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Abstract Atoms falling into a black hole (BH) through a cavity are shown to enable coherent amplification of light quanta powered by the BH-gravitational vacuum energy. This process can harness the BH energy towards useful purposes, such as propelling a spaceship trapped by the BH. The process can occur via transient amplification of a signal field by falling atoms that are partly excited by Hawking radiation reflected by an orbiting mirror. In the steady-state regime of thermally equilibrated atoms that weakly couple to the field, this amplifier constitutes a BH-powered quantum heat engine. The envisaged effects substantiate the thermodynamic approach to BH acceleration radiation.
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This content will become publicly available on April 1, 2026
Black Holes and de Sitter Space as Time Mirrors
It is usually assumed that matter disappears together with the spacetime at the center of a Schwarzschild black hole (BH). Here, we find that if we impose a boundary condition that the field does not disappear at the BH center (that is, field flux into the singularity vanishes), the BH acts as a time mirror that totally reflects the infalling light and matter outside the BH. Namely, the reflected field propagates backward in time, passes the event horizon and moves away from the BH. In this case, a BH can be used as a time machine that allows us to send a signal into the past. We also show that de Sitter spacetime acts as a time mirror provided particles do not disappear from the spacetime at r=∞.
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- Award ID(s):
- 2013771
- PAR ID:
- 10633306
- Publisher / Repository:
- MDPI
- Date Published:
- Journal Name:
- Universe
- Volume:
- 11
- Issue:
- 4
- ISSN:
- 2218-1997
- Page Range / eLocation ID:
- 109
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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