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

2 Contents 1.Introduction 2.Setup construction 3.Objectives for observation 4.Recent results 5.Cold damping spring. 6.Advanced instrument at SQL

3 Global network of Detectors VIRGO L LIGO GEO 600 H1 H2 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 Plancks time TAMA 300 Nautilus Auriga Explorer

4 Ligo interferometrs Hanford 4km+2km

6 1915 Theory of G.R 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 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: Strong E.M. Weak Gravitational s =1 e 2 =1/137 G F M 2 =10 -5 GM 2 = Some consequences of G smallness: 1)In stellar collapses Neutrinos undergo ~10 3 interactions before leaving the collapsing star, GW

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

9 INTERFEROMETRIC DETECTORS Large L High sensitivity Very Large Bandwidth Hz Laser LALA LBLB Mirrors Beam Splitter Signal L =L A -L B Displacement sensitivity can reach ~ m, then, for measuring L/L~ L A and L B should be km long.

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

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

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 15 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) GW emitted

16 16 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 chirp

17 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 18 Cosmological Stochastic Background Potential access to very early Universe Relic gravitons Relic neutrinos CMBR

19 LIGO Scientific 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 - ( ) main results

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

21 Results of the all-sky search for gravitational wave burst signals are presented for the first joint LIGO (S5) and Virgo VSR1 runs in The analysis has been performed with three different search algorithms in a wide frequency band between 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 × Hz 1/2 This rate limit is increased by more than an order of magnitude compared to the previous LIGO runs. S.Klimenko, GWDAW14, January 26, 2010, Rome, LIGO-G v8

24 N ν = effective number of neutrino species, parametrizes any extra energy contribution in the SM, N ν ~ (4.4 – 3.046) (due to residual interaction ν with e± QED effects). So in order of magnitude at time of NS there were no more GWs than photons it can be translated into a bound on the integrand What we known about SBGW from BBN bound ? gw =(1/ c )d gw /dlog(f) h 0 gw, h 0 =0.73(3) gw = d log(f) [d gw /dlog(f)] from the balance of H and Γ at nucleosynthesis, (H 2 =(8 π G/3) ρ) is a bound on the total energy density, integrated over all frequencies. f min Hz fixed by the horizon size at BBN gw <

27 Results S4, S5, [ last run S6 (04.09 – 09.10)] Unmodeled bursts : upper limit < 0.15 day -1, h rss < Hz – ½ Inspiral Bursts : upper limit Event Rate: R 1 event per years for NS binary for d H ~ 60 Mpc 1 event per years for binary ~ 5 M 0 1 event per 3 – 30 years for binary ~ 10 M 0 Pulsars : f ~ 150 Hz, h ~ , ε < R = (Number of events/ year. galaxy) Stochastic background: f ~(50 – 100) Hz, Ω < ^{-5}

28 Существенные результаты LIGO 1. Новый (значимый) верхний предел на ГВ-сигнал от гамма-всплесков. Во время серии S5 имело место событие: GRB – 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 t arv 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} M 0 c 2 (1M 0

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

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

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 ~ ) 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 LIGOs Hanford Observatory. The detector shown comprises a Michelson interferometer with a 4 km long Fabry–Perot cavity of finesse 220 placed in each arm to increase the sensitivity of the detector. Each mirror of the interferometer has mass M = 10.8 kg, and is suspended from a vibration- isolated platform on a fine wire to form a pendulum with frequency 0.74 Hz, to shield it from external forces To minimize the effects of laser shot noise, the interferometer operates with high power levels; approximately 400W of laser power of wavelength 1064 nm is incident on the beam splitter, resulting in over 15kW of laser power circulating in each arm cavity. The present detectors are sensitive to changes in relative mirror displacements of about 1018 m in a 100 Hz band centered around 150 Hz (figure 2). Differential arm cavity motion, which is the degree of freedom 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 of the four mirrors, xc = (x1 x2)(x3 x4), and has a reduced mass of Mr = 2.7 kg.

35 GW- интерферометр как «квадрупольный осциллятор, управляемый холодной электронно-оптической жесткостью (пружиной)» координата ц.масс Х C = (Х2 – Х1) – (Х3 – Х4), приведенная масса М r ~ 2.7 kg наблюдаемый сигнал Х S = X C – X N (тепловой шум зеркала + шум импульса фотонов) динамика эл.-опт. пружина при осциллятор управляется электронно-оптической жесткостью

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

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