Global network of Detectors

1. Прецизионные измерения гравитационных возмущенийоптическими интерферометрами с большой базойВ.Н.Руденко(ГАИШ МГУ, Москва)«Прецизионная физика и фундаментальные физические константы»ИТФ им.А.Ф.Иоффе, С.Петербург, 6-10 дек.2010 г.

2. Contents1.Introduction2.Setup construction3.Objectives for observation4.Recent results5.Cold damping spring.6.Advanced instrument at SQL

3. Global network of Detectors H1H2 LIGO Coherent Analysis: why? -Sensitivity increase -Source direction determination from time of flight differences -Polarizations measurement -Test of GW Theory and GW Physical properties Astrophysical targets - Far Universe expansion rate Measurement -GW energy density in the Universe -Knowledge of Universe at times close to Planck’s time TAMA 300 Nautilus Auriga Explorer GEO 600 VIRGO L LIGO

4. Hanford 4km+2km Ligo interferometrs

6. 1915 Theory of G.R. 1916 Einstein predicts gravitational waves (g.w.) 1960 Weber operates the first detector 1970 Construction of cryogenic detectors begins 1984 Taylor and Hulse find the first indirect evidence of g.w. (Nobel Prize 1993) 2003 First light in the large interferometer 2005-2009 First meaninful results (upper limits) 2015 Start upgraded machines first

7. Gravitational Waves (GW) Gravitational waves give fundamental informations on the Universe. The four fundamental interactions coupling constants are: StrongE.M. WeakGravitational s=1 e2=1/137 GFM2=10-5GM2=10-39 Some consequences ofGsmallness: 1)In stellar collapses Neutrinos undergo ~103interactions before leaving the collapsing star, GW<<1. 2)After Big-Bang ,electromagnetic waves decouple from hot matter after 13000 years, neutrinos after 1s, GW only after Planck’s Time (10-43s) . 3) It is extremely difficult to detect them.

8. Detection of GW Let’s consider two freely falling particles A and B, their separation ξα=(xA-xB)α satisfies the geodesic deviation equation: Riemann Force ξα Consequently the receiver is a device measuring space-time curvature i.e. the relative acceleration of two freely falling masses or their relative displacement. XA Effect of Riemann Force Effect of 2 Polarizations XB L h+  L hx

9. INTERFEROMETRIC DETECTORS Large L High sensitivity Very Large Bandwidth 10-10000 Hz Mirrors Beam Splitter   Signal L =LA-LB LA LB Laser Displacement sensitivity can reach ~10-19-10-20 m, then, for measuring L/L~10-22 LA and LB should be km long.

10. Astrophysical sources, expected amplitudes GW- luminosity: only relativistic stars are effective radiators GW amplitude estimate for NS frequency:

13. GW DETECTORS SENSITIVITY GEO600 TAMA 300 AURIGA, NAUTILUS, EXPLORER Virgo LIGO

14. Frequency Range: (50 – 1500) Hz • Blind All Sky Searching • Sources: • - compact binary systems evolution • (inspiral, merging, ring down) • - supernova collapse events • - continuous GW radiation (Pulsars) • - stochastic GW background • - Triggered Search ( Astro-gravity associations)

15. GW emitted Bursts • Classical sources: supernovae • Waveform poorly known • Several events/year in the Virgo cluster • Possibly detectable only within our Galaxy • Generally, whatever can cause short ( < 1s ) GW impulses • Include exotic things (strings) or classical things (NS, BH ringdowns)

16. chirp Coalescing Binaries • Source: coalescence of compact binary stars (BNS, BBH, NS/BH)‏ • Waveform accurately modeled in the first and last phase • Allows matched filtering • Less known in the “merger” phase • Interesting physics here, for instance for BNS • Rate very uncertain • A few events/year could be accessible to the LSC-Virgo network

17. Pulsars • Distorted NS, emitting “lines” of GW radiation • Things greatly complicated by the Doppler effect • Contrary to intuition, by the far the most computing intensive search • Thousands of known potential sources in our Galaxy • Most probably below detection threshold • Many more yet unknown NS could generate a detectable signal

