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BEGIN:VEVENT
SUMMARY:Chimere Anabanti (University of Technology (TU Graz) Austria)
DTSTART;VALUE=DATE-TIME:20200611T130000Z
DTEND;VALUE=DATE-TIME:20200611T140000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/1
DESCRIPTION:Title: On the classification of finite filled groups\nby Chimere Anabanti
(University of Technology (TU Graz) Austria) as part of MESS (Mathematics
Essex Seminar Series)\n\n\nAbstract\nWe give an introduction to product-fr
ee sets in finite groups\, discuss an application to Combinatorics\, and c
onclude with what is known about filled groups.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dmitry Savostyanov (University of Essex)
DTSTART;VALUE=DATE-TIME:20200618T130000Z
DTEND;VALUE=DATE-TIME:20200618T140000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/2
DESCRIPTION:Title: Epidemiological models on networks: Numerical approaches and challenges
(Work in progress)\nby Dmitry Savostyanov (University of Essex) as pa
rt of MESS (Mathematics Essex Seminar Series)\n\n\nAbstract\nMathematical
modelling of infectious disease is an important area of applied mathematic
s. The Kermack--McKendrick compartmental SIR model is quite simple but als
o quite powerful --- it describes the epidemics with a system of ordinary
differential equations (ODEs)\, which can be easily solved using a suitabl
e numerical method\, and predicts the behaviour of outbreaks very similar
to that observed in many recorded epidemics. Even though compartmental mod
els are almost hundred years old now\, they are still widely used not only
in a classroom\, but also to predict the development of dangerous disease
s and to inform Government strategies in case of emergency. The quality of
a mathematical model\, and our understanding of its assumptions and appli
cability in a particular scenario\, is therefore crucial to make correct d
ecisions to protect public health and respond to epidemics effectively whe
n they occur. The fundamental assumption of a compartmental model is that
the population is well-mixed: there is no firm boundary between susceptibl
e\, infected and recovered individuals. Everyone interacts with everyone a
t once\, similar to chemical molecules in a mixture. Although this assumpt
ion may be appropriate on a later stages of epidemic\, it clearly limits t
he model's capability to accurately describe and predict the early stages\
, when the infection is largely localised in one location and is carried t
o other locations through a network of transport and/or social and communi
ty links. If we consider how a disease progresses through a network\, only
neighbouring nodes can participate in transmission --- the network is not
well-mixed. Hence\, the compartmental model is no longer fit for purpose\
, and has to be replaced with a probabilistic model\, where we estimate th
e probability for each node to be in susceptible\, infected or recovered s
tate at a given time. Importantly\, the states of the neighbours are not
independent --- quite the opposite! --- a susceptible person in direct co
ntact with an infected person is likely to become infected soon. This mean
s that instead of considering individual probabilities\, we have to descri
be the evolution of the joint probability distribution\, accounting for th
e states of all nodes at once. This high--dimensional problem struggles fr
om the curse of dimensionality --- the number of unknowns grows exponentia
lly with the number of nodes\, and traditional ODE solvers can't cope with
he growing complexity when the number of nodes exceeds several tens. For
this reason\, the problem is typically solved using Stochastic Simulation
Algorithms (SSA)\, such as Monte Carlo and its variants. Using our experie
nce with high--dimensional problems\, such as Fokker--Planck\, Chemical Ma
ster Equation and Quantum Spin Dynamics\, we consider applying tensor prod
uct algorithms to solve this high--dimensional ODE with high accuracy\, an
d hence obtain a full probabilistic picture of the disease transfer throug
h the network. In preliminary experiments we find tensor product approach
to be successful in principle. In particular\, it can accurately estimate
the probabilities of rare events\, as well as higher moments of the observ
ed quantities\, where SSA often struggles. This is a work in progress! The
presented results are in preparation for publication. We will appreciate
all feedback and suggestions regarding this work.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:George Kinnear (University of Edinburgh)
DTSTART;VALUE=DATE-TIME:20200626T130000Z
DTEND;VALUE=DATE-TIME:20200626T140000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/3
DESCRIPTION:Title: Teaching mathematics online with STACK\nby George Kinnear (Universi
ty of Edinburgh) as part of MESS (Mathematics Essex Seminar Series)\n\n\nA
bstract\nAt the University of Edinburgh\, we have been increasing our use
of the STACK computer-aided assessment system to provide practice and home
work for students. I will give an overview of the features of STACK\, and
