Abstract

In this review we present the most general form of the Janis–Newman algorithm. This extension allows generating configurations which contain all bosonic fields with spin less than or equal to two (real and complex scalar fields, gauge fields, metric field) and with five of the six parameters of the Plebański–Demiański metric (mass, electric charge, magnetic charge, NUT charge and angular momentum). Several examples are included to illustrate the algorithm. We also discuss the extension of the algorithm to other dimensions.

Highlights

  • General relativity is the theory of gravitational phenomena

  • As explained in the previous section, the JN algorithm was formulated only for the metric and all other fields had to be found using the equations of motion

  • For example neither the Kerr–Newman gauge field or its associated field strength could be derived in [4]. The solution to this problem is to perform a gauge transformation in order to remove the radial component of the gauge field in null coordinates [57]

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Summary

Motivations

General relativity is the theory of gravitational phenomena It describes the dynamical evolution of spacetime through the Einstein–Hilbert action that leads to Einstein equations. As the complexity of the equations of motion increase, it is harder to find exact analytical solutions, and one often consider specific types of solutions (extremal, BPS), truncations (some fields are constant, equal or vanishing) or solutions with restricted number of charges. For this reason it is interesting to find solution generating algorithms – procedures which transform a seed configuration to another configuration with a greater complexity (for example with a higher number of charges). Even if in practice this kind of solution generating technique does not provide so many new solutions, it can help to understand better the underlying theory (which can be general relativity, modified gravities or even supergravity) and it may shed light on the structure of gravitational solutions

The Janis–Newman algorithm
Summary
Outlook
Overview
Algorithm: main ideas
Perform a complex change of coordinates and transform accordingly:
Algorithm
Seed metric and gauge fields
Janis–Newman prescription
Giampieri prescription
Transforming the functions
Boyer–Lindquist coordinates
Examples
Kerr–Newman
Magnetic charges: dyonic Kerr–Newman
Complex scalar fields
Complete algorithm
Seed configuration
Complex transformation
Function transformation
Null coordinates
Open questions
Derivation of the transformations
Action and equations of motion
Janis–Newman configuration
Static solution
Simplifying the equations
Summary of the equations
Relaxing assumptions
Gauge field integration constant
Kerr–Newman–NUT
Pure supergravity
Non-extremal rotating solution in T 3 model
SWIP solutions
Five dimensional algorithm
Myers–Perry black hole
Few properties and seed metric
Transforming the Maxwell potential
Another approach to BMPV
CCLP black hole
Algorithm in any dimension
Metric transformation
Seed metric and discussion
Iteration and final result
Flat space
Myers–Perry black hole with one angular momentum
Five-dimensional Myers–Perry
Three dimensions
Spherical
Spherical with direction cosines
Spheroidal with direction cosines
Mixed spherical–spheroidal
Group properties
Chaining transformations
Arbitrariness of the transformation
Full Text
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