We present possible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5– requires at least three detectors of sensitivity within a factor of of each other and with a broad frequency bandwidth. When all detectors, including KAGRA and the third LIGO detector in India, reach design sensitivity, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

We present our current best estimate of the plausible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next several years, with the intention of providing information to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals for the third (O3), fourth (O4) and fifth observing (O5) runs, including the planned upgrades of the Advanced LIGO and Advanced Virgo detectors. We study the capability of the network to determine the sky location of the source for gravitational-wave signals from the inspiral of binary systems of compact objects, that is binary neutron star, neutron star–black hole, and binary black hole systems. The ability to localize the sources is given as a sky-area probability, luminosity distance, and comoving volume. The median sky localization area (90% credible region) is expected to be a few hundreds of square degrees for all types of binary systems during O3 with the Advanced LIGO and Virgo (HLV) network. The median sky localization area will improve to a few tens of square degrees during O4 with the Advanced LIGO, Virgo, and KAGRA (HLVK) network. During O3, the median localization volume (90% credible region) is expected to be on the order of $$10^{5}, 10^{6}, 10^{7}\mathrm {\ Mpc}^3$$ 10 5 , 10 6 , 10 7 Mpc 3 for binary neutron star, neutron star–black hole, and binary black hole systems, respectively. The localization volume in O4 is expected to be about a factor two smaller than in O3. We predict a detection count of $$1^{+12}_{-1}$$ 1 - 1 + 12 ($$10^{+52}_{-10}$$ 10 - 10 + 52 ) for binary neutron star mergers, of $$0^{+19}_{-0}$$ 0 - 0 + 19 ($$1^{+91}_{-1}$$ 1 - 1 + 91 ) for neutron star–black hole mergers, and $$17^{+22}_{-11}$$ 17 - 11 + 22 ($$79^{+89}_{-44}$$ 79 - 44 + 89 ) for binary black hole mergers in a one-calendar-year observing run of the HLV network during O3 (HLVK network during O4). We evaluate sensitivity and localization expectations for unmodeled signal searches, including the search for intermediate mass black hole binary mergers.

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Spin is fundamental in physics. Gravitation is universal. Searches for the role of spin in gravitation dated before the firm establishment of the electron spin in 1925. Since mass and spin or helicity in the case of zero mass are the only invariants of the Poincaré group and mass participates in universal gravitation, these searches are natural steps to pursue. Here we review both the theoretical and experimental efforts in searching for the role of spin/polarization in gravitation. We discuss torsion, Poincaré gauge theories, teleparallel theories, metric-affine connection theories and pseudoscalar (axion) theories. We discuss laboratory searches for electron and nucleus spin-couplings ---the weak equivalence principle experiments for polarized-bodies, the finite-range spin-coupling experiments, the spin-spin coupling experiments and the cosmic-spin coupling experiments. The role played by angular momentum and rotation is explicitly discussed. We discuss astrophysical and cosmological searches for photon polarization coupling. Investigation in the implications and interrelations of equivalence principles led to a possible pseudoscalar or vector interaction, and led to the proposal of WEP II (Weak Equivalence Principle II) which include rotation in the universal free-fall motion. Evidences for WEP II are discussed and compiled.Cosmological searches for photon-polarization coupling test the possibility of violation of EEP and the existence of cosmic pseudoscalor/vector interaction and may reveal a potential influence to our presently-observed universe from a larger arena. In relativistic gravity, there is a Lense-Thirring frame-dragging on rotating body with angular momentum. In analog with gyromagnetic ratio in electromagnetism, one can define gyrogravitational ratio. A profound search for the role of spin in gravitation is to measure the gyrogravitational ratio of particles. This could lead us to probe and understand the microscopic origins of gravity. We discuss the strategies to perform such experiments. R. Acad. Sci., Paris 174 593 Cartan É 1923 Sur les variétés à connexion affine et la théorie de la relativitée généralisée I, Ann. Ec. Norm. Sup. 40, 325 Cartan É 1924 Sur les variétés à connexion affine et la théorie de la relativitée généralisée I (suite), Ann. Ec. Norm. Sup. 41 1 Cartan É 1925 Sur les variétés à connexion affine et la théorie de la relativitée généralisée II, Ann. Ec. Norm. Sup. 42 17 Carroll S M, Field G B and Jackiw R 1990 Limits on a Lorentz-and parity-violating modification of electrodynamics Phys. Rev. D 41 1231-1240 Carroll S M and Field G B 1991 Einstein equivalence principle and the polarization of radio galaxies A experiment to search for vacuum dichroism, pseudoscalar-photon interaction and millicharged fermions Mod. Phys. Lett. A 22 2815 [arXiv:hep-ex/0611050v1] Cheng H-C, Luty M A, Mukohyama and Thaler J 2006 Spontaneous Lorentz breaking at high energies J High Energy Phys. 0605 076 Cheng K-S and Ni W-T 1980 Conditions for the local existence of metric in a generic affine manifo...

KAGRA is a newly built gravitational-wave telescope, a laser interferometer comprising arms with a length of 3 km, located in Kamioka, Gifu, Japan. KAGRA was constructed under the ground and it is operated using cryogenic mirrors that help in reducing the seismic and thermal noise. Both technologies are expected to provide directions for the future of gravitational-wave telescopes. In 2019, KAGRA finished all installations with the designed configuration, which we call the baseline KAGRA. In this occasion, we present an overview of the baseline KAGRA from various viewpoints in a series of articles. In this article, we introduce the design configurations of KAGRA with its historical background.

