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Measurement of the Thermal spectrum of Hawking radiation from a Horizon

Bill Unruh, Department of Physics, University of British Columbia
Monday, October 8, 2012 - 4:00pm to 5:00pm
PAA A-102

​Almost 40 years ago Hawking predicted that black holes are not black but radiate thermally with a temperature inversely proportional to the mass. A few years later I suggested that the same arguments he made for black holes would lead to thermal radiation from other horizons (eg, sonic horizons in a flowing fluid). A couple of years ago, a group here at UBC measured the stimulated emission from a "blocking" horizon (the analog of a white hole horizon, or the time inverse of a black hole horizon) for water surface waves in a flume with the flow over an obstacle forming the horizon. These measurements showed that the quantum noise associated with this stimulated emission would have a thermal spectrum whose temperature depends just on the flow parameters at the horizon. With very general arguments about the quantum behaviour of linear systems of waves, this is the first measurement of the Hawking radiation from a horizon. Furthermore, it illustrates the incredible unity in physics, where the physics of water flow and that of black holes could be so closely connected.

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