Calf Seminar
About the Calf
Calf is the junior COW, an algebraic geometry seminar group primarily aimed at PhD students.
The organisers for academic year 2025/26 are Inés Chung-Halpern (LSGNT), Marc Truter (Warwick), and Charlotte Satchwell (Essex), as well as an extensive network of local organisers at different universities. Calf announcements are made using the COW mailing list. If you would like to get involved in the organisation, or suggest your institution as the next venue, please contact any of the people named above.
The COW seminar has some funding for travel expenses, and information on reimbursement can be found on the main COW webpage.
About the Calf
Calf is the junior COW, an algebraic geometry seminar group primarily aimed at PhD students.
The organisers for academic year 2025/26 are Inés Chung-Halpern (LSGNT), Marc Truter (Warwick), and Charlotte Satchwell (Essex), as well as an extensive network of local organisers at different universities. Calf announcements are made using the COW mailing list. If you would like to get involved in the organisation, or suggest your institution as the next venue, please contact any of the people named above.
The COW seminar has some funding for travel expenses, and information on reimbursement can be found on the main COW webpage.
Upcoming Meeting:
University of Warwick, Friday 28th November 2025
IAS Seminar Room, Zeeman Building, 13:00-17:00
13:00 Yaoqi Yang (University of Warwick)
Title: Bridging K-Stability and GIT Stability
Abstract: K-stability plays a central role in the study of Fano varieties and their moduli, linking algebraic geometry with differential geometry through the existence of Kähler–Einstein metrics. On the other hand, Geometric Invariant Theory (GIT) provides a classical notion of stability used to construct moduli spaces via group actions. In this talk, I’ll explain how K-stability can be viewed as an extension of GIT stability, comparing how both measure the behaviour of degenerations of polarized varieties. If time allows, I will also describe how similar ideas apply to log pairs.
14:30 Harry Shaw (University of Bath)
Title: The existence of quartic del Pezzo surfaces over global function fields which do not admit a quadratic point.
Abstract: Creutz and Viray have recently proven the existence of quartic del Pezzo surfaces over Q which do not admit a point defined over any quadratic field extension, despite every such surface admitting a quadratic point over any local field. We prove the analogous result over global function fields. This is joint work with Giorgio Navone, Katerina Santicola and Haowen Zhang.
16:00 Heath Pearson (University of Nottingham)
Title: Decombinatorialisation
Abstract: This is a case study in approaching algebraic-geometric questions by first interpreting them in a combinatorially tractable class of varieties, then systematically generalising the findings through a sequence of increasingly general classes. The end goal is a general statement. The prototypical starting point is the class of toric varieties. In this talk, we explore the additional geometric insight gained by passing to the more general—yet still combinatorial—spherical varieties. They are a natural generalisation of toric varieties, where the algebraic torus is replaced by an arbitrary reductive group.
University of Warwick, Friday 28th November 2025
IAS Seminar Room, Zeeman Building, 13:00-17:00
13:00 Yaoqi Yang (University of Warwick)
Title: Bridging K-Stability and GIT Stability
Abstract: K-stability plays a central role in the study of Fano varieties and their moduli, linking algebraic geometry with differential geometry through the existence of Kähler–Einstein metrics. On the other hand, Geometric Invariant Theory (GIT) provides a classical notion of stability used to construct moduli spaces via group actions. In this talk, I’ll explain how K-stability can be viewed as an extension of GIT stability, comparing how both measure the behaviour of degenerations of polarized varieties. If time allows, I will also describe how similar ideas apply to log pairs.
14:30 Harry Shaw (University of Bath)
Title: The existence of quartic del Pezzo surfaces over global function fields which do not admit a quadratic point.
Abstract: Creutz and Viray have recently proven the existence of quartic del Pezzo surfaces over Q which do not admit a point defined over any quadratic field extension, despite every such surface admitting a quadratic point over any local field. We prove the analogous result over global function fields. This is joint work with Giorgio Navone, Katerina Santicola and Haowen Zhang.
