Carlos Barceló

Affiliations

• Instituto de Astrofísica de Andalucía, CSIC

Identifiers

Channels

• arxiv
• institution
• orcid · 0000-0002-2134-377X

Bibliography

A bibliography listing does not establish authorship. Credits appear under attribution.

Published bibliography entries: 5. Showing 1–5 of 5.

0. Listed work

   Paper · 2011

   Analogue Gravity

   1. Carlos Barceló(Author)
   2. Stefano Liberati(Author)
   3. Matt Visser(Author)

   In this 2011 review, Barceló, Liberati and Visser explain how waves in materials can follow equations resembling those for fields in curved spacetime. A sufficiently fast fluid flow can prevent sound from travelling upstream, creating an acoustic counterpart of a black-hole horizon. The review compares water waves, ultracold atomic condensates and optical systems, examining where each analogy applies. It reports classical stimulated Hawking emission in water-wave experiments and a sonic horizon in a condensate kept stable for about eight milliseconds. At that time, reproducible detection of spontaneous quantum Hawking radiation remained an experimental target. The authors distinguish this effective geometry for waves from the equations governing gravity itself: reproducing curved-spacetime propagation does not automatically reproduce Einstein’s gravitational dynamics.

1. Listed work

   Paper · 2009

   Semiclassical instability of dynamical warp drives

   1. Stefano Finazzi(Author)
   2. Stefano Liberati(Author)
   3. Carlos Barceló(Author)

   Finazzi, Liberati and Barceló extend quantum corrections for warp drives from eternal bubbles at fixed speed to the more realistic case of a superluminal bubble created from initially flat spacetime. They map the causal structure of eternal and dynamical warp spacetimes and compute the renormalised stress-energy tensor of a quantum field in them. An observer at the centre of a superluminal bubble generically sees a thermal flux of Hawking particles, which becomes extremely high if the exotic matter comes from a quantum field obeying quantum inequalities. The stress-energy grows exponentially at the bubble's front wall, so these geometries are unstable to semiclassical backreaction.

2. Listed work

   Paper · 2022

   Warp Drive Aerodynamics

   1. Carlos Barceló(Author)
   2. Valentin Boyanov(Author)
   3. Luis J. Garay(Author)
   4. Eduardo Martín-Martínez(Author)
   5. Jose M. Sánchez Velázquez(Author)

   Barceló, Boyanov, Garay, Martín-Martínez and Sánchez Velázquez analyse whether quantum matter can destabilise a warp drive spacetime. They search for points of infinite blueshift, which resemble a black hole's inner horizon with its semiclassical instability, and classify them by how nearby geodesics behave. Warp bubbles in 2+1 dimensions or more turn out likely to be stable: they contain only isolated divergent points, so the destabilising energy that accumulates stays finite. The causal structure found in the 1+1 case carries over to higher dimensions, at least along one axis. Any remaining instability from energy-density build-up can be reduced further with more aerodynamic bubble shapes and trajectories.

3. Listed work

   Paper · 2001

   Analogue gravity from Bose-Einstein condensates

   1. Carlos Barceló(Author)
   2. S Liberati(Author)
   3. Matt Visser(Author)

   Carlos Barceló, S. Liberati and Matt Visser ask how far Bose-Einstein condensates can go in producing a generic effective metric that mimics the kinematics of general relativity. They use a very general nonlinear Schrödinger equation with a position-dependent tensor mass and arbitrary nonlinearity. At low momenta, phase excitations of the condensate obey a d'Alembertian equation for a generic Lorentzian effective metric in 3+1 dimensions set by the background field. At high momenta the eikonal approximation gives a Bogoliubov-like dispersion relation and recovers non-relativistic Newtonian physics. The effective metric appears generically unless interatomic forces are attractive, making condensates an extremely promising system for probing the kinematics of general relativity.

4. Listed work

   Paper · 2000

   Scalar fields, energy conditions and traversable wormholes

   1. Carlos Barceló(Author)
   2. Matt Visser(Author)

   Carlos Barceló and Matt Visser show how a simple, apparently harmless classical scalar field theory can violate the energy conditions. A scalar field coupled non-minimally to curvature with positive coupling easily violates every standard energy condition, including the averaged null energy condition. Solving gravity with such a massless field for static spherical configurations, they find a whole branch of traversable wormholes for every positive coupling. This generalises their earlier conformal coupling case of one sixth. For these wormholes to exist, the scalar field must reach trans-Planckian values somewhere, and the authors discuss how current theoretical physics can accommodate that.