Durham University News

Formation of human tissue to improve drug testing and reduce animal research
Innovative three dimensional (3D) cell culture technology is giving scientists the ability to grow realistic human tissues for more effective drug testing while reducing the need for animal research.

Durham’s cosmology research lights up London
Research by Durham University scientists into the evolution of galaxies will light up London as part of a major festival.

Philanthropist, filmmaker and children's champion receive honorary degrees
A leading philanthropist, a pioneering filmmaker and a children’s champion were awarded honorary degrees as thousands of students graduated from Durham University.

Work to begin on new colleges and student facilities
Work to develop new college and student facilities at Durham University will begin within weeks.

Seminars

Departmental Seminars

Sarah Heaps: Identifying the effect of public holidays on daily demand for gas (2018-01-22 00:00:00)

Gas distribution networks need to ensure the supply and demand for gas are balanced at all times. In practice, this is supported by a number of forecasting exercises which, if performed accurately, can substantially lower operational costs, for example through more informed preparation for severe winters. Amongst domestic and commercial customers, the demand for gas is strongly related to the weather and patterns of life and work. In regard to the latter, public holidays have a pronounced effect, which often extends into neighbouring days. In the literature, the days over which this protracted effect is felt are typically pre-specified as fixed windows around each public holiday. This approach fails to allow for any uncertainty surrounding the existence, duration and location of the protracted holiday effects. We introduce a novel model for daily gas demand which does not fix the days on which the proximity effect is felt. Our approach is based on a four-state, non-homogeneous hidden Markov model with cyclic dynamics. In this model the classification of days as public holidays is observed, but the assignment of days as ``pre-holiday'', ``post-holiday'' or ``normal'' is unknown. Explanatory variables recording the number of days to the preceding and succeeding public holidays guide the evolution of the hidden states and allow smooth transitions between normal and holiday periods. To allow for temporal autocorrelation, we model the logarithm of gas demand at multiple locations, conditional on the states, using a first-order vector autoregression (VAR(1)). We take a Bayesian approach to inference and consider briefly the problem of specifying a prior distribution for the autoregressive coefficient matrix of a VAR(1) process which is constrained to lie in the stationary region. We summarise the results of an application to data from Northern Gas Networks (NGN), the regional network serving the North of England, a preliminary version of which is already being used by NGN in its annual medium-term forecasting exercise.


Maja Volkov: Local geometric Galois representations (2018-01-22 16:00:00)

Let p be a prime number. Abelian varieties over the local field Q_p furnish an important class of p-adic representations of the absolute Galois group of Q_p, obtained from the Galois action on p^n-torsion points. Fontaine's p-adic Hodge theory provides an appropriate setting for describing such representations, highlighting their geometric properties. We show that these properties actually characterise the representations coming from abelian varieties over Q_p that acquire good reduction over a tame extension.


Theresa Abl: Exploring Reggeon bound states in strongly coupled N=4 super Yang-Mills theory (2018-01-22 17:00:00)

In recent years a lot of progress was made in the calculation of scattering amplitudes without the use of Feynman diagrams. In this talk I will discuss non-perturbative calculations in strongly coupled N=4 super Yang-Mills theory in the high-energy regime or more specifically, the multi-Regge limit. I will give a brief introduction to amplitudes in N=4 SYM and to the multi-Regge limit and why we can find all-loop results in this regime. Since we investigate scattering amplitudes at strong coupling, we can make use of the AdS/CFT-correspondence where the calculation reduces to the solution of a system of non-linear, coupled integral equations which simplify in the multi-Regge limit. I will review the calculation of the six-point amplitude which is fully known at all loop orders before we will investigate higher point amplitudes about which much less is known.


Maja Volkov: Supersingular abelian varieties with non semisimple Tate module (2018-01-23 14:00:00)

We show the existence of abelian varieties over Q_p with good supersingular reduction and non semisimple p-adic Tate module. This result is an application of the characterisation in terms of filtered phi-modules, via p-adic Hodge theory, of the p-adic representations of the absolute Galois group of Q_p coming from abelian schemes. We will show how to obtain varieties having the desired properties for the least possible dimension, namely surfaces. Our constructions easily generalise to higher dimensions.


