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MICROKELVIN: JRA3. Fundamental physics for the study of cosmological analogues in the laboratory. Task 1: Investigating quantum vortices as model cosmic strings (ULANC, TKK, CNRS).
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MICROKELVIN: JRA3 Fundamental physics for the study of cosmological analogues in the laboratory
Task 1: Investigating quantum vortices as model cosmic strings (ULANC, TKK, CNRS) • Deep analogies between the broken symmetries of superfluid 3He and those of the Universe mean that quantized vortices mirror cosmic strings. • ULANC will attempt the measurement in the high-resolution quasiparticle energy detector by observing the decay of a vortex tangle generated inside the bolometer. • TKK will observe the heat released in the inverse process when a previously stationary condensate in a rotating container is suddenly converted to a vortex lattice. Both methods will require high-sensitivity energy detection. • CNRS will investigate the effect of pressure on the dynamics associated with the competition between the two superfluid phases as the vortices are created. Milestones • M1: Determination of the energy released by a vortex tangle with known line density (12 month). • M2: Measurement of the dissipation when a vortex tangle is established (24). • M3: A precise determination of the effect of pressure on vortex creation via the dynamics of the second-order phase transition (30). Enluminure : en l’ an de grâce 2008, GRP me fît:
Task 2: Investigating condensate-condensate phase boundaries as analogue branes(ULANC, CNRS) • The several coherent phases of superfluid 3He provide us with phase boundaries which are absolutely unique in being boundaries between two fully-ordered condensates with different symmetries. • The most highly ordered 2D structure to which we have experimental access. • ULANC will devise methods to identify the topological defects left after boundary (“brane”) annihilation. • CNRS will investigate the direct interaction of a micromechanical oscillator with the recently observed 2D “cosmological defect” Milestones: • M4: Identification of the topological defects left after brane (phase boundary) annihilation (24). • M5: Observation of several “cosmological defects” in a microkelvin multi-cell detector (30).
Task 3: Horizons, ergo-regions and rotating Black Holes (TKK, CNRS) • 3He analogues to Black Holes and their associated horizons • Superfluid Landau critical velocity = velocity of light • Analogue of cosmological particle production during expansion simulated by the rapid change of the magnetic field; the analogue of the Unruh effect of particle creation, simulated by a potential gradient moving rapidly in the superfluid; the radiation of fermionic quasiparticles by a moving vortex in turbulent flow of 3He simulating the radiation of gravitational waves by evolving cosmic strings in early Universe, etc. • At TKK instabilities at the interface between the A and B phases mimic Black-Hole behaviour. The spectrum of excitations on the interface takes the relativistic form with the governing equations mimicking those for the event horizon of a black hole. • At CNRS, exploration of the percolation transition mechanism will give information on the fundamentals of the second order phase transition dynamics. Milestones • M6: Realization of a Black-Hole analogue in a rotating system with an A-B boundary (24). • M7: Test of the Unruh effect from rapid motion of a phase boundary (30). • M8: Test of the percolation theory of the A-B transition (36).
Task 4: Q-balls in superfluid 3He (CNRS, ULANC, TKK, SAS, RHUL) • Q-balls: bubbles of the “wrong” phase after phase transitions in the early Universe. • Example: supersymmetric particles trapped in the surrounding “normal” matrix. Such a Q-ball would be able to desintegrate a neutron star. • Analog: long-lived domains seen in superfluid 3He • Magnetization = conserved Q-ball charge "Q". • In 3He we can observe the deflected spin directly by NMR. • We can see the structure of the Q-ball, and test interactions • Milestones: • M9: The observation of the interaction between two independent precessing Q-balls (30). • M10: Creation of excited modes of a “Q-ball” under radial squeezing by rotation (36). • M11: Realization of microkelvin thermometry based on "Q-ball” behaviour (42).
Task 5: ULTIMA-Plus: Dark matter search with ultra-low temperature detectors (CNRS, ULANC, HEID) • The 3He condensate provides a “scintillator” material for dark-matter detection and other ultrasensitive energy measurements • The possibility of detecting astroparticles with a sensitivity of less than 1 keV using superfluid 3He at 100 μK (two orders of magnitude colder than current experiments) has been demonstrated in Lancaster and CNRS-Grenoble. • A prototype particle detector showing extreme sensitivity has been successfully tested in Grenoble (Projects MacHe3 and ULTIMA) • ULT techniques must be developed to exploit fully the potential of superfluid 3He Milestones: • M12: Microfabricated silicon vibrating wires tested in superfluid 3He below 100 microkelvin in underground laboratory conditions (30). • M13: Superfluid 3He microkelvin underground multicell particle-detector operating underground (42).
Deliverables • D1: Report on microfabricated silicon vibrating wires tested in superfluid 3He at 100 µK (12). • D2: Publication on vortex creation in superfluid 3He (24, 36). • D3: Publication on 2D defects (36). • D4: Publication on Black Holes (36) • D5: Publication on Q-balls in superfluid 3He (48) • D6: Report on ULTIMA multicell particle-detector operating underground (48).
