Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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 ei g 2 g1, ei g1, Raman transition 2 1 0 g2 k2 k1 mv g1 g 2 1 Interference The gravitational energy Eg mgg Phase during dt: d Eg ( x, t )dt / Accumulated Phase : g d mgg 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 109 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