Daniel Ballesteros-Chavez: The prescribed Weingarten curvatures problem in hyperbolic space (2018-01-25 13:00:00)

We will present a detailed proof for the existence of a closed convex hypersurface in the hyperbolic ball with prescribed 1 \le k < n - Weingarten curvature. Specifically, we deal with the equivariant problem for a sufficiently large group of hyperbolic automorhphisms. The proof proceeds by establishing (nonlinear) strict ellipticity of the associated PDE. Then we obtain existence in C^{1,a} for an auxiliary problem by Schauder theory, C^2 smoothness using ellipticity and a Lemma by Cheng-Yau, and C^{2,a} - regularity by Evans-Krylov. Finally, existence of a solution is established by degree theory in the equivariant setting. The results presented are part of the speakers PhD thesis.


Gim Seng Ng: Thermal Conformal Blocks and their AdS Representations (2018-01-26 13:00:00)

We study conformal blocks for thermal one-point-functions in higher-dimensional conformal field theories. These thermal one-point blocks can be represented as AdS Witten-diagram-like integrals. In the absence of angular potentials, the thermal one-point blocks are given analytically as generalised hypergeometric functions. As an application, by studying behavior of thermal one-point functions in the high-temperature limit, we deduce an asymptotic formula for three point coefficients of one light operator and two heavy operators. This result agrees with expectations coming from eigenstate thermalization hypothesis.


Mikhail Cherdantsev: Stochastic homogenisation of high-contrast media (2018-01-26 14:00:00)

It has been known for almost two decades (starting with a 2000 paper by Zhikov) that elliptic partial differential operators with periodic high-contrast coefficients, describing certain composite materials, have band gap spectrum described by Zhikov's beta-function in the homogenisation limit. The homogenised operator is of the two-scale nature, it has a macroscopic and microscopic (corresponding to the period of the composite) parts. While the stochastic homogenisation is a well established area of mathematics, the high-contrast stochastic homogenisation has hardly been addressed, and it seems that there is not a single paper studying the spectral problems in high-contrast stochastic homogenisation. We initiate the research in this direction and show that similarly to the periodic case in the stochastic high contrast setting(under some lenient conditions) the spectrum has a band gap structure characterised by a function similar to Zhikov's beta-function, we study the limit two-scale operator with the stochastic microscopic component and prove the convergence of the spectra.


Christina Goldschmidt: (2018-01-29 00:00:00)


Yuguo Qin: Equivariant spectrum on Toric Kaehler manifolds (2018-02-01 13:00:00)

We prove that compact toric Kaehler manifolds do not admit metrics that are critical for the equivariant first eigenvalue. This is joint work with Wang Zuoqin.


Andrea Fontanella: Integrability in lower dimensional AdS/CFT (2018-02-02 13:00:00)

In this talk, I shall consider integrable scattering processes of massless string modes in AdS2 and AdS3 backgrounds. In the first part, I will present a formulation of the Bethe ansatz in an AdS2 background by using a technique first developed in condensed matter. This technique relies on an particular algebraic equation which the S-matrix entries must satisfy, the so-called “free-fermion condition’’. This technique allows us to overcome the problem of lack of reference state in AdS2 backgrounds, which prevented for many years the Bethe ansatz formulation within the standard procedure. In the second part, I shall focus on an AdS3 background. I will show that the S-matrix, in addition to the background isometry, admits a further symmetry, the so-called "quantum deformed 2D Poincaré group". I will show how the novel symmetry allows us to interpret geometrically the scattering process in the fibre bundle language. This talk is based on arXiv:1608.01631 [hep-th] and arXiv:1706.02634 [hep-th].


Last modified on 30th September, 2014 at 12:23:05
© Andrew Iskauskas.