describe different ways it is being used across all years of our programme
. In particular\, I will show how STACK was a key part of the design of a
new optional course for incoming students\, "Fundamentals of Algebra and C
alculus"\, which covers key topics from Advanced Higher and A-Level syllab
uses. The course is delivered almost entirely online\, as a series of STAC
K quizzes which interleave textbook-style exposition with videos of worked
examples\, interactive applets\, and practice questions. I will describe
how ideas from education research and cognitive science (such as spacing a
nd retrieval practice) informed the course design\, from its overall struc
ture to the content of individual questions. I will also show some results
from our evaluation of the course\, including measures of the students' l
earning gains.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chris Antonopoulos (University of Essex)
DTSTART;VALUE=DATE-TIME:20201015T140000Z
DTEND;VALUE=DATE-TIME:20201015T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/4
DESCRIPTION:Title: An extended SIR model for the spread of COVID-19 in different communiti
es\nby Chris Antonopoulos (University of Essex) as part of MESS (Mathe
matics Essex Seminar Series)\n\n\nAbstract\nIn this paper\, we study the e
ffectiveness of the modelling approach on the pandemic due to the spreadin
g of the novel COVID-19 disease and develop an extended-susceptible-infect
ed-removed (eSIR) model that provides a theoretical framework to investiga
te its spread within a community. The eSIR model is based upon the well-kn
own susceptible-infected-removed (SIR) model with the difference that a to
tal population is not defined or kept constant per se and the number of su
sceptible individuals does not decline monotonically. To the contrary\, as
we show herein\, it can be increased in surge periods! In particular\, we
investigate the time evolution of different populations and monitor diver
se significant parameters for the spread of the disease in various communi
ties\, represented by countries and the state of Texas in the USA. The eSI
R model can provide us with insights and predictions of the spread of the
virus in communities that recorded data alone cannot. Our work shows the i
mportance of modelling the spread of COVID-19 by the eSIR model that we pr
opose here\, as it can help to assess the impact of the disease by offerin
g valuable predictions. Our analysis takes into account data from January
to June\, 2020\, the period that contains the data before and during the i
mplementation of strict and control measures. We propose predictions on va
rious parameters related to the spread of COVID-19 and on the number of su
sceptible\, infected and removed populations until September 2020. By comp
aring the recorded data with the data from our modelling approaches\, we d
educe that the spread of COVID-19 can be under control in all communities
considered\, if proper restrictions and strong policies are implemented to
control the infection rates early from the spread of the disease.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anne-Sophie Kaloghiros (Brunel University)
DTSTART;VALUE=DATE-TIME:20201112T150000Z
DTEND;VALUE=DATE-TIME:20201112T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/5
DESCRIPTION:Title: K-stability of Fano 3-folds\nby Anne-Sophie Kaloghiros (Brunel Univ
ersity) as part of MESS (Mathematics Essex Seminar Series)\n\n\nAbstract\n
Fano varieties are geometric shapes which are positively curved. They aris
e in a wide array of fields from theoretical physics to phylogenetic trees
. In fact\, every geometric shape which can be parametrised (or covered )
is - up to surgery - a family of Fano varieties. There are rich interacti
ons between differential geometric and algebro-geometric properties of Fan
o manifolds (and more generally of Kahler manifolds). An instance of this
phenomenon was conjectured by Yau Tian and Donaldson ( and proved by Donal
dson\, Chen and Sun): they proved that on Fano manifolds the existence of
special canonical metrics is equivalent to a stability property. This is
an equivalence between properties that are subtle\, and still little unde
rstood. I will discuss algebro-geometric approaches to this problem and wi
ll present recent developments and their applications to our understanding
of Fano surfaces and 3-folds.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Murat Akman (University of Essex)
DTSTART;VALUE=DATE-TIME:20201119T150000Z
DTEND;VALUE=DATE-TIME:20201119T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/6
DESCRIPTION:Title: A Minkowski problem for nonlinear capacity\nby Murat Akman (Univers
ity of Essex) as part of MESS (Mathematics Essex Seminar Series)\n\n\nAbst
ract\nThe classical Minkowski problem consists in finding a convex polyhed
ron from data consisting of normals to their faces and their surface areas
. In the smooth case\, the corresponding problem for convex bodies is to f
ind the convex body given the Gauss curvature of its boundary\, as a funct
ion of the unit normal. The proof consists of three parts: existence\, uni
