Quantum Backreaction Study Reveals Density Undulations in Analogue Black Hole Transonic Flows

The behaviour of quantum fields in curved spacetime remains a fundamental question in physics, and recent research explores this through the creation of analogue black holes using Bose-Einstein condensates. A team led by G. Ciliberto, R. Balbinot, and A. Fabbri, along with N. Pavloff, investigates how the seemingly faint acoustic Hawking radiation emitted by these analogue systems actually influences the underlying condensate itself. The researchers extended existing theoretical models to account for quantum fluctuations and applied this to a flowing condensate, revealing the emergence of stable patterns within the ‘black hole interior’ and measurable changes to the flow’s characteristics. This work represents a significant step forward in understanding the interplay between quantum fluctuations and curved spacetime, offering new avenues for exploring gravity’s quantum nature through condensed matter systems.

Quantum Fluctuations Modify Analogue Black Hole Geometry

Researchers investigate quantum backreaction effects in an analogue black hole, focusing on how a quantum field behaves in a curved spacetime created by a flowing Bose-Einstein condensate. This work demonstrates that quantum fluctuations of the field modify the background geometry, a phenomenon known as backreaction, and explores the implications for Hawking radiation and black hole evaporation. The approach combines quantum field theory in curved spacetime with fluid dynamics, allowing scientists to calculate the renormalized stress-energy tensor of the quantum field. This tensor, representing the energy and momentum density of the quantum field, then acts as a source term in the equations governing the fluid flow, effectively closing the loop of backreaction. The calculations reveal that these backreaction effects are significant, measurably modifying the analogue black hole horizon and suppressing Hawking radiation at high frequencies. These findings provide valuable insights into the interplay between quantum mechanics and gravity, and offer a potential pathway for experimental verification of theoretical predictions regarding black hole physics.

Bose-Einstein Condensates Simulate Black Hole Horizons

This document provides an overview of research into analogue gravity, Bose-Einstein condensates (BECs), and Hawking radiation, exploring how condensed matter systems can simulate black holes and study quantum phenomena. BECs, formed when bosons are cooled to near absolute zero, exhibit macroscopic quantum properties, making them ideal for simulating fields in curved spacetime. Researchers employ theoretical frameworks such as Bogoliubov theory and quantum hydrodynamics to describe these systems. Key areas of investigation include the observation of analogue Hawking radiation, the role of non-locality and back-reaction, and the application of techniques like functional integration and perturbation theory. Experimental setups involve creating analogue horizons by inducing supersonic flow in BECs, using obstacles or potential traps, and observing the emitted radiation as correlations within the condensate. Researchers are also exploring the possibility of creating analogue white holes, the time-reversed counterpart of a black hole.

Hawking Radiation Drives Condensate Undulations

This research extends the Gross-Pitaevskii equation to incorporate the influence of quantum fluctuations on a weakly interacting Bose-Einstein condensate. By applying this extended framework to an analogue black hole created within the condensate, the team investigated how acoustic Hawking radiation affects the surrounding environment. The results demonstrate the emergence of stationary density and velocity undulations within the supersonic region, analogous to the interior of a black hole, and quantify the changes in Mach numbers upstream and downstream caused by this radiation. These findings offer new insights into the interplay between fluctuations and analogue systems in Bose-Einstein condensates, providing a more complete picture of these complex quantum phenomena. The developed equations are broadly applicable, extending to time and space-dependent configurations in various dimensions. While the study focuses on a specific “waterfall” analogue black hole configuration, the authors acknowledge that further investigation is needed to explore different analogue settings and fully understand the range of possible behaviours.