Kazunori Itakura

We investigate properties of the ground state of a light quark matter with
heavy quark impurities. This system exhibits the "QCD Kondo effect" where the
interaction strength between a light quark near the Fermi surface and a heavy
quark increases ...

We discuss the ground state of a quark matter containing heavy quarks as
impurities in a simple model which exhibits the QCD Kondo effect. The model
includes a current-current interaction with the color exchange between a light
quark () and ...

The "QCD Kondo effect" stems from the color exchange interaction in QCD with
non-Abelian property, and can be realized in a high-density quark matter
containing heavy-quark impurities. We propose a novel type of the QCD Kondo
effect induced by a s...

We discuss properties of photons in extremely strong magnetic fields induced
by the relativistic heavy-ion collisions. We investigate the vacuum
birefringence, the real-photon decay, and the photon splitting which are all
forbidden in the ordinary...

We derive an analytic expression for one-loop effective action of QCD+QED at
zero and finite temperatures by using the Schwinger's proper time method. The
result is a nonlinear effective action not only for electromagnetic and
chromo-electromagnet...

We show that the Kondo effect occurs in light quark matter which contains
heavy quarks as impurities. We consider a scattering between a heavy-flavor
impurity and a light quark near a Fermi surface which is mediated by
gluon-exchange interactions....

We develop a Monte-Carlo event generator based on combination of a parton
production formula including the effects of parton saturation (called the DHJ
formula) and hadronization process due to the Lund string fragmentation model.
This event gener...

We investigate electron-positron pair creation from the vacuum in a pulsed
electric background field. Employing the Sauter-type pulsed field with height and width , we demonstrate
explicitly the interpl...

We present an argument to support the existence of dissipative modes in
relativistic field theories. In an O(N) theory in spatial dimension
, a relaxation constant of a two-point function in an infrared
region is shown...

We compute the refractive indices of a photon propagating in strong magnetic
fields on the basis of the analytic representation of the vacuum polarization
tensor obtained in our previous paper. When the external magnetic field is
strong enough for...

Photons propagating in strong magnetic fields are subject to a phenomenon
called the "vacuum birefringence" where refractive indices of two physical
modes both deviate from unity and are different from each other. We compute the
vacuum polarizatio...

We discuss potential attainability by the Hanbury Brown and Twiss (HBT)
interferometry of photons to probe the spacetime geometry of the primordial
plasma created by ultrarelativistic heavy-ion collisions. A possible effect to
distort the HBT imag...

We extend our previous analysis on the exchange statistics of vortices having
a single Dirac fermion trapped in each core, to the case where vortices trap
two Dirac fermions with U(2) symmetry. Such a system of vortices with
non-Abelian Dirac ferm...

We consider the exchange statistics of vortices, each of which traps an odd
number () of Majorana fermions. We assume that the fermions in a vortex
transform in the vector representation of the SO(N) group. Exchange of two
vortices turns out to...

We discuss gluon production by the Schwinger mechanism in collinear
color-electric and magnetic fields which may be realized in pre-equilibrium
stages of ultra-relativistic heavy-ion collisions. Fluctuations of non-Abelian
gauge fields around a pu...

Topological superconductors classified as type D admit zero-energy Majorana
fermions inside vortex cores, and consequently the exchange statistics of
vortices becomes non-Abelian, giving a promising example of non-Abelian anyons.
On the other hand...

We calculate the critical exponent in the 1/N expansion of the
two-particle-irreducible (2PI) effective action for the O(N) symmetric model in three spatial dimensions. The exponent controls the behavior
of a two-point functi...

We discuss statistics of vortices having zero-energy non-Abelian Majorana
fermions inside them. Considering the system of multiple non-Abelian vortices,
we derive a non-Abelian statistics that differs from the previously derived
non-Abelian statis...

We study the internal structure of a non-Abelian vortex in color
superconductivity with respect to quark degrees of freedom. Stable non-Abelian
vortices appear in the Color-Flavor-Locked phase whose symmetry SU(3)_{c+L+R}
is further broken to SU(2...

A system-size expansion method is incorporated into the Doi-Peliti formalism
for stochastic chemical kinetics. The basic idea of the incorporation is to
introduce a new decomposition of unity associated with a so-called Cole-Hopf
transformation. T...

