Wei-Tou Ni

Q & A EXPERIMENT TO SEARCH FOR VACUUM DICHROISM, PSEUDOSCALAR-PHOTON INTERACTION AND MILLICHARGED FERMIONS

A number of experiments are underway to detect vacuum birefringence and dichroism — PVLAS, Q & A, and BMV. Recently, PVLAS experiment has observed optical rotation in vacuum by a magnetic field (vacuum dichroism). Theoretical interpretations of this result include a possible pseudoscalar–photon interaction and the existence of millicharged fermions. Here, we report the progress and first results of Q & A (QED [quantum electrodynamics] and Axion) experiment proposed and started in 1994. We use a 3.5-m high-finesse (around 30,000) Fabry–Perot prototype detector extendable to 7-m with the cavity mirrors suspended using X-pendulum-double pendulums. To polarize the vacuum, we use a 2.3-T dipole permanent magnet rotated at 5–10 rev/s, with 27-mm-diameter clear borehole and 0.6-m field length. Our ellipsometer/polarization-rotation-detection-system is formed by a pair of Glan–Taylor type polarizing prisms with extinction ratio lower than 10-8 together with a polarization modulating Faraday Cell with/without a quarter wave plate. Our first results give (-0.2 ± 2.8) × 10-13 rad/pass with 18,700 passes through a 2.3 T 0.6 m long magnet for vacuum dichroism measurement. We present our experimental limit on pseudo-scalar-photon interaction and millicharged fermions.

Dark energy, co-evolution of massive black holes with galaxies, and ASTROD-GW

Allan Adams (MIT), Scott F. Anderson (Univ. of Washington), Andy Becker (U. Washington), Geoffrey C. Bower (UC Berkeley), Niel Brandt (Penn State), Bethany Cobb (UC Berkeley), Kem Cook (Lawrence Livermore National Laboratory/IGPP), Alessandra Corsi (INAF-Roma), Stefano Covino (INAF-Osservatorio Astronomico di Brera), Derek Fox (Penn State University), Andrew Fruchter (STSCI), Chris Fryer (Los Alamos National Laboratory), Jonathan Grindlay (Harvard/CfA), Dieter Hartmann (Clemson), Zoltan Haiman (Columbia), Bence Kocsis (IAS), Lynne Jones (U. Washington), Abraham Loeb (Harvard), Szabolcs Marka (Columbia University), Brian Metzger (UC Berkeley), Ehud Nakar (Tel Aviv University), Samaya Nissanke (CITA, Toronto), Daniel A. Perley (UC Berkeley), Tsvi Piran (The Hebrew University), Dovi Poznanski (UC Berkeley), Tom Prince (Caltech), Jeremy Schnittman (JHU), Alicia Soderberg (Harvard/CfA), Michael Strauss (Princeton), Peter S. Shawhan (University of Maryland), David H. Shoemaker (LIGO-MIT), Jonathan Sievers (CITA, Toronto), Christopher Stubbs (Harvard/CfA), Gianpiero Tagliaferri (INAF-Osservatorio Astronomico di Brera), Pietro Ubertini (INAF-Roma), and Przemyslaw Wozniak (Los Alamos National Laboratory)

ASTROD and ASTROD I - Overview and progress

In this paper, we present an overview of ASTROD (Astrodynamical Space Test of Relativity using Optical Devices) and ASTROD I mission concepts and studies. The missions employ deep-space laser ranging using drag-free spacecraft to map the gravitational field in the solar-system. The solar-system gravitational field is determined by three factors: the dynamic distribution of matter in the solar system; the dynamic distribution of matter outside the solar system (galactic, cosmological, etc.) and gravitational waves propagating through the solar system. Different relativistic theories of gravity make different predictions of the solar-system gravitational field. Hence, precise measurements of the solar-system gravitational field test all these. The tests and observations include: (i) a precise determination of the relativistic parameters beta and gamma with 3-5 orders of magnitude improvement over previous measurements; (ii) a 1-2 order of magnitude improvement in the measurement of G-dot; (iii) a precise determination of any anomalous, constant acceleration Aa directed towards the Sun; (iv) a measurement of solar angular momentum via the Lense-Thirring effect; (v) the detection of solar g-mode oscillations via their changing gravity field, thus, providing a new eye to see inside the Sun; (vi) precise determination of the planetary orbit elements and masses; (viii) better determination of the orbits and masses of major asteroids; (ix) detection and observation of gravitational waves from massive black holes and galactic binary stars in the frequency range 0.05 mHz to 5 mHz; and (x) exploring background gravitational-waves.

Astrodynamical Space Test of Relativity using Optical Devices

Abstract We present the ASTROD (Astrodynamical Space Test of Relativity using Optical Devices) mission concept of using drag-free spacecraft in solar orbits together with a constellation of Earth orbiting satellites (including spacecraft near the Lagrange points) which provides high-precision measurement of relativistic effects, better determination of the orbits of major asteroids, improvement in the measurement of G fot , measurement of solar angular momentum via Lense-Thirring effect and the detection of low-frequency gravitational waves in a single mission.

