5,054 research outputs found
Bounding Stochastic Dependence, Complete Mixability of Matrices, and Multidimensional Bottleneck Assignment Problems
We call a matrix completely mixable if the entries in its columns can be
permuted so that all row sums are equal. If it is not completely mixable, we
want to determine the smallest maximal and largest minimal row sum attainable.
These values provide a discrete approximation of of minimum variance problems
for discrete distributions, a problem motivated by the question how to estimate
the -quantile of an aggregate random variable with unknown dependence
structure given the marginals of the constituent random variables. We relate
this problem to the multidimensional bottleneck assignment problem and show
that there exists a polynomial -approximation algorithm if the matrix has
only columns. In general, deciding complete mixability is
-complete. In particular the swapping algorithm of Puccetti et
al. is not an exact method unless . For a
fixed number of columns it remains -complete, but there exists a
PTAS. The problem can be solved in pseudopolynomial time for a fixed number of
rows, and even in polynomial time if all columns furthermore contain entries
from the same multiset
Dynamics on resonant clusters for the quintic non linear Schr\"odinger equation
We construct solutions to the quintic nonlinear Schr\"odinger equation on the
circle with initial conditions supported on arbitrarily many different resonant
clusters. This is a sequel of a work of Beno\^it Gr\'ebert and the second
author.Comment: 11 page
Growth of Sobolev norms for the quintic NLS on
We study the quintic Non Linear Schr\"odinger equation on a two dimensional
torus and exhibit orbits whose Sobolev norms grow with time. The main point is
to reduce to a sufficiently simple toy model, similar in many ways to the one
used in the case of the cubic NLS. This requires an accurate combinatorial
analysis.Comment: 41 pages, 5 figures. arXiv admin note: text overlap with
arXiv:0808.1742 by other author
Logic Integer Programming Models for Signaling Networks
We propose a static and a dynamic approach to model biological signaling
networks, and show how each can be used to answer relevant biological
questions. For this we use the two different mathematical tools of
Propositional Logic and Integer Programming. The power of discrete mathematics
for handling qualitative as well as quantitative data has so far not been
exploited in Molecular Biology, which is mostly driven by experimental
research, relying on first-order or statistical models. The arising logic
statements and integer programs are analyzed and can be solved with standard
software. For a restricted class of problems the logic models reduce to a
polynomial-time solvable satisfiability algorithm. Additionally, a more dynamic
model enables enumeration of possible time resolutions in poly-logarithmic
time. Computational experiments are included
Theory of sub-10 fs Generation in Kerr-lens Mode-locked Solid-State Lasers with a Coherent Semiconductor Absorber
The results of the study of ultra-short pulse generation in continuous-wave
Kerr-lens mode-locked (KLM) solid-state lasers with semiconductor saturable
absorbers are presented. The issues of extremely short pulse generation are
addressed in the frames of the theory that accounts for the coherent nature of
the absorber-pulse interaction. We developed an analytical model that bases on
the coupled generalized Landau-Ginzburg laser equation and Bloch equations for
a coherent absorber. We showed, that in the absence of KLM semiconductor
absorber produces 2pi - non-sech-pulses of self-induced transparency, while the
KLM provides an extremely short sech-shaped pulse generation. 2pi- and
pi-sech-shaped solutions and variable-area chirped pulses have been found. It
was shown, that the presence of KLM removes the limitation on the minimal
modulation depth in absorber. An automudulational stability and self-starting
ability were analyzed, too.Comment: revised version, 18 pages, 6 figures, LaTeX, Maple program is
available on http://www.geocities.com/optomaple
Controllability of quasi-linear Hamiltonian NLS equations
We prove internal controllability in arbitrary time, for small data, for
quasi-linear Hamiltonian NLS equations on the circle. We use a procedure of
reduction to constant coefficients up to order zero and HUM method to prove the
controllability of the linearized problem. Then we apply a
Nash-Moser-H\"ormander implicit function theorem as a black box
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