We use a paramagnetic salt TbF 3 with a dc SQUID to search for a possible axionlike s ? r interaction of a rotating copper mass with the salt. We set new limits on the axion coupling constant g s g p ͞hc and the finite-range Leitner -Okubo -Hari Dass coupling constant A. Our limit for range l at 30 mm is 2 orders of magnitude better than previous results. For l . 30 mm, g s g p ͞hc is ͑0.14 6 0.67͒ 3 10 228 , and A is less than 10. The outlook for further improvement is discussed.[S0031-9007(99)08656-1] PACS numbers: 14.80.Mz, 04.80.Cc, 12.20.Fv, 13.10. + q There are a number of groups experimentally searching for spin-dependent (semi-)long-range forces. These works are largely motivated to explore the role of spin in gravitation, and to explore the interaction associated with the exchange of a light or massless pseudoscalar Goldstone boson or similar interactions, e.g., arion interaction or axion interaction. Among the works to search for the spin-dependent (semi-)long-range forces, we can classify them into two categories: those searching for the monopole-dipole interactions [1-9] and those searching for the dipole-dipole interactions [5,[10][11][12][13][14][15][16][17].In connection with P (parity), and T (time reversal) noninvariance, Leitner and Okubo [18], and Hari Dass [19] suggested some time ago the following type of spingravity interaction, H int f͑r͒r ? s , (1) wherer is the unit vector from the massive body to the particle with spinhs . They assumed f͑r͒ 2AUm with U the gravitational potential of the massive body.Fujii [20] proposed finite-range mass-mass interactions. More recently, Fischbach et al. proposed a fifth force which violates the equivalence principle with finite-range monopole-monopole interactions and stimulated many experimental efforts [21].In our previous investigation [6], we used torsion balance with two cylindrical copper test masses and two cylindrical polarized "attracting" Dy 6 Fe 23 masses to search for finite-range mass-spin interactions with the Hamiltonian of the form (1). Our preliminary result showed that for the range of 3-5 cm, the upper limit of this interaction for our test mass and the Dy 6 Fe 23 polarized mass were below 1% of their gravitational interaction. We considered, in particular, the case of f͑r͒ 2Au 2mr mU with U the gravitational potential of the unpolarized body; that is, the finite-range mass-spin interaction is of the following form:H int 2Ae 2mr mUr ? s .(2) Ritter et al. [8], in a recent experiment, used spinpolarized Dy 6 Fe 23 masses acting on unpolarized copper masses in a dynamic-mode torsion pendulum and searched for the interaction of the axion [22][23][24] form,(3) In (3), l is the range of the interaction, g s and g p are the coupling constants of vertices at the polarized and unpolarized particles, and m is the mass of the polarized particle. Constraints on the coupling g s g p ͞hc with respect to the range are plotted in a logarithmic plot (Fig. 1). For l , 0.3 m, Refs. [6] and [8] give more stringent constraints than Refs. [5] and [7], a...

The Zhaoshan long-baseline Atom Interferometer Gravitation Antenna (ZAIGA) is a new type of underground laser-linked interferometer facility, and is currently under construction. It is in the 200-meter-on-average underground of a mountain named Zhaoshan which is about 80 km southeast to Wuhan. ZAIGA will be equipped with long-baseline atom interferometers, high-precision atom clocks, and large-scale gyros. ZAIGA facility will take an equilateral triangle configuration with two 1-km-apart atom interferometers in each arm, a 300-meter vertical tunnel with atom fountain and atom clocks mounted, and a tracking-and-ranging 1-km-arm-length prototype with lattice optical clocks linked by locked lasers. The ZAIGA facility will be used for experimental research on gravitation and related problems including gravitational wave detection, high-precision test of the equivalence principle of micro-particles, clock based gravitational red-shift measurement, rotation measurement and gravito-magnetic effect. arXiv:1903.09288v4 [physics.atom-ph]

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 pseudoscalarphoton 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. A 3.5-m high-finesse (around 30,000) Fabry-Perot prototype detector extendable to 7-m has been built and tested. We use X-pendulums and automatic control schemes developed by the gravitational-wave detection community for mirror suspension and cavity control. To polarize the vacuum, we use a 2.3-T dipole permanent magnet, with 27-mm-diameter clear borehole and 0.6-m field length,. In the experiment, the magnet is rotated at 5-10 rev/s to generate time-dependent polarization signal with twice the rotation frequency. Our ellipsometer/polarization-rotationdetection-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. We made an independent calibration of our apparatus by performing a measurement of gaseous Cotton-Mouton effect of nitrogen. At present, the sensitivity (and noise floor) for dichroism detection is about 1 × 10 -6 rad Hz -1/2 at 10-20 Hz. With this sensitivity, it would be possible to check the polarization rotation effect obtained by PVLAS. Our first results give (-0.2 ± 2.8) × 10 -13 rad/pass, at 2.3 T with 18,700 passes through a 0.6 m long magnet for vacuum dichroism measurement. We present a brief discussion of our experimental limit on pseudo-scalar-photon interaction and millicharged fermions.