740 research outputs found
Convergence rate enhancement of navier-stokes codes on clustered grids
Our Sensitivity-Based Minimal Residual (SBMR) method which is based on our earlier Distributed Minimal Residual (DMR) method allows each component of the solution vector in a system of equations to have its own convergence speed. Our global SBMR method was found to consistently outperform the DMR method while requiring considerably less computer memory. Recently, we have developed and tested a new Line SBMR or LSBMR method and a Time-Step-Scaling (TSS) method that are even more robust and computationally efficient than our global SBMR method, especially on highly clustered computational grids in laminar and turbulent flow computations
Anomalous frequency and intensity scaling of collective and local modes in a coupled spin tetrahedron system
We report on the magnetic excitation spectrum of the coupled spin tetrahedral
system CuTeOCl using Raman scattering on single
crystals. The transition to an ordered state at T=18.2 K evidenced
from thermodynamic data leads to the evolution of distinct low-energy magnetic
excitations superimposed by a broad maximum. These modes are ascribed to
magnons with different degree of localization and a two-magnon continuum. Two
of the modes develop a substantial energy shift with decreasing temperature
similar to the order parameter of other Neel ordered systems. The other two
modes show only a negligible temperature dependence and dissolve above the
ordering temperature in a continuum of excitations at finite energies. These
observations point to a delicate interplay of magnetic inter- and
intra-tetrahedra degrees of freedom and an importance of singlet fluctuations
in describing a spin dynamics.Comment: 7pages, 6figures, 1tabl
Supersymmetry Breaking and Moduli Stabilization with Anomalous U(1) Gauge Symmetry
We examine the effects of anomalous U(1)_A gauge symmetry on soft
supersymmetry breaking terms while incorporating the stabilization of the
modulus-axion multiplet responsible for the Green-Schwarz (GS) anomaly
cancellation mechanism. In case of the KKLT stabilization of the GS modulus,
soft terms are determined by the GS modulus mediation, the anomaly mediation
and the U(1)_A mediation which are generically comparable to each other,
thereby yielding the mirage mediation pattern of superparticle masses at low
energy scale. Independently of the mechanism of moduli stabilization and
supersymmetry breaking, the U(1)_A D-term potential can not be an uplifting
potential for de Sitter vacuum when the gravitino mass is smaller than the
Planck scale by many orders of magnitude. We also discuss some features of the
supersymmetry breaking by red-shifted anti-brane which is a key element of the
KKLT moduli stabilization.Comment: 32 pages; references are adde
Sparticle masses in deflected mirage mediation
We discuss the sparticle mass patterns that can be realized in deflected
mirage mediation scenario of supersymmetry breaking, in which the moduli,
anomaly, and gauge mediations all contribute to the MSSM soft parameters.
Analytic expression of low energy soft parameters and also the sfermion mass
sum rules are derived, which can be used to interpret the experimentally
measured sparticle masses within the framework of the most general mixed
moduli-gauge-anomaly mediation. Phenomenological aspects of some specific
examples are also discussed.Comment: 43 pages, 17 figures, references adde
Characteristics of switching plasma in an inverse-pinch switch
Characteristics of the plasma that switches on tens of giga volt-ampere in an inverse-pinch plasma switch (INPIStron) have been made. Through optical and spectroscopic diagnostics of the current carrying plasma, the current density, the motion of current paths, dominant ionic species have been determined in order to access their effects on circuit parameters and material erosion. Also the optimum operational condition of the plasma-puff triggering method required for azimuthally uniform conduction in the INPIStron has been determined
Phenomenology of Mixed Modulus-Anomaly Mediation in Fluxed String Compactifications and Brane Models
In some string compactifications, for instance the recently proposed KKLT
set-up, light moduli are stabilized by nonperturbative effects at
supersymmetric AdS vacuum which is lifted to a dS vacuum by supersymmetry
breaking uplifting potential. In such models, soft supersymmetry breaking terms
are determined by a specific mixed modulus-anomaly mediation in which the two
mediations typically give comparable contributions to soft parameters. Similar
pattern of soft terms can arise also in brane models to stabilize the radion by
nonperturbative effects. We examine some phenomenological consequences of this
mixed modulus-anomaly mediation, including the pattern of low energy sparticle
spectrum and the possibility of electroweak symmetry breaking. It is noted that
adding the anomaly-mediated contributions at amounts to replacing the
messenger scale of the modulus mediation by a mirage messenger scale
where
for denoting the
modulus-mediated contribution to the gaugino mass at . The minimal
KKLT set-up predicts . As a consequence, for ,
the model can lead to a highly distinctive pattern of sparticle masses at TeV
scale, particularly when .Comment: 20 pages, 15 figures, some notations are changed, typos are corrected
and discussions on the CP phase from and B are adde
Gauge mediation to effective SUSY through U(1)s with a dynamical SUSY breaking, and string compactification
We investigate the possibility of U(1)' mediation, leading to an effective
SUSY where the first two family sfermions are above 100 TeV but the third
family sfermions and the Higgs doublets are in the TeV region(or the light stop
case). The U(1)' gaugino, Zprimino, needs not to be at a TeV scale, but needs
to be somewhat lighter than the messenger scale. We consider two cases, one the
mediation is only through U(1)' and the other through U(1)' and the electroweak
hypercharge U(1)_Y. In the SUSY field theory framework, we calculate the
superpartner mass spectra for these two cases. We also point out that the
particle species needed for these mechanisms are already obtained from a
Z(12-I) orbifold compactification
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