60,189 research outputs found

### Behind the success of the quark model

The ground-state three-quark (3Q) potential $V_{\rm 3Q}^{\rm g.s.}$ and the
excited-state 3Q potential $V_{\rm 3Q}^{\rm e.s.}$ are studied using SU(3)
lattice QCD at the quenched level. For more than 300 patterns of the 3Q
systems, the ground-state potential $V_{\rm 3Q}^{\rm g.s.}$ is investigated in
detail in lattice QCD with $12^3\times 24$ at $\beta=5.7$ and with $16^3\times
32$ at $\beta=5.8, 6.0$. As a result, the ground-state potential $V_{\rm
3Q}^{\rm g.s.}$ is found to be well described with Y-ansatz within the 1%-level
deviation. From the comparison with the Q-$\rm\bar Q$ potential, we find the
universality of the string tension as $\sigma_{\rm 3Q}\simeq\sigma_{\rm Q\bar
Q}$ and the one-gluon-exchange result as $A_{\rm 3Q}\simeq\frac12 A_{\rm Q\bar
Q}$. The excited-state potential $V_{\rm 3Q}^{\rm e.s.}$ is also studied in
lattice QCD with $16^3\times 32$ at $\beta=5.8$ for 24 patterns of the 3Q
systems.The energy gap between $V_{\rm 3Q}^{\rm g.s.}$ and $V_{\rm 3Q}^{\rm
e.s.}$, which physically means the gluonic excitation energy, is found to be
about 1GeV in the typical hadronic scale, which is relatively large compared
with the excitation energy of the quark origin. This large gluonic excitation
energy justifies the great success of the simple quark model.Comment: Talk given at 16th International Conference on Particles and Nuclei
(PANIC 02), Osaka, Japan, 30 Sep - 4 Oct 200

### Role of Large Gluonic Excitation Energy for Narrow Width of Penta-Quark Baryons in QCD String Theory

We study the narrow decay width of low-lying penta-quark baryons in the QCD
string theoryin terms of gluonic excitations. In the QCD string theory, the
penta-quark baryon decays via a gluonic-excited state of a baryon and meson
system, where a pair of Y-shaped junction and anti-junction is created. Since
lattice QCD shows that the lowest gluonic-excitation energy takes a large value
of about 1 GeV, the decay of the penta-quark baryon near the threshold is
considered as a quantum tunneling process via a highly-excited state (a
gluonic-excited state) in the QCD string theory. This mechanism strongly
suppresses the decay and leads to an extremely narrow decay width of the
penta-quark system.Comment: Talk given at International Conference on the Structure of Baryons
(Baryons 04) October 25 - 29, 2004, Ecole Polytechnique, Palaiseau, Franc

### A New Current Regularization of Thirring Model

We study an ambiguity of the current regularization in the Thirring model. We
find a new current definition which enables to make a comprehensive treatment
of the current. Our formulation is simpler than Klaiber's formulation. We
compare our result with other formulations and find a very good agreement with
their result. We also obtain the Schwinger term and the general formula for any
current regularization.Comment: 7 pages, some comments and references added, to appear in Prog.
Theor. Phy

### Y-type Flux-Tube Formation in Baryons

For more than 300 different patterns of the 3Q systems, the ground-state 3Q
potential $V_{\rm 3Q}^{\rm g.s.}$ is investigated using SU(3) lattice QCD with
$12^3\times 24$ at $\beta=5.7$ and $16^3\times 32$ at $\beta=5.8, 6.0$ at the
quenched level. As a result of the detailed analyses, we find that the
ground-state potential $V_{\rm 3Q}^{\rm g.s.}$ is well described with so-called
Y-ansatz as $V_{\rm 3Q}=-A_{\rm 3Q}\sum_{i<j}\frac1{|{\bf r}_i-{\bf r}_j|}
+\sigma_{\rm 3Q} L_{\rm min}+C_{\rm 3Q}$, with the accuracy better than 1%.
Here, $L_{\rm min}$ denotes the minimal value of total flux-tube length. We
also studythe excited-state potential $V_{\rm 3Q}^{\rm e.s.}$ using lattice QCD
with $16^3\times 32$ at $\beta=5.8, 6.0$ for more than 100 patterns of the 3Q
systems. The energy gap between $V_{\rm 3Q}^{\rm g.s.}$ and $V_{\rm 3Q}^{\rm
e.s.}$, which physically means the gluonic excitation energy, is found to be
about 1 GeV in the typical hadronic scale. Finally, we suggest a possible
scenario which connects the success of the quark model to QCD.Comment: Talk given at Color Confinement and Hadrons in Quantum Chromodynamics
(Confinement 2003), Saitama, Japan, 21-24 July 2003; 5 pages, 4 figure

