Disputation: Sabrina Pauli
Doctoral candidate Sabrina Pauli at the Department of Mathematics, Faculty of Mathematics and Natural Sciences, is defending the thesis Computations in A1homotopy theory  Contractibility and enumerative geometry for the degree of Philosophiae Doctor.
Doctoral candidate Sabrina Pauli
The University of Oslo is partially closed. The PhD defence and trial lecture will therefore be fully digital and streamed directly using Zoom. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation.
Ex auditorio questions: the chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking 'Participants > Raise hand'.

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The meeting opens for participation just before the disputation starts, and closes for new participants approximately 15 minutes after the defence has begun.
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Trial lecture
16th September, 10:15, Zoom
"The Milnor Conjecture"

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The meeting opens for participation just before 10:15 (a.m.) and closes for new participants approximately 15 minutes after the trial lecture has begun.
Main research findings
The zero set of a degree 3 polynomial in 3 variables is a surface. Already in 1849 Cayley and Salmon
showed that on such a surface there are in general 27 lines. In algebraic geometry one studies those geometric spaces that are the zero sets of polynomials in several variables, called algebraic varieties.
Homotopy theory studies geometric spaces up to continuous deformations called homotopies. For example a disc can be deformed to a point. One calls such shapes that can be deformed to a point, contractible. An annulus is not contractible because it has a hole. To a homotopy theorist it looks like a circle.
My thesis work is in the area of A1homotopy theory which combines the two fields, algebraic geometry and homotopy theory. More precisely, in A1homotopy theory we study algebraic varieties up to deformations. This yields new ways to study geometric questions as the following example shows.
The count of 27 lines is only true when one uses the complex numbers. There could for example only be 3 lines when one works with the real numbers, while to find the other 24, one needs the imaginary numbers. Techniques from A1homotopy theory yield a new way to refine such geometric counts and get information over fields other than the complex numbers, for example the real or rational numbers.
In my thesis work, I provide several refinements of classical geometric counts, in particular the count of lines on a quintic threefold for which I introduce a refined version of dynamic intersection theory. Furthermore, I provide new methods to construct examples of A1contractible varieties, that is, algebraic varieties that can be deformed to a single point.