# All Upcoming Events

On Friday, January 19, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Physics Colloquia series:

Siddharth Parameswaran (Oxford)

Quantum order and criticality at infinite temperature

On Monday at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Astrophysics Colloquia series:

Prof. Steven Finkelstein (Univ. of Texas)

Reionizing the Universe with Low Galaxy Ionizing Escape Fractions and Implications for First Light with JWST

On Monday at 14:15 in L5, a seminar in
the Geometry and Analysis series:

Brent Doran (Oxford)

Geometry of subrings

*The basic algebra-geometry dictionary for finitely generated k-algebras is one of the triumphs of 19th and early 20th century mathematics. However, classes of related rings, such as their k-subalgebras, lack clean general properties or organizing principles, even when they arise naturally in problems of smooth projective geometry. “Stabilization” in smooth topology and symplectic geometry, achieved by products with Euclidean space, substantially simplifies many problems. We discuss an analog in the more rigid setting of algebraic and arithmetic geometry, which, among other things (e.g., applications to counting rational points), gives some structure to the study of k-subalgebras. We focus on the case of the moduli space of stable rational n-pointed curves to illustrate.*

**Further information:**
On Tuesday at 15:45 in L4, a seminar in
the Algebraic Geometry series:

Dominic Joyce (Oxford)

Lie brackets on the homology of moduli spaces, and wall-crossing formulae

*Let $\mathbb K$ be a field, and $\mathcal M$ be the “projective linear' moduli stack of objects in a suitable $\mathbb K$-linear abelian category $\mathcal A$ (such as the coherent sheaves coh($X$) on a smooth projective $\mathbb K$-scheme $X$) or triangulated category $\mathcal T$ (such as the derived category $D^b$coh($X$)). I will explain how to define a Lie bracket [ , ] on the homology $H_*({\mathcal M})$ (with a nonstandard grading), making $H_*({\mathcal M})$ into a graded Lie algebra. This is a new variation on the idea of Ringel-Hall algebra. There is also a differential-geometric version of this: if $X$ is a compact manifold with a geometric structure giving instanton-type equations (e.g. oriented Riemannian 4-manifold, $G_2$-manifold, Spin(7)-manifold) then we can define Lie brackets both on the homology of the moduli spaces of all $U(n)$ or $SU(n)$ connections on $X$ for all $n$, and on the homology of the moduli spaces of instanton $U(n)$ or $SU(n)$ connections on $X$ for all $n$. All this is (at least conjecturally) related to enumerative invariants, virtual cycles, and wall-crossing formulae under change of stability condition. Several important classes of invariants in algebraic and differential geometry — (higher rank) Donaldson invariants of 4-manifolds (in particular with $b^2_+=1$), Mochizuki invariants counting semistable coherent sheaves on surfaces, Donaldson-Thomas type invariants for Fano 3-folds and CY 4-folds — are defined by forming virtual classes for moduli spaces of “semistable” objects, and integrating some cohomology classes over them. The virtual classes live in the homology of the “projective linear' moduli stack. Yuuji Tanaka and I are working on a way to define virtual classes counting strictly semistables, as well as just stables / stable pairs. I conjecture that in all these theories, the virtual classes transform under change of stability condition by a universal wall-crossing formula (from my previous work on motivic invariants) in the Lie algebra $(H_*({\mathcal M}), [ , ])$.*

**Further information:**
On Thursday at 12:45 in L6, a seminar in
the Strings Junior series:

Mark van Loon

6d (2,0) SCFT

On Thursday at 13:00 in Dalitz Institute, a seminar in
the Dalitz Seminar in Fundamental Physics series:

Edward Hardy (Liverpool)

The QCD axion and other possible new light particles

*http:/*

**Further information:**
On Thursday at 16:00 in L6, a seminar in
the Number Theory series:

Lucia Mocz (Princeton)

A New Northcott Property for Faltings Height

*The Faltings height is a useful invariant for addressing questions in arithmetic geometry. In his celebrated proof of the Mordell and Shafarevich conjectures, Faltings shows the Faltings height satisfies a certain Northcott property, which allows him to deduce his finiteness statements. In this work we prove a new Northcott property for the Faltings height. Namely we show, assuming the Colmez Conjecture and the Artin Conjecture, that there are finitely many CM abelian varieties of a fixed dimension which have bounded Faltings height. The technique developed uses new tools from integral p-adic Hodge theory to study the variation of Faltings height within an isogeny class of CM abelian varieties. In special cases, we are able to use these techniques to moreover develop new Colmez-type formulas for the Faltings height.*

