243 citations · 3k across the 96 of their papers we have counts for
30 papers · 1 filter
Evolution of baryon density perturbation in a relativistic MOND model based on Lorentz-violating vector field
Jai-chan Hwang, Hyerim Noh
A candidate for relativistic MOND with successful cosmology was proposed recently by using a Lorentz-violating vector field in Einstein's gravity. We show that the dynamic nature o…
Massive-photon electrodynamics and MHD in curved spacetime and cosmology
Jai-chan Hwang, Hyerim Noh
We study a massive-photon electrodynamics and magnetohydrodynamics (MHD) in the curved spacetime of Einstein's gravity. We consider a Proca-type photon mass and present equations i…
Cosmological perturbations of a relativistic MOND theory
Jai-chan Hwang, Hyerim Noh
A relativistic MOND theory, promising in reproducing cosmology as well as the MOND phenomenology in the low acceleration regime, was recently proposed. We present the post-Newtonia…
Graviton-photon conversions in Euler-Heisenberg nonlinear electrodynamics
Jai-chan Hwang, Hyerim Noh
We study graviton-photon conversions in an environment of the uniform and constant magnetic field considering Euler-Köckel-Heisenberg-type nonlinear corrections in electrodynamics.…
On gravity as a medium property in Maxwell equations
Jai-chan Hwang, Hyerim Noh
The effect of gravity in Maxwell's equations is often treated as a medium property. The commonly used formulation is based on managing Maxwell's equations in exactly the same form…
On graviton-photon conversions in magnetic environments
Jai-chan Hwang, Hyerim Noh
Graviton-photon conversions in a given external electric or magnetic field, known as the Gertsenshtein mechanism, are usually treated using the four-potential for photons. In terms…
Maxwell equations in curved spacetime
Jai-chan Hwang, Hyerim Noh
In curved spacetime, Maxwell's equations can be expressed in forms valid in Minkowski background, with the effect of the metric (gravity) appearing as effective polarizations and m…
Definition of electric and magnetic fields in curved spacetime
Jai-chan Hwang, Hyerim Noh
Defining the electric and magnetic field vectors in curved spacetime requires a proper choice of the observer's frame four-vector. Related literature shows that this fundamental is…
Perturbations and Linearization Stability of Closed Friedmann Universes
Hyerim Noh, Jai-chan Hwang, John D. Barrow
We consider perturbations of closed Friedmann universes. Perturbation modes of two lowest wavenumbers ( and ) are generally known to be fictitious, but here we show that bo…
Cosmological hydrodynamics with relativistic pressure and velocity
Hyerim Noh, Jai-chan Hwang, Chan-Gyung Park
We present hydrodynamic equations with relativistic pressure and velocity in the presence of weak gravity, in a cosmological context. Previously we consistently derived special rel…
Perturbation initial conditions for a couple of dark energy scalar field potentials
Jai-chan Hwang, Hyerim Noh, Chan-Gyung Park +1
We present perturbation initial conditions for two types of scalar field potential often used in the dark energy study: one inverse power-law and the other exponential. The solutio…
Axion as a cold dark matter candidate: Proof to fully nonlinear order
Hyerim Noh, Jai-chan Hwang, Chan-Gyung Park
We present a proof of the axion as a cold dark matter candidate to the fully nonlinear order perturbations based on Einstein's gravity. We consider the axion as a coherently oscill…
Exact non-linear equations for cosmological perturbations
Jinn-Ouk Gong, Jai-chan Hwang, Hyerim Noh +2
We present a complete set of exact and fully non-linear equations describing all three types of cosmological perturbations -- scalar, vector and tensor perturbations. We derive the…
Special relativistic hydrodynamics with gravitation
Jai-chan Hwang, Hyerim Noh
The special relativistic hydrodynamics with weak gravity is hitherto unknown in the literature. Whether such an asymmetric combination is possible was unclear. Here, the hydrodynam…
Newtonian hydrodynamic equations with relativistic pressure and velocity
Jai-chan Hwang, Hyerim Noh, J'ulio Fabris +2
We present a new approximation to include fully general relativistic pressure and velocity in Newtonian hydrodynamics. The energy conservation, momentum conservation and two Poisso…
Fully nonlinear cosmological perturbations of multi-component fluid and field systems
Jai-chan Hwang, Hyerim Noh, Chan-Gyung Park
We present fully nonlinear and exact cosmological perturbation equations in the presence of multiple components of fluids and minimally coupled scalar fields. We ignore the tensor-…
Newtonian, post-Newtonian and Relativistic Cosmological Perturbation Theory
Jai-chan Hwang, Hyerim Noh
Newtonian cosmological perturbation equations valid to full nonlinear order are well known in the literature. Assuming the absence of the transverse-tracefree part of the metric, w…
Axion as a cold dark matter candidate: Analysis to third order perturbation for classical axion
Hyerim Noh, Jai-chan Hwang, Chan-Gyung Park
We investigate aspects of axion as a coherently oscillating massive classical scalar field by analyzing third order perturbations in Einstein's gravity in the axion-comoving gauge.…
Conformal invariance of curvature perturbation
Jinn-Ouk Gong, Jai-chan Hwang, Wan Il Park +2
We show that in the single component situation all perturbation variables in the comoving gauge are conformally invariant to all perturbation orders. Generally we identify a specia…
Third order perturbations of a zero-pressure cosmological medium: Pure general relativistic nonlinear effects
J. Hwang, H. Noh
We consider a general relativistic zero-pressure irrotational cosmological medium perturbed to the third order. We assume a flat Friedmann background but include the cosmological c…
Relativistic-Newtonian correspondence of the zero-pressure but weakly nonlinear cosmology
H. Noh, J. Hwang
It is well known that couplings occur among the scalar-, vector-, and tensor-type perturbations of Friedmann world model in the second perturbational order. Here, we prove that, ex…
Cosmological perturbations in a gravity with quadratic order curvature couplings
H. Noh, J. Hwang
We present a set of equations describing the evolution of the scalar-type cosmological perturbation in a gravity with general quadratic order curvature coupling terms. Equations ar…
The Origin of Structures in Generalized Gravity
J. Hwang
In a class of generalized gravity theories with general couplings between the scalar field and the scalar curvature in the Lagrangian, we can describe the quantum generation and th…
Gravitational Wave Spectrums from Pole-like Inflations based on Generalized Gravity Theories
J. Hwang
We present a general and unified formulation which can handle the classical evolution and quantum generation processes of the cosmological gravitational wave in a broad class of ge…