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Overview of Research, Results and Next Steps
Fundamental Interactions Lab
C. S. Unnikrishnan
Gravitation Group,
Tata Institute of Fundamental Research,
Homi Bhabha Road, Mumbai 400005, India
E-mail address: [email protected]
Website: www.tifr.res.in/~filab
Multi-pronged studies with Gravity and Quantum Electrodynamics as focus themes
Equivalence principle, its Root
Cosmic Gravity as causal interaction for
relativistic effects and laws of dynamics
(Cosmic Relativity)
Quantum vacuum
and its physical effects
Atom-light interactions
Cavity-optics
Gravitational Waves, LIGO-India
Laser cooling physics
2011-2016 publications
Cold atoms physics: 4
Gravity studies: 15
Other: 3
LIGO Collaboration 2013 - : 30
Talks : ~50 (30 invited, 10 contributed, 10 colloquium/seminars)
Matter-wave interferometers
(metrology, gravity, inertia)
Rubidium Magneto-Optical Trap
Rb Optical dipole trap
Potassium MOT
5 Ph. D thesis:
Ashok Mohapatra,
Saptarishi Chaudhuri,
Sanjukta Roy,
Vandna Gokhroo,
Dipankar Nath
Rb BEC
5 post-doctoral:
Charles Antoine
Yeshpal Singh
R. Raghavan
Jorge Fiscina
G. Rajalakshmi
Trapping and Cooling of both bosonic and fermionic atoms (Potassium 39 and 40)
1) Sub-Doppler deep-cooled bosonic and fermionic isotopes of potassium in a compact 2D+ - 3D MOT set-up, V. Gokhroo,
G. Rajalakshmi, K. E. Raghavan and C. S. Unnikrishnan, , J. Phys. B: At. Mol. Opt. Phys. 44, 115307 (2011).
2) Accelerated thermalisation of 39K atoms in a magnetic trap with superimposed optical potential, Dipankar Nath, K. E
Raghavan, G. Rajalakshmi, and C. S. Unnikrishnan, Jl. Phys. B 46 155303 (2013).
3) Quantum-interference-enhanced deep sub-Doppler cooling of 39K atoms in gray molasses, Dipankar Nath, K. E
Raghavan, G. Rajalakshmi, and C. S. Unnikrishnan, Phys. Rev. A 88, 053407 (2013).
K 39 : 35  40  K , K 40 : 40  K ,
K 41, Rb87, Rb85
K39
K40
Latest on cooling with Potassium:
Why Potassium?
1) Both Bosonic (39K and Fermionic (40K) isotopes  Spin-Statistics is a focus issue
2) All optical elements for Rubidium are more or less compatible with K
3) Handling metal vapor with dispensers is relatively easy.
Deepest cooling achieved by then – 30-40 micro-K (Vandna Gokhroo et al, J. Phys. B, 2011)
New cooling technique for Potassium (Dipankar Nath)
(simultaneously with similar ideas for Lithium in a group in Paris)
Where do we want to go from here?
Precision metrology in gravitational and inertial fields with atom interferometers
Cosmic gravitational effects
Equivalence principle
Navigational devices (mentoring)
Gravitational wave detection
|e>
|g>
|g>
|e>
p h/  k
|g>
1) Univeraslity in the gravitational stretching of clocks, waves and quantum states, (GRF Honorable Mention Essay2010),
C.S. Unnikrishnan and G. T. Gillies, Int. Jl. Mod. Phys. D 20, 2853, (2011).
2) Renewed relevance of new tests of the equivalence principle involving intrinsic properties of particles and antiparticles,
C. S. Unnikrishnan and G. T. Gillies, Class. Quantum. Grav. 29, 232001 (2012).
3) Reexamining the roles of gravitational and inertial masses in gravimetry with atom interferometers, C. S. Unnikrishnan
and G. T. Gillies, Phys. Lett. A 377, 60 (2012).
4) Falling right while moving slow: true tests of the weak equivalence principle for antiparticles, (GRF Honorable Mention
Essay2011), C.S. Unnikrishnan and G. T. Gillies, Int. Jl. Mod. Phys. D 21, 1242016 (2012).
5) True dynamical tests of the equivalence principle, C. S. Unnikrishnan, Int. Jl. Mod. Phys (2014).
Beam splitter:
g 2, p 
Mirror:
1
2
 g 2, p
 ei g1, p  
g 2, p  ei g1, p  
Beam combiner:
g 2  g1,  
e
1
2
 g2
 ei g 2  g1,   ei g1, 
Raman transition
2  1  0
g2
k2  k1    mv
g1


g
2
1
Interference
The gravitational energy Eg  mgg
Phase during dt: d  Eg ( x, t )dt /
Accumulated Phase :  g   d   mgg T /
Phase difference  g  mg  1   2  l / v  mg gd T /
  gT 2  108 T 2 rad!
Number of
atoms
g, l, t
A measurement of phase difference of mrad
(106 atoms) over 10 cm (140 ms) free fall is
equivalent to  g / g  109
For light,
 d  2 R  R / c  2 A / c
2
4
 