**Further information:**
On Thursday at 16:15 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Particle Physics series:

Peter Richardson (CERN Geneva)

Tools for colliders: HERWIG

On Monday, January 29, at 12:45 in L3, a seminar in
the String Theory series:

Andreas Braun (Oxford)

Compact G2 manifolds and the Duality between M-Theory and Heterotic String Theory

*M-theory on K3 surfaces and Heterotic Strings on T^3 give rise to dual theories in 7 dimensions. Applying this duality fibre-wise is expected to connect G2 manifolds with Calabi-Yau threefolds (together with vector bundles). We make these ideas explicit for a class of G2 manifolds realized as twisted connected sums and prove the equivalence of the spectra of the dual theories. This naturally gives us examples of singular TCS G2 manifolds realizing non-abelian gauge theories with non-chiral matter.*

**Further information:**
On Monday, January 29, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Astrophysics Colloquia series:

Prof. Giovanna Tinetti (UCL)

TBD

On Monday, January 29, at 14:15 in L5, a seminar in
the Geometry and Analysis series:

Reto Buzano (Queen Mary University London)

Compactness results for minimal hypersurfaces with bounded index

*First, we will discuss sequences of closed minimal hypersurfaces (in closed Riemannian manifolds of dimension up to 7) that have uniformly bounded index and area. In particular, we explain a bubbling result which yields a bound on the total curvature along the sequence and, as a consequence, topological control in terms of index and area. We then specialise to minimal surfaces in ambient manifolds of dimension 3, where we use the bubbling analysis to obtain smooth multiplicity-one convergence under bounds on the index and genus. This is joint work with Lucas Ambrozio, Alessandro Carlotto, and Ben Sharp*

**Further information:**
On Tuesday, January 30, at 11:30 in Conference Room, DWB, a seminar in
the Cosmology series:

Cora Uhlemann (Cambridge)

TBD

On Tuesday, January 30, at 12:00 in L4, a seminar in
the Quantum Field Theory series:

Roger Penrose

to be announced

On Thursday, February 1, at 12:45 in L6, a seminar in
the Strings Junior series:

Pietro Benetti Genolini

Branes

On Thursday, February 1, at 13:00 in Dalitz Institute, a seminar in
the Dalitz Seminar in Fundamental Physics series:

Ed Daw (Sheffield)

Searching for Axions with ADMX

*http:/*

**Further information:**
On Thursday, February 1, at 16:00 in L6, a seminar in
the Number Theory series:

Nils Bruin (Simon Fraser University)

TBA

On Thursday, February 1, at 16:15 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Particle Physics series:

Tim Jones (KITP and Liverpool U)

Scale invariant quantum gravity

*https:/*

**Further information:**
On Friday, February 2, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Physics Colloquia series:

Juergen Berges (University of Heidelberg)

Juergen Berges (Heidelberg)

On Monday, February 5, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Astrophysics Colloquia series:

Prof. Wyn Evans (Cambridge)

Paradigm Shifts in Galactic Astrophysics with Gaia

On Monday, February 5, at 14:15 in L5, a seminar in
the Geometry and Analysis series:

Ailsa Keating (Cambridge)

On symplectic stabilisations and mapping classes

*In real dimension two, the symplectic mapping class group of a surface agrees with its `classical' mapping class group, whose properties are well-understood. To what extend do these generalise to higher-dimensions? We consider specific pairs of symplectic manifolds (S, M), where S is a surface, together with collections of Lagrangian spheres in S and in M, say v_1, ...,v_k and V_1, ...,V_k, that have analogous intersection patterns, in a sense that we will make precise. Our main theorem is that any relation between the Dehn twists in the V_i must also hold between Dehn twists in the v_i. Time allowing, we will give some corollaries, such as embeddings of certain interesting groups into auto-equivalence groups of Fukaya categories.*

**Further information:**
On Tuesday, February 6, at 11:30 in Conference Room, DWB, a seminar in
the Cosmology series:

Elena Sellentin (Geneva)

TBD

On Tuesday, February 6, at 12:00 in L4, a seminar in
the Relativity series:

James Drummond (Southampton)

