Seminars this semester

Series:

 May 21 Mon Angelo Rendina (Sheffield) Number Theory Learning Seminar 14:00 J-11 Geometric definition of modular forms May 22 Tue Paolo Stellari (Universita' degli studi di Milano) Algebra / Algebraic Geometry seminar 14:00 J11 TBA Abstract: TBA May 22 Tue Joseph Fernandez (Liverpool John Moores) Cosmology, Relativity and Gravitation 16:00 J11, Hicks Tidal encounters of compact binaries with massive black holes as a source of gravitational waves Abstract: Massive black holes (MBHs) are ubiquitous in galactic centres. The extreme potential due to these objects dominates the surrounding dynamics, giving rise to physics not possible in other regions. These regions are of particular interest for gravitational wave astronomy, as several dynamical processes which can give rise to black hole (BH) binary mergers have been postulated. We show that compact binaries can survive close encounters with the MBH without being disrupted, and that they tend to become hard and eccentric. Since the GW merger time of binaries is sensitive to the semi-major axis length and eccentricity, we find that this leads to a reduction of the merger time by several orders of magnitude in some cases. Therefore, tidal encounters of stellar mass BH binaries with a MBH at the centre of galaxies can provide a new formation channel of BH mergers. We use Monte Carlo simulations to evaluate the effective spin of the binaries after the encounter We also provide a description of a simple scenario to understand how this process could take place the a larger astrophysical context. May 23 Wed Ciaran Meachan (University of Glasgow) Algebra / Algebraic Geometry seminar 13:00 Hicks LT09 Derived equivalent Hilbert schemes of points on K3 surfaces which are not birational Abstract: Starting with two non-birational derived equivalent K3 surfaces, one can ask whether their Hilbert schemes of points are birational. In this talk, we will show that in some cases they are but in most cases they are not. This is joint work with Giovanni Mongardi and Kota Yoshioka. May 23 Wed Daniil Proskurin (Kiev Taras Shevchenko University) Pure Maths Colloquium 14:00 J11 $C^*$-algebras generated by quonic commutation relations and extensions of non-commutative tori Abstract: We consider $C^*$-algebras $A_{q_i}\Theta$ generated by relations of the following form $$a_i^*a_i=1+q_i a_ia_i^* a_i^*a_j=e^{2\pi\theta_{ij}} a_ja_i^*, \quad i\ne j i, \quad j=1,\ldots,d$$ where $-1 \lt q_i \lt 1$, $\theta_{ij}=-\theta_{ji}$, $i\ne j$. We show that $A_{q_i}\Theta \simeq A_{0}\Theta$ is an extension of higher-dimensional non-commutative tori and study its properties. May 23 Wed Xiaolei Zhao (Northeastern University) Algebra / Algebraic Geometry seminar 15:00 Hicks LT09 Twisted cubics on cubic fourfolds and stability conditions Abstract: It is a classical result of Beauville and Donagi that Fano varieties of lines on cubic fourfolds are hyper-Kahler. More recently, Lehn, Lehn, Sorger and van Straten constructed a hyper-Kahler eightfold out of twisted cubics on cubic fourfolds. In this talk, I will explain a new approach to these hyper-Kahler varieties via moduli of stable objects on the Kuznetsov components. Along the way, we will derive several properties of cubic fourfolds as consequences. This is based on a joint work with Chunyi Li and Laura Pertusi. May 23 Wed Chunyi Li (University of Warwick) Algebra / Algebraic Geometry seminar 16:15 Hicks LT09 Bogomolov type inequality for Fano varieties with Picard number 1 Abstract: I will talk about some basic facts about slope stable sheaves and the Bogomolov inequality. New techniques from stability conditions will imply new stronger bounds on Chern characters of stable sheaves on some special varieties, including Fano varieties, quintic threefolds and etc. I will discuss the progress in this direction and some related open problems. May 24 Thu Adel Betina (Sheffield) Number Theory Learning Seminar 14:00 J-11 The modular curve May 29 Tue Scott Balchin (Sheffield) Magnitude Homology 13:00 J11 Mangitude homology and persistent homology?? May 29 Tue Elisa Postinghel (University of Loughborough) Algebra / Algebraic Geometry seminar 14:00 J11 May 29 Tue Jessie Durk (Queen Mary UL) Cosmology, Relativity and Gravitation 16:00 LT09, Hicks Black hole lattices as inhomogeneous cosmological models Abstract: The standard model of cosmology, ΛCDM, is based on the assumption that the Universe can be described by the homogeneous and isotropic FLRW solution to the Einstein field equations. The need to test whether the large-scale expansion of space is that of FLRW, or is instead modified by the presence of inhomogeneities, has lead to this assumption being