In-Saeng Suh

Cold Ideal Equation of State for Strongly Magnetized Neutron Star Matter: Effects on Muon Production and Pion Condensation

Neutron stars with very strong surface magnetic fields have been suggested as the site for the origin of observed soft gamma repeaters (SGRs). In this paper we investigate the influence of such strong magnetic fields on the properties and internal structure of these strongly magnetized neutron stars (magnetars). We study properties of a degenerate equilibrium ideal neutron-proton-electron (npe) gas with and without the effects of the anomalous nucleon magnetic moment in a strong magnetic field. The presence of a sufficiently strong magnetic field changes the ratio of protons to neutrons as well as the neutron drip density. We also study the appearance of muons as well as pion condensation in strong magnetic fields. We discuss the possibility that boson condensation in the interior of magnetars might be a source of SGRs.

Mass-Radius Relation for Magnetic White Dwarfs

Recently, several white dwarfs with very strong surface magnetic fields have been observed. In this paper we explore the possibility that such stars could have sufficiently strong internal fields to alter their structure. We obtain a revised white dwarf mass-radius relation in the presence of strong internal magnetic fields. We first derive the equation of state for a fully degenerate ideal electron gas in a magnetic field using an Euler-MacLaurin expansion. We use this to obtain the mass-radius relation for magnetic 4He, 12C, and 56Fe white dwarfs of uniform composition.

Analysis of white dwarfs with strange-matter cores

We summarize masses and radii for a number of white dwarfs as deduced from a combination of proper motion studies, Hipparcos parallax distances, effective temperatures and binary or spectroscopic masses. A puzzling feature of these data, however, is that some stars appear to have radii which are significantly smaller than that expected for a standard electron-degenerate white-dwarf equations of state. We construct a projection of white-dwarf radii for fixed effective mass and conclude that there is at least marginal evidence for bimodality in the radius distribution for white dwarfs. We argue that if such compact white dwarfs exist it is unlikely that they contain an iron core. We propose an alternative of strange-quark matter within the white-dwarf core. We also discuss the impact of the so-called color-flavour-locked (CFL) state in strange-matter core associated with color superconductivity. We show that the data exhibit several features consistent with the expected mass-radius relation of strange dwarfs. We identify eight nearby white dwarfs which are possible candidates for strange-matter cores and suggest observational tests of this hypothesis.

MAGNETIC DOMAINS IN MAGNETAR MATTER AS AN ENGINE FOR SOFT GAMMA-RAY REPEATERS AND ANOMALOUS X-RAY PULSARS

Magnetars have been suggested as the most promising site for the origin of observed soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs). In this work, we investigate the possibility that SGRs and AXPs might be observational evidence for a magnetic phase separation in magnetars. We study magnetic domain formation as a new mechanism for SGRs and AXPs in which magnetar matter separates into phases containing different flux densities. We identify the parameter space in matter density and magnetic field strength at which there is an instability for magnetic domain formation. We conclude that such instabilities will likely occur in the deep outer crust for the magnetic Baym, Pethick, and Sutherland model and in the inner crust and core for magnetars described in the relativistic Hartree theory. Moreover, we estimate that the energy released by the onset of this instability is comparable with the energy emitted by SGRs.

Star formation and gas phase history of the cosmic web

We present a new method of tracking and characterizing the environment in which galaxies and their associated circumgalactic medium evolve. We use a structure finding algorithm we developed to self-consistently parse and follow the evolution of poor clusters, filaments and voids in large scale simulations. We trace the complete evolution of the baryons in the gas phase and the star formation history within each structure in our simulated volume. We vary the structure measure threshold to probe the complex inner structure of star forming regions in poor clusters, filaments and voids. We find the majority of star formation occurs in cold, condensed gas in filaments at intermediate redshifts (z ~ 3). We also show that much of the star formation above a redshift z = 3 occurs in low contrast regions of filaments, but as the density contrast increases at lower redshift star formation switches to the high contrast regions, or inner parts, of filaments. Since filaments bridge the void and cluster regions, it suggests that the majority of star formation occurs in galaxies in intermediate density regions prior to the accretion onto poor clusters. We find that at the present epoch, the gas phase distribution is 43.1%, 30.0%, 24.7% and 2.2% in the diffuse, WHIM, hot halo and condensed phases, respectively. The majority of the WHIM is associated with filaments. However, their multiphase nature and the fact that the star formation occurs predominantly in the condensed gas both point to the importance of not conflating the filamentary environment with the WHIM. Moreover, in our simulation volume 8.77%, 79.1%, 2.11% of the gas at z = 0 is located in poor clusters, filaments, and voids, respectively. We find that both filaments and poor clusters are multiphase environments distinguishing themselves by different distribution of gas phases.

Constraints on preinflation fluctuations in a nearly flat open Λ CDM cosmology

We analyze constraints on parameters characterizing the pre-inflating universe in an open inflation model with a present slightly open

A new multi-scale structure finding algorithm to identify cosmological structure

\Lambda

Weak reaction freeze-out constraints on primordial magnetic fields

CDM universe. We employ an analytic model to show that for a broad class of inflation-generating effective potentials, the simple requirement that some fraction of the observed dipole moment represents a pre-inflation isocurvature fluctuation allows one to set upper and lower limits on the magnitude and wavelength scale of pre-inflation fluctuations in the inflaton field, and the curvature of the pre-inflation universe, as a function of the fraction of the total initial energy density in the inflaton field as inflation begins. We estimate that if the pre-inflation contribution to the current CMB dipole is near the upper limit set by the {\it Planck} Collaboration then the current constraints on

Finite temperature effects on baryon transport scattering in the early Universe

\Lambda

Nuclear equation of state and internal structure of magnetars

CDM cosmological parameters allow for the possibility of a significantly open