Scattering of electromagnetic waves by static wormholes

Scattering of electromagnetic waves by static and traversable wormholes is discussed. Based on the fact that these spacetimes have no horizon, and regarding their non-trivial topology, we have developed the perturbation theory of scattering and the Born approximation for obtaining the differential scattering cross section. Some of the zeros of the scattering pattern at long wavelengths are determined which can be used for estimating the radius of the throat. The known result that in scattering by static spacetimes the linear polarization remains unchanged is verified here.     

Letter: Delta-String—A Hybrid Between Wormhole and String

The flux tube solutions in 5D Kaluza-Klein theory can be considered as string-like objects—–strings. The initial 5D metric can be reduced to some inner degrees of freedom living on the –string. The propagation of electromagnetic waves through the –string is considered. It is shown that the difference between and ordinary strings are connected with the fact that for the –string such limitations as critical dimensions are missing.     

Quantifying energy condition violations in traversable wormholes

The ‘theoretical’ existence of traversable Lorentzian wormholes in the classical, macroscopic world is plagued by the violation of the well-known energy conditions of general relativity. In this brief article we show: (i) how the extent of violation can be quantified using certain volume integrals and (ii) whether this ‘amount of violation’ can be minimised for some specific cut-and-paste geometric constructions. Examples and possibilities are also outlined.     

Diving into traversable wormholes

We study various aspects of wormholes that are made traversable by an interaction beween the two asymptotic boundaries. We concentrate on the case of nearly‐ gravity and discuss a very simple mechanical picture for the gravitational dynamics. We derive a formula for the two sided correlators that includes the effect of gravitational backreaction, which limits the amount of information we can send through the wormhole. We emphasize that the process can be viewed as a teleportation protocol where the teleportee feels nothing special as he/she goes through the wormhole. We discuss some applications to the cloning paradox for old black holes. We point out that the same formula we derived for gravity is also valid for the simple SYK quantum mechanical theory, around the thermofield double state. We present a heuristic picture for this phenomenon in terms of an operator growth model. Finally, we show that a similar effect is present in a completely classical chaotic system with a large number of degrees of freedom.     

A single model of traversable wormholes supported by generalized phantom energy or Chaplygin gas

This paper discusses a new variable equation of state parameter leading to exact solutions of the Einstein field equations describing traversable wormholes. In addition to generalizing the notion of phantom energy, the equation of state generates a mathematical model that combines the generalized phantom energy and the generalized Chaplygin gas models.     

d-Dimensional non-asymptotically flat thin-shell wormholes in Einstein-Yang-Mills-dilaton gravity

Thin-shell wormholes in Einstein-Yang-Mills-dilaton (EYMD) gravity are considered. We show that a non-asymptotically flat (NAF) black hole solution of the d-dimensional EYMD theory provides stable thin-shell wormholes which are supported entirely by exotic matter. The presence of dilaton makes the spacetime naturally NAF, and with our conclusion it remains still open to construct wormholes supported by normal matter between two such spacetimes.     

Wormhole with varying cosmological constant

It has been suggested that the cosmological constant is a variable dynamical quantity. A class of solution has been presented for the spherically symmetric space time describing wormholes by assuming the erstwhile cosmological constant Λ to be a space variable scalar, viz., Λ = Λ (r) . It is shown that the averaged null energy condition (ANEC) violating exotic matter can be made arbitrarily small.     

Experimental Test for Extra Dimensions in Kaluza–Klein Gravity

5D Kaluza–Klein gravity has several nonasymptotically flat solutions which generally, possess both electric and magnetic charges. In this paper we suggest that these solutions can act as quantum virtual handles (wormholes) in spacetime foam models. In the presence of a sufficently large, external electric and/or magnetic field it may be possible to inflate these solutions from a quantum to a classical state. This effect would lead to a possible experimental signal for higher dimensions in multidimensional gravity.