Rencontres de Moriond, La Thuile, 23/03/2015
GINGER
A terrestrial experiment
to verify the Lense-Thirring effect or
possible deviations from General Relativity
Angelo Tartaglia
Angelo Tartaglia
Giroscopes in General Relativity, Politecnico di Torino, DISAT
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Rencontres de Moriond, La Thuile, 23/03/2015
Small effects of General Relativity
du

0 2
  00 u  2 0i u 0u i   iju i u j  0
ds
 
Free fall


Static metric


0i
0i
1   g 0  g i g 0i 
 g  i  0   
2
x
x 
 x
1   g 0  g 0i  1  0 g 00 1  j  g 0 j g 0i 
 g  i     g
 g  i  j 
i
2
x  2
x
2
x 
 x
 x
GM k
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
Best covering of space-time by means of null geodesics
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
Chiral symmetry about a time axis
Light → ds = 0
 g 0i dx 
i
dt 
g
0i
dx

i 2
 g 00 g ij dx dx
i
j
cg 00
+
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
Closed path in space (proper length L)
xi(ℓ)= xi(ℓ+L)
i
dt 
dx
 g 0i
d 
d
2

dx 
dx i dx j
 g 0i
  g 00 g ij
d
d 
d d

cg 00
i
g 0i dx i
2
        
g 00 
d
c
g 00 d
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
A ringlaser
Resonant loop
Mirrors
Beat frequency
Active cavity
Length of the loop
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
Weak field (the earth), spherical space coordinates.
Expected signal
Angular velocity of the device
Angular momentum of the earth
Scale factor
Area of the loop
Sagnac
Mass of the earth
Bosi F., et al., Phys. Rev. D, vol. 84, p. 122002/1-23 (2011)
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
Ringlasers at rest on the rotating earth
Ω coincides with Ω
GR terms  10-9  the kinematical
contribution (Sagnac term)
de Sitter (geodetic) term: almost same
order as the Lense-Thirring term
Angelo Tartaglia
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03/02/2015, Padova
Metric theories other than GR
In the expected results two ppN parameters appear:
 and 1
GR:
 =1
1=0
Gyroscopes in General Relativity
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Rencontres de Moriond, La Thuile, 23/03/2015
G instrument at the Geodätisches Observatorium Wettzell
Absolute sensitivity:
~ 10-12 rad/s/√Hz
Side: 4 m
Power: 20nW
Zerodur support
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
GINGER: proposed and under development
• Three-dimensional ring lasers array (three to six
or more)
• Laser power: ~ 200 nW
• Quality factor of the cavity: Q  31012
• Square loop, 6 m in side
• Underground location (LNGS)
• Purpose: to measure the LT effect with a 1%
accuracy (one year integration time)
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
Configurations
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
GINGERino (assembled 2014, now working at LNGS)
3.6 m side
Piezoelecric
control of
the
perimeter
Angelo Tartaglia
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Rencontres de Moriond, La Thuile, 23/03/2015
Collaboration
P.I. Angela Di Virgilio
Pisa-INFN
J. Belfi, N. Beverini, F. Bosi, B. Bouhadef,
G. Carelli, G. Cella, E. Maccioni,
R. Santagata, A. Simonelli, G. Terreni
Pisa-University and
INFN
A. Beghi, D. Cuccato, G. Naletto
and A. Ortolan
Padua-University and
Legnaro INFN Labs
C. Altucci, G. Passeggio, A. Porzio
R. Velotta
Naples-CNR and INFN
M.L. Ruggiero and A. Tartaglia
Turin-Politecnico and INFN
C. Zarra
Assergi-LNGS
-----------------------------------------------------------------------------------------------------Ulrich Schreiber
Technische Universität München
Jon-Paul Wells
University of Canterbury,
Christchurch, New Zealand
Angelo Tartaglia
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References
• A. Di Virgilio, et al., Comptes Rendus Physique, vol. 15, 866874 (2014)
• N. Beverini, et al., Laser Phys., vol. 74, 074005 (2014)
• M.L. Ruggiero and A. Tartaglia, Eur. Phis. J. Plus, vol. 129, 126 (2014)
• F. Bosi, et al., Phys. Rev. D, vol. 84, 122002/1-23 (2011)
Angelo Tartaglia
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