16:00 Heath Pearson (University of Nottingham)
Title: Decombinatorialisation
Abstract: This is a case study in approaching algebraic-geometric questions by first interpreting them in a combinatorially tractable class of varieties, then systematically generalising the findings through a sequence of increasingly general classes. The end goal is a general statement. The prototypical starting point is the class of toric varieties. In this talk, we explore the additional geometric insight gained by passing to the more general—yet still combinatorial—spherical varieties. They are a natural generalisation of toric varieties, where the algebraic torus is replaced by an arbitrary reductive group.
Recent Meeting:
University of Nottingham, Wednesday 26th March 2025
University Park Campus, 13:00 - 17:00
13:00 (School of Mathematical Sciences, A17): Hamdi Dërvodeli (University of Warwick)
Title: Reducible varieties and tropical geometry
Abstract: The factoring locus of a polynomial is a list of conditions on its coefficients under which the polynomial factors. The aim of this talk is to explore connections tropical geometry has with this factoring locus. More generally, we want to know if the reducibility of a classical variety is detected by the tropicalization of its defining ideal. We wonder the same about the singular locus of a classical variety.
14:30 (School of Physics & Astronomy, C29): Jingxiang Ma (University of Sheffield)
Title: Mirror symmetry for ADE resolutions
Abstract: I will discuss two constructions associated with ADE Dynkin diagrams. The first is the quantum cohomology of minimal resolutions of du Val singularities, which admit an ADE classification. The second is a family of curves on a one-dimensional extension of the Cartan subalgebra, arising purely from a representation of the corresponding Lie algebra. I will explain how this second construction provides mirrors for all ADE resolutions and discuss potential applications. This talk is based on recent joint work with Andrea Brini and Ian Strachan.
16:00 (Trent building, B46): Parth Shimpi (University of Glasgow)
Title: Heart-to-heart on rational curves
Abstract: Bounded hearts on derived categories have been an indispensable homological tool for studying equivalences of categories in algebra and geometry. Neighbourhoods of rational curves provide a natural playground where algebra and geometry collide and interact— the categories of coherent sheaves are derived equivalent to finite dimensional algebras and we find machinery from both worlds at our disposal. I will talk through some of the story, and explain recent work on classification of all possible hearts in such a category.
University of Nottingham, Wednesday 26th March 2025
University Park Campus, 13:00 - 17:00
13:00 (School of Mathematical Sciences, A17): Hamdi Dërvodeli (University of Warwick)
Title: Reducible varieties and tropical geometry
Abstract: The factoring locus of a polynomial is a list of conditions on its coefficients under which the polynomial factors. The aim of this talk is to explore connections tropical geometry has with this factoring locus. More generally, we want to know if the reducibility of a classical variety is detected by the tropicalization of its defining ideal. We wonder the same about the singular locus of a classical variety.
14:30 (School of Physics & Astronomy, C29): Jingxiang Ma (University of Sheffield)
Title: Mirror symmetry for ADE resolutions
Abstract: I will discuss two constructions associated with ADE Dynkin diagrams. The first is the quantum cohomology of minimal resolutions of du Val singularities, which admit an ADE classification. The second is a family of curves on a one-dimensional extension of the Cartan subalgebra, arising purely from a representation of the corresponding Lie algebra. I will explain how this second construction provides mirrors for all ADE resolutions and discuss potential applications. This talk is based on recent joint work with Andrea Brini and Ian Strachan.
16:00 (Trent building, B46): Parth Shimpi (University of Glasgow)
Title: Heart-to-heart on rational curves
Abstract: Bounded hearts on derived categories have been an indispensable homological tool for studying equivalences of categories in algebra and geometry. Neighbourhoods of rational curves provide a natural playground where algebra and geometry collide and interact— the categories of coherent sheaves are derived equivalent to finite dimensional algebras and we find machinery from both worlds at our disposal. I will talk through some of the story, and explain recent work on classification of all possible hearts in such a category.
