1,885 research outputs found
Study of Quark Confinement in Baryons with Lattice QCD
In SU(3) lattice QCD, we perform the detailed study for the ground-state
three-quark (3Q) potential and the 1st excited-state 3Q
potential , i.e., the energies of the ground state and
the 1st excited state of the gluon field in the presence of the static three
quarks. From the accurate calculation for more than 300 different patterns of
3Q systems, the static ground-state 3Q potential is
found to be well described by the Coulomb plus Y-type linear potential
(Y-Ansatz) within 1%-level deviation. As a clear evidence for Y-Ansatz, Y-type
flux-tube formation is actually observed on the lattice in maximally-Abelian
projected QCD. For about 100 patterns of 3Q systems, we calculate the 1st
excited-state 3Q potential , and find a large
gluonic-excitation energy of about 1 GeV, which gives a physical reason of
the success of the quark model even without gluonic excitations. We present
also the first study for the penta-quark potential in lattice QCD,
and find that is well described by the sum of the OGE Coulomb plus
multi-Y type linear potential.Comment: Invited talk at International Workshop on QCD Down Under, Adelaide,
Australia, 10-19 Mar 200
Random matrix model at nonzero chemical potentials with anomaly effects
Phase diagram of the chiral random matrix model with U(1)A breaking term is
studied with the quark chemical potentials varied independently at zero
temperature, by taking the chiral and meson condensates as the order
parameters. Although, without the U(1)A breaking term, chiral transition of
each flavor can happen separately responding to its chemical potential, the
U(1)A breaking terms mix the chiral condensates and correlate the phase
transitions. In the three flavor case, we find that there are mixings between
the meson and chiral condensates due to the U(1)A anomaly, which makes the
meson condensed phase more stable. Increasing the hypercharge chemical
potential () with the isospin and quark chemical potentials (,
) kept small, we observe that the kaon condensed phase becomes the
ground state and at the larger the pion condense phase appears
unexpectedly, which is caused by the competition between the chiral restoration
and the meson condensation. The similar happens when and are
exchanged, and the kaon condensed phase becomes the ground state at larger
below the full chiral restoration.Comment: 12 pages, 8 figure
The back reaction and the effective Einstein's equation for the Universe with ideal fluid cosmological perturbations
We investigate the back reaction of cosmological perturbations on the
evolution of the Universe using the renormalization group method. Starting from
the second order perturbed Einstein's equation, we renormalize a scale factor
of the Universe and derive the evolution equation for the effective scale
factor which includes back reaction due to inhomogeneities of the Universe. The
resulting equation has the same form as the standard Friedman-Robertson-Walker
equation with the effective energy density and pressure which represent the
back reaction effect.Comment: 16 pages, to appear in Phys. Rev.
Back Reaction Problem in the Inflationary Universe
We investigate the back reaction of cosmological perturbations on an
inflationary universe using the renormalization-group method. The second-order
zero mode solution which appears by the nonlinearity of the Einstein equation
is regarded as a secular term of a perturbative expansion, we renormalized a
constant of integration contained in the background solution and absorbed the
secular term to this constant in a gauge-invariant manner. The resultant
renormalization-group equation describes the back reaction effect of
inhomogeneity on the background universe. For scalar type classical
perturbation, by solving the renormalization-group equation, we find that the
back reaction of the long wavelength fluctuation works as a positive spatial
curvature, and the short wavelength fluctuation works as a radiation fluid. For
the long wavelength quantum fluctuation, the effect of back reaction is
equivalent to a negative spatial curvature.Comment: 17 page
Responses of quark condensates to the chemical potential
The responses of quark condensates to the chemical potential, as a function
of temperature T and chemical potential \mu, are calculated within the
Nambu--Jona-Lasinio (NJL) model. We compare our results with those from the
recent lattice QCD simulations [QCD-TARO Collaboration, Nucl. Phys. B (Proc.
Suppl.) 106, 462 (2002)]. The NJL model and lattice calculations show
qualitatively similar behavior, and they will be complimentary ways to study
hadrons at finite density. The behavior above T_c requires more elaborated
analyses.Comment: 3 pages, 2 figs, based on a contribution to the Prof. Osamu Miyamura
memorial symposium, Hiroshima University, Nov. 16-17, 2001; slightly revised,
accepted for publication in Physical Review
Evolution of Non-linear Fluctuations in Preheating after Inflation
We investigate the evolution of the non-linear long wavelength fluctuations
during preheating after inflation. By using the separate universe approach, the
temporal evolution of the power spectrum of the scalar fields and the curvature
variable is obtained numerically. We found that the amplitude of the large
scale fluctuations is suppressed after non-linear evolution during preheating.Comment: To be published in Class. Quantum Gra
The Nambu-Jona-Lasinio Model at O(1/N^2)
We write down the anomalous dimensions of the fields of the
Nambu--Jona-Lasinio model or chiral Gross Neveu model with a continuous global
chiral symmetry for the two cases and
at in a expansion.Comment: 9 latex pages, 4 figures (available on request from the author),
LTH-308, (2 eqns corrected
Postmodern String Theory: Stochastic Formulation
In this paper we study the dynamics of a statistical ensemble of strings,
building on a recently proposed gauge theory of the string geodesic field. We
show that this stochastic approach is equivalent to the Carath\'eodory
formulation of the Nambu-Goto action, supplemented by an averaging procedure
over the family of classical string world-sheets which are solutions of the
equation of motion. In this new framework, the string geodesic field is
reinterpreted as the Gibbs current density associated with the string
statistical ensemble. Next, we show that the classical field equations derived
from the string gauge action, can be obtained as the semi-classical limit of
the string functional wave equation. For closed strings, the wave equation
itself is completely analogous to the Wheeler-DeWitt equation used in quantum
cosmology. Thus, in the string case, the wave function has support on the space
of all possible spatial loop configurations. Finally, we show that the string
distribution induces a multi-phase, or {\it cellular} structure on the
spacetime manifold characterized by domains with a purely Riemannian geometry
separated by domain walls over which there exists a predominantly Weyl
geometry.Comment: 24pages, ReVTe
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