M. S. Ravi | Search arXiv

arXiv2000

Output Feedback Invariants

The paper is concerned with the problem of determining a complete set of invariants for output feedback. Using tools from geometric invariant theory it is shown that there exists a quasi-projective variety whose points parameterize the output feedback orbits in a unique way. If the McMillan degree $n\geq mp$, the product of number of inputs and number of outputs, then it is shown that in the closure of every feedback orbit there is exactly one nondegenerate system.

math.OC↗

arXiv1994

Degree of the generalized Plücker embedding of a Quot scheme and Quantum cohomology

We compute the degree of the generalized Plücker embedding $κ$ of a Quot scheme $X$ over $\PP^1$. The space $X$ can also be considered as a compactification of the space of algebraic maps of a fixed degree from $\PP^1$ to the Grassmanian $\rm{Grass}(m,n)$. Then the degree of the embedded variety $κ(X)$ can be interpreted as an intersection product of pullbacks of cohomology classes from $\rm{Grass}(m,n)$ through the map $ψ$ that evaluates a map from $\PP^1$ at a point $x\in \PP^1$. We show that our formula for the degree verifies the formula for these intersection products predicted by physicists through Quantum cohomology~\cite{va92}~\cite{in91}~\cite{wi94}. We arrive at the degree by proving a version of the classical Pieri's formula on the variety $X$, using a cell decomposition of a space that lies in between $X$ and $κ(X)$.

alg-geom↗