HOPEGA Seminars & Activities 2025-26

• 16/6/2026 

• 14.00-15.00 D. Fink (Johannes Gutenberg University Mainz): A Structural Factorization of Ring Maps in Positive Characteristic 

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• 8/6/2026

• 10.00-11.00 F. Yamauti (University of Regensburg): An invitation to the shape theory of topoi (Part I) 

• 11.30-12.30 HOPEGA-AG: Recent developments in homological functional analysis

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• 25/5/2026

• 10.00-11.30 N. Müller (University of Mainz/AUTh): Report on recent advances in dg (co)algebras

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• 18/5/2026

• 10.00-11.00 A. Slaftsos (University of Padova): Varying exact structures in additive categories 

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• 4/5/2026

• 10.00-11.00 HOPEGA-AG: Recent developments in dg (co)algebras and Koszul duality

• 11.30-12.30 K. Kartas (University of Münster): Tame Banach rings 

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• 27/4/2026   

• 10.00-11.00 S. Afentoulidis (Bar-Ilan University): An introduction to the Representation Theory of complex semi-simple Lie algebras, Part II

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• 30/3/2026

• 10.00-11.00 M. Karakikes (NKU Athens): Homological aspects of equivariant triangulated categories via separability 

• 11.30-12.30 B. Cnossen (University of Regensburg): Construction of six-functor formalisms 

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• 23/3/2026

• 10.00-11.00 P. Kostas (AUTh): Remarks on the global dimension of dg algebras 

• 11.30-12.30 N. Müller (University of Mainz/AUTh): Span categories and their uses (7): The six functors in topology

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• 18/3/2026

    • 18.15-19.15 F. De Leger (NTU Athens): Sweedler theory for double categories

• 17/3/2026

    • 12.15-13.15 F. De Leger (NTU Athens): A-infinity algebras, Stasheff associahedron and Massey products 

• 16/3/2026

• 10.00-11.00 F. De Leger (NTU Athens): Koszul duality for operads

• 11.30-12.30 A. Mustata (University of Copenhagen): Q-Shaped Derived Categories, Part 2 

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• 9/3/2026

• 10.00-11.00 A. Mustata (University of Copenhagen): Q-Shaped Derived Categories, Part 1 

• 11.30-12.30 A. Hayash (AUTh): Span categories and their uses (6): Universality of the span category, Part II 

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• 2/3/2026

• 13.00-14.00 Ch. Psaroudakis (AUTh): Cleft Extensions of Triangulated Categories 

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• 9/2/2026

• 10.00-11.00 HOPEGA-AG: Thinking about a theorem of Evens and Culler, Part II 

• 11.30-12.30 N. Müller (University of Mainz/AUTh): Span categories and their uses (5): Universality of the span category, Part I

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• 2/2/2026

• 10.00-11.00 G. Raptis (AUTh): Thinking about a theorem of Evens and Culler

• 11.30-12.30 D. M. Carpena (University of Barcelona): Span categories and their uses (4): Universal biadjointable functors

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• 26/1/2026

• 10.00-11.30 N. Müller (University of Mainz/AUTh): Span categories and their uses (3): Review, examples and applications of Mackey 2-functors 

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• 19/1/2026

• 10.00-11.00 O. Giatagantzidis (AUTh): Homological aspects of cyclic Nakayama algebras via minimal zero paths

 • 11.30-12.30 M. Karakikes (NKU Athens): Span categories and their uses (2): Mackey 2-functors 

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• 12/1/2026

• 10.00-11.00 K. M. Rahul (University of Bonn): Transferring structures on triangulated categories via metric techniques 

• 11.30-12.30 Ch. Psaroudakis (AUTh): Span categories and their uses (1): Bicategories of spans 

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• 15/12/2025

     Workshop: Algebra & Geometry Day in Thessaloniki

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• 8/12/2025

• 10.00-11.00 P. Kostas (AUTh): Classical Brown and Adams representability (after Neeman)

• 11.30-12.30 G. Raptis (AUTh): Higher (n-categorical) Brown representability

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• 1/12/2025

• 10.00-11.00 D. M. Carpena (University of Barcelona): Classical and oo-categorical Brown-Adams representability 

• 11.30-12.30 Ch. Verasdanis (AUTh): tt geometry (7) 

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• 24/11/2025

• 10.00-11.00 G. Raptis (AUTh): What is a stable n-category? 

