19,356 research outputs found
The ordered K-theory of a full extension
Let A be a C*-algebra with real rank zero which has the stable weak
cancellation property. Let I be an ideal of A such that I is stable and
satisfies the corona factorization property. We prove that 0->I->A->A/I->0 is a
full extension if and only if the extension is stenotic and K-lexicographic. As
an immediate application, we extend the classification result for graph
C*-algebras obtained by Tomforde and the first named author to the general
non-unital case. In combination with recent results by Katsura, Tomforde, West
and the first author, our result may also be used to give a purely
K-theoretical description of when an essential extension of two simple and
stable graph C*-algebras is again a graph C*-algebra.Comment: Version IV: No changes to the text. We only report that Theorem 4.9
is not correct as stated. See arXiv:1505.05951 for more details. Since
Theorem 4.9 is an application to the main results of the paper, the main
results of this paper are not affected by the error. Version III comments:
Some typos and errors corrected. Some references adde
Probing dipole-forbidden autoionizing states by isolated attosecond pulses
We propose a general technique to retrieve the information of
dipole-forbidden resonances in the autoionizing region. In the simulation, a
helium atom is pumped by an isolated attosecond pulse in the extreme
ultraviolet (EUV) combined with a few-femtosecond laser pulse. The excited wave
packet consists of the , , and states, including the background
continua, near the doubly excited state. The resultant electron
spectra with various laser intensities and time delays between the EUV and
laser pulses are obtained by a multilevel model and an ab initio time-dependent
Schr\"odinger equation calculation. By taking the ab initio calculation as a
"virtual measurement", the dipole-forbidden resonances are characterized by the
multilevel model. We found that in contrast to the common assumption, the
nonresonant coupling between the continua plays a significant role in the
time-delayed electron spectra, which shows the correlation effect between
photoelectrons before they leave the core. This technique takes the advantages
of ultrashort pulses uniquely and would be a timely test for the current
attosecond technology.Comment: 10 pages, 6 figure
Quark Coalescence with Quark Number Conservation and the Effect on Quark-Hadron Scaling
We develop a new formulation of the quark coalescence model by including the
quark number conservation in order to describe the hadronization of the bulk of
the quark-gluon plasma. The scalings between hadron and quark phase space
distributions are shown to depend on the transverse momentum. For hard quarks,
our general scalings reproduce the usual quadratic scaling relation for mesons
and the cubic scaling relation for baryons. For softer quarks, however, the
inclusion of the quark number conservation leads to a linear scaling for the
hadron species that dominates the quark number of each flavor, while the
scalings of non-dominant hadrons depend on the coalescence dynamics. For charm
mesons, we find that the distribution of soft mesons does not depend on the
light quark distribution but the distribution of soft mesons is
inversely correlated to the light quark distribution.Comment: Added 6 more equations to explain the derivations; added discussions;
final published versio
The Transmission Property of the Discrete Heisenberg Ferromagnetic Spin Chain
We present a mechanism for displaying the transmission property of the
discrete Heisenberg ferromagnetic spin chain (DHF) via a geometric approach. By
the aid of a discrete nonlinear Schr\"odinger-like equation which is the
discrete gauge equivalent to the DHF, we show that the determination of
transmitting coefficients in the transmission problem is always bistable. Thus
a definite algorithm and general stochastic algorithms are presented. A new
invariant periodic phenomenon of the non-transmitting behavior for the DHF,
with a large probability, is revealed by an adoption of various stochastic
algorithms.Comment: 16 pages, 7 figure
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