29,567 research outputs found
A strongly polynomial algorithm for generalized flow maximization
A strongly polynomial algorithm is given for the generalized flow
maximization problem. It uses a new variant of the scaling technique, called
continuous scaling. The main measure of progress is that within a strongly
polynomial number of steps, an arc can be identified that must be tight in
every dual optimal solution, and thus can be contracted. As a consequence of
the result, we also obtain a strongly polynomial algorithm for the linear
feasibility problem with at most two nonzero entries per column in the
constraint matrix.Comment: minor correction
Aspects of Bifurcation Theory for Piecewise-Smooth, Continuous Systems
Systems that are not smooth can undergo bifurcations that are forbidden in
smooth systems. We review some of the phenomena that can occur for
piecewise-smooth, continuous maps and flows when a fixed point or an
equilibrium collides with a surface on which the system is not smooth. Much of
our understanding of these cases relies on a reduction to piecewise linearity
near the border-collision. We also review a number of codimension-two
bifurcations in which nonlinearity is important.Comment: pdfLaTeX, 9 figure
On the moduli space of elliptic Maxwell-Chern-Simons theories
We analyze the moduli space of the low-energy limit of 3-dimensional N=3
Maxwell-Chern-Simons theories described by circular quiver diagrams, as for
4-dimensional elliptic models. We define the theories by using
D3-NS5-(k,1)5-brane systems with an arbitrary number of fivebranes. The
supersymmetry is expected to be enhanced to N=4 in the low-energy limit. We
show that the Higgs branch, in which all bifundamental scalar fields develop
vacuum expectation values, is an abelian orbifold of C^4. We confirm that the
same geometry is obtained as an M-theory dual of the brane system. We also
consider theories realized by introducing more than two kinds of fivebranes,
and obtain nontoric fourfolds as moduli spaces.Comment: 15 pages, 4 figures; published versio
Flavour from partially resolved singularities
In this letter we study topological open string field theory on D--branes in
a IIB background given by non compact CY geometries on with a singular point at which an extra fiber sits. We wrap
D5-branes on and effective D3-branes at singular points, which
are actually D5--branes wrapped on a shrinking cycle. We calculate the
holomorphic Chern-Simons partition function for the above models in a deformed
complex structure and find that it reduces to multi--matrix models with
flavour. These are the matrix models whose resolvents have been shown to
satisfy the generalized Konishi anomaly equations with flavour. In the
case, corresponding to a partial resolution of the singularity, the
quantum superpotential in the unitary SYM with one adjoint and
fundamentals is obtained. The case is also studied and shown to give rise
to two--matrix models which for a particular set of couplings can be exactly
solved. We explicitly show how to solve such a class of models by a quantum
equation of motion technique
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