Random systems of polynomial equations. The expected number of roots under smooth analysis.
Diego Armentano and Mario Wschebor
2009
We consider random systems of equations over the reals, with m equations and m unknowns P_i(t) + X_i(t) = 0, t 2 Rm, i = 1...m, where the P_i's are non-random polynomials having degrees d_i's (the "signal") and the X_i's (the "noise") are indepen- dent real-valued Gaussian centered random polynomial fields defined on R^m, with a probability law satisfying some invariance properties. For each i, P_ i and X_ i have degree d_ i. The problem is the behavior of the number of roots for large m. We prove that under specified conditions on the relation signal over noise, which imply that in a certain sense this relation is neither too large nor too small, it follows that the quotient between the expected value of the number of roots of the perturbed system and the expected value corresponding to the centered system (i.e. P_i identically zero for all i = 1...m), tends to zero geometrically fast as m tends to in¯nity. In particular, this means that the behavior of this expected value, is governed by the noise part.
Bernoulli
1
249-266
DOI http://dx.doi.org/10.3150/08-BEJ149
Febrero
Mario Wschebor: In memoriam
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