16,237 research outputs found
Anomalous Viscosity of an Expanding Quark-Gluon Plasma
We argue that an expanding quark-gluon plasma has an anomalous viscosity,
which arises from interactions with dynamically generated color fields. We
derive an expression for the anomalous viscosity in the turbulent plasma domain
and apply it to the hydrodynamic expansion phase, when the quark-gluon plasma
is near equilibrium. The anomalous viscosity dominates over the collisional
viscosity for weak coupling and not too late times. This effect may provide an
explanation for the apparent ``nearly perfect'' liquidity of the matter
produced in nuclear collisions at the Relativistic Heavy Ion Collider without
the assumption that it is a strongly coupled state.Comment: Final version accepted for publicatio
Momentum dependence of the energy gap in the superconducting state of optimally doped Bi2(Sr,R)2CuOy (R=La and Eu)
The energy gap of optimally doped Bi2(Sr,R)2CuOy (R=La and Eu) was probed by
angle resolved photoemission spectroscopy (ARPES) using a vacuum ultraviolet
laser (photon energy 6.994 eV) or He I resonance line (21.218 eV) as photon
source. The results show that the gap around the node at sufficiently low
temperatures can be well described by a monotonic d-wave gap function for both
samples and the gap of the R=La sample is larger reflecting the higher Tc.
However, an abrupt deviation from the d-wave gap function and an opposite R
dependence for the gap size were observed around the antinode, which represent
a clear disentanglement between the antinodal pseudogap and the nodal
superconducting gap.Comment: Submitted as the proceedings of LT2
A simple SO(10) GUT in five dimensions
A simple supersymmetric SO(10) GUT in five dimensions is considered. The
fifth dimension is compactified on the orbifold
possessing two inequivalent fixed points. In our setup, all matter and Higgs
multiplets reside on one brane (PS brane) where the original SO(10) gauge group
is broken down to the Pati-Salam (PS) gauge group, SU(4)_c \timesSU(2)_L
\times SU(2), by the orbifold boundary condition, while only the SO(10)
gauge multiplet resides in the bulk. The further breaking of the PS symmetry to
the Standard Model gauge group is realized by Higgs multiplets on the PS brane
as usual in four dimensional models. Proton decay is fully suppressed. In our
simple setup, the gauge coupling unification is realized after incorporating
threshold corrections of Kaluza-Klein modes. When supersymmetry is assumed to
be broken on the other brane, supersymmetry breaking is transmitted to the PS
brane through the gaugino mediation with the bulk gauge multiplet.Comment: 12 pages, 1 figure, some errors have been corrected (no change in
conclusions
Spatial Distributions of Cold and Warm Interstellar Dust in M101 Resolved with AKARI/Far-Infrared Surveyor (FIS)
The nearby face-on spiral galaxy M101 has been observed with the Far-Infrared
Surveyor (FIS) onboard AKARI. The far-infrared four-band images reveal fine
spatial structures of M101, which include global spiral patterns, giant HII
regions embedded in outer spiral arms, and a bar-like feature crossing the
center. The spectral energy distribution of the whole galaxy shows the presence
of the cold dust component (18 K) in addition to the warm dust component (55
K). The distribution of the cold dust is mostly concentrated near the center,
and exhibits smoothly distributed over the entire extent of the galaxy, whereas
the distribution of the warm dust indicates some correlation with the spiral
arms, and has spotty structures such as four distinctive bright spots in the
outer disk in addition to a bar-like feature near the center tracing the CO
intensity map. The star-formation activity of the giant HII regions that
spatially correspond to the former bright spots is found to be significantly
higher than that of the rest of the galaxy. The latter warm dust distribution
implies that there are significant star-formation activities in the entire bar
filled with molecular clouds. Unlike our Galaxy, M101 is a peculiar normal
galaxy with extraordinary active star-forming regions.Comment: 18 pages, 9 figures, accepted for publication in PASJ AKARI special
issu
Solving problems of 4D minimal SO(10) model in a warped extra dimension
The minimal renormalizable supersymmetric SO(10) model, an SO(10) framework
with only one 10 and one 126 Higgs multiplets in the Yukawa sector, is
attractive because of its high predictive power for the neutrino oscillation
data. However, this model suffers from problems related to running of gauge
couplings. The gauge coupling unification may be spoiled due to the presence of
Higgs multiplets much lighter than the grand unification (GUT) scale. In
addition, the gauge couplings blow up around the GUT scale because of the
presence of Higgs multiplets of large representations. We consider the minimal
SO(10) model in the warped extra dimension and find a possibility to solve
these problems.Comment: 12 pages, no figure; version to appear in Phys. Rev.
- …