10,232 research outputs found
On duality relations for session types
Session types are a type formalism used to describe communication protocols over private session channels. Each participant in a binary session owns one endpoint of a session channel. A key notion is that of duality: the endpoints of a session channel should have dual session types in order to guarantee communication safety. Duality relations have been independently defined in different ways and different works, without considering their effect on the type system. In this paper we systematically study the existing duality relations and some new ones, and compare them in order to understand their expressiveness. The outcome is that those relations are split into two groups, one related to the na¨ıve inductive duality, and the other related to a notion of mutual compliance, which we borrow from the literature on contracts for web-services
Information criteria for efficient quantum state estimation
Recently several more efficient versions of quantum state tomography have
been proposed, with the purpose of making tomography feasible even for
many-qubit states. The number of state parameters to be estimated is reduced by
tentatively introducing certain simplifying assumptions on the form of the
quantum state, and subsequently using the data to rigorously verify these
assumptions. The simplifying assumptions considered so far were (i) the state
can be well approximated to be of low rank, or (ii) the state can be well
approximated as a matrix product state. We add one more method in that same
spirit: we allow in principle any model for the state, using any (small) number
of parameters (which can, e.g., be chosen to have a clear physical meaning),
and the data are used to verify the model. The proof that this method is valid
cannot be as strict as in above-mentioned cases, but is based on
well-established statistical methods that go under the name of "information
criteria." We exploit here, in particular, the Akaike Information Criterion
(AIC). We illustrate the method by simulating experiments on (noisy) Dicke
states
Far-Ultraviolet and Far-Infrared Bivariate Luminosity Function of Galaxies: Complex Relation between Stellar and Dust Emission
Far-ultraviolet (FUV) and far-infrared (FIR) luminosity functions (LFs) of
galaxies show a strong evolution from to , but the FIR LF
evolves much stronger than the FUV one. The FUV is dominantly radiated from
newly formed short-lived OB stars, while the FIR is emitted by dust grains
heated by the FUV radiation field. It is known that dust is always associated
with star formation activity. Thus, both FUV and FIR are tightly related to the
star formation in galaxies, but in a very complicated manner. In order to
disentangle the relation between FUV and FIR emissions, we estimate the UV-IR
bivariate LF (BLF) of galaxies with {\sl GALEX} and {\sl AKARI} All-Sky Survey
datasets. Recently we invented a new mathematical method to construct the BLF
with given marginals and prescribed correlation coefficient. This method makes
use of a tool from mathematical statistics, so called "copula". The copula
enables us to construct a bivariate distribution function from given marginal
distributions with prescribed correlation and/or dependence structure. With
this new formulation and FUV and FIR univariate LFs, we analyze various FUV and
FIR data with {\sl GALEX}, {\sl Spitzer}, and {\sl AKARI} to estimate the UV-IR
BLF. The obtained BLFs naturally explain the nonlinear complicated relation
between FUV and FIR emission from star-forming galaxies. Though the faint-end
of the BLF was not well constrained for high- samples, the estimated linear
correlation coefficient was found to be very high, and is remarkably
stable with redshifts (from 0.95 at to 0.85 at ). This implies
the evolution of the UV-IR BLF is mainly due to the different evolution of the
univariate LFs, and may not be controlled by the dependence structure.Comment: 10 pages, 7 figures, Earth, Planets and Space, in pres
Quantum Kelvin-Helmholtz instability in phase-separated two-component Bose-Einstein condensates
We theoretically study the Kelvin-Helmholtz instability in phase-separated
two-component Bose-Einstein condensates using the Gross-Pitaevskii and
Bogoliubov-de Gennes models. A flat interface between the two condensates is
shown to deform into sawtooth or Stokes-like waves, leading to the formation of
singly quantized vortices on the peaks and troughs of the waves. This scenario
of interface instability in quantum fluids is quite different from that in
classical fluids.Comment: 5 pages, 4 figure
Error Estimates on Parton Density Distributions
Error estimates on parton density distributions are presently based on the
traditional method of least squares minimisation and linear error propagation
in global QCD fits. We review the underlying assumptions and the various
mathematical representations of the method and address some technical issues
encountered in such a global analysis. Parton distribution sets which contain
error information are described.Comment: Latex, 12 pages, 5 figures. Needs iopart.cls and iopart12.clo.
Presented at New Trends in HERA Physics 2001, Ringberg Castle, Tegernsee,
Germany, June 17-22, 200
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