102,554 research outputs found
Genetic Exponentially Fitted Method for Solving Multi-dimensional Drift-diffusion Equations
A general approach was proposed in this article to develop high-order
exponentially fitted basis functions for finite element approximations of
multi-dimensional drift-diffusion equations for modeling biomolecular
electrodiffusion processes. Such methods are highly desirable for achieving
numerical stability and efficiency. We found that by utilizing the one-one
correspondence between continuous piecewise polynomial space of degree
and the divergence-free vector space of degree , one can construct
high-order 2-D exponentially fitted basis functions that are strictly
interpolative at a selected node set but are discontinuous on edges in general,
spanning nonconforming finite element spaces. First order convergence was
proved for the methods constructed from divergence-free Raviart-Thomas space
at two different node set
Is the meson a dynamically generated resonance? -- a lesson learned from the O(N) model and beyond
O(N) linear model is solvable in the large limit and hence
provides a useful theoretical laboratory to test various unitarization
approximations. We find that the large limit and the
limit do not commute. In order to get the correct large spectrum one has
to firstly take the large limit. We argue that the meson may
not be described as generated dynamically. On the contrary, it is most
appropriately described at the same level as the pions, i.e, both appear
explicitly in the effective lagrangian. Actually it is very likely the
meson responsible for the spontaneous chiral symmetry breaking in a lagrangian
with linearly realized chiral symmetry.Comment: 15 pages, 3 figurs; references added; discussions slightly modified;
revised version accepted by IJMP
The structural, mechanical, electronic, optical and thermodynamic properties of t-XAs (X Si, Ge and Sn) by first-principles calculations
The structural, mechanical, electronic, optical and thermodynamic properties
of the t-XAs (X Si, Ge and Sn) with
tetragonal structure have been investigated by first principles calculations.
Our calculated results show that these compounds are mechanically and
dynamically stable. By the study of elastic anisotropy, it is found that the
anisotropic of the t-SnAs is stronger than that
of t-SiAs and
t-GeAs. The band structures and density of states
show that the t-XAs (Si, Ge and Sn) are
semiconductors with narrow band gaps. Based on the analyses of electron density
difference, in t-XAs As atoms get electrons, X
atoms lose electrons. The calculated static dielectric constants,
, are 15.5, 20.0 and 15.1 eV for
t-XAs (X Si, Ge and Sn), respectively. The
Dulong-Petit limit of t-XAs is about 10 J
molK. The thermodynamic stability successively
decreases from t-SiAs to
t-GeAs to t-SnAs.Comment: 14 pages, 10 figures, 6 table
Scalars in the hadron world: the Higgs sector of the strong interaction
Scalar mesons are a key expression of the strong physics regime of QCD and
the role condensates, particularly , play in breaking chiral
symmetry.
What new insights have been provided by recent experiments on and
decays to light hadrons is discussed. We need to establish whether all
the claimed scalars , , , etc., really exist and
with what parameters before we can meaningfully speculate further about which
is transiently , , multi-meson molecule or largely
glue.Comment: 10 pages, 4 figures. Invited talk at the International Conference on
QCD and Hadronic Physics, Beijing, June 2005. A shortened version will appear
in the Proceeding
First-principles study of phenyl ethylene oligomers as current-switch
We use a self-consistent method to study the distinct current-switch of
-amino-4-ethynylphenyl-4'-ethynylphenyl-5'-nitro-1-benzenethiol, from
the first-principles calculations. The numerical results are in accord with the
early experiment [Reed et al., Sci. Am. \textbf{282}, 86 (2000)]. To further
investigate the transport mechanism, we calculate the switching behavior of
p-terphenyl with the rotations of the middle ring as well. We also study the
effect of hydrogen atom substituting one ending sulfur atom on the transport
and find that the asymmetry of I-V curves appears and the switch effect still
lies in both the positive and negative bias range.Comment: 6 pages, 6 figure
Identity of the imaginary-time and real-time thermal propagators for scalar bound states in a one-generation Nambu-Jona-Lasinio model
By rigorous reanalysis of the results, we have proven that the propagators at
finite temperature for scalar bound states in one-generation fermion condensate
scheme of electroweak symmetry breaking are in fact identical in the
imaginary-time and the real-time formalism. This dismisses the doubt about
possible discrepancy between the two formalisms in this problem. Identity of
the derived thermal transformation matrices of the real-time matrix propagators
for scalar bound states without and with chemical potential and the ones for
corresponding elementary scalar particles shows similarity of thermodynamic
property between the two types of particles. Only one former inference is
modified, i.e. when the two flavors of fermions have unequal nonzero masses,
the amplitude of the composite Higgs particle will decay instead grow in time.Comment: 5 pages, revtex4, no figure
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