Historical research guide · 0772 · 2024
Motivating Emissions from Positive Energy Warp Bubbles
Erik W. Lentz · Ryan C. Felton
In one minute
Erik Lentz and Ryan Felton ask the question that follows directly from the last few years of warp-drive work: if somebody actually flew one, what would we see? Their answer is that a warp bubble is a noisy object. Anything sourced by real stress-energy and moving through the galaxy radiates — gravitational waves from an oscillating source, radio and optical light from the charges that carry it, and a scattered spray of interstellar photons, gas and neutrinos swept up along the way. They compute first estimates for each, and they find one signature no known natural process makes: a craft outrunning its own emissions is seen twice at once, one image running forward through the journey and one running backward, separated on the sky. Lentz and Felton then set out the programme that would turn these sketches into a real search — full non-linear simulations of a bubble across acceleration, coast and deceleration, then a hunt through the Keck, Green Bank and European Southern Observatory archives around stars with a confirmed planet.
Connection
Chapter 4 says the metric is something you build; this paper is the first serious attempt to say what a built one looks like from the outside, and it turns warp drive from an argument about energy conditions into an observing proposal with named telescopes and archives. It also makes chapter 1’s point about the evidence ladder concrete: here is the measurement, here is the instrument, here is what a positive result would look like.
From the source
Warp drive research has moved on from the negative-energy era. Since 2021 a series of papers — Lentz’s own soliton, Bobrick and Martire’s general shell, Fell and Heisenberg, Huey, and Fuchs and colleagues — have produced geometries requiring only positive energy sources, and a drive satisfying all four energy conditions would be far more feasible in a laboratory setting, leaving the energy magnitude and the construction mechanism as the standing challenges.Section 2, A brief primer on warp drive research, final two paragraphs
A craft moving faster than the emissions it broadcasts produces a bi-modal signature: the observatory records emissions from two different moments at once, one branch moving in the apparent direction of travel and presenting the journey forward in time, the other moving opposite and presenting it in reverse. The authors state they are unaware of any natural phenomenon that could produce such a signal, and it is distinct from other proposed technosignatures.Section 3, Figs. 2 and 3; Section 4.2, Technosignature Search
For an economical bubble one kilometre across carrying a source of about a billion kilograms at 100 light years, the estimated radio flux density from a resonant electromagnetic dipole loss is of the order of two million Janskys in a one hertz resonance — set against Green Bank Telescope noise measured in tens of micro-Janskys to milli-Janskys, and visible-band thermal noise of the order of ten thousand Janskys.Section 3.3.1, Eq. 14 and the preceding observatory noise figures
The bubble also lights up by scattering what it passes through. Interstellar photons scattered by the craft give a flux of the order of three ten-millionths of a Jansky-hertz at the same reference distance, while interstellar gas and dust, whose energy density is a billion times higher, would re-radiate at the order of three hundred Jansky-hertz if the scattered excess thermalises in the surrounding medium.Section 3.3.1, Eqs. 12 and 13; Fig. 6 for the scattered photon spectrum
On the gravitational side the same resonance gives an estimated strain spectral amplitude of about seven times ten to the minus twenty-nine per root hertz at 100 light years, and the observed frequency is pushed up by several orders of magnitude — placing the waveform above the roughly 30 hertz to 100 kilohertz band where interferometers are most sensitive. Gravitational sensitivity falls only as one over distance rather than as the inverse square, which is why the authors keep it in the search.Section 3.3.2, Eq. 15
The proposed programme is specific: simulate warp drives self-consistently in geometry and stress-energy across acceleration, coast and deceleration, in vacuum and in an interstellar-medium environment, build semi-analytic emission templates from those runs, then search the public Keck, Green Bank and European Southern Observatory archives in the optical, near-infrared and radio, restricted to stellar systems with at least one confirmed exoplanet, before moving to narrow-band observing time on Keck, the Allen Telescope Array and Green Bank.Section 4, Sections 4.1 and 4.2, including the Archival Search Campaign list
The way in
https://arxiv.org/abs/2405.19381How to cite it
Erik W. Lentz, Ryan C. Felton (2024) Motivating Emissions from Positive Energy Warp Bubbles arXiv:2405.19381