Felice Ronga

All-sky search of NAUTILUS data

A search for periodic gravitational-wave signals from isolated neutron stars in the NAUTILUS detector data is presented. We have analyzed half a year of data over the frequency band � 922.2; 923.2� Hz, the spindown range �− 1.463 × 10 −8 ; 0� Hz/s and over the entire sky. We have divided the data into two day stretches and we have analyzed each stretch coherently using matched filtering. We have imposed a low threshold for the optimal detection statistic to obtain a set of candidates that are further examined for coincidences among various data stretches. For some candidates we have also investigated the change of the signal-to-noise ratio when we increase the observation time from 2 to 4 days. Our analysis has not revealed any gravitational-wave signals. Therefore we have imposed upper limits on the dimensionless gravitationalwave amplitude over the parameter space that we have searched. Depending on frequency, our upper limit ranges from 3.4 × 10 −23 to 1.3 × 10 −22 .W e haveA search for periodic gravitational-wave signals from isolated neutron stars in the NAUTILUS detector data is presented. We have analyzed half a year of data over the frequency band � 922.2; 923.2� Hz, the spindown range �− 1.463 × 10 −8 ; 0� Hz/s and over the entire sky. We have divided the data into two day stretches and we have analyzed each stretch coherently using matched filtering. We have imposed a low threshold for the optimal detection statistic to obtain a set of candidates that are further examined for coincidences among various data stretches. For some candidates we have also investigated the change of the signal-to-noise ratio when we increase the observation time from 2 to 4 days. Our analysis has not revealed any gravitational-wave signals. Therefore we have imposed upper limits on the dimensionless gravitationalwave amplitude over the parameter space that we have searched. Depending on frequency, our upper limit ranges from 3.4 × 10 −23 to 1.3 × 10 −22 .W e have

Diffeomorfismi birazionali del piano proiettivo reale

We study real birational transformations of the real projective plane which are diffeomorphisms. It turns out that their degree must be congruent to 1 mod 4, and that they are generated by linear automorphisms and transformations of degree 5 centred at 3 pairs of conjugated imaginary points. Our approach is inspired by recent proofs of the classical theorem of Noether and Castelnuovo that use the Sarkisov program

A real Riemann-Hurwitz theorem

We prove a real version of the Riemann-Hurwitz theorem and apply it to solve a problem of enumerative geometry in the real case: the number of plane projective curves tangent to a line and passing through the appropriate number of points.

On open real polynomial maps

We study open polynomial maps from Iw” to Iw “. For n = p we give a complete characterization, and for p = 2, n 2 3 we obtain some partial information.

Felix Klein's paper on real flexes vindicated

In a paper written in 1876 [4], Felix Klein gave a formula relating the number of real flexes of a generic real plane projective curve to the number of real bitangents at non-real points and the degree, which shows in particular that the number of real flexes cannot exceed one third of the total number of flexes. We show that Klein’s arguments can be made rigorous using a little of the theory of singularities of maps, justifying in particular his resort to explicit examples. 0. Introduction. Recently, there has been a renewed interest for enumerative problems over the reals in algebraic geometry [1], which were abandoned after a few attempts by the founders of modern algebraic geometry. In general, in algebraic geometry, the number of solutions of an enumerative problem over the reals is bounded by the number of solutions over the complex. So, two natural questions arise: 1) Is it possible to arrange that all the solutions are real? If it is the case, the problem is called fully real in [6]. 2) Which intermediate number of solutions can be obtained?