I am a professor of mathematics at Bielefeld University. I obtained my doctorate at the WWU Münster in 2014 and my habilitation at the RFWU Bonn in 2022, and was a lecturer at the University of Aberdeen before coming to Bielefeld in 2024.
Stefan Bauer and I are organising the 34th NRW Topology Meeting in Bielefeld; it will take place on November 22nd and 23rd and the accompanying webpage is here.
Contact Information
Address: 
Universität Bielefeld
Fakultät für Mathematik
Universitätsstraße 25 2
33615 Bielefeld Germany 
Office:  V4211

Phone:  +49 (0)521 106 5002

eMail:  hebestreit@math.unibielefeld.de 


Research interests
Algebraic & geometric topology, homotopical algebra and more specifically: The homotopy theory of diffeomorphism groups, manifold bundles and cobordism categories and their relation to arithmetic groups and algebraic K and Ltheory; higher categories as foundations for the above.
I am a member of the TRR 358 'Integral structures in geometry and representation theory', joint between the Universities of Bielefeld and Paderborn. My workgroup currently has two further members:
Teaching
During the winter term 24/25 I will teach Lineare Algebra II and Higher categories and algebraic Ktheory II.
Some lecture notes on algebraic topology, higher categories and algebraic Ktheory are here.
Publications and Preprints
Commutative algebra
Algebraic & geometric topology
 with M.Land, C.Winges & M.Weiss: Homology manifolds and euclidean bundles.
arXiv: 2406.14677 (11 pages, 2024, in revision)
 with I.Bokor, D.Crowley, S.Friedl, D.Kasprowski, M.Land & J.Nicholson: Connected sum decompositions of highdimensional manifolds.
Matrix Annals, vol. 4 (2021), pp. 530
 with S.Sagave: Homotopical and operator algebraic twisted Ktheory.
Mathematische Annalen, vol. 378 (2020), pp. 10211059
 with C.Schlichtkrull & S.Sagave: Multiplicative parametrized homotopy theory via symmetric spectra in retractive spaces.
Forum of Mathematics Sigma, vol. 8 (2020), article no. e16, 84 pages
 with M.Land, W.Lück & O.RandalWilliams: A vanishing theorem for tautological classes of aspherical manifolds.
Geometry & Topology, vol. 25 (2021), pp. 47110
 with N.Perlmutter: Cobordism categories and moduli spaces of odd dimensional manifolds.
Advances in Mathematics, vol. 353, no. 7 (2019), pp. 526590
 with M.Joachim: Twisted Spin cobordism and positive scalar curvature.
Journal of Topology, vol. 13, no. 1 (2020), pp. 158
 with S.Büscher, O.Röndigs & M.Stelzer: The Goodwillie Spectral Sequence for iterated loopspaces and topological realisation at odd primes.
Algebraic and Geometric Topology, vol. 13, no. 1 (2013), pp. 127169
Category theory
 with J.Steinebrunner: A short proof that Rezk's nerve is fully faithful.
arXiv: 2312.09889 (12 pages, 2023, in revision)
 with R.Haugseng, S.Linskens & J.Nuiten: Twovariable fibrations, factorisation systems and categories of spans.
Forum of Mathematics Sigma, vol. 11 (2023), article no. e111, 70 pages
 with R.Haugseng, S.Linskens & J.Nuiten: Lax monoidal adjunctions, twovariable fibrations and the calculus of mates.
Proceedings of the London Mathematical Society, vol. 127, no. 4 (2023), pp. 889957
 with G.Heuts & J.Ruit: A short proof of the straightening theorem.
arXiv: 2111.00069 (41 pages, 2021, in revision)
 with A.Krause: Mapping spaces in coherent nerves.
arXiv: 2011.09345 (14 pages, 2020)
Algebraic & hermitian Ktheory
 with A.Lachmann & W.Steimle: The localisation theorem for the Ktheory of stable categories.
to appear in Proceedings of the Royal Society of Edinburgh (37 pages, 2023, available here)
 with W.Steimle: Stable moduli spaces of hermitian forms.
arXiv: 2103.13911 (with an appendix by Y.Harpaz, 94 pages, 2021, in revision)
 with B.Calmès, E.Dotto, Y.Harpaz, M.Land, K.Moi, D.Nardin, T.Nikolaus & W.Steimle: Hermitian KTheory for stable ∞categories III: GrothendieckWitt groups of rings.
arXiv: 2009.07225 (63 pages, 2020, in revision)
 with B.Calmès, E.Dotto, Y.Harpaz, M.Land, K.Moi, D.Nardin, T.Nikolaus & W.Steimle: Hermitian KTheory for stable ∞categories II: Cobordism categories and Additivity.
arXiv: 2009.07224 (159 pages, 2020, in revision)
 with B.Calmès, E.Dotto, Y.Harpaz, M.Land, K.Moi, D.Nardin, T.Nikolaus & W.Steimle: Hermitian KTheory for stable ∞categories I: Foundations.
Selecta Mathematica, vol. 29, no. 1 (2023), article no. 10, 269 pages
 with M.Land & T.Nikolaus: On the homotopy type of Lspectra of the integers.
Journal of Topology, vol. 14, no. 1 (2021), pp. 183214, Erratum
Other writing
 Homology manifolds and Euclidean bundles.
to appear in Oberwolfach Reports
 with M.Land: Apprenticeship with an algebraic surgeon.
Celebratio Mathematica, Ranicki memorial issue (2022)
 with M.Land & T.Nikolaus: The initial quadratic form on an abelian group.
 Parametrised algebraic surgery.
Oberwolfach Reports vol. 17, no. 23, Workshop: Topologie (2020), pp. 11161121
 Algebraic Cobordism categories and GrothendieckWitt theory.
Oberwolfach Reports vol. 17, no. 1, Workshop: Manifolds and Groups (2020), pp. 437440
 The Tate Diagonal.
Oberwolfach Reports vol. 15, no. 1, Arbeitsgemeinschaft: Topological Cyclic Homology (2018), pp. 825838
 Twisted Spin Cobordism.
Oberwolfach Reports vol. 11, no. 3, Workshop: Analysis, Geometry and Topology of positive scalar curvature (2014), pp. 20132014