TBA

On Tuesday, February 6, at 15:45 in L4, a seminar in
the Algebraic Geometry series:

Tom Ducat (University of Bristol)

Constructing Q-Fano 3-folds from Cluster Algebras

On Thursday, February 8, at 12:45 in L6, a seminar in
the Strings Junior series:

Diego Berdeja Suárez

BRST Quantization

On Thursday, February 8, at 16:00 in L6, a seminar in
the Number Theory series:

Netan Dogra (Imperial College, London)

TBA

On Thursday, February 8, at 16:15 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Particle Physics series:

John Dixon (CAP Edmonton)

Genuine and effective actions, the master equation and suppressed SUSY

*https:/*

**Further information:**
On Monday, February 12, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Astrophysics Colloquia series:

Prof. Chris Reynolds (Cambridge)

Booms, Rumbles, and Whistles in the Night - Diving into the Physics of AGN Feedback in Galaxy Clusters

On Monday, February 12, at 14:15 in L5, a seminar in
the Geometry and Analysis series:

Paul Ziegler (Oxford)

TBA

On Tuesday, February 13, at 12:00 in L4, a seminar in
the Quantum Field Theory series:

Tim Palmer (Oxford Physics)

A Finte Theory of Quantum Physics

*Hardy's axiomatic approach to quantum theory revealed that just one axiom distinguishes quantum theory from classical probability theory: there should be continuous reversible transformations between any pair of pure states. It is the single word `continuous' that gives rise to quantum theory. This raises the question: Does there exist a finite theory of quantum physics (FTQP) which can replicate the tested predictions of quantum theory to experimental accuracy? Here we show that an FTQP based on complex Hilbert vectors with rational squared amplitudes and rational phase angles is possible providing the metric of state space is based on p-adic rather than Euclidean distance. A key number-theoretic result that accounts for the Uncertainty Principle in this FTQP is the general incommensurateness between rational $\phi$ and rational $\cos \phi$. As such, what is often referred to as quantum `weirdness' is simply a manifestation of such number-theoretic incommensurateness. By contrast, we mostly perceive the world as classical because such incommensurateness plays no role in day-to-day physics, and hence we can treat $\phi$ (and hence $\cos \phi$) as if it were a continuum variable. As such, in this FTQP there are two incommensurate Schr\'{o}dinger equations based on the rational differential calculus: one for rational $\phi$ and one for rational $\cos \phi$. Each of these individually has a simple probabilistic interpretation - it is their merger into one equation on the complex continuum that has led to such problems over the years. Based on this splitting of the Schr\'{o}dinger equation, the measurement problem is trivially solved in terms of a nonlinear clustering of states on $I_U$. Overall these results suggest we should consider the universe as a causal deterministic system evolving on a finite fractal-like invariant set $I_U$ in state space, and that the laws of physics in space-time derive from the geometry of $I_U$. It is claimed that such a deterministic causal FTQP will be much easier to synthesise with general relativity theory than is quantum theory.*

**Further information:**
On Tuesday, February 13, at 15:45 in L4, a seminar in
the Algebraic Geometry series:

Amos Turchet (University of Washington)

TBA

*TBA*

**Further information:**
On Thursday, February 15, at 13:00 in Dalitz Institute, a seminar in
the Dalitz Seminar in Fundamental Physics series:

Andreas Crivellin (PSI)

TBA

On Thursday, February 15, at 16:00 in L6, a seminar in
the Number Theory series:

Alexandra Florea (Bristol)

TBA

On Thursday, February 15, at 16:15 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Particle Physics series:

Fedor Bezrukov (University of Manchester)

Status of Higgs inflation

On Friday, February 16, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Physics Colloquia series:

Subir Sarkar (Oxford)

Testing the Cosmolgical Principle

On Monday, February 19, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Astrophysics Colloquia series:

Dr. Adam Ingram (Oxford)

TBD

On Monday, February 19, at 14:15 in L5, a seminar in
the Geometry and Analysis series:

Vicky Hoskins (Freie Universität Berlin)

TBA

On Tuesday, February 20, at 11:30 in Conference Room, DWB, a seminar in
the Cosmology series:

Silvia Galli (IAP)

TBD

On Tuesday, February 20, at 12:00 in L4, a seminar in
the Quantum Field Theory series:

Simon Wood (Cardiff)

to be announced

On Tuesday, February 20, at 15:45 in L4, a seminar in
the Algebraic Geometry series:

