5,262 research outputs found

### Computational procedure for finite difference solution of one-dimensional heat conduction problems reduces computer time

Computational procedure reduces the numerical effort whenever the method of finite differences is used to solve ablation problems for which the surface recession is large relative to the initial slab thickness. The number of numerical operations required for a given maximum space mesh size is reduced

### 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

### Detection of flux emergence, splitting, merging, and cancellation of network field. I Splitting and Merging

Frequencies of magnetic patch processes on supergranule boundary, namely flux
emergence, splitting, merging, and cancellation, are investigated through an
automatic detection. We use a set of line of sight magnetograms taken by the
Solar Optical Telescope (SOT) on board Hinode satellite. We found 1636 positive
patches and 1637 negative patches in the data set, whose time duration is 3.5
hours and field of view is 112" \times 112". Total numbers of magnetic
processes are followed: 493 positive and 482 negative splittings, 536 positive
and 535 negative mergings, 86 cancellations, and 3 emergences. Total numbers of
emergence and cancellation are significantly smaller than those of splitting
and merging. Further, frequency dependences of merging and splitting processes
on flux content are investigated. Merging has a weak dependence on flux content
only with a power- law index of 0.28. Timescale for splitting is found to be
independent of parent flux content before splitting, which corresponds to \sim
33 minutes. It is also found that patches split into any flux contents with a
same probability. This splitting has a power-law distribution of flux content
with an index of -2 as a time independent solution. These results support that
the frequency distribution of flux content in the analyzed flux range is
rapidly maintained by merging and splitting, namely surface processes. We
suggest a model for frequency distributions of cancellation and emergence based
on this idea.Comment: 32 pages, 10 figures, 1 table, accepted to Ap

### Charmonium properties in deconfinement phase in anisotropic lattice QCD

J/Psi and eta_c above the QCD critical temperature T_c are studied in
anisotropic quenched lattice QCD, considering whether the c\bar c systems above
T_c are spatially compact (quasi-)bound states or scattering states. We adopt
the standard Wilson gauge action and O(a)-improved Wilson quark action with
renormalized anisotropy a_s/a_t =4.0 at \beta=6.10 on 16^3\times (14-26)
lattices, which correspond to the spatial lattice volume V\equiv
L^3\simeq(1.55{\rm fm})^3 and temperatures T\simeq(1.11-2.07)T_c. We
investigate the c\bar c system above T_c from the temporal correlators with
spatially-extended operators, where the overlap with the ground state is
enhanced. To clarify whether compact charmonia survive in the deconfinement
phase, we investigate spatial boundary-condition dependence of the energy of
c\bar c systems above T_c. In fact, for low-lying S-wave c \bar c scattering
states, it is expected that there appears a significant energy difference
\Delta E \equiv E{\rm (APBC)}-E{\rm (PBC)}\simeq2\sqrt{m_c^2+3\pi^2/L^2}-2m_c
(m_c: charm quark mass) between periodic and anti-periodic boundary conditions
on the finite-volume lattice. In contrast, for compact charmonia, there is no
significant energy difference between periodic and anti-periodic boundary
conditions. As a lattice QCD result, almost no spatial boundary-condition
dependence is observed for the energy of the c\bar c system in J/\Psi and
\eta_c channels for T\simeq(1.11-2.07)T_c. This fact indicates that J/\Psi and
\eta_c would survive as spatially compact c\bar c (quasi-)bound states below
2T_c. We also investigate a $P$-wave channel at high temperature with maximally
entropy method (MEM) and find no low-lying peak structure corresponding to
\chi_{c1} at 1.62T_c.Comment: 13 pages, 11 figure