queness and regularity. In this talk\, we study a Minkowski problem for ce
rtain measure associated with a compact convex set E with nonempty interio
r and its A-harmonic capacitary function in the complement of E. Here A-ha
rmonic PDE is a non-linear elliptic PDE whose structure is modeled on the
p-Laplace equation. If \\mu_E denotes this measure\, then the Minkowski
problem we consider in this setting is that\; for a given finite Borel mea
sure \\mu on S^(n-1)\, find necessary and sufficient conditions for which
there exists E as above with \\mu_E =\\mu. We will discuss the existence\,
uniqueness\, and regularity of this problem in this setting. The talk wil
l be related with the following papers: https://arxiv.org/abs/1906.01576\,
https://arxiv.org/abs/1810.03752\, https://arxiv.org/abs/1709.00447.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alastair Litterick (University of Essex)
DTSTART;VALUE=DATE-TIME:20201126T150000Z
DTEND;VALUE=DATE-TIME:20201126T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/7
DESCRIPTION:Title: Variations on a theme of J.-P. Serre: Complete reducibility in groups\,
representations\, buildings and geometric invariant theory\nby Alasta
ir Litterick (University of Essex) as part of MESS (Mathematics Essex Semi
nar Series)\n\n\nAbstract\nWhen studying modules or other algebraic object
s\, it is common to try and break things up and study the simple pieces. C
omplete reducibility asks the question: Under what conditions do these sim
ple objects fully describe the object we started with? In representation t
heory this becomes: Under what condition is every module a direct sum of i
ts irreducible factors? This question\, which a priori has nothing to do w
ith geometry\, topology or combinatorics\, turns out to have deep connecti
ons with all these other areas. In this talk we will look at these connect
ions\, and we will see how fundamental representation-theoretic results ha
ve analogues and generalisations in other areas of pure mathematics.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nicola Walker (Centre for Environment\, Fisheries and Aquaculture
Science)
DTSTART;VALUE=DATE-TIME:20201203T150000Z
DTEND;VALUE=DATE-TIME:20201203T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/8
DESCRIPTION:Title: Cod on the menu? Using mathematical modelling to provide fisheries mana
gement advice\nby Nicola Walker (Centre for Environment\, Fisheries an
d Aquaculture Science) as part of MESS (Mathematics Essex Seminar Series)\
n\n\nAbstract\nScientific advice on the management of fish stocks is often
informed by mathematical assessment models that fit to information from c
atches\, research surveys and life history. North Sea cod is a high-profil
e and commercially important stock with a long history of highs and lows.
In particular\, the latest assessment estimates that the stock is below sa
fe biological limits\, which comes just two years after the fishery was ce
rtified sustainable. Using North Sea cod as a case study\, Dr Walker will
present the state-space assessment model (SAM) and detail the process of t
urning model outputs into scientific advice for fisheries management. She
will discuss diagnostics for assessing the quality of input data and model
fits and highlight some of the problems facing the assessment of this sto
ck.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marina Iliopolou (University of Kent)
DTSTART;VALUE=DATE-TIME:20210204T150000Z
DTEND;VALUE=DATE-TIME:20210204T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/9
DESCRIPTION:Title: A discrete Kakeya-type inequality\nby Marina Iliopolou (University
of Kent) as part of MESS (Mathematics Essex Seminar Series)\n\n\nAbstract\
nThe Kakeya conjectures of harmonic analysis claim that congruent tubes th
at point in different directions rarely meet. In this talk we discuss the
resolution of an analogous problem in a discrete setting (where the tubes
are replaced by lines)\, and provide some structural information on quasi-
extremal configurations. This is joint work with A. Carbery.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jesús M. Seoane (Universidad Rey Juan Carlos)
DTSTART;VALUE=DATE-TIME:20210211T150000Z
DTEND;VALUE=DATE-TIME:20210211T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/10
DESCRIPTION:Title: Relativistic chaotic scattering\nby Jesús M. Seoane (Universidad
Rey Juan Carlos) as part of MESS (Mathematics Essex Seminar Series)\n\n\nA
bstract\n"The phenomenon of chaotic scattering is very relevant in differe
nt fields of science and engineering. It has been mainly studied in the co
ntext of Newtonian mechanics\, where the velocities of the particles are l
ow in comparison with the speed of light. In this talk\, we analyze global
properties such as the escape time distribution and the decay law of the
Hénon-Heiles system in the context of special relativity. Our results sho
w that the average escape time decreases with increasing values of the rel
ativistic factor β. As a matter of fact\, we have found a crossover point
for which the KAM islands in the phase space are destroyed when β ≃ 0.
