Found at least 20 result(s)
regular seminar [to be confirmed] ()
at: 01:00 - 01:00 KCL, Strand room: S3.32 abstract: | Keywords: |
regular seminar Taufiq Murtadho (Nanyang Technological University)
at: 01:00 - 01:00 KCL, Strand room: abstract: | Keywords: |
regular seminar Jon Cockayne (Southampton)
at: 01:00 - 01:00 KCL, Strand room: Strand 4.29 abstract: | Keywords: |
regular seminar Iacopo Iacopini (Network Science Institute)
at: 01:00 - 01:00 KCL, Strand room: S5.20 abstract: | Keywords: |
regular seminar Mustazee Rahman (Durham University)
at: 01:00 - 01:00 KCL, Strand room: S3.32 abstract: | Last passage percolation is a model of random planar geometry which captures notions of distances and geodesics. It admits a rich scaling limit, called the directed landscape, that is conjectured to be universal for all geometric models in the so called KPZ universality class. A closely related notion is the KPZ fixed point, which represents the scaling limit of certain growing interfaces. A variational formula links the evolution of the KPZ fixed point to the directed landscape. The optimizer of the variational formula is akin to the polymer endpoint of a point-to-line last passage percolation problem. I will explain how to compute the law of this endpoint using the integrability of the KPZ fixed point. Joint work with Jeremy Quastel and Sourav Sarkar. Keywords: |
Regular Seminar Georgios Papathanasiou (City, University of London)
at: 01:00 - 01:00 KCL Strand room: LIMS abstract: | Scattering amplitudes provide crucial theoretical input in collider and gravitational wave physics, and at the same time exhibit a remarkable mathematical structure. These lectures will introduce essential concepts and modern techniques exploiting this structure so as to efficiently compute amplitudes and their building blocks, Feynman integrals, in perturbation theory. We will start by decomposing gauge theory amplitudes into simpler pieces based on colour and helicity information. Focusing on tree level, we will then show how these may be determined from their analytic properties with the help of Britto-Cachazo-Feng-Witten recursion. Moving on to loop level, we will define the the class of polylogarithmic functions amplitudes and integrals often evaluate to, and explain their properties as well as relate them to the universal framework for predicting their singularities, known as the Landau equations. Time permitting, we will also summarise the state of the art in the calculation of the aforementioned singularities, and their intriguing relation to mathematical objects known as cluster algebras. Keywords: |
regular seminar François Caron (Oxford)
at: 01:00 - 01:00 KCL, Strand room: Strand 4.29 abstract: | Keywords: |
Regular Seminar Costas Bachas (Ecole Normale Superieure)
at: 01:00 - 01:00 KCL Strand room: K3.11 abstract: | Keywords: |
regular seminar Federico Corberi (Università di Salerno)
at: 01:00 - 01:00 KCL, Strand room: S5.20 abstract: | Keywords: |
regular seminar Francesco Lin (Columbia University )
at: 01:00 - 01:00 KCL, Strand room: STRAND BLDG S4.29 abstract: | Gromov used convex integration to prove that any closed
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regular seminar Nelly Ng Huei Ying (Nanyang Technological University)
at: 01:00 - 01:00 KCL, Strand room: Online only, contact Matteo Tanzi for link abstract: | Keywords: |
regular seminar Alexandre Legrand (Institut Camille Jordan)
at: 01:00 - 01:00 KCL, Strand room: S3.32 abstract: | We are interested in the recurrence and transience of a branching random walk in Z^d indexed by a critical Galton-Watson tree conditioned to survive. When the environment is homogeneous, deterministic, and if the offspring distribution has a finite third moment, it is known to be recurrent for d at most 4, and transient for d larger than 4. In this talk we consider an environment made of random conductances, and we prove that, if the conductances satisfy suitable technical assumptions, the same result holds. The argument is based on the combination of a 0-1 law and a truncated second moment method, which only requires to have good estimates on the quenched Green's function of a (non-branching) random walk in random conductances. Keywords: |
Regular Seminar Georgios Papathanasiou (City, University of London)
at: 01:00 - 01:00 KCL Strand room: LIMS abstract: | Scattering amplitudes provide crucial theoretical input in collider and gravitational wave physics, and at the same time exhibit a remarkable mathematical structure. These lectures will introduce essential concepts and modern techniques exploiting this structure so as to efficiently compute amplitudes and their building blocks, Feynman integrals, in perturbation theory. We will start by decomposing gauge theory amplitudes into simpler pieces based on colour and helicity information. Focusing on tree level, we will then show how these may be determined from their analytic properties with the help of Britto-Cachazo-Feng-Witten recursion. Moving on to loop level, we will define the the class of polylogarithmic functions amplitudes and integrals often evaluate to, and explain their properties as well as relate them to the universal framework for predicting their singularities, known as the Landau equations. Time permitting, we will also summarise the state of the art in the calculation of the aforementioned singularities, and their intriguing relation to mathematical objects known as cluster algebras. Keywords: |