relaxed. An interesting subset of inhomogeneous cosmologies include those dubbed black hole lattices. These are exact, fully-relativistic treatments of universes with a discretised matter content. We generalise an existing family of these to include a cosmological constant, structure formation and electric charge. For each new generalisation, we find a common behaviour of tending towards FLRW-like as the number of masses is increased, and for the addition of structures, we investigate the effect of gravitational interaction energies between clustered masses. May 30 Wed Nebojsa Pavic (Sheffield) ShEAF: postgraduate pure maths seminar 16:00 J11 Hicks Intersection theory in algebraic geometry: History and motivation. Abstract: In this talk I'm going to motivate the notion of intersection theory in algebraic geometry by considering the example of Riemannian surfaces and only requiring a basic knowledge of complex analysis and a little bit of complex differential geometry. If time permits, I will give a rigorous definition of intersection groups, so called Chow groups, and relate them to the example. May 31 Thu S. Shelyag (Northumbria University) 10:00 LT 10 Do photospheric non-magnetic bright points exist? Abstract: Recent high-resolution simulations of non-magnetic solar photospheric convection suggest the presence of a separate class of small-scale photospheric brightenings, which coincide with intergranular vortex tubes. In contrast to well-known magnetic bright points, these brightenings are not related to magnetic fields. In our presentation, using high-resolution simulations with MURaM and detailed radiative diagnostics of the simulated models, I will analyse the physical characteristics of these brightenings and their observability with current and future instruments for solar observations. May 31 Thu Adel Betina (Sheffield) Number Theory Learning Seminar 14:00 J-11 Modular curve- Part 2 Jun 4 Mon Ariel Weiss (Sheffield) Number Theory Learning Seminar 14:00 J-11 Hasse invariant Jun 5 Tue Algebra / Algebraic Geometry seminar 14:00 J11 Jun 6 Wed Ciaran Schembri (Sheffield) ShEAF: postgraduate pure maths seminar 16:00 J11 Hicks Fuchsian group Abstract: Fuchsian groups are discrete subgroups of the special projective linear group. They act as isometries on the hyperbolic plane and are studied because of their role in generating Riemann surfaces among other things. In this talk I will outline their geometric properties and if time permits will discuss how they relate to modern number theory. Jun 7 Thu Adel Betina (Sheffield) Number Theory Learning Seminar 14:00 J-11 Introduction to rigid analytic geometry- Part (1) Jun 11 Mon Adel Betina (Sheffield) Number Theory Learning Seminar 14:00 J-11 Introduction to rigid analytic geometry- Part (2) Jun 12 Tue Algebra / Algebraic Geometry seminar 14:00 J11 Jun 14 Thu Adel Betina (Sheffield) Number Theory Learning Seminar 14:00 J-11 Introduction to rigid analytic geometry- Part (3) Jun 18 Mon Adel Betina (Sheffield) Number Theory Learning Seminar 14:00 J-11 The canonical subgroup Jun 19 Tue Algebra / Algebraic Geometry seminar 14:00 J11 Jun 21 Thu Adel Betina (Sheffield) Number Theory Learning Seminar 14:00 J-11 Classicality Jun 25 Mon Adel Betina (Sheffield) Number Theory Learning Seminar 14:00 J-11 Classicality of overconvergent modular forms Jun 26 Tue Algebra / Algebraic Geometry seminar 14:00 J11 Jun 27 Wed Ariel Weiss (Sheffield) Number Theory Learning Seminar 14:00 J-11 Hida families (classical treatment) Jun 28 Thu Adel Betina (Sheffield) Number Theory Learning Seminar 14:00 J-11 Hida families (a la Pilloni) Jul 3 Tue K-Theory, Hecke Algebras and Representation Theory 16:00 Lecture Theatre C Jul 4 Wed K-Theory, Hecke Algebras and Representation Theory 09:30 Lecture Theatre C Jul 4 Wed K-Theory, Hecke Algebras and Representation Theory 11:00 Lecture Theatre C Jul 4 Wed K-Theory, Hecke Algebras and Representation Theory 14:00 Lecture Theatre C Jul 4 Wed K-Theory, Hecke Algebras and Representation Theory 15:30 Lecture Theatre C Jul 5 Thu K-Theory, Hecke Algebras and Representation Theory 09:30 Lecture Theatre C Jul 5 Thu K-Theory, Hecke Algebras and Representation Theory 11:00 Lecture Theatre C Jul 5 Thu K-Theory, Hecke Algebras and Representation Theory 14:00 Lecture Theatre C Jul 5 Thu K-Theory, Hecke Algebras and Representation Theory 15:30 Lecture Theatre C Jul 6 Fri K-Theory, Hecke Algebras and Representation Theory 09:30 Lecture Theatre C Jul 6 Fri K-Theory, Hecke Algebras and Representation Theory 11:00 Lecture Theatre C Jul 6 Fri K-Theory, Hecke Algebras and Representation Theory 14:00 Lecture Theatre C Jul 6 Fri K-Theory, Hecke Algebras and Representation Theory 15:30 Lecture Theatre C