( d ) 
A

c
For atoms,
100%
Fraction of
atoms in |g1>
0%
4
4
4
 
A 
A 
mA
dB v
hv / mv
h
Rotation angle
Since the mass-energy of an atom (100 GeV for about 100 protons/neutrons)
about 1011 times the energy of a photon, the sensitivity of atom interferometer
to inertial and gravitational effects is 1011 times larger!
Quantum Vacuum
Conflict with cosmology: so we ‘know’ that there is no zero-point energy is vacuum
modes in empty space. All known physical effects usually ascribed to vacuum can be
explained as matter interactions with only the finite zero-point fluctuations of matter
involved. So, can we re-write quantum optics without a physical vacuum mode ?
(Ninad Jetty).
(Poster by Ninad and P V Sudeersanan)
The other interest is the physical context of cavity quantum electrodynamics – high finesse
cavities. We are exploring high-Q evanescent modes in time dependent cavities, to be
realized with liquid drops. Has some relevance to the speculated repulsive Casimir effect in
spherical cavities (Meenakshi Gaira)
Gravity and Fundamental Interactions
“Cosmic Relativity” as a new paradigm for dynamics and relativity:
Velocity dependent gravitational potentials due to all the matter in the
universe determine ALL relativistic phenomena, including time dilation,
length contraction, limit of the speed of propagation etc.
(Advances in Theoretical Physics (World Scientific, 2008))
Cosmic gravity determines the law of motion , and the Principle of
Equivalence is its direct consequence. , Int. Jl. Mod. Phys 30, 1460267
(2014).
Agrees with ALL known experimental results in relativity.
All our fundamental theories of the physical world were completed well before we
acquired ANY significant knowledge about the physical universe, its content and its
long term evolution.
In particular, the theories of relativity and dynamics (including QM) as well as the
theory of gravity were developed assuming an EMPTY universe.
However, the gravitational potentials of the matter in the universe is a billion (109)
times larger than our local potentials, and if these have any say in dynamics, then we
have completely missed that out in our theories. All our experimental tests, in
contrast, are in the unavoidable presence of cosmic gravity.
So, empirical evidence includes all cosmic gravitational effects, whereas fundamental
theories, as constructed, do not – A reconsideration becomes essential.
The necessary paradigm change
 gU  1017 m2 / s2
 gE  108 m2 / s2
300 Million
Light years
(up to Coma)
2
v
1  v2 2
1 c
U
11
12
1
10
2
3
9
8
4
7
F gU » c !
2
U 
6
5
10 Billion
Light years

All Galaxies
G  (4 R2dR) / R  2 G R 2 H
Relativity and the Universe
Experiments:
1) Electrodynamics of moving systems (Repetition of Faraday and Ampere)
2) Chiral motion in matter-filled universe (TIFR, Weizman Inst.)
3) Relative speed of light (TIFR)
4) Inertial ‘pseudo-forces’ in physics (TIFR)
1) ALL experimental results during past 200 years are consistent with Galilean
velocity of light (1830-40 Faraday, Ampere; 1882-1925 Michelson et al., 1913
Sagnac, 2006-2015: Unnikrishnan).
2) Logic and physics dictates that the matter around has large observable
gravitational effects on dynamics. (any claim to the contrary remains unproven!)
3) Direct experiments show that light behave exactly like sound for relative velocity.
4) The equivalent of an Ampere experiment on current-current interaction in gravity
shows easily the action of cosmic matter (relative) current on dynamics
Books in preparation
a) Cosmic Relativity: Relativity and Dynamics in the Real Universe (2016)
b) Gravity’s Time (2017)
Everything we know (experimentally) from Galilean physics
x '  x  Vt , t '  t , (c '  c  v )
 g00'  1 g01'  0 
 g '  0 g '  1
 10

11
ds  dt  {dx  dy  dz }
2
2
2
2
2
ds 2  c 2 dt 2  {dx 2  V 2 dt 2  2vdxdt}
 c 2 (1  v 2 / c 2 )dt 2  2c( v / c )dxdt  dx 2
 '   g00 t '
 (1  v 2 / c 2 )1/2 t '
Time dilation
 g00'  (1  v 2 / c 2 ) g 01'   v / c 
 g '  v / c