• 11.30-12.30 Ch. Psaroudakis (AUTh): tt geometry (6): Stratification in tensor triangular geometry

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• 10/11/2025

• 10.00-11.00 I. Emmanouil (NKU Athens): Compactly generated tt-categories of Gorenstein projective modules over infinite groups 

• 11.30-12.30 Ch. Verasdanis (AUTh): tt geometry (5)

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• 3/11/2025

• 10.00-11.00 P. Giagtzoglou (AUTh): Persistent modules 

• 11.30-12.30 Ch. Verasdanis (AUTh): tt geometry (4)

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• 20/10/2025

• 10.00-11.00 M. Lupini (University of Bologna): Phantom extensions of modules 

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• 13/10/2025

• 10.00-11.00 F. Andriopoulos (University of Chicago): From non-commutative to commutative world: variations of Hochschild homology 

• 11.30-12.30 M. Karakikes (NKU Athens): tt geometry (3): Supports and filtrations 

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• 6/10/2025

• 11.30-12.30 Ch. Psaroudakis (AUTh): tt geometry (2): Supports and filtrations

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• 29/9/2025

• 10.00-11.00 Ch. Psaroudakis (AUTh): Regular triangulated categories

• 11.30-12.30 P. Kostas (AUTh): tt geometry (1): The spectrum of prime ideals

• 18/6/2026

• 16.00–17.00 S. Pedretti (University of Bologna): Non-singular and Symmetric Simplicial Sets

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• 12/6/2026

• 15.00–16.00 I. Gkeneralis (AUTh): How Much of the Homeomorphism Type Is Determined in Toric Topology?

• 16.30–17.30 F. Yamauti (University of Regensburg): An Invitation to the Shape Theory of Topoi, Part II

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• 5/6/2026

• 14.00–15.00 P. Batakidis (AUTh): Topological and Delzant-Type Classification of Quaternionic Torus Actions

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• 29/5/2026

• 15.00–16.00 HOPEGA-AG: Report on Recent Advances in Bounded Cohomology

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• 22/5/2026

• 15.00–16.00 Ch. Psaroudakis (AUTh): An Introduction to the Representation Theory of Complex Semisimple Lie Algebras, Part V

• 16.30–18.00 HOPEGA-AG: Thinking about the Category O

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• 15/5/2026

• 15.00–16.00 S. Afentoulidis (Bar-Ilan University): An Introduction to the Representation Theory of Complex Semisimple Lie Algebras, Part IV

• 16.30–18.00 N. Fachravar (AUTh): An Introduction to Grothendieck Topologies and Sheaves

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• 8/5/2026

• 15.00–16.00 P. Capovilla (University of Cyprus): Aspherical 4-Manifolds with Positive Euler Characteristic

• 16.30–18.00 S. Afentoulidis (Bar-Ilan University): An Introduction to the Representation Theory of Complex Semisimple Lie Algebras, Part III

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• 24/4/2026

• 15.00–16.00 S. Afentoulidis (Bar-Ilan University): An Introduction to the Representation Theory of Complex Semisimple Lie Algebras, Part I

• 16.30–18.00 M. Maridakis (AUTh): Bounded Cohomology and Simplicial Volume (21): The Milnor–Wood Inequality, Part II

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• 3/4/2026

• 15.00–16.00 HOPEGA-AG: The h-Principle and Its Applications (4)

• 16.30–18.00 M. Maridakis (AUTh): Bounded Cohomology and Simplicial Volume (20): The Milnor–Wood Inequality

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• 27/3/2026

• 15.00–16.00 S. Pedretti (University of Bologna): Introduction to Gromov's Multicomplexes

• 16.30–18.00 G. Raptis (AUTh): Bounded Cohomology and Simplicial Volume (19): A Homotopical Approach to Gromov's Vanishing Theorem and           Generalizations

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• 20/3/2026

• 15.00–16.00 HOPEGA-AG: The h-Principle and Its Applications (3)

• 16.30–18.00 M. Maridakis (AUTh): Bounded Cohomology and Simplicial Volume (19): The Milnor–Wood Inequality, Part I

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• 13/3/2026

• 15.00–16.00 HOPEGA-AG: The h-Principle and Its Applications (2)

• 16.30–18.00 HOPEGA-AG: Bounded Cohomology and Simplicial Volume (18½): More on Bounded Products

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• 6/3/2026

• 15.00–16.00 HOPEGA-AG: The h-Principle and Its Applications (1): Introduction

• 16.30–18.00 G. Raptis (AUTh): Bounded Cohomology and Simplicial Volume (18): Why Bounded Products Matter, Part II

