654 research outputs found
A molecular dynamics computer simulation study of room-temperature ionic liquids. I. Equilibrium solvation structure and free energetics
Solvation in 1-ethyl-3-methylmidazolium chloride and in
1-ethyl-3-methylimidazolium hexafluorophosphate near equilibrium is
investigated via molecular dynamics computer simulations with diatomic and
benzenelike molecules employed as probe solutes. It is found that
electrostriction plays an important role in both solvation structure and free
energetics. The angular and radial distributions of cations and anions become
more structured and their densities near the solute become enhanced as the
solute charge separation grows. Due to the enhancement in structural rigidity
induced by electrostriction, the force constant associated with solvent
configuration fluctuations relevant to charge shift and transfer processes is
also found to increase. The effective polarity and reorganization free energies
of these ionic liquids are analyzed and compared with those of highly polar
acetonitrile. Their screening behavior of electric charges is also
investigated.Comment: 12 page
Gauge coupling renormalization in orbifold field theories
We investigate the gauge coupling renormalization in orbifold field theories
preserving 4-dimensional N=1 supersymmetry in the framework of 4-dimensional
effective supergravity. As a concrete example, we consider the 5-dimensional
Super-Yang-Mills theory on a slice of AdS_5. In our approach, one-loop gauge
couplings can be determined by the loop-induced axion couplings and the tree
level properties of 4-dimensional effective supergravity which are much easier
to be computed.Comment: 18 pages, JHEP style; 1-loop corrections to gauge kinetic functions
are fully computed, references are adde
Patterning of ferroelectric nanodot arrays using a silicon nitride shadow mask
We grew well-ordered arrays of ferroelectric Pb (Zr0.2 Ti0.8) O3 (PZT) nanodots on a SrRu O3 SrTi O3 substrate by pulsed laser deposition. A silicon nitride shadow mask with ordered holes was used for patterning of the PZT arrays. Each dot has a height of ???15 nm and a diameter of ???120 nm with a similar dome shape over a large area. The ferroelectric properties of individual PZT dots were investigated by piezoresponse force microscopy. A single dot could be polarized individually and the polarized state remained unrelaxed to ???20 min.open232
1/f spectrum and memory function analysis of solvation dynamics in a room-temperature ionic liquid
To understand the non-exponential relaxation associated with solvation
dynamics in the ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate,
we study power spectra of the fluctuating Franck-Condon energy gap of a
diatomic probe solute via molecular dynamics simulations. Results show 1/f
dependence in a wide frequency range over 2 to 3 decades, indicating
distributed relaxation times. We analyze the memory function and solvation time
in the framework of the generalized Langevin equation using a simple model
description for the power spectrum. It is found that the crossover frequency
toward the white noise plateau is directly related to the time scale for the
memory function and thus the solvation time. Specifically, the low crossover
frequency observed in the ionic liquid leads to a slowly-decaying tail in its
memory function and long solvation time. By contrast, acetonitrile
characterized by a high crossover frequency and (near) absence of 1/f behavior
in its power spectra shows fast relaxation of the memory function and
single-exponential decay of solvation dynamics in the long-time regime.Comment: 10 pages, 4 figure
Radius-dependent gauge unification in AdS5
We examine the relation of the 4-dimensional low energy coupling of bulk
gauge boson in a slice of AdS5 to the 5-dimensional fundamental couplings as a
function of the orbifold radius R. This allows us to address the gauge coupling
unification in AdS5 by means of the radius running as well as the conventional
momentum running. We then compute the radius dependence of 1-loop low energy
couplings in generic AdS5 theory with 4-dimensional supersymmetry, and discuss
the low energy predictions when the 5-dimensional couplings are assumed to be
unified.Comment: 11 pages, 2 figures, revtex, v3: analysis was generalized to
S^1/Z_2*Z_2 orbifoldin
TeV scale 5D unification and the fixed point anomaly cancellation with chiral split multiplets
A possibility of 5D gauge unification of in
is examined. The orbifold compactification allows fixed points where
representations can be assigned. We present a few
possibilities which give long proton lifetime, top-bottom mass hierarchy from
geometry, and reasonable neutrino masses. In general, these {\it chiral models}
can lead to fixed point anomalies. We can show easily, due to the simplicity of
the model, that these anomalies are cancelled by the relevant Chern-Simons
terms for all the models we consider. It is also shown that the fixed point
U(1)--graviton--graviton anomaly cancels without the help from the Chern-Simons
term. Hence, we conjecture that the fixed point anomalies can be cancelled if
the effective 4D theory is made anomaly free by locating chiral fermions at the
fixed points.Comment: LaTeX file of 19 pages with 1 figur
Mixed Bino-Wino-Higgsino Dark Matter in Gauge Messenger Models
Almost degenerate bino and wino masses at the weak scale is one of unique
features of gauge messenger models. The lightest neutralino is a mixture of
bino, wino and higgsino and can produce the correct amount of the dark matter
density if it is the lightest supersymmetric particle. Furthermore, as a result
of squeezed spectrum of superpartners which is typical for gauge messenger
models, various co-annihilation and resonance regions overlap and very often
the correct amount of the neutralino relic density is generated as an interplay
of several processes. This feature makes the explanation of the observed amount
of the dark matter density much less sensitive to fundamental parameters. We
calculate the neutralino relic density assuming thermal history and present
both spin independent and spin dependent cross sections for the direct
detection. We also discuss phenomenological constraints from b to s gamma and
muon g-2 and compare results of gauge messenger models to well known results of
the mSUGRA scenario.Comment: 27 pages, 9 figures, references added, version to appear at JCA
Dynamical solution to the problem at TeV scale
We introduce a new confining force (\mu-color) at TeV scale to dynamically
generate a supersymmetry preserving mass scale which would replace the \mu
parameter in the minimal supersymmetric standard model (MSSM). We discuss the
Higgs phenomenology and also the pattern of soft supersymmetry breaking
parameters allowing the correct electroweak symmetry breaking within the
\mu-color model, which have quite distinctive features from the MSSM and also
from other generalizations of the MSSM.Comment: 12 pages, REVte
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