18. CMBR Relic neutrinos Relic gravitons Cosmological Stochastic Background • Potential access to very early Universe

19. LIGOScientific Runs (2000 – 2007) S1 – (08-09) 2000 y. ( noise 100 times projected level) S2 , S3 - during 2003 y (bad seismic isolation) S4 - (02-03) 2005 y ( duty cycle 70%, but selected 15,5 days data !) joint operation of 3 interferometers S5 - (06. 2006 - 10.2007) main results

20. Basic searching algorithms Non modeled Bursts outputs of two GW detectors: vectors a , b total energy : E = normalized and integrated at the it is reduced to variables: Burst’s Excess Power: Burst’s Cross Power:

21. S.Klimenko, GWDAW14, January 26, 2010, Rome, LIGO-G1000033-v8 Results of the all-sky search for gravitational waveburst signals are presented for the first joint LIGO (S5) and Virgo VSR1 runs in 2006-2007. The analysis has been performed with three differentsearch algorithms in a wide frequency band between50-6000 Hz. No plausible GW candidates have been identified. As a result, a limit on the rate of burst GW signals(combined with the LIGO results from the first S5 year)has been established: less than 2 events per year at 90% confidence level with sensitivity in the range 6-20 × 10−22 Hz−1/2  This rate limit is increased by more than an order ofmagnitude compared to the previous LIGO runs.

24. What we known about SBGW from BBN bound ? gw=(1/c)dgw/dlog(f) h0 gw , h0=0.73(3) gw =  d log(f) [dgw/dlog(f)] • from the balance of H and Γ at nucleosynthesis, (H2=(8πG/3) ρ) • is a bound on the total energy density,integrated over all frequencies. fmin≈10-10 Hz fixed by the horizon size at BBN • Nν = effective number of neutrino species,parametrizes any extra energy contribution • in the SM, Nν ~ (4.4 – 3.046) (due to residual interaction νwith e± QEDeffects). •So in order of magnitude at time of NS therewere no more GWs than photons • it can be translated into a bound on the integrand gw < 6.9 10-6

27. Results S4 , S5 , [last run S6 (04.09 – 09.10)] Unmodeled bursts : upper limit → < 0.15 day -1 , h rss < 10-20 Hz – ½ Inspiral Bursts : upper limit → Event Rate: R R = (Number of events/ year. galaxy) 1 event per 20-300 years for NS binary for dH ~ 60 Mpc 1 event per 20-2000 years for binary ~ 5 M0 1 event per 3 – 30 years for binary ~ 10 M0 Pulsars : f ~ 150 Hz , h ~ 10-25 , ε < 10-5 Stochastic background: f ~(50 – 100) Hz, Ω < 6.5 10^{-5}

28. Существенныерезультаты LIGO 1. Новый (значимый)верхний предел на ГВ-сигнал от гамма-всплесков. Во время серии S5 имело место событие: GRB 070201 – короткий г-всплеск (< 2 сек), положение источника отождествлено с М31 (~770 кпс) (reg. Integral, Messenger, Swift) fl.~10^{-5}erg/cm^{2}. В окне 180 сек. вокруг tarv искали сопровождающий ГВ-импульс. С вероятностью ~95% ГВ сигнал не обнаружен. Предел на его интенсивность в модели NS, BH – “binary coalescence” оценен как E < 4.4 10^{-4} M0c2 (1M0<m1<3M0 , 3M0<m2<40M0) f~150 Hz (теор. pасчет для ВС NS допускает E ~10^{-2} !) 2.Перекрытие «предела замедления» на ГВ излучение пульсаров PSR BO531+21, PSR JO534-22, Crab Neb. (ν~30 Hz, dν/dt~-3 10^{-10} Hz/s ) Теор. оценка по “spin-down rate” даёт hgw ~ 1.4 10^{-24}. Наблюдения S5, 3 мес.(~200 дн.) на частоте ν ~ 60 Hz дали hgw<3.4 10^{-25} или для степени несферичности: ε < 1.8 10^{-4} 3.Перекрытие предела стохастического ГВ-фона по нуклеоситезу в ранней Вселенной теория нуклеосинтеза дает ограничение на интегральную (по частоте) плотность ГВ фона из предположения, что гравитонов было не больше, чем фотонов; это даёт при равномернойспектральной плотности ГВ фона gw~ 9.7 10^{-6}. Экспериментально за время наблюдения ~200 дней на детекторах H1, L1 получена оценка gw~ 6.9 10^{-6} с достоверностью 95%

