2,659 research outputs found
Phase Transition in a One-Dimensional Extended Peierls-Hubbard Model with a Pulse of Oscillating Electric Field: II. Linear Behavior in Neutral-to-Ionic Transition
Dynamics of charge density and lattice displacements after the neutral phase
is photoexcited is studied by solving the time-dependent Schr\"odinger equation
for a one-dimensional extended Peierls-Hubbard model with alternating
potentials. In contrast to the ionic-to-neutral transition studied previously,
the neutral-to-ionic transition proceeds in an uncooperative manner as far as
the one-dimensional system is concerned. The final ionicity is a linear
function of the increment of the total energy. After the electric field is
turned off, the electronic state does not significantly change, roughly keeping
the ionicity, even if the transition is not completed, because the ionic
domains never proliferate. As a consequence, an electric field with frequency
just at the linear absorption peak causes the neutral-to-ionic transition the
most efficiently. These findings are consistent with the recent experiments on
the mixed-stack organic charge-transfer complex, TTF-CA. We artificially modify
or remove the electron-lattice coupling to discuss the origin of such
differences between the two transitions.Comment: 17 pages, 9 figure
Structure of Strange Dwarfs with Color Superconducting Core
We study effects of two-flavor color superconductivity on the structure of
strange dwarfs, which are stellar objects with similar masses and radii with
ordinary white dwarfs but stabilized by the strange quark matter core. We find
that unpaired quark matter is a good approximation to the core of strange
dwarfs.Comment: 8 pages 5 figures, J. Phys. G, accepte
High-K Precession modes: Axially symmetric limit of wobbling motion
The rotational band built on the high-K multi-quasiparticle state can be
interpreted as a multi-phonon band of the precession mode, which represents the
precessional rotation about the axis perpendicular to the direction of the
intrinsic angular momentum. By using the axially symmetric limit of the
random-phase-approximation (RPA) formalism developed for the nuclear wobbling
motion, we study the properties of the precession modes in W; the
excitation energies, B(E2) and B(M1) values. We show that the excitations of
such a specific type of rotation can be well described by the RPA formalism,
which gives a new insight to understand the wobbling motion in the triaxial
superdeformed nuclei from a microscopic view point.Comment: 14 pages, 8 figures (Spelling of the authors name was wrong at the
first upload, so it is corrected
Weyl Card Diagrams and New S-brane Solutions of Gravity
We construct a new card diagram which accurately draws Weyl spacetimes and
represents their global spacetime structure, singularities, horizons and null
infinity. As examples we systematically discuss properties of a variety of
solutions including black holes as well as recent and new time-dependent
gravity solutions which fall under the S-brane class. The new time-dependent
Weyl solutions include S-dihole universes, infinite arrays and complexified
multi-rod solutions. Among the interesting features of these new solutions is
that they have near horizon scaling limits and describe the decay of unstable
objects.Comment: 78 pages, 32 figures. v2 added referenc
A Solution for Little Hierarchy Problem and b --> s gamma
We show that all the parameters which destabilize the weak scale can be taken
around the weak scale in the MSSM without conflicting with the SM Higgs mass
bound set by LEP experiment. The essential point is that if the lightest
CP-even Higgs h in the MSSM has only a small coupling to Z boson, g_{ZZh}, LEP
cannot generate the Higgs sufficiently. In the scenario, the SM Higgs mass
bound constrains the mass of the heaviest CP-even Higgs H which has the SM like
g_{ZZH} coupling. However, it is easier to make the heaviest Higgs heavy by the
effect of off-diagonal elements of the mass matrix of the CP-even Higgs because
the larger eigenvalue of 2 times 2 matrix becomes larger by introducing
off-diagonal elements. Thus, the smaller stop masses can be consistent with the
LEP constraints. Moreover, the two excesses observed at LEP Higgs search can
naturally be explained as the signals of the MSSM Higgs h and H in this
scenario. One of the most interesting results in the scenario is that all the
Higgs in the MSSM have the weak scale masses. For example, the charged Higgs
mass should be around 130 GeV. This looks inconsistent with the lower bound
obtained by the b --> s gamma process as m_{H^\pm}>350GeV. However, we show
that the amplitude induced by the charged Higgs can naturally be compensated by
that of the chargino if we take the mass parameters by which the little
hierarchy problem can be solved. The point is that the both amplitudes have the
same order of magnitudes when all the fields in the both loops have the same
order of masses.Comment: 14 pages, 5 figures, input parameter slightly changed, figures
replaced, references correcte
Lepton Flavor Violation in SUSY GUT Model with Non-universal Sfermion Masses
We analyze lepton flavor violating and processes in SUSY GUT model in which sfermions have special mass
spectrum. It is assumed that only third generation sfermions which are
contained in of SU(5) can have a different mass from
the others. This mass spectrum is led from GUT model with horizontal
symmetries. It is shown that branching ratios of and depend strongly on a right-handed stau mass. The weak scale
stability requires the light stau, so large decay rates can be expected in this
scenario. When stau is around 150 GeV and , the branching
ratios can be larger than and , which are within reach of future
experiments. In addition, this model has an interesting feature that the final
state charged lepton tends to have the right-handed chirality.Comment: 17 pages, 12 figures, v3 a reference adde
Charge-Transfer Excitations in One-Dimensional Dimerized Mott Insulators
We investigate the optical properties of one-dimensional (1D) dimerized Mott
insulators using the 1D dimerized extended Hubbard model. Numerical
calculations and a perturbative analysis from the decoupled-dimer limit clarify
that there are three relevant classes of charge-transfer (CT) states generated
by photoexcitation: interdimer CT unbound states, interdimer CT exciton states,
and intradimer CT exciton states. This classification is applied to
understanding the optical properties of an organic molecular material,
1,3,5-trithia-2,4,6-triazapentalenyl (TTTA), which is known for its
photoinduced transition from the dimerized spin-singlet phase to the regular
paramagnetic phase. We conclude that the lowest photoexcited state of TTTA is
the interdimer CT exciton state and the second lowest state is the intradimer
CT exciton state.Comment: 6 pages, 6 figures, to be published in J. Phys. Soc. Jp
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