We discuss in detail the shear viscosity coefficient eta and the viscosity to
entropy density ratio eta/s of a hadronic gas comprised of pions and nucleons.
In particular, we study the effects of baryon chemical potential on eta and
eta/s. We solv...

I discuss recent results on the Color Glass Condensate which is a dense
saturated gluonic state and appears as the universal picture of hadrons or
nuclei at very high energies.

We study the properties of light mesons in the scalar, pseudo-scalar, and
vector channels within the light-front quantization, by using the (one flavor)
Nambu--Jona-Lasinio model with vector interaction. After taking into account
the effects of ch...

The proton structure function F_2(x,Q^2) for x < 0.01 and 0.045< Q^2 < 45
GeV^2, measured in the deep inelastic scattering at HERA, can be well described
within the framework of the Color Glass Condensate.

We show that the HERA data for the inclusive structure function F_2(x,Q^2)
for x < 0.01 and 0.045 < Q^2 < 45 GeV^2 can be well described within the color
dipole picture, with a simple analytic expression for the dipole-proton
scattering amplitude,...

We apply the light-front quantization to the Nambu--Jona-Lasinio model with
the vector interaction, and compute vector meson's mass and light-cone
wavefunction in the large N limit. Following the same procedure as in the
previous analyses for scal...

We argue that the amount of baryon stopping observed in the central rapidity
region of heavy ion collisions at RHIC is proportional to the nuclear valence
quark distributions at small x. By generalizing Mueller's dipole model to
describe Reggeons ...

We construct a Gaussian approximation to the effective theory for the Colour
Glass Condensate which describes correctly the gluon distribution both in the
low density regime at high transverse momenta (above the saturation scale
), and in the...

We discuss a possibility of transition from color superconductivity of the
standard BCS type at high density, to Bose-Einstein Condensation (BEC) of
Cooper pairs at lower density. Examining two-flavor QCD over a wide range of
baryon density, we fo...

The two-flavor color superconductivity is examined over a wide range of
baryon density with a single model. To study the structural change of Cooper
pairs, quark correlation in the color superconductor is calculated both in the
momentum space and ...

We show that the evolution equations in QCD predict geometric scaling for
quark and gluon distribution functions in a large kinematical window, which
extends above the saturation scale up to momenta of order . For $Q^2 < Q^2...

The two-flavor color superconductivity is studied over a wide range of baryon
density with a single model. We pay a special attention to the spatial-momentum
dependence of the gap and to the spatial-structure of Cooper pairs. At
extremely high bar...

We study the hard color dipole-nucleon cross section within perturbative QCD
and discuss its relation to observables in diffractive leptoproduction of heavy
quarkonium. The dipole cross section calculated with the unintegrated gluon
density of the...

An investigation of dynamical chiral symmetry breaking on the light front is
made in the Nambu--Jona-Lasinio model with one flavor and N colors. Analysis of
the model suffers from extraordinary complexity due to the existence of a
"fermionic const...

Dynamical chiral symmetry breaking in the DLCQ method is investigated in
detail using a chiral Yukawa model closely related to the Nambu-Jona-Lasinio
model. By classically solving three constraints characteristic of the
light-front formalism, we s...

We investigate how the gap equations are obtained in the light-front
formalism within the four-Fermi theories. Instead of the zero-mode constraint,
we find that the "fermionic constraints" on nondynamical spinor components are
responsible for symm...

Spontaneous symmetry breaking of the light-front Gross-Neveu model is studied
in the framework of the discretized light-cone quantization. Introducing a
scalar auxiliary field and adding its kinetic term, we obtain a constraint on
the longitudinal...

We derive a bosonic Hamiltonian from two dimensional QCD on the light-front.
To obtain the bosonic theory we find that it is useful to apply the boson
expansion method which is the standard technique in quantum many-body physics.
We introduce bilo...

We reexamine a unitary-transformation method of extracting a physical
Hamiltonian from a gauge field theory after quantizing all degrees of freedom
including redundant variables. We show that this {\it quantum Hamiltonian
reduction} method suffers...