243 citations · 3k across the 96 of their papers we have counts for
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Nonlinear cosmological power spectra in Einstein's gravity
Hyerim Noh, Jai-chan Hwang
Is Newton's gravity sufficient to handle the weakly nonlinear evolution stages of the cosmic large-scale structures? Here we resolve the issue by analytically deriving the density…
Third-order cosmological perturbations of zero-pressure multi-component fluids: Pure general relativistic nonlinear effects
J. Hwang, H. Noh
Present expansion stage of the universe is believed to be mainly governed by the cosmological constant, collisionless dark matter and baryonic matter. The latter two components are…
Second-order perturbations of cosmological fluids: Relativistic effects of pressure, multi-component, curvature, and rotation
J. Hwang, H. Noh
We present general relativistic correction terms appearing in Newton's gravity to the second-order perturbations of cosmological fluids. In our previous work we have shown that to…
Evolution of linear perturbations through a bouncing world model: Is the near Harrison-Zel'dovich spectrum possible via a bounce?
Han Seek Kim, Jai-chan Hwang
We present a detailed numerical study of the evolutions of cosmological linear perturbations through a simple bouncing world model based on two scalar fields. We properly identify…
Second-order perturbations of a zero-pressure cosmological medium: comoving vs. synchronous gauge
J. Hwang, H. Noh
Except for the presence of gravitational wave source term, the relativistic perturbation equations of a zero-pressure irrotational fluid in a flat Friedmann world model coincide ex…
Newtonian versus relativistic nonlinear cosmology
Jai-chan Hwang, Hyerim Noh
Both for the background world model and its linear perturbations Newtonian cosmology coincides with the zero-pressure limits of relativistic cosmology. However, such successes in N…
Why Newton's gravity is practically reliable in the large-scale cosmological simulations
J. Hwang, H. Noh
Until now, it has been common to use Newton's gravity to study the non-linear clustering properties of the large-scale structures. Without confirmation from Einstein's theory, howe…
Cosmological nonlinear hydrodynamics with post-Newtonian corrections
Jai-chan Hwang, Hyerim Noh, Dirk Puetzfeld
The post-Newtonian (PN) approximation, based on the assumptions of weak gravitational fields and slow motions, provides a way to estimate general relativistic effects in the fully…
Second-order Perturbations of the Friedmann World Model
H. Noh, J. Hwang
We consider instability of the Friedmann world model to the second-order in perturbations. We present the perturbed set of equations up to the second-order in the Friedmann backgro…
Non-singular big-bounces and evolution of linear fluctuations
J. Hwang, H. Noh
We consider evolutions of linear fluctuations as the background Friedmann world model goes from contracting to expanding phases through smooth and non-singular bouncing phases. As…
Cosmological structure problem of the ekpyrotic scenario
J. Hwang
We address the perturbation power spectrum generated in the recently proposed ekpyrotic scenario by Khoury et al. The issue has been raised recently by Lyth who used the convention…
Quintessential perturbations during scaling regime
J. Hwang, H. Noh
The scalar field with an exponential potential allows a scaling solution where the the density of the field follows the density of the dominating fluid. Such a scaling regime is of…
On the 1/3 factor in the CMB Sachs-Wolfe effect
J. Hwang, T. Padmanabhan, O. Lahav +1
We point out that a pseudo-Newtonian interpretations of the factor in the Sachs-Wolfe effect, which relates the fluctuations in temperature and potential, $(δT/ T) = (1/ 3)…
Inflationary spectra in generalized gravity: Unified forms
H. Noh, J. Hwang
The classical evolution and the quantum generation processes of the scalar- and tensor-type cosmological perturbations in the context of a broad class of generalized gravity theori…
Evolution of cosmological perturbations in non-singular string cosmologies
Cyril Cartier, Jai-chan Hwang, Edmund J. Copeland
In a class of non-singular cosmologies derived from higher-order corrections to the low-energy bosonic string action, we derive evolution equations for the most general cosmologica…
Cosmological Perturbations with Multiple Fluids and Fields
J. Hwang, H. Noh
We consider the evolution of perturbed cosmological spacetime with multiple fluids and fields in Einstein gravity. Equations are presented in gauge-ready forms, and are presented i…
f(R) gravity theory and CMBR constraints
J. Hwang, H. Noh
We consider the large-scale cosmic structure generation by an inflation based on a pure f(R)-type gravity theory. Comparison with recent CMBR observations gives the following resul…
Observational constraints on inflation models with nonminimal scalar field
H. Noh, J. Hwang
We present the power spectra of the scalar- and tensor-type structures generated in an inflation model based on the nonminimally coupled scalar field with a self coupling. By compa…
Gauge-ready formulation of the cosmological kinetic theory in generalized gravity theories
J. Hwang, H. Noh
We present cosmological perturbations of kinetic components based on relativistic Boltzmann equations in the context of generalized gravity theories. Our general theory considers a…
Cosmological Perturbations with Multiple Scalar Fields
J. Hwang, H. Noh
We consider the evolution of perturbed cosmological spacetime with multiple scalar fields in Einstein gravity. A complete set of scalar-type perturbation equations is presented in…
Conserved cosmological structures in the one-loop superstring effective action
J. Hwang, H. Noh
A generic form of low-energy effective action of superstring theories with one-loop quantum correction is well known. Based on this action we derive the complete perturbation equat…
Conserved quantities in the perturbed Friedmann world model
J. Hwang
The evolutions of linear structures in a spatially homogeneous and isotropic world model are characterized by some conserved quantities: the amplitude of gravitational wave is cons…
COBE constraints on inflation models with a massive non-minimal scalar field
J. Hwang, H. Noh
We derive power spectra of the scalar- and tensor-type structures generated in an inflation model based on a massive non-minimally coupled scalar field with the strong coupling ass…
A conserved variable in the perturbed hydrodynamic world model
J. Hwang
We introduce a scalar-type perturbation variable which is conserved in the large-scale limit considering general sign of three-space curvature (), the cosmological constant…