2,118 research outputs found
07021 Abstracts Collection -- Symmetric Cryptography
From .. to .., the Dagstuhl Seminar 07021 ``Symmetric Cryptography\u27\u27 automatically
was held in the International Conference and Research Center (IBFI),
Schloss Dagstuhl.
During the seminar, several participants presented their current
research, and ongoing work and open problems were discussed. Abstracts of
the presentations given during the seminar as well as abstracts of
seminar results and ideas are put together in this paper. The first section
describes the seminar topics and goals in general.
Links to extended abstracts or full papers are provided, if available
Levelable Sets and the Algebraic Structure of Parameterizations
Asking which sets are fixed-parameter tractable for a given parameterization
constitutes much of the current research in parameterized complexity theory.
This approach faces some of the core difficulties in complexity theory. By
focussing instead on the parameterizations that make a given set
fixed-parameter tractable, we circumvent these difficulties. We isolate
parameterizations as independent measures of complexity and study their
underlying algebraic structure. Thus we are able to compare parameterizations,
which establishes a hierarchy of complexity that is much stronger than that
present in typical parameterized algorithms races. Among other results, we find
that no practically fixed-parameter tractable sets have optimal
parameterizations
Quantum randomness and value indefiniteness
As computability implies value definiteness, certain sequences of quantum
outcomes cannot be computable.Comment: 13 pages, revise
Exact solutions and superposition rules for Hamiltonian systems generalizing stochastic SIS epidemic models with variable infection rates
Using the theory of Lie-Hamilton systems, formal generalized stochastic
Hamiltonian systems that enlarge a recently proposed stochastic SIS epidemic
model with a variable infection rate are considered. It is shown that,
independently on the particular interpretation of the time-dependent
coefficients, these systems generally admit an exact solution, up to the case
of the maximal extension within the classification of Lie-Hamilton systems, for
which a superposition rule is constructed. The method provides the algebraic
frame to which any SIS epidemic model that preserves the above mentioned
properties is subjected. In particular, we obtain exact solutions for
generalized SIS Hamitonian models based on the book and oscillator algebras,
denoted respectively by and . The last
generalization corresponds to a SIS system possessing the so-called two-photon
algebra symmetry , according to the embedding chain
, for which an
exact solution cannot generally be found, but a nonlinear superposition rule is
explicitly given.Comment: 24 page
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