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In the pioneering work of Alcubierre, to power a warp drive-like geometry it is necessary to employ an amount of negative energy larger (in absolute value) than the whole observable universe mass. A later refinement by Den Broeck brings the requirements down to a few solar masses.

What is the current minimum amount of negative energy required to build a warp drive-like spacetime? (with link to the reference please)

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    $\begingroup$ The Wikipedia article discusses the various exotic mass requirements. A common figure given these days is around Jupiter's mass. $\endgroup$
    – PM 2Ring
    Commented May 5, 2019 at 20:47
  • $\begingroup$ @PM2Ring Are there any compelling reasons to think that any exotic mass suitable for an Alcubierre drive could be created, or is it just wishful thinking that such a thing could exist? If it is just wishful thinking, then I will vote to close this question as non-mainstream physics. $\endgroup$
    – G. Smith
    Commented May 5, 2019 at 20:53
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    $\begingroup$ @G.Smith Personally, I'm extremely sceptical that negative mass exotic matter can exist. But there are quite a few unclosed questions in the warp-drive & exotic-matter tags, so I guess it's considered borderline, rather than definitely non-mainstream. $\endgroup$
    – PM 2Ring
    Commented May 5, 2019 at 21:08
  • $\begingroup$ @G.Smith: Are there any compelling reasons to think that any exotic mass suitable for an Alcubierre drive could be created, or is it just wishful thinking that such a thing could exist? There isn't a simple answer to your question. Relativists don't really talk about negative energy, they talk about energy conditions, and there are a bunch of different energy conditions. We pretty much know that none of the energy conditions are universally valid, but we also expect them to hold in bulk matter. A nice summary is Barcelo and Visser, arxiv.org/abs/gr-qc/0205066 $\endgroup$
    – user4552
    Commented May 5, 2019 at 21:58
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    $\begingroup$ @G.Smith Negative energy is allowed in Quantum Field Theory, very famously in the Casimir effect. $\endgroup$
    – Rexcirus
    Commented May 6, 2019 at 9:10

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According to this paper by Krasnikov, the energy requirement can be brought down to approximately $10^{-3} g$ for a human-usable warp drive:

The quantum inequalities do not forbid spacetime shortcuts

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I got an answer to this after some time: Hyperwave: Hyper-Fast Communication within General Relativity

For Planckian warp space-times the negative energy can be as low as $10^8 J$, less (in absolute magnitude) than the energy contained in an average lighting bolt or in about 10kg of crude oil. The caveat is that being so small it cannot be used for interstellar travel, so not really a traditional warp drive.

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