23,570 research outputs found
Theory of quasiballistic transport through nanocrystalline silicon dots
A model to describe the underlying physics of high-energy electron emission from a porous silicon diode is presented. The model is based on an atomistic tight-binding method combined with semiclassical Monte Carlo simulation. It well reproduces essential features of experimental findings. An initial acceleration region is shown to play a crucial role in generating quasiballistic electron emission
Magnetic strong coupling in a spin-photon system and transition to classical regime
We study the energy level structure of the Tavis-Cumming model applied to an
ensemble of independent magnetic spins coupled to a variable number of
photons. Rabi splittings are calculated and their distribution is analyzed as a
functin of photon number and spin system size . A sharp
transition in the distribution of the Rabi frequency is found at . The width of the Rabi frequency spectrum diverges as
at this point. For increased number of photons , the Rabi
frequencies converge to a value proportional to . This
behavior is interpreted as analogous to the classical spin resonance mechanism
where the photon is treated as a classical field and one resonance peak is
expected. We also present experimental data demonstrating cooperative, magnetic
strong coupling between a spin system and photons, measured at room
temperature. This points towards quantum computing implementation with magnetic
spins, using cavity quantum-electrodynamics techniques.Comment: Received 8 April 2010; revised manuscript received 17 June 2010;
published 14 July 201
Scaling properties of the relaxation time near the mean-field spinodal
We study the relaxation processes of the infinitely long-range interaction
model (the Husimi-Temperley model) near the spinodal point. We propose a
unified finite-size scaling function near the spinodal point, including the
metastable region, the spinodal point, and the unstable region. We explicitly
adopt the Glauber dynamics, derive a master equation for the probability
distribution of the total magnetization, and perform the so-called van Kampen
Omega expansion (an expansion in terms of the inverse of the systems size),
which leads to a Fokker-Planck equation. We analyze the scaling properties of
the Fokker-Planck equation and confirm the obtained scaling plot by direct
numerical solution of the original master equation, and by kinetic Monte Carlo
simulation of the stochastic decay process.Comment: 9 pages, 3 figure
Light Scalar Mesons as Manifestation of Spontaneously Broken Chiral Symmetry
Attention is paid to the production mechanisms of light scalars that reveal
their nature. We reveal the chiral shielding of the \sigma(600) meson. We show
that the kaon loop mechanism of the \phi radiative decays, ratified by
experiment, points to the four-quark nature of light scalars. We show also that
the light scalars are produced in the two photon collisions via four-quark
transitions in contrast to the classic P wave tensor q\bar q mesons that are
produced via two-quark transitions . The history of
spontaneous breaking of symmetry in quantum physics is discussed in Appendix.Comment: Talk at The International Bogolyubov Conference "Problems of
Theoretical and Mathematical Physics" devoted to the 100th anniversary of
N.N.Bogolyubov's birth that was held from August 21 to August 22,2009 in
Moscow at the Russian Academy of Sciences (RAS) and from August 23 to August
27, 2009 in Dubna at the Joint Institute for Nuclear Research (JINR
Multi-Orbital Molecular Compound (TTM-TTP)I_3: Effective Model and Fragment Decomposition
The electronic structure of the molecular compound (TTM-TTP)I_3, which
exhibits a peculiar intra-molecular charge ordering, has been studied using
multi-configuration ab initio calculations. First we derive an effective
Hubbard-type model based on the molecular orbitals (MOs) of TTM-TTP; we set up
a two-orbital Hamiltonian for the two MOs near the Fermi energy and determine
its full parameters: the transfer integrals, the Coulomb and exchange
interactions. The tight-binding band structure obtained from these transfer
integrals is consistent with the result of the direct band calculation based on
density functional theory. Then, by decomposing the frontier MOs into two
parts, i.e., fragments, we find that the stacked TTM-TTP molecules can be
described by a two-leg ladder model, while the inter-fragment Coulomb energies
are scaled to the inverse of their distances. This result indicates that the
fragment picture that we proposed earlier [M.-L. Bonnet et al.: J. Chem. Phys.
132 (2010) 214705] successfully describes the low-energy properties of this
compound.Comment: 5 pages, 4 figures, published versio
Lightest scalar and tensor resonances in after the Belle experiment
New high statistics Belle data on the reaction
cross section measured in the range of pion-pair invariant masses
between 0.8 GeV and 1.5 GeV are analyzed to clarify the current situation
around the , , and resonances in
collisions. The present analysis shows that the direct coupling
constants of the and resonances to are
small, and the and
decays are four-quark transitions caused by the and loop
mechanisms, respectively. The chiral shielding of the resonance
takes place in the reactions as well as in
scattering. Some results of a simultaneous description of the
and Belle data are also
presented. In particular, the following tentative estimate of the
decay width is obtained:
keV.Comment: 14 pages, 5 figures. Fitted for the publication in Physical Review
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