Chul H. Lee

Preparation of barium titanate by homogeneous precipitation

The barium titanyl oxalate, which was the precursor of barium titanate, was prepared by homogeneous precipitation using the diethyl oxalate as a precipitating agent. The oxalate dried at 80 °C was the crystalline phase, which was converted to amorphous-like phase after drying at 120 °C. The weight loss of oxalate was 47.3 wt%. The chemical formula of the oxalate could correspond to BaTiO(C2O4)2 · 4H2O. The barium titanate obtained from the calcination of oxalate at 850 °C was a tetragonal phase with a particle size of 0.2 μm.

Magnetic alignment process: a new mechanism for extracting energy from rotating black holes

The magnetic alignment process is proposed as a complementary or companion process to the Blandford–Znajek mechanism for the rotational energy extraction from a Kerr black hole, to serve as a viable model for the central engine of quasars, AGN, and even GRB. In contrast to the environment assumed in the Blandford–Znajek mechanism, in which the rotating holes spin axis and the asymptotic direction of the magnetic field are aligned, this new process operates when they are generally misaligned, which obviously is the more natural situation likely to happen. The time scales over which these two processes take place and the total radiated powers released at the horizon by them have been estimated and found to be nearly comparable. This may imply that in a random, non-axisymmetric configuration, the magnetic alignment process would operate first, during which some of the holes rotational energy is released, and then upon completion of the alignment, the Blandford–Znajek mechanism may follow and the rest of the holes rotational energy, if any left, would be further released.

False vacuum bubble nucleation due to a nonminimally coupled scalar field

We study the possibility of forming the false vacuum bubble nucleated within the true vacuum background via the true-to-false vacuum phase transition in curved spacetime. We consider a semiclassical Euclidean bubble in the Einstein theory of gravity with a nonminimally coupled scalar field. In this paper we present the numerical computations as well as the approximate analytical computations. We mention the evolution of the false vacuum bubble after nucleation.

Oscillating instanton solutions in curved space

We investigate oscillating instanton solutions of a self-gravitating scalar field between degenerate vacua. We show that there exist O(4)-symmetric oscillating solutions in a de Sitter background. The geometry of this solution is finite and preserves the

Dynamics of false vacuum bubbles with nonminimal coupling

Z_{2}

Electric charge and magnetic flux on rotating black holes in a force-free magnetosphere

symmetry. The nontrivial solution corresponding to tunneling is possible only if the effect of gravity is taken into account. We present numerical solutions of this instanton, including the phase diagram of solutions in terms of the parameters of the present work and the variation of energy densities. Our solutions can be interpreted as solutions describing an instanton-induced domain wall or braneworld-like object rather than a kink-induced domain wall or braneworld. The oscillating instanton solutions have a thick wall and the solutions can be interpreted as a mechanism providing nucleation of the thick wall for topological inflation. We remark that

CMBR anisotropy with primordial magnetic fields

Z_{2}

Multiple extramedullary relapses without bone marrow involvement after second allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia

invariant solutions also exist in a flat and anti-de Sitter background, though the physical significance is not clear.

Molecular cytogenetic analysis of the monoblastic cell line U937: karyotype clarification by G-banding, whole chromosome painting, microdissection and reverse painting, and comparative genomic hybridization

We study the dynamics of false vacuum bubbles. A nonminimally coupled scalar field gives rise to the effect of negative tension. The mass of a false vacuum bubble from an outside observers point of view can be positive, zero, or negative. The interior false vacuum has de Sitter geometry, while the exterior true vacuum background can have geometry depending on the vacuum energy. We show that there exist expanding false vacuum bubbles without the initial singularity in the past.We study the dynamics of false vacuum bubbles within a true vacuum background by employing modified junction conditions. A nonminimally coupled scalar field give rise to the effect of negative tension. In this framework it is possible that the mass of a false vacuum bubble from outside observer’s point of view is positive, zero, or negative. It is considered that the interior false vacuum has de Sitter geometry and a exterior true vacuum background has arbitrary vacuum energy. We show that false vacuum bubbles, without singularity in their past, can expand within the true vacuum background. PACS numbers: 04.62.+v, 11.15.Kc, 98.80.Cq, 98.80.Es, 98.80.-k email:bhl@sogang.ac.kr email:chulhoon@hanyang.ac.kr email:warrior@sogang.ac.kr email:stringphy@gmail.com email:cyong21@sogang.ac.kr

A spherically symmetric electro-vacuum solution of the Poincaré gauge field theory of gravitation

The electric charge on rotating black holes is calculated to be ~ BJ in the force-free configuration of Ghosh (2000), with a horizon flux of ~ BM^2. This charge is gravitationally weak for B ~ 10^{15} G, so that the Kerr metric applies. Being similar to the electric charge of a magnetar, both electric charge and magnetic flux should be, in sign and order of magnitude, continuous during stellar collapse into a black hole. Extraction of the rotational energy from newly formed black holes may proceed by interaction with the magnetic field. Keywords:black hole physics --magnetic fields