'
g

1


10
11
2 L '   '( c  v )   '(c  v )  2 ' c
cL
L '  ct ' 1  v 2 / c 2 
1  v2 / c2  L 1  v2 / c2
c
Length contraction
Other obvious cosmic gravity effects (speculated and even calculated
earlier)
Universe in rotating frame
Currents of mass generate large vector potential
And its ‘curl’ is a strong gravito-magnetic field
Coriolis forces are clearly of cosmic gravitational origin
Sagnac as integral over area of the interferometer loop.
Cosmic Gravity and Spin Physics
SPIN (both classical and quantum) will couple to this because spin and
angular momentum are currents of the charge of gravity – mass currents
So, ALL spin-orbit effects (including second order effects) on neutral
particles are due to gravitational interaction, coupled to the gravitational
mass of the particle – there is no exception.
An Ampere Experiment in Electromagnetism
The flip of the magnetic moment is due to a reversed current-current
interaction or reversed magnetic field, now written as
R. Naaman, D. W. Waldeck, Ann. Rev. Phys. Chem. 2015
r ∼ 0.5 nm,v ∼ 5 ´10 m / s ® W ∼ 10 rad / s
5
15
s × Bg ∼ 1eV > kBT
Gravity-controlled spin valve!
11
12
1
10
2
3
9
8
4
7
11
6
12
5
1
10
2
3
9
8
4
7
6
5
An experiment to measure the one-way speed of waves
You may check that LT is same as GT for start and end points of this experiment
0.9 m
4.0E-18
3.0E-18
2.0E-18
T ( s)
1.0E-18
0.0E+00
-0.1
-0.05
0
0.05
0.1
-1.0E-18
-2.0E-18
-3.0E-18
Velocity (m/s)
The relative one-way velocity of light is Galilean to first order
Light behaves exactly as Sound for one-way relative velocity
Gravitational Waves
Participation as an enabling member: IndIGO Consortium, LIGO-Australia, LIGO-India, LIGO
Scientific Collaboration…
Member of IndIGO Council, LSC Council, Site selection committee, LIGO-India coordinators.
Main events:
Terrestrial detection of GW and discovery of binary black holes merger
LIGO-India cabinet approval
Next steps:
Site finalization (2016 April-May)
Prototype construction and experiments (2016-2019)
Feasibility study of a tunable low frequency resonant interferometer detector
LIGO-India commissioning (2021-2023)
Prototype (optical) interferometer detector at TIFR
Vibration isolation
schematic
Laser table
Sensing &
Control
180 cm
All mirros and beamsplitters
are suspended from 4-stage vib. isolators
Power recycling
Detector
6m
Vacuum
tanks
F-P cavity
3.5 meters
0.8 m
Mirror
60 cm
15 cm dia. mirrors (3 kg), 1 W NPRO laser, 2 stage passive pre-isolation, 10-8 mbar UHV
(Sensing and control, Poster by P G Rodrigues)
Reference Design Parameters
Sub-system
Design
Interferometer
Power recycled, Michelson-FP, 3m
FP:300, PR: 35
UHV volume
10 m3
Pressure
10 -8 mbar
Total Pumping speed
800 l/s IP + 3000 l/s NEG
Laser (NPRO) power
1 W,
Optics + suspension
15 cm mirrors, 3kg, CVI RRCAT
SS wires  Silica
Mode cleaners
Triangular cavity + Optical Fiber
Vibration attenuation
3 vertical stages , < 1 Hz, 109 @100 Hz
4 horizontal stages <1 Hz, >10 10 @ 100 Hz
Feedback controls
Optical and magnetic
PXI/NI + Labview
Displacement sensitivity
<1x10-17 m/√Hz @200 Hz
200-300 mW to interferometer
Physics with the TIFR prototype interferometer
Short range forces and Casimir force
Precision studies of Casimir force and short-range gravity employing prototypes of interferometric gravitational
wave detectors, G. Rajalakshmi and C. S. Unnikrishnan, Class. Quantum Grav. 27, 215007 (2010).
Multi-pronged studies with Gravity and Quantum Electrodynamics as focus themes
Equivalence principle, its Root
Cosmic Gravity as causal interaction for
relativistic effects and laws of dynamics
(Cosmic Relativity)
Quantum vacuum
and its physical effects
Atom-light interactions
Cavity-optics
Gravitational Waves, LIGO-India
Laser cooling physics
2011-2016 publications
Cold atoms physics: 4
Gravity studies: 15
Other: 3
LIGO Collaboration 2013 - : 30
Talks : ~50 (30 invited, 10 contributed, 10 colloquium/seminars)
Matter-wave interferometers
(metrology, gravity, inertia)
Relativity and the Universe
Note that ‘applying’ Lorentz transformation to any known experiment does not test
the first order velocity dependent ‘circular’ term vx in the Lorentz transformation.
c2
vx
 c2 
+x
-x
(0,y)
(0,0)
(x,y)

vx
0
2
c
This term is untestable by any
conceivable experiment and
hence not falsifiable.
(x,0)
Just this in itself is a fundamental discovery