Wei-Tou Ni Department of Physics National Tsing Hua University [1] W.-T. Ni, (MPLA 25 [2010] pp ; arXiv: v1 [astro-ph.CO]). [2] S. di Serego Alighieri, W.-T. Ni and W.-P. Pan, Astrophys. J. 792, 35 (2014). [3] Mei, Ni, Pan, Xu, di Serego Alighieri, Ap J accepted; arXiv: arXiv:1412. Gravitational Waves: Spectrum Classification BeijingGWs: Spectrum Classification W.-T. Ni1

Complete GW Classification (MPLA 25 [2010] pp ; arXiv: v1 [astro-ph.CO]) Beijing GWs: Spectrum Classification W.-T. Ni 2 Space Detection: LF (100 nHz- 100 mHz) & MF (100 mHz- 10 Hz)

Complete GW Classification (I) Ultra high frequency band (above 1 THz): Detection methods include Terahertz resonators, optical resonators, and ingenious methods to be invented. Very high frequency band (100 kHz – 1 THz): Microwave resonator/wave guide detectors, optical interferometers and Gaussian beam detectors are sensitive to this band. High frequency band (10 Hz – 100 kHz): Low-temperature resonators and laser-interferometric ground detectors are most sensitive to this band. Middle frequency band (0.1 Hz – 10 Hz): Space interferometric detectors of short armlength ( km). Low frequency band (100 nHz – 0.1 Hz): Laser-interferometer space detectors are most sensitive to this band Beijing GWs: Spectrum Classification W.-T. Ni 3

Complete GW Classification (II) Very low frequency band (300 pHz – 100 nHz): Pulsar timing observations are most sensitive to this band. Ultra low frequency band (10 fHz – 300 pHz): Astrometry of quasar proper motions are most sensitive to this band. Extremely low (Hubble) frequency band （ 1 aHz – 10 fHz): Cosmic microwave background experiments are most sensitive to this band. Beyond Hubble frequency band (below 1 aHz): Inflationary cosmological models give strengths of GWs in this band. They may be verified indirectly through the verifications of inflationary cosmological models Beijing GWs: Spectrum Classification W.-T. Ni 4

Improved Upper Limits on the Stochastic Gravitational-Wave Background from LIGO and Virgo Data arXiv Beijing GWs: Spectrum Classification W.-T. Ni 5

Beijing 6 Primordial Gravitational Waves [ strain sensitivity  (ω^2) energy sensitivity] GWs: Spectrum Classification W.-T. Ni

CMB observations 7 orders or more improvement in amplitude, 15 orders improvement in power since Gamow – hot big bang theory; Alpher & Hermann – about 5 K CMB Dicke -- oscillating (recycling) universe: entropy  CMB 1965 Penzias-Wilson excess antenna temperature at 4.08 GHz 3.5±1 K 2.5  4.5 (CMB temperature measurement ) Precision to 10 -(3-4)  dipolar (earth) velocity measurement to 10 -(5-6) 1992 COBE anisotropy meas.  acoustic osc Polarization measurement (DASI) 2013 Lensing B-mode polarization (SPTpol) 2014 POLARBEAR, BICEP2 and PLANCK (lensing & dust B- mode) Beijing GWs: Spectrum Classification W.-T. Ni 7

Example sensitivity goals at 2008: Litebird (also CMBpol and B-POL) Beijing GWs: Spectrum Classification W.-T. Ni 8

Constraints on Tensor-to-Scalar Ratio r (  n t /n s ) before ExperimentConstraint Goal/Perspective (precision) WMAP 9< 0.38 WMAP 7 + ACT< 0.28 WMAP 7 + SPT< 0.18 PLANCK + WMAP Polarization < 0.11 (2σ) PLANCK0.0? QUIET (1 st session) – 0.87 (43 GHz)0.1 (43 GHz) QUIET (2 nd session)< 2.7 (2σ) (95 GHz)0.01 (95 GHz) POLARBEAR0.007 B-pol, CMB-pol, Litebird Beijing GWs: Spectrum Classification W.-T. Ni 9

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BICEP Beijing GWs: Spectrum Classification W.-T. Ni 11 The BICEP-2 team has a lot to be proud of. They made a wonderful instrument, and collected great data. N. Czakon

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Three processes can produce CMB B-mode polarization observed (i) gravitational lensing from E-mode polarization (Zaldarriaga & Seljak 1997), (ii) local quadrupole anisotropies in the CMB within the last scattering region by large scale GWs (Polnarev 1985) (iii) cosmic polarization rotation (CPR) due to pseudoscalar-photon interaction (Ni 1973; for a review, see Ni 2010). (The CPR has also been called Cosmological Birefringence) Beijing GWs: Spectrum Classification W.-T. Ni 15

consistent with no CPR detection The constraint on CPR fluctuation is about 1. 5 ◦ Beijing GWs: Spectrum Classification W.-T. Ni 16 NEW CONSTRAINTS ON COSMIC POLAR- IZATION ROTATION FROM DETECTIONS OF B- MODE POLARIZATION IN CMB Alighieri, Ni and Pan

Fitting with dust, GWs and Lensing plus CPR Beijing GWs: Spectrum Classification W.-T. Ni 17

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Discussion & Outlook GW detection Planck has releases its polarization data on the dust. Due to Planck’s frequency coverage, we understand now that the dust foreground agrees with the BICEP2 B-mode observation. The GW interpretation needs to subtract this. 100 GHz Keck Array data will be available soon Three frequency BICEP3/Keck Array data (coming 2015?), should be able to characterize foregrounds.BICEP/Keck has 2 more years If r is small, it may take 5 years or more for next generation CMB experiments to come out to detect primordial GWs. PTAs: any time around 2020; more data from binary orbit decays Space: 20 years later, 2034 launch + 1 yr orbit transfer + Earth-based interferometer: Beijing GWs: Spectrum Classification W.-T. Ni 19

Beijing GWs: Spectrum Classification W.-T. Ni 20 Thank You ！