2,007,967 research outputs found
Time-independent Anisotropic Plastic Behavior by Mechanical Subelement Models
The paper describes a procedure for modelling the anisotropic elastic-plastic behavior of metals in plane stress state by the mechanical sub-layer model. In this model the stress-strain curves along the longitudinal and transverse directions are represented by short smooth segments which are considered as piecewise linear for simplicity. The model is incorporated in a finite element analysis program which is based on the assumed stress hybrid element and the iscoplasticity-theory
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
Andreev Edge State on Semi-Infinite Triangular Lattice: Detecting the Pairing Symmetry in Na_0.35CoO_2.yH_2O
We study the Andreev edge state on the semi-infinite triangular lattice with
different pairing symmetries and boundary topologies. We find a rich phase
diagram of zero energy Andreev edge states that is a unique fingerprint of each
of the possible pairing symmetries. We propose to pin down the pairing symmetry
in recently discovered Na_xCoO_2 material by the Fourier-transformed scanning
tunneling spectroscopy for the edge state. A surprisingly rich phase diagram is
found and explained by a general gauge argument and mapping to 1D tight-binding
model. Extensions of this work are discussed at the end.Comment: 4 pages, 1 table, 4 figure
Theory of AC Anomalous Hall Conductivity in d-electron systems
To elucidate the intrinsic nature of anomalous Hall effect (AHE) in
-electron systems, we study the AC anomalous Hall conductivity (AHC) in a
tight-binding model with ()-orbitals. We drive a general
expression for the AC AHC , which is valid for finite
quasiparticle damping rate =, and find that the AC AHC is
strongly dependent on . When , the AC AHC shows a spiky peak
at finite energy that originates from the interband particle-hole
excitation, where represents the minimum band-splitting measured from
the Fermi level. In contrast, we find that this spiky peak is quickly
suppressed when is finite. By using a realistic value of
at in -electron systems, the spiky peak
is considerably suppressed. In the present model, the obtained results also
represents the AC spin Hall conductivity in a paramagnetic state.Comment: 13pages, 9 figure
Quantum Crooks fluctuation theorem and quantum Jarzynski equality in the presence of a reservoir
We consider the quantum mechanical generalization of Crooks Fluctuation
Theorem and Jarzynski Equality for an open quantum system. The explicit
expression for microscopic work for an arbitrary prescribed protocol is
obtained, and the relation between quantum Crooks Fluctuation Theorem, quantum
Jarzynski Equality and their classical counterparts are clarified. Numerical
simulations based on a two-level toy model are used to demonstrate the validity
of the quantum version of the two theorems beyond linear response theory
regime.Comment: 6 pages, 3 figures, any comments are welcom
On thermal phase structure of deformed Gross-Neveu model
We illustrate the phase structure of a deformed two-dimensional Gross-Neveu
model which is defined by undeformed field contents plus deformed Pauli
matrices. This deformation is based on two motives to find a more general
polymer model and to estimate how -deformed field theory affects on its
effective potential. There found some regions where chiral symmetry breaking
and restoration take place repeatedly as temperature increasing.Comment: 13 pages plus 6 figure
Resolving the extended stellar atmospheres of Asymptotic Giant Branch stars at (sub-)millimetre wavelengths
The initial conditions for the mass loss during the asymptotic giant branch
(AGB) phase are set in their extended atmospheres, where, among others,
convection and pulsation driven shocks determine the physical conditions. High
resolution observations of AGB stars at (sub)millimetre wavelengths can now
directly determine the morphology, activity, density, and temperature close to
the stellar photosphere. We used the Atacama Large Millimeter/submillimeter
Array (ALMA) high angular resolution observations to resolve the extended
atmospheres of four of the nearest AGB stars: W Hya, Mira A, R Dor and R Leo.
We interpreted the observations using a parameterised atmosphere model. We
resolve all four AGB stars and determine the brightness temperature structure
between and stellar radii. For W Hya and R Dor we confirm the existence
of hotspots with brightness temperatures to ~K. All four stars
show deviations from spherical symmetry. We find variations on a timescale of
days to weeks, and for R Leo we directly measure an outward motion of the
millimetre wavelength surface with a velocity of at least
~km~s. For all objects but W Hya we find that the
temperature-radius and size-frequency relations require the existence of a
(likely inhomogeneous) layer of enhanced opacity. The ALMA observations provide
a unique probe of the structure of the extended AGB atmosphere. We find highly
variable structures of hotspots and likely convective cells. In the future,
these observations can be directly compared to multi-dimensional chromosphere
and atmosphere models that determine the temperature, density, velocity, and
ionisation structure between the stellar photosphere and the dust formation
region. However, our results show that for the best interpretation, both very
accurate flux calibration and near-simultaneous observations are essential.Comment: 18 pages, 13 figures, Accepted to A&A, final version after language
editin
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