5,021 research outputs found
End wall flows in rotors and stators of a single stage compressor
A computer code for solving the parabolized Navier-Stokes equations for internal flows was developed. Oscillations that develop in the calculation procedure are discussed. The measurements made in the hub and annulus wall boundary layers are summarized. The flow in the hub wall boundary layer, starting ahead of the inlet guide vanes to the inlet of the rotor is traced
Re-equilibration after quenches in athermal martensites:Conversion-delays for vapour to liquid domain-wall phases
Entropy barriers and ageing states appear in martensitic
structural-transition models, slowly re-equilibrating after temperature
quenches, under Monte Carlo dynamics. Concepts from protein folding and ageing
harmonic oscillators turn out to be useful in understanding these
nonequilibrium evolutions. We show how the athermal, non-activated delay time
for seeded parent-phase austenite to convert to product-phase martensite,
arises from an identified entropy barrier in Fourier space. In an ageing state
of low Monte Carlo acceptances, the strain structure factor makes
constant-energy searches for rare pathways, to enter a Brillouin zone `golf
hole' enclosing negative energy states, and to suddenly release entropically
trapped stresses. In this context, a stress-dependent effective temperature can
be defined, that re-equilibrates to the quenched bath temperature.Comment: 11 pages, 12 figures. Under process with Phys. Rev. B (2015
Critical Crossover Between Yosida-Kondo Dominant Regime and Magnetic Frustration Dominant Regime in the System of a Magnetic Trimer on a Metal Surface
Quantum Monte Carlo simulations were carried out for the system of a magnetic
trimer on a metal surface. The magnetic trimer is arranged in two geometric
configurations, viz., isosceles and equilateral triangles. The calculated
spectral density and magnetic susceptibility show the existence of two phases:
Yosida-Kondo dominant phase and magnetic frustration dominant phase.
Furthermore, a critical transition between these two phases can be induced by
changing the configuration of the magnetic trimers from isosceles to
equilateral triangle.Comment: 8 pages, 4 figures; accepted for publication in J. Phys. Soc. Jp
Evolution of Magnetism in Single-Crystal Honeycomb Iridates
We report the successful synthesis of single-crystals of the layered iridate,
(NaLi)IrO, , and a thorough study of
its structural, magnetic, thermal and transport properties. The new compound
allows a controlled interpolation between NaIrO and LiIrO,
while maintaing the novel quantum magnetism of the honeycomb Ir planes.
The measured phase diagram demonstrates a dramatic suppression of the N\'eel
temperature, , at intermediate suggesting that the magnetic order in
NaIrO and LiIrO are distinct, and that at , the
compound is close to a magnetically disordered phase that has been sought after
in NaIrO and LiIrO. By analyzing our magnetic data with a
simple theoretical model we also show that the trigonal splitting, on the
Ir ions changes sign from NaIrO and LiIrO, and the
honeycomb iridates are in the strong spin-orbit coupling regime, controlled by
\jeff=1/2 moments.Comment: updated version with more dat
On supersymmetry breaking in string theory from gauge theory in a throat
We embed the supersymmetry breaking mechanism in N=1 SQCD of hep-th/0602239
in a smooth superstring theory using D-branes in the background R^4 \times
SL(2)_{k=1}/U(1) which smoothly captures the throat region of an intersecting
NS5-brane configuration. A controllable deformation of the supersymmetric
branes gives rise to the mass deformation of the magnetic SQCD theory on the
branes. The consequent instability on the open string worldsheet can be
followed onto a stable non-supersymmetric configuration of D-branes which
realize the metastable vacuum configuration in the field theory. The new brane
configuration is shown to backreact onto the background such as to produce
different boundary conditions for the string fields in the radial direction
compared to the supersymmetric configuration. In the string theory, this is
interpreted to mean that the supersymmetry breaking is explicit rather than
spontaneous.Comment: 29 pages, harvmac, 8 figures; v2 typos corrected, reference adde
Electric Dipolar Susceptibility of the Anderson-Holstein Model
The temperature dependence of electric dipolar susceptibility \chi_P is
discussed on the basis of the Anderson-Holstein model with the use of a
numerical renormalization group (NRG) technique. Note that P is related with
phonon Green's function D. In order to obtain correct temperature dependence of
P at low temperatures, we propose a method to evaluate P through the Dyson
equation from charge susceptibility \chi_c calculated by the NRG, in contrast
to the direct NRG calculation of D. We find that the irreducible charge
susceptibility estimated from \chi_c agree with the perturbation calculation,
suggesting that our method works well.Comment: 4 pages, 4 figure
Kondo Effect in an Electron System with Dynamical Jahn-Teller Impurity
We investigate how Kondo phenomenon occurs in the Anderson model dynamically
coupled with local Jahn-Teller phonons. It is found that the total angular
moment composed of electron pseudo-spin and phonon angular moments is screened
by conduction electrons. Namely, phonon degrees of freedom essentially
contribute to the formation of singlet ground state. A characteristic
temperature of the Kondo effect due to dynamical Jahn-Teller phonons is
explained by an effective - Hamiltonian with anisotropic exchange
interaction obtained from the Jahn-Teller-Anderson model in a non-adiabatic
region.Comment: 5 pages, 3 figure
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