Gravitational waves, dark energy and inflation

In this paper we first present a complete classification of gravitational waves according to their frequencies: (i) Ultra high frequency band (above 1 THz); (ii) Very high frequency band (100 kHz–1 THz); (iii) High frequency band (10 Hz–100 kHz); (iv) Middle frequency band (0.1 Hz–10 Hz); (v) Low frequency band (100 nHz–0.1 Hz); (vi) Very low frequency band (300 pHz–100 nHz); (vii) Ultra low frequency band (10 fHz–300 pHz); (viii) Hubble (extremely low) frequency band (1 aHz–10 fHz); (ix) Infra-Hubble frequency band (below 1 aHz). After briefly discussing the method of detection for different frequency bands, we review the concept and status of space gravitational-wave missions — LISA, ASTROD, ASTROD-GW, Super-ASTROD, DECIGO and Big Bang Observer. We then address to the determination of dark energy equation, and probing the inflationary physics using space gravitational wave detectors.

Non-minimal coupling of photons and axions

We establish a new self-consistent system of equations accounting for a non-minimal interaction of gravitational, electromagnetic and axion fields. The procedure is based on a non-minimal extension of the standard Einstein-Maxwell-axion action. The general properties of a ten-parameter family of non-minimal linear models are discussed. We apply this theory to the models with pp-wave symmetry and consider propagation of electromagnetic waves non-minimally coupled to the gravitational and axion fields. We focus on exact solutions of electrodynamic equations, which describe quasi-minimal and non-minimal optical activity induced by the axion field. We also discuss empirical constraints on coupling parameters from astrophysical birefringence and polarization rotation observations.

ASTROD, ASTROD I and their gravitational-wave sensitivities

Astrodynamical space test of relativity using optical devices (ASTROD) is a mission concept with three spacecraft-one near the L1/L2 point, one with an inner solar orbit and one with an outer solar orbit, ranging coherently with one another using lasers to test relativistic gravity, measure the solar system and detect gravitational waves. ASTROD I with one spacecraft ranging optically with ground stations is the first step towards the ASTROD mission. In this paper, we present the ASTROD I payload and accelerometer requirements, discuss the gravitational-wave sensitivities for ASTROD and ASTROD 1, and compare them with LISA and radio-wave Doppler tracking of spacecraft.

Spacetime structure and asymmetric metric from the premetric formulation of electromagnetism

Abstract We address the issue of spacetime structure determined empirically from the premetric formulation of electromagnetism and explore the role of skewons in the construction of spacetime metric. Type II skewon part is not constrained in the first order. In the second order it induces birefringence and is constrained to ∼ 10 − 19 . However, an additional nonmetric induced second-order contribution to the core-metric principal part makes it nonbirefringent. This second-order contribution is just the extra piece to the core-metric principal constitutive tensor induced by the antisymmetric part of the asymmetric metric which is nonbirefringent. The antisymmetric metric induced constitutive tensor has a pseudoscalar part. The variation of this part is constrained by observation on cosmic polarization rotation to

PICO-WATT AND FEMTO-WATT WEAK-LIGHT PHASE LOCKING

Advances in laser physics and its applications have triggered the proposition and development of Laser Astrodynamics. In carrying out research projects on Laser Space Programs, it is necessary to process the laser signal sent back from remote spacecraft. After traveling an extremely long distance, the power of this signal is greatly reduced. Weak-light phase-locking is the key technique used for signal amplification in these space projects. After the returning laser beam is collected by telescope, it is used to phase-lock a local laser oscillator. The local laser then carries the phase information of the remote spacecraft laser. we used diode-pumped non-planar ring cavity Nd:YAG lasers to serve as the remote weak-light laser and the local strong-light laser. We then built an optical phase-locked loop to phase-lock them. The weak-light laser signal was simulated using ND (neutral density)-filters to decrease the light intensity. In the phase detection, we used balanced detection to eliminate laser intensity noise and improve the S/N ratio. Combining this with an appropriate loop filter, we were able to control the laser frequency and improve the phase-locking ability. We phase-locked a 2 nW weak-light beam and a 2 mW strong-light beam with a 57 mrads(rms)phase error. The locking duration was very long. Locking of a 200 pW and a 2007thinsp;μW light beam, with phase error of 200 mrad (rms) and duration of over 2 hours was achieved. The phase error for locking a 200 μW to a 20pW light beam was 160 mrad (rms). The locking duration was also longer than 2 hours. the last locking performed was carried out with a 2 pW and a 200 μW light beam. The phase error and the locking duration were 290 mrad(rms) and 1.5 min respectively.

Acceleration disturbances and requirements for ASTROD I

ASTRODynamical Space Test of Relativity using Optical Devices I (ASTROD I) mainly aims at testing relativistic gravity and measuring the solar-system parameters with high precision, by carrying out laser ranging between a spacecraft in a solar orbit and ground stations. In order to achieve these goals, the magnitude of the total acceleration disturbance of the proof mass has to be less than 10(-13) m s(-2) Hz(-1/2) at 0.1 m Hz. In this paper, we give a preliminary overview of the sources and magnitude of acceleration disturbances that could arise in the ASTROD I proof mass. Based on the estimates of the acceleration disturbances and by assuming a simple control-loop model, we infer requirements for ASTROD I. Our estimates show that most of the requirements for ASTROD I can be relaxed in comparison with Laser Interferometer Space Antenna (LISA).