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• 27/2/2026

• 16.30–18.00 G. Raptis (AUTh): Bounded Cohomology and Simplicial Volume (17): Why Bounded Products Matter, Part I

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• 13/2/2026

• 15.00–18.00 HOPEGA-AG: Bounded Cohomology and Simplicial Volume (16): Exact Categories of G-Banach Spaces and Their Derived Categories

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• 6/2/2026

• 15.00–18.00 HOPEGA-AG: Bounded Cohomology and Simplicial Volume (15): Exact Categories of Banach Spaces, Derived Categories, and t-Structures

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• 30/1/2026

• 15.00–18.00 HOPEGA-AG: Bounded Cohomology and Simplicial Volume (14½): Research Perspectives in Homological Functional Algebra

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• 23/1/2026

• 15.00–16.00 M. Moraschini (University of Bologna): Introduction to Boundedly Acyclic Groups

• 16.30–18.00 P. Kostas (AUTh): Bounded Cohomology and Simplicial Volume (14): Preliminaries to Homological Functional Algebra (continued)

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• 16/1/2026

• 15.00–16.30 P. Kostas (AUTh): Bounded Cohomology and Simplicial Volume (13): Preliminaries to Functional Homological Algebra

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• 19/12/2025

• 15.00–16.00 A. Hayash (AUTh): Constructible Sheaves of Categories, Animated Path Algebras, and n-Affineness

• 16.30–18.00 G. Raptis (AUTh): Bounded Cohomology and Simplicial Volume (12): Bounded Acyclicity of Homeo(ℝⁿ), Part II

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• 12/12/2025

• 15.00–16.00 P. Giagtzoglou (AUTh): Stability of Persistence

• 16.30–18.00 V. Patzalis (AUTh): Bounded Cohomology and Simplicial Volume (11): Bounded Acyclicity of Homeo(ℝⁿ), Part I

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• 5/12/2025

• 15.00–16.00 M. Maridakis (AUTh): Bounded Cohomology and Simplicial Volume (10): Negative Curvature and Simplicial Volume

• 16.30–18.00 M. Maridakis (AUTh): Bounded Cohomology and Simplicial Volume: The Proportionality Principle

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• 28/11/2025

• 16.30–18.00 G. Raptis (AUTh): Bounded Cohomology and Simplicial Volume (9): Homeo(S¹) (after Monod–Nariman)

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• 21/11/2025

• 15.00–16.00 G. Raptis (AUTh): What Is... Catastrophe Theory?

• 16.30–18.00 V. Patzalis (AUTh): Bounded Cohomology and Simplicial Volume (8): Additivity of Simplicial Volume

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• 14/11/2025

• 15.00–16.00 M. Maridakis (AUTh): Introduction to Morse Theory (7)

• 16.30–18.00 G. Raptis (AUTh): Bounded Cohomology and Simplicial Volume (7): The Mapping Theorem

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• 7/11/2025

• 15.00–16.00 A. Valaristou (AUTh): Introduction to Morse Theory (6)

• 16.30–18.00 G. Raptis (AUTh): Bounded Cohomology and Simplicial Volume (6): Amenability in Bounded Cohomology

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• 31/10/2025

• 15.00–16.00 R. Tsiavou (AUTh): Introduction to Morse Theory (5)

• 16.30–18.00 G. Raptis (AUTh): Bounded Cohomology and Simplicial Volume (5)

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• 24/10/2025

• 15.00–16.00 R. Tsiavou (AUTh): Introduction to Morse Theory (4)

• 16.30–18.00 G. Raptis (AUTh): Bounded Cohomology and Simplicial Volume (4)

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• 17/10/2025

• 15.00–16.00 M. Maridakis (AUTh): Introduction to Morse Theory (3)

• 16.30–18.00 V. Patzalis (AUTh): Bounded Cohomology and Simplicial Volume (3): Simplicial Volume

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• 10/10/2025

• 15.00–16.00 M. Maridakis (AUTh): Introduction to Morse Theory (2)

• 16.30–18.00 V. Patzalis (AUTh): Bounded Cohomology and Simplicial Volume (2): Quasimorphisms, Bounded Cohomology of Topological Spaces

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• 3/10/2025

• 15.00–16.00 M. Maridakis (AUTh): Introduction to Morse Theory (1)

• 16.30–18.00 V. Patzalis (AUTh): Bounded Cohomology and Simplicial Volume (1): Bounded Cohomology of Groups