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GRS Measurement

GRS Measurement. By A. Cacciani Frascati, March 21th 2006. Introduction. GRS … one of the three classical tests of General Relativity … so far it has been tested only to the first order in m/r, THAT IS, no test for the Einstein field eqn. Theoretical background for gravity. In general

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GRS Measurement

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  1. GRSMeasurement By A. Cacciani Frascati, March 21th 2006

  2. Introduction • GRS … one of the three classical tests of General Relativity • … so far it has been tested only to the first order in m/r, • THAT IS, no test for the Einstein field eqn

  3. Theoretical background for gravity In general where with α, β, γ constants. Einstein puts them all = 1.

  4. Theoretical background for gravity • GRS depends only on gtt. • A large mass is needed to increase the expected signal • Also, it should be at rest or perfectly known relative velocity: • The Sun is the only choise. • To the first order, for the Sun: Δν/ν is 633 m/s Doppler equivalent , that is 10-6 the speed of light. • The second order adds another term 10- 4 smaller, that is, a signal of about 1 mm/s Doppler equivalent.

  5. Competing instruments Masers, radio,.. • They have enough stability ( claimed 10-14 ) • But they need to be launched in orbits around the Sun

  6. Competing instruments Our instrument: the MOF • It is already proven to the level of 10-12 • It does not need to be launched around the Sun, • We are looking at the SOLAR SPECTRUM • Previous measurements (not MOF) of the Solar GRS did not go better than few % (LoPresto et al. - 1991)

  7. MISURADEL GRS SOLARE by: Alessandro Cacciani Runa Briguglio University of Rome “LA SAPIENZA”, Italy Fabrizio Massa INFN sez. Di Roma Paolo Rapex External collaborator James LoPresto Edinboro University of Pennsylvania, USA

  8. A sensitive test of Fundamental Physics, especially General Relativity • Previous results: Snider 1971: GRS Lo Presto 1991: GRS Vessot & al. 1980: Maser Pound & al. 1960: Effetto Mossbauer

  9. How to improve? Instrumental progress such as MOF Technology • Two narrow bands trasmission filter: • FWHM= 50 mA, tuned on a Solar Line • Image detector • High efficiency (30%) • Photon-shot noise limited • Intrinsic stability

  10. Real test of General Relativity • requires time dilation effect at a second order • 10-5-10-6 times the first order effect. On the sun we expect a second order effect of 10-5-10-6 x 636 m/s  1mm/s In order to reach this sensitivity, a comparison between the solar MOF signals from two satellites, one near the Earth and the other close to the Sun, will cancel all the unwanted effects, but the GRS alone. The second order signal is in the range of a mm/s (Doppler equivalent), well within the capability of our MOF.

  11. Typical Doppler image with MOF

  12. Doppler signal on the solar equator

  13. Preliminary Results

  14. Human Resource Activity A.Cacciani (70%) 1) General Supervisor 2) External contacts 3) Cell fabrication a) Lab set up b) Fabrication c) Test 4) Observations F. Massa (70%) 5) Data Acquisition Software Developm. a) Design b) Test 6) Observations R. Briguglio (70%) 7) Instrument set up, test and maintenance 8) Observations P. Rapex (50%) 9) Data reduction Software a) Analysis b) Test and implementations c) Final results production 10) Electronic design support a) Cell heaters b) CCD synchronization

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