The most profound
question: What is the universe?
The most
embarrassing question: What is not the
universe??



Assistant Professor 

affiliation 
: 
School
of Computational Science 

address 
: 
20743 Cheongnyangni 2dong, Dongdaemungu, 


Email 
: 
scikid(a)kias.re.kr 


phone 
: 
+8229583755 


FAX 
: 
+8229583820 

Research Topics
1. Cosmology
My
main research subjects in cosmology are DM, DE and inflation.
1) We suggest Dark energy is energy of cosmic
Hawking radiation and related to entanglement
Articles about our model in Newscientist , Sciencenews, and Korean news papers

Expansion of a cosmic
horizon with a radius r induces information erasing at the horizon and it
consumes energy due to the Landauer's principle. This energy can be dark energy.
If this information is represented by entanglement entropy this model
becomes entanglement dark
energy model which well fit observations. Inflation can solve
easily the cosmic
coincidence problem with this model. Finally we concluded that Hawking radiation from cosmic event
horizon could be DE!. 
2) We suggest Dark matter is in BEC or coherent
scalar field (Boson star, fuzzy, SFDM)!

In 1992
Prof. Sin suggested galactic dark matter halos are in BEC. In the same year, I generalized this model to the first scalar field dark matter (SFDM) (boson star) model. These models are free from the cusp problem and satellite galaxies problem threatening
the standard LambdaCDM model. Recently
it was also shown that the rotation curves of dwarf galaxies fit well with
predictions of these models! These two models are now known as fuzzy CDM,
repulsive DM or SFDM. 
BEC
DM acts as cold dark matter at the
supergalactic scale while it gives a finite length scale
suppressing
subgalactic structures
à ideal alternative to standard CDM
This model explains
l Cusp, Missing satellite, Angular momentum Catastrophe
l Rotation curves
& ripples in them
l Bullet cluster collision
mystery
l Size evolution of massive
galaxy
l Large scale structure formation
More and more observational evidences
support this idea!
3) Black hole and quantum
information

We
are studying relation between black hole (BH) and quantum information
erasing. We apply the same idea of information dark energy to BH. When
matter enter BH horizon its information can be erased and this consumes
energy due to the Landauer's principle. This energy can be black hole mass. We are studying also
the black hole information paradox with this idea. 
2. Entanglement and Qauntum Cryptography
(QKD)
1) Entanglement

My
main research subject is entanglement in quantum fields, cosmology and
computational complexity. I also interested in relativistic entanglement and
foundations of quantum physics. Phys.Rev.
A74 (2006) 044304 
2) Korean quantum cryptography system by
ETRI team

ETRI,
KIAS and Korea University team developed Korean QKD system in 2005 in a
project of korean government. I played a role of theoretian in this project
and studied privacy amplification and error correction of this system. 