### Bound States of (Anti-)Scalar-Quarks in SU(3)_c Lattice QCD

Light scalar-quarks \phi (colored scalar particles or idealized diquarks) and
their color-singlet hadronic states are studied with quenched SU(3)_c lattice
QCD in terms of mass generation. We investigate ``scalar-quark mesons''
\phi^\dagger \phi and ``scalar-quark baryons'' \phi\phi\phi as the bound states
of scalar-quarks \phi. We also investigate the bound states of scalar-quarks
\phi and quarks \psi, i.e., \phi^\dagger \psi, \psi\psi\phi and \phi\phi\psi,
which we name ``chimera hadrons''. All the new-type hadrons including \phi are
found to have a large mass due to large quantum corrections by gluons, even for
zero bare scalar-quark mass m_\phi=0 at a^{-1}\sim 1{\rm GeV}. We conjecture
that all colored particles generally acquire a large effective mass due to
dressed gluon effects.Comment: Talk given at The 17th International Spin Physics Symposium
(SPIN2006), Kyoto, Japan, 2-7 Oct 200

### Universal low-temperature properties of quantum and classical ferromagnetic chains

We identify the critical theory controlling the universal, low temperature,
macroscopic properties of both quantum and classical ferromagnetic chains. The
theory is the quantum mechanics of a single rotor. The mapping leads to an
efficient method for computing scaling functions to high accuracy.Comment: 4 pages, 2 tables and 3 Postscript figure

### The Fate of Dark Energy

By studying the present cosmological data, particularly on CMB, SNeIA and
LSS, we find that the future fate of the universe, for simple linear models of
the dark energy equation-of-state, can vary between the extremes of (I) a
divergence of the scale factor in as little as 7 Gyr; (II) an infinite lifetime
of the universe with dark energy dominant for all future time; (III) a
disappearing dark energy where the universe asymptotes as $t \to \infty$ to
$a(t) \sim t^{2/3}$ {\it i.e.} matter domination. Our dreadful conclusion is
that no amount of data from our past light-cone can select between these future
scenarios.Comment: 10 pages LaTeX including 4 eps figures. Minor corrections in tex

### An Improved Search Method for Gravitational Ringing of Black Holes

A black hole has characteristic quasi-normal modes that will be excited when
it is formed or when the geometry is perturbed. The state of a black hole when
the quasi-normal modes are excited is called the gravitational ringing, and
detections of it will be a direct confirmation of the existence of black holes.
To detect it, a method based on matched filtering needs to be developed.
Generically, matched filtering requires a large number of templates, because
one has to ensure a proper match of a real gravitational wave with one of
template waveforms to keep the detection efficiency as high as possible. On the
other hand, the number of templates must be kept as small as possible under
limited computational costs. In our previous paper, assuming that the
gravitational ringing is dominated by the least-damped (fundamental) mode with
the least imaginary part of frequency, we constructed an efficient method for
tiling the template space. However, the dependence of the template space metric
on the initial phase of a wave was not taken into account. This dependence
arises because of an unavoidable mismatch between the parameters of a signal
waveform and those given discretely in the template space. In this paper, we
properly take this dependence into account and present an improved, efficient
search method for gravitational ringing of black holes.Comment: 19 pages, 9 figure

### Candidates for Inflaton in Quiver Gauge Theory

The inflaton necessary to implement the mechanism of inflationary cosmology
has natural candidates in quiver gauge theory. We discuss the dimensionless
coefficients of quartic couplings and enumerate scalars which are singlet under
the low-energy gauge group. The inflaton mass is generally predicted to be in
the TeV region, close to 4 TeV for one specific unified model. A quartic
inflaton potential, and a mutated hybrid inflation, are discussed. They can
give adequate inflation and appropriate fluctuations but different spectral
indices.Comment: LaTeX 10 page

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