Simon Pepin Lehalleur (Freie Universität Berlin)

On the motive of the stack of vector bundles on a curve

*Following Grothendieck's vision that many cohomological invariants of of an algebraic variety should be captured by a common motive, Voevodsky introduced a triangulated category of mixed motives which partially realises this idea. After describing this category, I will explain how to define the motive of certain algebraic stacks in this context. I will then report on joint work in progress with Victoria Hoskins, in which we study the motive of the moduli stack of vector bundles on a smooth projective curve and show that this motive can be described in terms of the motive of this curve and its symmetric powers.*

**Further information:**
On Thursday, February 22, at 12:45 in L6, a seminar in
the Strings Junior series:

Max Hubner

Resurgence

On Thursday, February 22, at 16:00 in L6, a seminar in
the Number Theory series:

Toby Gee (Imperial College, London)

Potential modularity of abelian surfaces

*I will give a gentle introduction to joint work in progress with George Boxer, Frank Calegari, and Vincent Pilloni, in which we prove that all abelian surfaces over totally real fields are potentially modular. We also prove that infinitely many abelian surfaces over Q are modular.*

**Further information:**
On Thursday, February 22, at 16:15 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Particle Physics series:

Maxim Pospelov (Perimeter Institute, Waterloo)

Cosmology of light scalars and the Higgs portal

On Monday, February 26, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Astrophysics Colloquia series:

Dr. Emily Petroff (ASTRON)

Fast Radio Bursts: New discoveries and future prospects

On Monday, February 26, at 14:15 in L5, a seminar in
the Geometry and Analysis series:

Amihay Hanany (Oxford)

TBA

On Tuesday, February 27, at 11:30 in Conference Room, DWB, a seminar in
the Cosmology series:

Licia Verde (Barcelona)

TBD

On Tuesday, February 27, at 12:00 in L4, a seminar in
the Quantum Field Theory series:

Cecile Huneau (Ecole Polytechnique)

to be announced

On Tuesday, February 27, at 15:45 in L4, a seminar in
the Algebraic Geometry series:

Stefan Schroeer (University of Dusseldorf)

TBA

*TBA*

**Further information:**
On Thursday, March 1, at 12:45 in L6, a seminar in
the Strings Junior series:

Mohamed Elmi

F-Theory

On Thursday, March 1, at 13:00 in Dalitz Institute, a seminar in
the Dalitz Seminar in Fundamental Physics series:

Susanne Westhoff (Heidelberg)

TBA

On Thursday, March 1, at 16:15 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Particle Physics series:

Mairi Sakellariadou (King's College London)

Gravitational waves: a new window into the early universe

On Friday, March 2, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Theoretical Physics Colloquia series:

Holger Stark (TU Berlin)

Flowing soft matter: Colloidal jamming and collective active motion

On Monday, March 5, at 14:00 in Dennis Sciama Lecture Theatre, a seminar in
the Astrophysics Colloquia series:

Prof. Zoltan Haiman (Columbia University)

TBD

On Monday, March 5, at 14:15 in L5, a seminar in
the Geometry and Analysis series:

Maxence Mayrand (Oxford)

TBA

On Tuesday, March 6, at 12:00 in L4, a seminar in
the Relativity series:

Dr Jake Bourjaily (NBI Copenhagen)

TBA

On Tuesday, March 6, at 15:45 in L4, a seminar in
the Algebraic Geometry series:

Yalong Cao

Zero dimensional Donaldson-Thomas invariants of Calabi-Yau 4-folds

*We study Hilbert schemes of points on a smooth projective Calabi-Yau 4-fold X and define DT4 invariants by integrating the Euler class of a tautological vector bundle against the virtual class. We conjecture a formula for their generating series, which we prove in certain cases when L corresponds to a smooth divisor on X. A parallel equivariant conjecture for toric Calabi-Yau 4-folds is proposed. This conjecture is proved for smooth toric divisors and verified for more general toric divisors in many examples. Combining the equivariant conjecture with a vertex calculation, we find explicit positive rational weights, which can be assigned to solid partitions. The weighted generating function of solid partitions is given by exp(M(q) − 1), where M(q) denotes the MacMahon function. This is joint work with Martijn Kool.*

**Further information:**
On Thursday, March 8, at 12:45 in L6, a seminar in
the Strings Junior series:

Wenzhe Yang

Pure spinors