regular seminar Matthew Thorpe (University of Warwick)
at: 01:00 - 01:00 KCL, Strand room: K2.31 (Nash Lecture Theatre) abstract: | Talk 1 (15:00): Introduction to Graph-based Learning
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colloquium Mike Cates (Cambridge)
at: 01:00 - 01:00 KCL, Strand room: Bush House Lecture Theatre 1, BH(S)1.01 abstract: | Classical statistical mechanics describes the macroscopic properties of large numbers of particles. It has a hidden weakness: it assumes that the microscopic forces derive from a Hamiltonian. The same mathematical object then controls both the equations of motion, and the Boltzmann distribution. This is why quantities like pressure are not only time averages of forces (on a wall), but also thermodynamic state functions (which exist independently of any wall). Active matter systems are different. Their particles take energy out of the environment, and use it for dissipative self-propulsion, violating Hamiltonian dynamics. Examples include swimming micro-organisms, and synthetic colloids propelled by optical or chemical energy. The absence of a Hamiltonian-derived detailed balance principle requires a rebuild of statistical mechanics, with some surprising outcomes. For example: (i) the pressure of an active fluid on a wall is not a state function -- it depends on the type of wall\DSEMIC (ii) various interfacial phenomena, governed in equilibrium by a single surface tension, now involve different tensions, some of which can be negative. I will survey these among other surprises and, if time allows, say how they affect kinetic questions such as nucleation rates. Keywords: |
regular seminar Artemis Vogiatzi (Queen Mary)
at: 01:00 - 01:00 KCL, Strand room: S5.20 abstract: | By using a sharp quartic curvature pinching for the mean curvature flow in $\mathbb{S}^{n+m}$, $m\ge2$, we improve the quadratic curvature conditions. Through a blow-up argument, we establish both a codimension and a cylindrical estimate, which show that in regions of high curvature, the submanifold quantitatively becomes codimension one. In these regions, the submanifold is shown to be weakly convex and moves by translation or evolves is a self-shrinker. Additionally, a decay estimate ensures that the rescaled flow converges smoothly to a totally geodesic limit as time tends to infinity, without the need for iteration methods or integral estimates. Our approach relies on the preservation of the quartic pinching condition along the flow and gradient estimates that control the mean curvature in regions of high curvature. Keywords: |
Regular Seminar Andrew Strominger (Harvard U.)
at: 01:00 - 01:00 KCL Strand room: K2.31 abstract: | Flat space admits a foliation by AdS leaves. One seeks to derive the bulk to boundary dictionary for flat space holography as the uplift of the AdS/CFT dictionary.Over the last year progress on this front has been made by isolating the contribution to bulk amplitudes associated to a single AdS leaf. This has culminated in the construction of a 2D leaf CFT, consisting of a Liouville field, a level one current algebra and a weight -3/2 fermion, which reproduces the bulk tree MHV gluon amplitude. This talk will review these developments. Keywords: |
regular seminar Barbara Roos (Universität Tübingen)
at: 01:00 - 01:00 KCL, Strand room: S5.20 abstract: | A closed quantum system thermalizes in the sense of typicality, if any initial state will reach a suitable equilibrium subspace and stay there most of the time. For non-degenerate Hamiltonians, a sufficient condition for thermalization is the eigenstate thermalization hypothesis (ETH). Shiraishi and Tasaki recently proved the ETH for a perturbation of the Hamiltonian of free fermions on a one-dimensional lattice. The perturbation is needed to remove the high degeneracies of the Hamiltonian. We point out that also for degenerate Hamiltonians ETH implies thermalization. Additionally, we develop another strategy for proving thermalization by adding small generic perturbations. This is joint work with Stefan Teufel, Roderich Tumulka, and Cornelia Vogel. Keywords: |
regular seminar Tommaso Cremaschi (Trinity College Dublin )
at: 01:00 - 01:00 KCL, Strand room: abstract: | We will give a short overview of the Nielsen-Thurston Classification problem (classifying the homeomorphism type of surfaces) on finite-type surfaces and then move to infinite-type surface mentioning what is known and pointing out some difficulties. We will then discuss how to approximate, in the compact-open topology, a general self-homeomorphism of an infinite-type surface (joint with Y.Chandran) and potential definitions of pseudo-anosov mapping classes in the infinite-type setting (joint with F.Valdez). Keywords: |
regular seminar Xusheng Zhang (University of Oxford)
at: 01:00 - 01:00 KCL, Strand room: S3.32 abstract: | A common challenge in using Markov chain for sampling from high-dimensional distributions is multimodality, where the chain may get trapped far from stationarity. However, this issue often applies only to worst-case initializations and can be mitigated by using high-entropy initializations, such as product or weakly correlated distributions. From such starting points, the dynamics can escape saddle points and spread mass correctly across dominant modes.
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