Progetto Buchi Neri Acustici (Resp. R. Balbinot)

Progetto Buchi Neri Acustici (Resp. R. Balbinot)
R. Balbinot, A. Fabbri
Centro Fermi
Roma, 19 Aprile 2012
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
1 / 15
Black Holes
In General Relativity black holes are ‘black’ objects:
light is trapped inside their event horizon (RS = 2GM/c2 )
they form from the gravitational collapse of massive stars (M ≥ 3MSun )
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
2 / 15
Black Holes and Quantum Mechanics
BHs are not ‘black’:
Hawking 1974: they behave as ‘hot’ (black) bodies with a temperature TH
Basic mechanism: conversion of vacuum fluctuations into on shell particles
due to horizon formation
For M ∼ MSun we have TH ∼ 10−7 K ≪ TCMB ∼ 3 K..... sigh!
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
3 / 15
Acoustic black holes
A stationary fluid undergoing transition from subsonic to supersonic
motion is for sound what a black hole is for light
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
4 / 15
Hawking radiation in condensed matter systems
Features of HR
It is a “kinematical” instead of a “dynamical” effect, and it can be found also
in systems other than gravity
Unruh 1981: A process identical to that found by Hawking for BHs works for
acoustic bhs: they emit a thermal flux of phonons from their acoustic horizon
Domain of application and advantages wrt gravity
Domain of application: fluids and other CM systems in the long wavelength
(hydrodynamic) approximation
They allow to test experimentally the existence of Hawking radiation
The existence of HR can be studied from first principles, overcoming the
transplanckian problem in gravity
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
5 / 15
What is the best experimental setting?
Different directions are being explored
Water tanks experiments (stimulated HR from white hole flows)
Laser pulse filaments (controversial)
Experimental realization of an acoustic black hole in a Bose-Einstein
condensate
Problems
The signal is tiny and there are competing effects (nonzero background
temperature, quantum noise, ..)
In BECs TH ∼ 10 nK < TC ∼ 100 nK: much better wrt gravity, but not
enough to allow a direction detection of the emitted phonons
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
6 / 15
Balbinot et al. 2008: A major breakthrough
Hawking radiation in correlations in BECs
HR is a pairs production process:
Hawking quanta (outside the horizon)/partner (inside)
This leads to a characteristic signal in density-density correlations for points
situated on both sides of the acoustic horizon (these correlations cannot be
measured in gravity) Balbinot, Fabbri, Fagnocchi, Recati, Carusotto 2008
Prediction confirmed by numerical “ab initio” simulations: this signature can
be exploited to isolate HR from competing processes and experimental noise
Carusotto, Fagnocchi, Recati, Balbinot, Fabbri 2008
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
7 / 15
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
8 / 15
Advantages of this application
Density correlations measurements appear to be the most promising way to
detect experimentally the Hawking-Unruh effect
Inserting numbers for realistic experiments one anticipates correlations of
order 10−3 , not far from the sensitivity of actual experiments
Eric Cornell (Valencia, 2009) proposed to amplify the signal by following the
formation of the acoustic bh with a period of free expansion
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
9 / 15
2011: A new signal
Hawking radiation from acoustic white holes
Mayoral, Recati, Fabbri, Parentani, Balbinot, Carusotto 2011: In BECs the
characteristic signal is inside the horizon: correlations are nonstationary and
grow with time
Similarities with the undulation observed in water tanks experiments
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
10 / 15
Comments and future directions
The study of HR in BECs allows to better understand its origin (negative
energy states and energy conservation, the role of the horizon)
Transverse/massive modes and undulation
...
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
11 / 15
Collaborators to the Project
I. Carusotto, A. Recati (INO-CNR BEC Center, Dip. Fisica Univ. Trento)
R. Parentani (Laboratoire Physique Théorique, Univ. Paris Sud Orsay)
P. Anderson (Dept. of Physics, Wake Forest University, USA)
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
12 / 15
Organization of international congresses
‘Towards the observation of Hawking radiation in condensed-matter systems’,
Valencia (2009)
‘New trends in the physics of the quantum vacuum: from condensed matter,
to gravitation and cosmology’, Trento (2011)
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
13 / 15
Publications
C. Mayoral, A. Recati, A. Fabbri, R. Parentani, R. Balbinot and I. Carusotto,
New J. Phys. 13, 025007 (2011)
R. Balbinot, I. Carusotto, A. Fabbri and A. Recati, Int. J. Mod. Phys. D19,
2371 (2010)
I. Carusotto, R. Balbinot, A. Fabbri and A. Recati, Eur. Phys. J. D56, 391
(2010)
I. Carusotto, S. Fagnocchi, A. Recati, R. Balbinot and A. Fabbri, New J.
Phys. 10, 103001 (2008)
R. Balbinot, A. Fabbri, S. Fagnocchi, A. Recati and I. Carusotto, Phys. Rev.
A78, 021603 (2008)
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
14 / 15
R. Balbinot, S. Fagnocchi and A. Fabbri, Phys. Rev. A75, 043622 (2007)
R. Balbinot, A. Fabbri, S. Fagnocchi and A. Nagar, Nuovo Cim. B121, 201
(2006)
R. Balbinot, A. Fabbri, S. Fagnocchi and R. Parentani, Riv. Nuovo Cim. 28,
1 (2005)
R. Balbinot, S. Fagnocchi and A. Fabbri, Phys. Rev. 71, 064019 (2005)
R. Balbinot, S. Fagnocchi, A. Fabbri and G.P. Procopio, Phys. Rev. Lett.
94, 161302 (2005)
Resp. R. Balbinot (Università di Bologna)
Progetto Buchi Neri Acustici
Centro Fermi Roma, 19 Aprile 2012
15 / 15