Tests of the Equivalence Principle

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Loren Manning
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1 1 Tests of the Equivalence Principle Stephan Schlainger with Todd Wagner, Ki-Young Choi, Jens Gundlachand Eric Adelberger Friday 1/5/2007 AAPT-Visit

2 2 Outline What is the Equivalence Principle? Why do we want to test it? How has it been tested? The principle of our Apparatus What will you see in the lab tour? Results

3 3 The Equivalence Principle Our Current theory of gravity, General Relativity, is based on the Equivalence Principle: All bodies fall in a gravitational field with the sae acceleration regardless of their ass or internal structure. Einstein realized, that: A unifor gravitational field is the sae as an accelerated reference frae.

4 4 The Equivalence Principle Gravitational field g Acceleration a g -a F=g F=-a Inertial ass = gravitational ass, I = G for all bodies

5 5 General Relativity and the EP Three classical tests: Perihelion shift of Mercury Deflection of light by the Sun Gravitational red shift of light The last two can be explained and calculated with the EP alone!

6 6 Motivation GR is one of the ost essential pillars of odern physics. We should continue to test it. GR should be cobined with quantu echanics for a full description of Nature. New theories like string theory, quantu gravity, etc., ost of which violate the equivalence principle at sall level Tests like this can be used to find new interactions ( fifth force ) Tests of the equivalence principle are the ost sensitive probes of fundaental physics.

7 7 Historical overview Galileo Bessel η = 1 2 a 1 ( a + a2) 1 a 2 Type of experient drop Potter pendula torsion balance Newton Eötvös Dicke Braginsky UW odulated torsion balance

8 8 1st Tests of the Equivalence Principle g F G = g a I G = g a I G = a 2 a 1 g h t I G 2 = g a I G = a F I = h Tie t to fall fro h: 1600 Galileo: 1 0. ( 2) = a a a a η

9 9 2 nd Generation Tests Measureent of the swing periods of pendula: l T = 2π L I g G Newton (1686), Bessel (183), Porter (1923) η 2x10 5

10 10 EötvösExperients ω ε F I = ω 2 r cosθ I θ F r G = G g ε = I G 2 ω r 2g sin(2θ )

11 11 Why a torsion balance? A violation of the EP would yield to different plub-line for different aterials. A torsion balance can be used to easure the difference in plub-lines: Torsion fiber hangs like the average plub line. Difference in plub lines produces a torque on the bea. η 5x10 Eötvös (1922) 9

12 12 Principle of our Experient Rotation 1 rev./ 20in Coposition dipole pendulu (Be-Ti) 13.3in a Be source ass a Ti EP-Violating signal Autocolliator (=optical readout) λ () local asses (hill) entire earth Sun Milky Way (incl. DM) Source Mass

1 g) 4 irrors tuning screws for adjusting tiny asyetries 5 c

13 13 EP Torsion Pendulu 20 µ diaeter tungsten fiber (length: 108 c) 8test asses (4 Be & 4 Ti ) 4.84 g each (within 0.1 g) 4 irrors tuning screws for adjusting tiny asyetries 5 c frequency: Hz quality factor: 4000 decay tie: 11d 6.5 hrs achining tolerance: 5 µ total ass : 70 g

14 14 The Apparatus electrical feedthrough upper part of the apparatus on a concrete bridge (not shown) theral & agnetic shield (non rotating) lower part of the apparatus ion pup (10-5 Pa) agnetic shield (rotating) turntable on air bearing & angle encoder theral legs to adjust tilt rotating adapter pieces fiber positioner (x,y,z,φ) rotating vacuu vessel autocolliator pendulu

15 15 The Upper Part of the Apparatus feedthrough for electric signals theral insulation air bearing turntable electronics of angle encoder theral expansion feet to level turntable

16 16 The Lower Part of the Apparatus vacuu chaber ion pup support structure for gravity gradient copensators autocolliator gravity gradient copensators

17 17 Systeatic Effects (c/s 2 ) Gravitational Coupling Magnetic Teperature Tilt Turntable Rate Total Systeatic StatisticalUncertainty

18 18 Results Excluded Strength relative to gravity with 95 % confidence Range of a hypothetical fifth force ()

19 19 THE END

Modern tests of Einstein s Equivalence Principle. Eric Adelberger University of Washington

Modern tests of Einstein s Equivalence Principle Eric Adelberger University of Washington outline a brief account of a long history motivations old and new experimental techniques modern results what next?