In Euclidean quantum gravity, Euclidean wormholes are allowed, which explains the creation of paired twin universes. Each universe is then in a mixed state, and the mutual entanglement shall leave signatures in the cosmic microwave background (CMB) power spectrum. Invoking the Klebanov-Susskind-Banks wormhole as a toy model for tractability, we show that entanglement selects a novel, unique...
I will review the highlights and lessons learned from gravitational-wave (GW) observations with the LIGO-Virgo-KAGRA detectors. I will then discuss the opportunities and challenges for GW astrophysics with next generation detectors. This talk will focus on compact binaries consisting of black holes and neutron stars and on observations with ground-based gravitational-wave detectors.
The classical instability of the Reissner-Nordström black hole's inner Cauchy horizon leads to mass inflation. To address this, we construct a canonical quantization of the black hole interior using the Wheeler-DeWitt equation within the Einstein-Maxwell framework. We find that horizon boundary conditions dictate distinct quantum evolution scenarios: monotonic decay, quantum bounce, or...
Building on the conformal construction proposed by Ashtekar et al., we implement a conformal-mapping method (CMM) to compute geometrically defined black-hole horizon multipoles without assuming axisymmetry. Unlike approximate-symmetry-based methods, which can suffer from abrupt frame changes when the preferred axis becomes unstable, the CMM provides smooth multipole evolution in a fixed...
In this talk I will discuss the displacement memory effect of gravitational wave firstly. Then the local Carroll symmetry of gravitational waves formulated in Baldwin-Jeffery-Rosen coordinates is extended to a globally well-defined symmetry via a coordinate transformation to Brinkmann coordinates. Two independent global solutions to the Sturm-Liouville equation are derived to characterize the...
A tensor-type cosmological perturbation, defined as a transverse and traceless spatial metric fluctuation, is interpreted as gravitational waves. It decouples from scalar perturbations at linear order but is sourced by them at second order. These induced tensor modes are widely studied, yet all previous work adopts the zero-shear gauge without justification. We show that the induced tensor...
We revisit instanton-induced compactification in eight-dimensional Einstein–Yang–Mills theory, where a self-dual SU(2) instanton on the internal $S^4$ triggers four-dimensional expansion — extending arXiv:1810.12291 (Kim et al) (2018). We show that the minimal model fails to support successful inflation- it has neither a stabilized vacuum nor a slow-roll plateau. Introducing an...
Among the various sources, the hot plasma in the early universe is quite interesting since it produces the Cosmic Gravitational Cosmic Microwave (CGMB) signal. Lambda CDM gives quite small value to be detected from the present technology based detectors. We show that the higher curvature term can enhance the signal. To be specific, the Einstein-dilaton-Gauss-Bonnet (EdGB) Gravity, one of the...
In this talk, we consider the Ellis-Bronnikov wormhole to see the gravitational waves generation due to the particle motion around the wormhole. The orbiting-around and the falling-into cases are also discussed. The ringdown phase of the wormhole is also studied from the perturbation equation driven by the particle motion.
We investigate scalarized Einstein-Euler-Heisenberg (EEH) black holes
in the EEH-scalar theory. Firstly, we carry out negative potential-induced scalarization by considering the minimally scalar coupling. Spontaneous scalarization of EEH black hole is also performed by introducing an exponential scalar coupling to Maxwell term and nonlinear electrodynamics (NED) term.
We propose an inflationary mechanism for primordial magnetic-field generation based on the reduced open-system dynamics of photon modes in de~Sitter space. The observable photon sector inside a causal patch is treated as a Gaussian subsystem, while the de~Sitter horizon acts as an effective environment at the Gibbons--Hawking temperature. Since the reduced state relaxes only with a finite...
Recent baryon acoustic oscillation and supernova data have stimulated renewed interest in possible departures from the cosmological constant, often interpreted within (w)CDM or (w_0w_a)CDM parametrizations. In particular, redshift-dependent trends in the dark-energy equation of state have been discussed as potential evidence for dynamical dark energy. In this talk, I argue that such an...
We investigate the impact of repulsive self-interaction in ultralight dark matter (ULDM)on dynamical friction in circular orbits in ULDM halos and its implications for the Fornax dwarfspheroidal (dSph) galaxy's globular clusters. Using the Gross-Pitaevskii-Poisson equations, wederive the dynamical friction force considering soliton density profiles for both non-interactingand strongly...
I review my personal contribution to the dark matter as the Bose liquid and the holographic mean field theory of non-fermi liquid.
Finally I will describe how disorders can introduce the non-locality out of local quantum field theory, which is essential for the recent development of
the strange metal.
I will introduce Double Field Theory as the gravitational framework of string theory, describing the massless sector of closed strings. It is built on a novel differential geometry that goes beyond conventional Riemannian geometry and provides a testable, robust alternative to General Relativity. I will then discuss its relevance to late-time cosmological observations, with particular emphasis...
We present an exact four-parameter rotating vacuum solution of the pure NS--NS sector, or equivalently of Double Field Theory. The solution is generated by applying a compact (\mathrm{SO}(2)) (S)-duality transformation to a rotating Einstein--scalar seed and is specified by ({m,j,q,\zeta}). It gives analytic expressions for the metric, Kalb--Ramond field, and dilaton, with independent...
Applying a rule-based holographic method, we investigate the reconstruction of dual gravity theories from the quantum field theory (QFT) data, specifically, entanglement entropy. We first derive a three-dimensional black hole geometry from the entanglement entropy of a two-dimensional thermal system. Using the reconstructed solution, we extract various thermodynamic quantities with small...
I will revisit Horava stars that have been first studied in 2010 since there has been some important progress recently.
We formulate a continuous operator-algebraic recovery path for black-hole information based on modular (L^p)-interpolation. The starting point is the canonical shift of algebraic teleportation, which relocates hidden information from one relative commutant to another. In local quantum field theory, this finite-step picture cannot be implemented through ordinary tensor-factor decompositions...
We discuss the role of ultralight dark matter (ULDM) in the formation and merger of supermassive black holes. ULDM can trigger direct-collapse SMBH seeds in the early Universe, potentially explaining the recently observed Little Red Dots, and resolve the final parsec problem through wave dynamical friction, leading to efficient SMBH mergers and potentially observable gravitational-wave signals.
We explore O(2N) scalar theory with fractional Laplacian in d-dimension, √–∇² and its Hamiltonian dynamics which is described by a Schrödinger type equation. In classical limit, this reduces to Hamilton-Jacobi equation, which is widely used to describe holographic renormalization group of multi-trace deformation in dual field theory. This equation is a kind of current conservation equation,...
The precise determination of the Newtonian gravitational constant, G, remains one of the most challenging problems in experimental physics, with existing measurements showing significant discrepancies despite continual improvements in accuracy. This work aims to develop a high-precision torsion balance apparatus designed to measure G with a target relative uncertainty of approximately 2 ppm....
To improve the analytical description of the gravitational-wave ringdown phase, this work investigates black hole spectroscopy via the pseudo-spectral method, which solves eigenvalue problems to compute the full frequency spectrum of black holes. Although highly promising, the complete spectrum remains elusive; while quasinormal modes (QNMs) are well understood, the physical nature of the...
We establish, for the first time, an exact correspondence between Einstein–scalar–Maxwell theory and gauged Skyrme–Maxwell–Einstein models in (3+1) dimensions. By constructing the simplest consistent ansatz within the gauged Skyrme–Maxwell framework, we reveal a remarkable equivalence in a sector that admits nonvanishing, highly magnetized baryonic charge. This correspondence has a...
