell field. This coupling is described by the functions α and β . Here ζ acquires a non-minimal kinetic term ω . In the context of low-energy string theory, fields φ and ξ can be identified as massless scalar dilaton and pseudo scalar axion fields, respectively. 

With the above action, Eq. (1), Sur, et al. , [21] found the most general class of black-hole solutions and ob- tained two types of metrics, classified as asymptotically flat and asymptotically non-flat. Since we are interested in obtaining a thin-shell wormhole from this new black hole, we adopt the asymptotically flat metric given by 

<img src='content_image/382698.jpg'>

where 

and 

where, according to Ref. [21], the exponent n is a dimen- sionless constant stricly greater than 0 and stricly less 

<img src='content_image/382696.jpg'>

<img src='content_image/382699.jpg'>

<img src='content_image/382700.jpg'>

