1,612 research outputs found
Coherent states, Path integral, and Semiclassical approximation
Using the generalized coherent states we argue that the path integral
formulae for and (in the discrete series) are WKB exact,if
the starting point is expressed as the trace of with
being given by a linear combination of generators. In our case,WKB
approximation is achieved by taking a large ``spin'' limit: . The result is obtained directly by knowing that the each coefficient
vanishes under the () expansion and is examined by another
method to be legitimated. We also point out that the discretized form of path
integral is indispensable, in other words, the continuum path integral
expression leads us to a wrong result. Therefore a great care must be taken
when some geometrical action would be adopted, even if it is so beautiful, as
the starting ingredient of path integral.Comment: latex 33 pages and 2 figures(uuencoded postscript file),
KYUSHU-HET-19 We have corrected the proof of the WKB-exactness in the section
Exchange Gate on the Qudit Space and Fock Space
We construct the exchange gate with small elementary gates on the space of
qudits, which consist of three controlled shift gates and three "reverse"
gates. This is a natural extension of the qubit case.
We also consider a similar subject on the Fock space, but in this case we
meet with some different situation. However we can construct the exchange gate
by making use of generalized coherent operator based on the Lie algebra su(2)
which is a well--known method in Quantum Optics. We moreover make a brief
comment on "imperfect clone".Comment: Latex File, 12 pages. I could solve the problems in Sec. 3 in the
preceding manuscript, so many corrections including the title were mad
SBML models and MathSBML
MathSBML is an open-source, freely-downloadable Mathematica package that facilitates working with Systems Biology Markup Language (SBML) models. SBML is a toolneutral,computer-readable format for representing models of biochemical reaction networks, applicable to metabolic networks, cell-signaling pathways, genomic regulatory networks, and other modeling problems in systems biology that is widely supported by the systems biology community. SBML is based on XML, a standard medium for representing and transporting data that is widely supported on the internet as well as in computational biology and bioinformatics. Because SBML is tool-independent, it enables model transportability, reuse, publication and survival. In addition to MathSBML, a number of other tools that support SBML model examination and manipulation are provided on the sbml.org website, including libSBML, a C/C++ library for reading SBML models; an SBML Toolbox for MatLab; file conversion programs; an SBML model validator and visualizer; and SBML specifications and schemas. MathSBML enables SBML file import to and export from Mathematica as well as providing an API for model manipulation and simulation
Thermoelectric properties of the layered Pd oxide R_2PdO_4 (R = La, Nd, Sm and Gd)
We prepared polycrystalline samples of RPdO (R = La, Nd, Sm and Gd)
using a NaCl-flux technique. The measured resistivity is of the order of
10 cm at room temperature, which is two orders of magnitude
smaller than the values reported so far. We further studied the substitution
effects of Ce for Nd in NdCePdO, where the substituted Ce
decreases the resistivity and the magnitude of the thermopower. The activation
energy gap of 70-80 meV and the effective mass of 15 evaluated from the
measured data are suitable for thermoelectric materials, but the mobility of
10 cm/Vs is much lower than a typical value of 1-10 cm/Vs for
other thermoelectric oxides.Comment: 5 pages, 5 figures, to appear in J. Phys. Soc. Jp
Splay states in finite pulse-coupled networks of excitable neurons
The emergence and stability of splay states is studied in fully coupled
finite networks of N excitable quadratic integrate-and-fire neurons, connected
via synapses modeled as pulses of finite amplitude and duration. For such
synapses, by introducing two distinct types of synaptic events (pulse emission
and termination), we were able to write down an exact event-driven map for the
system and to evaluate the splay state solutions. For M overlapping post
synaptic potentials the linear stability analysis of the splay state should
take in account, besides the actual values of the membrane potentials, also the
firing times associated to the M previous pulse emissions. As a matter of fact,
it was possible, by introducing M complementary variables, to rephrase the
evolution of the network as an event-driven map and to derive an analytic
expression for the Floquet spectrum. We find that, independently of M, the
splay state is marginally stable with N-2 neutral directions. Furthermore, we
have identified a family of periodic solutions surrounding the splay state and
sharing the same neutral stability directions. In the limit of -pulses,
it is still possible to derive an event-driven formulation for the dynamics,
however the number of neutrally stable directions, associated to the splay
state, becomes N. Finally, we prove a link between the results for our system
and a previous theory [Watanabe and Strogatz, Physica D, 74 (1994), pp. 197-
253] developed for networks of phase oscillators with sinusoidal coupling.Comment: 27 pages, 12 Figures, submitted to SIAM Journal on Applied Dynamical
Systems (SIADS
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