29. Cold Spring Damping of Thermal Noise in the LIGO setup New Journal of Physics 11 (2009) 073032, B Abbott1 et.al. (LSC) Observation of quantum effects such as ground statecooling, quantum jumps,optical squeezing,and entanglement thatinvolve macroscopic mechanicalsystems are the subject of intense experimental effort. The first step toward engineering a non-classical state of a mechanical oscillator is to coolit, minimizing the thermal occupation number of the mode. Any mechanical coupling to theenvironment admits thermal noise that randomly drives the system’s motion, as dictated by the fluctuation–dissipation theorem, but ‘cold’ frictionless forces, such as optical or electronicfeedback, can suppress this motion, hence cooling the oscillator.

30. Thermal standard: T0 , Q  , (H0) Quantum standard: LIGO displacement sensitivity: S5 scientific run

31. Quantum behaviour of macroscopic test body (?) V.B.Braginskii. Physics Uspekhi, v.48, 595, 2005 a pendulum in gravity field, mode of acoustical resonator etc. can demonstrate quantum features under the following requirement: instead of usual condition • Dodonov V.V., Manko V.I., Rudenko V.N., Quantum Electronics, v.7 (№10), p.2124, 1980 • «Quantum properties of macroscopic resonator with a high quality factor» • a) classical calculation mean values and a system evolution corresponds to quantum calculation with the accuracy ~ O(1/n) • b) transition probability requires only the quantum calculation; • c) observation of «energy steps» requires unrealistic measurement accuracy (Q ~ 1018 ) Realistic objective is a preparation of macroscopic system (oscillator) in the ground energetic state, i.e. with n ~ 1. «procedure of super cooling»in expectation of «macroscopic quantum effects»

34. LIGO’s Hanford Observatory. The detector shown comprises a Michelson interferometer with a 4 km long Fabry–Perot cavity of finesse 220 placed in eacharm to increase the sensitivity of the detector. Each mirror of the interferometer has massM = 10.8 kg, and is suspended from a vibration-isolated platform on a fine wire to form apendulum with frequency 0.74 Hz, to shield it from external forces To minimize the effects of laser shot noise, the interferometer operates with highpower levels; approximately 400W of laser power of wavelength 1064 nm is incident on thebeam splitter, resulting in over 15kW of laser power circulating in each arm cavity. The presentdetectors are sensitive to changes in relative mirror displacements of about 10−18 m in a 100 Hz band centered around 150 Hz (figure 2). Differential arm cavity motion, which is the degree offreedom excited by a passing gravitational wave, and hence also the most sensitive to mirror displacements. This mode corresponds to the differential motion of the centers of mass ofthe four mirrors, xc = (x1 −x2)−(x3 −x4), and has a reduced mass of Mr = 2.7 kg.

35. GW- интерферометр как «квадрупольный осциллятор, управляемый холоднойэлектронно-оптической жесткостью (пружиной)» координата ц.масс ХC = (Х2 – Х1) – (Х3 – Х4) , приведенная масса Мr ~ 2.7 kg наблюдаемый сигнал ХS = XC – XN (тепловой шум зеркала + шум импульса фотонов) динамика эл.-опт. пружина осциллятор управляется электронно-оптической жесткостью при

38. Результаты измерений на интерферометре Н1 Advanced LIGO (2015) – планирует снижение эффективного шумового уровня в 20 – 30 раз. Это позволит вплотную приблизиться к реализации макроскопического осциллятора с флуктуациями энергии вблизи низшего энергетического состояния, т.е. эффективность искусственного охлаждения достигнет квантового предела. Классические измерительные методы перестанут работать, потребуется практическое развитие методов т.н.«квантовых не возмущающих измерений».

43. GW-experiment: News Fig. 1. Advanced Virgo sensitivity curve compared with Virgo and LIGO design and current bar sensitivity. Violin modes are not displayed for clarity