### Single domain YBCO/Ag bulk superconductors fabricated by seeded infiltration and growth

We have applied the seeded infiltration and growth (IG) technique to the processing of samples containing Ag in an attempt to fabricate Ag-doped Y-Ba-Cu-O (YBCO) bulk superconductors with enhanced mechanical properties. The IG technique has been used successfully to grow bulk Ag-doped YBCO superconductors of up to 25 mm in diameter in the form of single grains. The distribution of Ag in the parent Y-123 matrix fabricated by the IG technique is observed to be at least as uniform as that in samples grown by conventional top seeded melt growth (TSMG). Fine Y-211 particles were observed to be embedded within the Y-123 matrix for the IG processed samples, leading to a high critical current density, Jc, of over 70 kA/cm2 at 77.3 K in self-field. The distribution of Y-211 in the IG sample microstructure, however, is inhomogeneous, which leads to a variation in the spatial distribution of Jc throughout the bulk matrix. A maximum-trapped field of around 0.43 T at 1.2 mm above the sample surface (i.e. including 0.7 mm for the sensor mould thickness) is observed at liquid nitrogen temperature, despite the relatively small grain size of the sample (20 mm diameter × 7 mm thickness)

### Survival of charmonia above Tc in anisotropic lattice QCD

We find a strong evidence for the survival of $J/\Psi$ and $\eta_c$ as
spatially-localized $c\bar c$ (quasi-)bound states above the QCD critical
temperature $T_c$, by investigating the boundary-condition dependence of their
energies and spectral functions. In a finite-volume box, there arises a
boundary-condition dependence for spatially spread states, while no such
dependence appears for spatially compact states. In lattice QCD, we find almost
{\it no} spatial boundary-condition dependence for the energy of the $c\bar c$
system in $J/\Psi$ and $\eta_c$ channels for $T\simeq(1.11-2.07)T_c$. We also
investigate the spectral function of charmonia above $T_c$ in lattice QCD using
the maximum entropy method (MEM) in terms of the boundary-condition dependence.
There is {\it no} spatial boundary-condition dependence for the low-lying peaks
corresponding to $J/\Psi$ and $\eta_c$ around 3GeV at $1.62T_c$. These facts
indicate the survival of $J/\Psi$ and $\eta_c$ as compact $c\bar c$
(quasi-)bound states for $T_c < T < 2T_c$.Comment: 4 pages, 1 figur

### Scalar-Quark Systems and Chimera Hadrons 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 in strong interaction without chiral symmetry
breaking. We investigate ``scalar-quark mesons'' \phi^\dagger \phi and
``scalar-quark baryons'' \phi\phi\phi which are 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 even for zero bare scalar-quark mass m_\phi=0 at
a^{-1}\simeq 1GeV. We find that the constituent scalar-quark and quark picture
is satisfied for all the new-type hadrons. Namely, the mass of the new-type
hadron composed of m \phi's and n \psi's, M_{{m}\phi+{n}\psi}, satisfies
M_{{m}\phi+{n}\psi}\simeq {m} M_\phi +{n} M_\psi, where M_\phi and M_\psi are
the constituent scalar-quark and quark mass, respectively. M_\phi at m_\phi=0
estimated from these new-type hadrons is 1.5-1.6GeV, which is larger than that
of light quarks, M_\psi\simeq 400{\rm MeV}. Therefore, in the systems of
scalar-quark hadrons and chimera hadrons, scalar-quarks acquire large mass due
to large quantum corrections by gluons. Together with other evidences of mass
generations of glueballs and charmonia, we conjecture that all colored
particles generally acquire a large effective mass due to dressed gluon
effects.Comment: 9 pages, 9 figure

### Anisotropic Lattice QCD Studies of Penta-quark Anti-decuplet

Anti-decuplet penta-quark baryon is studied with the quenched anisotropic
lattice QCD for accurate measurement of the correlator. Both the positive and
negative parity states are studied using a non-NK type interpolating field with
I=0 and J=1/2. After the chiral extrapolation, the lowest positive parity state
is found at m_{Theta} \simeq 2.25 GeV, which is too massive to be identified
with the experimentally observed Theta^+(1540). The lowest negative parity
state is found at m_{Theta}\simeq 1.75 GeV, which is rather close to the
empirical value. To confirm that this state is a compact 5Q resonance, a new
method with ``hybrid boundary condition (HBC)'' is proposed. The HBC analysis
shows that the observed state in the negative parity channel is an NK
scattering state.Comment: A talk given at International Workshop PENTAQUARK04, July 20-23, 2004
at SPring-8, Japan, 8 pages, 7 figures, 2 table

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