243 citations · 3k across the 96 of their papers we have counts for
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Pulsar Timing Array Signature from Oscillating Metric Perturbations due to Ultra-light Axion
Jai-chan Hwang, Donghui Jeong, Hyerim Noh +1
A coherently oscillating ultra-light axion can behave as dark matter. In particular, its coherently oscillating pressure perturbations can source an oscillating scalar metric pertu…
CMASS galaxy sample and the ontological status of the cosmological principle
Yigon Kim, Chan-Gyung Park, Hyerim Noh +1
The cosmological principle (CP), assuming spatially homogeneous and isotropic background geometry in the cosmological scale, is a fundamental assumption in modern cosmology. Recent…
Oscillating gravitational potential due to ultralight axion: linear theory
Jai-chan Hwang, Hyerim Noh
We derive oscillating gravitational potential caused by an ultralight axion as the cosmic dark matter, assuming the Compton wavelength smaller than the horizon scale. A new oscilla…
Axion as a fuzzy-dark-matter candidate: Proofs in different gauges
Jai-chan Hwang, Hyerim Noh
Axion as a coherently oscillating massive scalar field is known to behave as a zero-pressure irrotational fluid with characteristic quantum stress on a small scale. In relativistic…
Gauge-Invariant Tensor Perturbations Induced from Baryon-CDM Relative Velocity and the B-mode Polarization of the CMB
James Gurian, Donghui Jeong, Jai-chan Hwang +1
At second-order, scalar perturbations can source traceless and transverse perturbations to the metric, called induced gravitational waves (IGW). The apparent gauge-dependence of th…
Special Relativistic Magnetohydrodynamics with Gravitation
Hyerim Noh, Jai-chan Hwang, Martin Bucher
We present a fully nonlinear and exact perturbation formulation of Einstein's gravity with a general fluid and the ideal magnetohydrodynamics (MHD) without imposing the slicing (te…
Gauge dependence of gravitational waves generated from scalar perturbations
Jai-chan Hwang, Donghui Jeong, Hyerim Noh
A tensor-type cosmological perturbation, defined as a transverse and traceless spatial fluctuation, is often interpreted as the gravitational waves. While decoupled from the scalar…
The cosmological principle is not in the sky
Chan-Gyung Park, Hwasu Hyun, Hyerim Noh +1
The homogeneity of matter distribution at large scales, known as the cosmological principle, is a central assumption in the standard cosmological model. The case is testable though…
Cosmological nonlinear density and velocity power spectra including nonlinear vector and tensor modes
Jai-chan Hwang, Donghui Jeong, Hyerim Noh
We present the leading order non-linear density and velocity power spectra in the complete form; previous studies have omitted the vector- and tensor-type perturbations simultaneou…
Non-linear power spectra in the synchronous gauge
Jai-chan Hwang, Hyerim Noh, Donghui Jeong +2
We study the non-linear corrections to the matter and velocity power spectra in the synchronous gauge (SG). We consider the perturbations up to third order in a zero-pressure fluid…
Observational effects of the early episodically dominating dark energy
Chan-Gyung Park, Jae-heon Lee, Jai-chan Hwang +1
We investigate observational consequences of the early episodically dominating dark energy on the evolution of cosmological structures. For this aim, we introduce the minimally cou…
Newtonian Hydrodynamics with General Relativistic Pressure
Jai-chan Hwang, Hyerim Noh
We present the general relativistic pressure correction terms in Newtonian hydrodynamic equations to the nonlinear order: these are equations (\ref{mass-conservation-Mink})-(\ref{P…
Axion as a Cold Dark Matter Candidate: Proof to Second order
Hyerim Noh, Chan-Gyung Park, Jai-chan Hwang
We prove that the axion as a coherently oscillating scalar field acts as a cold dark matter (CDM) to the second-order perturbations in all cosmological scales including the super-h…
Cosmological post-Newtonian equations from nonlinear perturbation theory
Hyerim Noh, Jai-chan Hwang
We derive the basic equations of the cosmological first-order post-Newtonian approximation from the recently formulated fully nonlinear and exact cosmological perturbation theory i…
Newtonian limit of fully nonlinear cosmological perturbations in Einstein's gravity
Jai-chan Hwang, Hyerim Noh
We prove that in the infinite speed-of-light limit (i.e., non-relativistic and subhorizon limits), the relativistic fully nonlinear cosmological perturbation equations in two gauge…
Axion as a cold dark matter candidate: low-mass case
Chan-Gyung Park, Jai-chan Hwang, Hyerim Noh
Axion as a coherently oscillating scalar field is known to behave as a cold dark matter in all cosmologically relevant scales. For conventional axion mass with 10^{-5} eV, the axio…
Fully nonlinear and exact perturbations of the Friedmann world model
Jai-chan Hwang, Hyerim Noh
In 1988 Bardeen has suggested a pragmatic formulation of cosmological perturbation theory which is powerful in practice to employ various fundamental gauge conditions easily depend…
Cosmological post-Newtonian approximation compared with perturbation theory
Hyerim Noh, Jai-chan Hwang
We compare the cosmological first-order post-Newtonian (1PN) approximation with the relativistic cosmological linear perturbation theory in a zero-pressure medium with the cosmolog…
Second order solutions of cosmological perturbation in the matter dominated era
Jai-chan Hwang, Hyerim Noh, Jinn-Ouk Gong
We present the growing mode solutions of cosmological perturbations to the second order in the matter dominated era. We also present several gauge-invariant combinations of perturb…
Classical non-Gaussianity from non-linear evolution of curvature perturbations
Jinn-Ouk Gong, Jai-chan Hwang, Hyerim Noh
We study the non-linear evolution of the curvature perturbations during matter dominated era. We show that regardless of the origin of the primordial perturbation, the Bardeen pote…
Local anomalies around the third peak in the CMB angular power spectrum of the WMAP 7-year data
Kyeong Yeon Ko, Chan-Gyung Park, Jai-chan Hwang
We estimate the power spectra of CMB temperature anisotropy in localized regions on the sky using the WMAP 7-year data. Here, we report that the north hat and the south hat regions…
Constraints on a gravity dark energy model with early scaling evolution
Chan-Gyung Park, Jai-chan Hwang, Hyerim Noh
The modified gravity with () allows a scaling solution where the density of gravity sector follows the density of the dominant fluid. We present initial conditi…
On cosmologically designed modified gravity theories
Jai-chan Hwang, Hyerim Noh, Chan-Gyung Park
Versions of parameterized pseudo-Newtonian gravity theories specially designed for cosmology have been introduced in recent cosmology literature. The modifications demand a zero-pr…
General relativistic effects on non-linear power spectra
Donghui Jeong, Jinn-Ouk Gong, Hyerim Noh +1
Non-linear nature of Einstein equation introduces genuine relativistic higher order corrections to the usual Newtonian fluid equations describing the evolution of cosmological pert…