Profile
Francisco S. N. Lobo
Researcher at the Institute of Astrophysics and Space Sciences; Assistant Professor with Habilitation, University of Lisbon
Lobo studies wormholes and proposed warp geometries by calculating the matter and energy they require. With Matt Visser, he finds that the Alcubierre and Natário models violate classical energy conditions even at low speeds, not only during faster-than-light motion. These conditions describe restrictions on energy density and pressure. With Miguel Alcubierre, he explains how horizons in faster-than-light models prevent an onboard observer from creating or controlling the bubble on demand.
Affiliations
- Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa
Channels
Bibliography
A bibliography listing does not establish authorship. Credits appear under attribution.
Published bibliography entries: 2. Showing 1–2 of 2.
Listed work
Paper · 2004
Fundamental limitations on 'warp drive' spacetimes
- Francisco S N Lobo(Author)
- Matt Visser(Author)
Francisco Lobo and Matt Visser use warp drive spacetimes as thought experiments that probe the foundations of general relativity. They formulate the Alcubierre and Natário spacetimes carefully, make the notion of superluminal communication precise and confirm that both violate the classical energy conditions non-perturbatively. They apply linearised gravity to weak-field Alcubierre and Natário drives and test the energy conditions to first and second order in bubble velocity. They highlight a feature not remarked on before: a warp drive would be a reactionless drive. For both drives, significant energy condition violations persist even at arbitrarily low speeds. Treating the ship as a finite mass, the net negative energy in the warp field must be a significant fraction of the ship's mass.
Listed work
Paper · 2017
Warp drive basics
- Miguel Alcubierre(Author)
- Francisco S. N. Lobo(Author)
In this 2017 chapter, Alcubierre and Lobo examine warp geometries as mathematical ways to shorten distant journeys without the ship outrunning light in its immediate surroundings. For the Alcubierre geometry, they calculate negative energy density in the bubble walls, even at low speeds. Their analysis with a finite-mass ship relates the energy requirement to bubble speed, size and wall thickness. At faster-than-light bubble speeds, onboard signals cannot reach the outer front edge, so the crew cannot simply create or control the entire bubble on demand. They discuss Krasnikov’s alternative: modify the route during an initial outward journey to enable a shortened round trip. Suitably combined routes can form paths returning to an earlier time, although the original single Alcubierre geometry does not itself contain such loops.