Ljiljana Primorac Gajčić
Senior Assistant Department of Mathematics Josip Juraj Strossmayer University of Osijek Trg Ljudevita Gaja 6 Osijek, HR31000, Croatia¸

Research Interests
 PseudoRiemannian Geometry
 Differential Geometry
Degrees
 PhD in theoretical mathematics, Department of Mathematics, University of Zagreb , 2016.
 BSc in Mathematics and Computer Science, Department of Mathematics, University of Osijek, Croatia, 2007.
Publications
Journal Publications
 Lj. Primorac Gajčić, Ž. MilinŠipuš, I. Protrka, Null scrolls with prescribed curvatures in LorentzMinkowski 3space, Analele Stiintifice ale Universitatii Ovidius Constanta Seria Matematica (2020), prihvaćen za objavljivanje
 R. Lopez, Ž. MilinŠipuš, Lj. Primorac Gajčić, I. Protrka, Harmonic evolutes of Bscrolls with constant mean curvature in Lorentz–Minkowski space, International Journal of Geometric Methods in Modern Physics 16/5 (2019)
 Ž. MilinŠipuš, Lj. Primorac Gajčić, Minding isometries of ruled surfaces in LorentzMinkowski space, Rad HAZU, Matematičke znanosti. 23 (2019), 107122
 Ž. MilinŠipuš, Lj. Primorac Gajčić, I. Protrka, Null scrolls as Bscrolls in LorentzMinkowski 3space, Turkish Journal of Mathematics 43/6 (2019), 29082920Null scrolls, i.e. ruled surfaces whose base curve and rulings are both lightlike (null), are Lorentzian surfaces having no Euclidean counterparts. In this work we present reparametrization of nondegenerate null scroll as a Bscroll, i.e. as a ruled surface whose rulings correspond to the binormal vectors of a base curve. We prove that the curvature of a base curve, which determines the Gaussian and mean curvature of a null scroll, is invariant under such a reparametrization. We also determine a oneparameter family of null curves on null scroll which serve as base curves for this kind of reparametrization.
Refereed Proceedings
 Lj. Primorac Gajčić, Ž. MilinŠipuš, I. Protrka, Structure Functions of Ruled Surfaces with Null Rulings , The 18th International Conference on Geometry and Graphics, Milano, 2018, 371380In this paper we analyze ruled surfaces in LorentzMinkowski space in terms of their structure functions. We are especially interested in ruled surfaces which do not have a Euclidean counterpart, that is, surfaces with null rulings, and in particular, socalled B scrolls. For ruled surfaces in Lorentz Minkowski space, we establish relations between their structure functions and curvatures. Structure functions can be used for e.g. proving the classical DiniBeltrami theorem which states (in Euclidean space) that a ruled skew Weingarten surface is a piece of a helicoidal surface. In LorentzMinkowski space, the problem is more complex, due to the different types of surfaces with respect to their inherited metrics. It turns out that all nullruled surfaces are Weingarten, however their structure functions need not be constant. In this paper we analyze helicoidal surfaces among Weingarten nullruled surfaces in terms of their structure functions.
 Lj. Primorac Gajčić, On local isometries of Bscrolls in Minkowski space, The Young Researcher Workshop on Differential Geometry in Minkowski Space, Granada, Spain, 2017, 125132
 Lj. Primorac Gajčić, Ž. MilinŠipuš, Ruled Surfaces of Constant Slope in 3Minkowski Space, 16th International Conference on Geometry and Graphics, Innsbruck, 2014
Others
 Lj. Primorac Gajčić, A. Corn, Pravilni zvjezdasti mnogokuti, Osječki matematički list 17/2 (2018), 161170
 Lj. Primorac Gajčić, AlKhwarizmijeva metoda rješavanja kvadratnih jednadžbi, Matematika i škola 27/83 (2016), 122124
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Professional Activities
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Teaching
Zimski semestar:
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Konzultacije (Office Hours): Četvrtkom(Thu) u 11h ili po dogovoru.
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