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:
Imperial College London, Friday 20th March 2026
ICBS 100 - LT1, Imperial College Business School, 13:00-17:00
13:00 Diana Bergerova (University of Edinburgh)
Title: Darboux theorem for derived schemes with (-1)-shifted symplectic structure
Abstract: The Darboux theorem in classical geometry guarantees that any symplectic manifold, such as a moduli space of sheaves on a smooth projective symplectic surface, is locally a cotangent bundle. However, moduli spaces of sheaves on higher-dimensional varieties fail to be smooth and thus fail to be symplectic. In an effort to recover, we turn to derived algebraic geometry. Our goal is to formulate an analogue of the Darboux theorem for derived schemes with (-1)-shifted symplectic structure in sense of Brav-Bussi-Joyce and Pantev-Toën-Vaquié-Vezzosi, and time permitting, explore some implications of the theorem for categorification of Donaldson-Thomas invariants.
14:30 Cat Rust (Queen Mary University London)
Title: Topological Invariants of Stable Maps to Toric Pairs via Tropicalisation
Abstract: We begin with an overview of moduli spaces of stable maps to pairs and their role in enumerative geometry. Specialising to stable maps to toric pairs with prescribed tangency conditions to the toric boundary, we will cover the stratification of the moduli space by combinatorial types of associated tropical maps. Finally, we will use this stratification to study the class of the moduli space in the Grothendieck ring of varieties, describing a wall-and-chamber decomposition of the tangency space such that on open chambers, the class of the moduli space is constant.
16:00 Calum Crossley (University College London)
Title: Gluing curves and quivers
Abstract: Normalization is the most well-behaved step in resolving singularities, but it has one major defect: it completely forgets which singularity you came from. This is fixed by remembering some gluing data, which we can treat as a "non-commutative space" whose category of sheaves relates to both the singularity and the resolution. We will explore some 1-dimensional examples where this boils down to gluing quivers together, and look at special quiver representations which perfectly match the properties of special sheaves on a 3-fold resolution of singularities.
Imperial College London, Friday 20th March 2026
ICBS 100 - LT1, Imperial College Business School, 13:00-17:00
13:00 Diana Bergerova (University of Edinburgh)
Title: Darboux theorem for derived schemes with (-1)-shifted symplectic structure
Abstract: The Darboux theorem in classical geometry guarantees that any symplectic manifold, such as a moduli space of sheaves on a smooth projective symplectic surface, is locally a cotangent bundle. However, moduli spaces of sheaves on higher-dimensional varieties fail to be smooth and thus fail to be symplectic. In an effort to recover, we turn to derived algebraic geometry. Our goal is to formulate an analogue of the Darboux theorem for derived schemes with (-1)-shifted symplectic structure in sense of Brav-Bussi-Joyce and Pantev-Toën-Vaquié-Vezzosi, and time permitting, explore some implications of the theorem for categorification of Donaldson-Thomas invariants.
14:30 Cat Rust (Queen Mary University London)
Title: Topological Invariants of Stable Maps to Toric Pairs via Tropicalisation
Abstract: We begin with an overview of moduli spaces of stable maps to pairs and their role in enumerative geometry. Specialising to stable maps to toric pairs with prescribed tangency conditions to the toric boundary, we will cover the stratification of the moduli space by combinatorial types of associated tropical maps. Finally, we will use this stratification to study the class of the moduli space in the Grothendieck ring of varieties, describing a wall-and-chamber decomposition of the tangency space such that on open chambers, the class of the moduli space is constant.
16:00 Calum Crossley (University College London)
Title: Gluing curves and quivers
Abstract: Normalization is the most well-behaved step in resolving singularities, but it has one major defect: it completely forgets which singularity you came from. This is fixed by remembering some gluing data, which we can treat as a "non-commutative space" whose category of sheaves relates to both the singularity and the resolution. We will explore some 1-dimensional examples where this boils down to gluing quivers together, and look at special quiver representations which perfectly match the properties of special sheaves on a 3-fold resolution of singularities.
Recent 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.
