1,761 research outputs found
Resonant-state expansion of the Green's function of open quantum systems
Our series of recent work on the transmission coefficient of open quantum
systems in one dimension will be reviewed. The transmission coefficient is
equivalent to the conductance of a quantum dot connected to leads of quantum
wires. We will show that the transmission coefficient is given by a sum over
all discrete eigenstates without a background integral. An apparent
"background" is in fact not a background but generated by tails of various
resonance peaks. By using the expression, we will show that the Fano asymmetry
of a resonance peak is caused by the interference between various discrete
eigenstates. In particular, an unstable resonance can strongly skew the peak of
a nearby resonance.Comment: 7 pages, 7 figures. Submitted to International Journal of Theoretical
Physics as an article in the Proceedings for PHHQP 2010
(http://www.math.zju.edu.cn/wjd/
Low Energy Theorems For Nucleon-Nucleon Scattering
Low energy theorems are derived for the coefficients of the effective range
expansion in s-wave nucleon-nucleon scattering valid to leading order in an
expansion in which both and (where is the scattering length)
are treated as small mass scales. Comparisons with phase shift data, however,
reveal a pattern of gross violations of the theorems for all coefficients in
both the and channels. Analogous theorems are developed for the
energy dependence parameter which describes mixing.
These theorems are also violated. These failures strongly suggest that the
physical value of is too large for the chiral expansion to be valid in
this context. Comparisons of with phenomenological scales known to
arise in the two-nucleon problem support this conjecture.Comment: 12 pages, 1 figure, 1 table; appendix added to discuss behavior in
chiral limit; minor revisions including revised figure reference to recent
work adde
Star-unitary transformations. From dynamics to irreversibility and stochastic behavior
We consider a simple model of a classical harmonic oscillator coupled to a
field. In standard approaches Langevin-type equations for {\it bare} particles
are derived from Hamiltonian dynamics. These equations contain memory terms and
are time-reversal invariant. In contrast the phenomenological Langevin
equations have no memory terms (they are Markovian equations) and give a time
evolution split in two branches (semigroups), each of which breaks time
symmetry. A standard approach to bridge dynamics with phenomenology is to
consider the Markovian approximation of the former. In this paper we present a
formulation in terms of {\it dressed} particles, which gives exact Markovian
equations. We formulate dressed particles for Poincar\'e nonintegrable systems,
through an invertible transformation operator \Lam introduced by Prigogine
and collaborators. \Lam is obtained by an extension of the canonical
(unitary) transformation operator that eliminates interactions for
integrable systems. Our extension is based on the removal of divergences due to
Poincar\'e resonances, which breaks time-symmetry. The unitarity of is
extended to ``star-unitarity'' for \Lam. We show that \Lam-transformed
variables have the same time evolution as stochastic variables obeying Langevin
equations, and that \Lam-transformed distribution functions satisfy exact
Fokker-Planck equations. The effects of Gaussian white noise are obtained by
the non-distributive property of \Lam with respect to products of dynamical
variables. Therefore our method leads to a direct link between dynamics of
Poincar\'e nonintegrable systems, probability and stochasticity.Comment: 24 pages, no figures. Made more connections with other work.
Clarified ideas on irreversibilit
Automated generation of program translation and verification tools using annotated grammars
Automatically generating program translators from source and target language specifications is a non-trivial problem. In this paper we focus on the problem of automating the process of building translators between operations languages, a family of DSLs used to program satellite operations procedures. We exploit their similarities to semi-automatically build transformation tools between these DSLs. The input to our method is a collection of annotated context-free grammars. To simplify the overall translation process even more, we also propose an intermediate representation common to all operations languages. Finally, we discuss how to enrich our annotated grammars model with more advanced semantic annotations to provide a verification system for the translation process. We validate our approach by semi-automatically deriving translators between some real world operations languages, using the prototype tool which we implemented for that purpose
Characterization of human mesothelin transcripts in ovarian and pancreatic cancer
BACKGROUND: Mesothelin is an attractive target for cancer immunotherapy due to its restricted expression in normal tissues and high level expression in several tumor types including ovarian and pancreatic adenocarcinomas. Three mesothelin transcript variants have been reported, but their relative expression in normal tissues and tumors has been poorly characterized. The goal of the present study was to clarify which mesothelin transcript variants are commonly expressed in human tumors. METHODS: Human genomic and EST nucleotide sequences in the public databases were used to evaluate sequences reported for the three mesothelin transcript variants in silico. Subsequently, RNA samples from normal ovary, ovarian and pancreatic carcinoma cell lines, and primary ovarian tumors were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and nucleotide sequencing to directly identify expressed transcripts. RESULTS: In silico comparisons of genomic DNA sequences with available EST sequences supported expression of mesothelin transcript variants 1 and 3, but there were no sequence matches for transcript variant 2. Newly-derived nucleotide sequences of RT-PCR products from tissues and cell lines corresponded to mesothelin transcript variant 1. Mesothelin transcript variant 2 was not detected. Transcript variant 3 was observed as a small percentage of total mesothelin amplification products from all studied cell lines and tissues. Fractionation of nuclear and cytoplasmic RNA indicated that variant 3 was present primarily in the nuclear fraction. Thus, mesothelin transcript variant 3 may represent incompletely processed hnRNA. CONCLUSION: Mesothelin transcript variant 1 represents the predominant mature mRNA species expressed by both normal and tumor cells. This conclusion should be important for future development of cancer immunotherapies, diagnostic tests, and gene microarray studies targeting mesothelin
The Long and Short of Nuclear Effective Field Theory Expansions
Nonperturbative effective field theory calculations for NN scattering seem to
break down at rather low momenta. By examining several toy models, we clarify
how effective field theory expansions can in general be used to properly
separate long- and short-range effects. We find that one-pion exchange has a
large effect on the scattering phase shift near poles in the amplitude, but
otherwise can be treated perturbatively. Analysis of a toy model that
reproduces 1S0 NN scattering data rather well suggests that failures of
effective field theories for momenta above the pion mass can be due to
short-range physics rather than the treatment of pion exchange. We discuss the
implications this has for extending the applicability of effective field
theories.Comment: 22 pages, 9 figures, references corrected, minor modification
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