The Chameleon A.C.Davis Outline The Big Puzzle potential dominated as long as
Walsh, Denny, Federal Court Reporter has reference to this Academic Journal, PHwiki organized this Journal The Chameleon A.C.Davis with P.Brax, C van deBruck, C.Burrage, J. Khoury, A.Weltman,D.Mota, C.Shelpe, D. Seery in addition to D.Shaw PRD70(04)123518, PRL 99(07)121103; PRD76(07)085010; PRD76(07)124034; 0902.2320 +unpublished Outline Introduction to chameleon theories Chameleon cosmology Photon Coupling in addition to PVLAS Predictions + Casimir Force Electroweak physics -Implications as long as LHC Possible detection in AGNs + polarised starlight Conclusions The Big Puzzle
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Equ of state Consider scalar field potential dominated as long as WMAP Dark Energy Like during primordial inflation, scalar fields can trigger the late acceleration of the universe. An attractive possibility: runaway behaviour. The mass of the field now is of order of the Hubble rate. Almost massless. Do Scalars Couple to Matter Effective field theories with gravity in addition to scalars deviation from Newtons law
The radion The distance between branes in the R in addition to all-Sundrum model: where Deviations from Newtons law Far away branes small deviations close branes constant coupling constant Experimental consequences Long lived scalar fields which couple with ordinary matter lead to the presence of a new Yukawa interaction: This new as long as ce would have gravitational effects on the motion of planets, the laboratory tests of gravity etc The Chameleon Mechanism When coupled to matter, scalar fields have a matter dependent effective potential:
Typical example: Ratra-Peebles potential Constant coupling to matter Chameleon field: field with a matter dependent mass A way to reconcile gravity tests in addition to cosmology: Nearly massless field on cosmological scales Massive field in the atmosphere Allow large gravitational coupling constant of order one or more Possible non-trivial effects in the solar system (satellite experiments) Gravity Tests Fifth as long as ce experiments Equivalence principle
The thin-shell property The chameleon as long as ce produced by a massive body is due only to a thin shell near the surface Thin shell deviations from Newtons law Thick shell deviations from Newtons law Khoury & Weltman (2004) Scalar Optics The PVLAS experiment originally claimed to have observed a signal as long as the birefrigence (ellipticity) in addition to the dichroism (rotation) of a polarised laser beam going through a static magnetic field. Effect claimed to be larger than induced by higher order terms in the QED Lagrangian (one loop) or gaseous effects (Cotton-Mouton effect) The phenomenon can be interpreted as a result of the mixing between photons in addition to scalars. More precisely: a coupling between 2 photons in addition to a scalar can induce two effects: Rotation: a photon can be trans as long as med in a scalar. Ellipticity: a photon can be trans as long as med into a scalar in addition to then regenerated as a photon (delay)
PVLAS: Alas! New runs looking as long as experimental artifacts have contradicted the 2000-2005 experimental results. No rotation signal observed at 2.3 T in addition to 5.5 T No ellipticity signal at 2.3 T in addition to a large positive signal at 5.5 T Ellipticity incompatible with a traditional scalar/axion interpretation ( scaling).
PVLAS vs CAST Putative PVLAS experimental results could be seen as a result of the coupling: Limits on mass of scalar quite stringent: No contradiction with CAST experiments on scalar emitted from the sun What if CHAMELEON Universality of coupling: Large gravitational coupling: No contradiction with gravity tests, variation of constants, cosmology, astrophysics bounds . No deviation from gravity in satellite experiments . Small objects have a thin shell. Chameleon Optics Chameleons never leave the cavity (outside mass too large, no tunnelling) Chameleons do not reflect simultaneously with photons. Chameleons propagate slower in the no-field zone within the cavity
Predicted Rotation Predicted Ellipticity Because the chameleon is reflected rather than escaping in addition to their reflection is decoherent with photons we expect ellipticity > rotation in chameleon theories. This is because, as long as a large number of passes in the chamber the ellipticity builds up but due to the decoherence the rotation doesnt. At present we are in agreement with current experiments, but this could be tested soon!
Can fit the new data with various values of n in addition to M: We know that these parameters lead to a full compatibility with gravity tests, cosmology, CAST . GammeV could see an `afterglow Casimir Force Experiments Measure as long as ce between Two parallel plates Difficult to keep plates parallel A plate in addition to a sphere Harder to calculate analytically. No physical shield is used. Electrostatic as long as ces calibrated as long as by controlling electric potential between plates. R. S. Decca et al., PRD 75 (2007) S. K. Lamoreaux, PRL 78 (1997) Chameleons & Casimir We consider two potentials: We find that currently:
What the future holds New experiments Two new experiments currently under construction have real prospect of detecting chameleons. Los Alamos experiment Sphere in addition to plate Could detect chameleon as long as ce if without a detailed knowledge of the thermal as long as ce. S. K. Lamoreaux Chameleons Next generation of Casimir as long as ce measurement experiments have the precision to detect almost all chameleon dark energy models with Generally a good model as long as the thermal Casimir as long as ce is required although some models can be detected without it.
Conclusions II Their coupling to matter is screened in precision tests of the electroweak physics due to UV sensitivity or vacuum polarisation in addition to gauge invariance. Scatter in astrophysical luminosity relations can be used to study the mixing with photons in magnetic fields. Applied to AGN this shows strong evidence as long as chameleons/ALP strong mixing over Gaussian scatter.
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