4 [1]. On the other hand\, the study of the survival probability of partic
les in the scattering region shows an algebraic decay for values of β ≤
0.4\, and this law becomes exponential for β >\; 0.4. Surprisingly\, a
scaling law between the exponent of the decay law and the β factor is un
covered where a quadratic fitting between them is found. The results of ou
r numerical simulations agree faithfully with our qualitative arguments. B
esides\, we compute the basin entropy and the fractal dimension of the set
of singularities of the scattering function in function of β [2]. Finall
y\, we apply these results in the scattering in three-body problem in rela
tivistic regime [3]. We expect this work to be useful for a better underst
anding of both chaotic and relativistic systems.\n[1] J. D. Bernal\, J. M.
Seoane\, and M. A. F. Sanjuán. Global relativistic effects in chaotic sc
attering. Phys. Rev. E 95\, 032205 (2017).\n[2] J. D. Bernal\, J. M. Seoan
e\, and M. A. F. Sanjuán. Basin entropy and fractal dimension in relativi
stic chaotic scattering. Phys. Rev. E 97 042214 (2018).\n[3] J. D. Bernal\
, J. M. Seoane\, J. C. Vallejo\, L. Huang\, and M. A. F. Sanjuán. Influen
ce of the gravitational radius o asymptotic behaviour of the relativistic
Sitnikov problem. Phys. Rev. E 102 042204 (2020)."\n
LOCATION:https://researchseminars.org/talk/EssexMaths/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christina de Filippis (University of Turin)
DTSTART;VALUE=DATE-TIME:20210225T150000Z
DTEND;VALUE=DATE-TIME:20210225T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/11
DESCRIPTION:Title: Differentiable vs non-differentiable systems\nby Christina de Fili
ppis (University of Turin) as part of MESS (Mathematics Essex Seminar Seri
es)\n\n\nAbstract\n"Nonautonomous\, nonuniformly elliptic functionals are
variational integrals characterized by quite a wild behavior of the ellipt
icity ratio associated to their integrand\, in the sense that it may blow
up as the modulus of the gradient variable goes to infinity. We analyze th
e interaction between the space-depending coefficient of the integrand and
a possible forcing term and derive optimal Lipschitz criteria for minimiz
ers. We catch the main model cases appearing in the literature\, such as f
unctionals with unbalanced power growth or with fast exponential growth. W
e also find new borderline regularity results also in the uniformly ellipt
ic case\, i.e. when the ellipyicity ratio is uniformly bounded. This appro
ach yields optimal regularity results for obstacle problems associated for
instance to iterated exponential models\, which have been treated in [2]
for the first time. Finally\, we look at general nonautonomous integrands
with (p\,q)-growth and show general interpolation properties allowing to g
et basic higher integrability results for either bounded or Hölder contin
uous minimizers under improved bounds for the gap q-p.\nThis talk is based
on papers [1\,2\,3].\nReferences\n[1] C. De Filippis\, G. Mingione\, Inte
rpolative gap bounds for nonautonomous integrals. Preprint (2020)\, submit
ted.\n[2] C. De Filippis\, G. Mingione\, Lipschitz bounds and nonautonomou
s integrals. Preprint (2020)\, submitted. https://arxiv.org/pdf/2007.07469
.pdf\n[3] C. De Filippis\, G. Mingione\, On the regularity of minima of no
n-autonomous functionals. Journal of Geometric Analysis 30:1584-1626\, (20
20). https://doi.org/10.1007/s12220-019-00225-z"\n
LOCATION:https://researchseminars.org/talk/EssexMaths/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Charles Cox (University of Bristol)
DTSTART;VALUE=DATE-TIME:20210304T150000Z
DTEND;VALUE=DATE-TIME:20210304T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/12
DESCRIPTION:Title: Spread and infinite groups\nby Charles Cox (University of Bristol)
as part of MESS (Mathematics Essex Seminar Series)\n\n\nAbstract\nMy rece
nt work has involved taking questions asked for finite groups and consider
ing them for infinite groups. There are various natural directions with th
is. In finite group theory\, there exist many beautiful results regarding
generation properties. One such notion is that of spread\, and Scott Harpe
r and Casey Donoven have raised several intriguing questions for spread fo
r infinite groups (in https://arxiv.org/abs/1907.05498). A group G has spr
ead k if for every g_1\, …\, g_k in G we can find an h in G such that <
g_i\, h > = G for i = 1\, ...\, k. For any group we can say that if it has
a proper quotient that is non-cyclic\, then it has spread 0. In the finit
e world there is then the astounding result - which is the work of many au
thors - that this condition on proper quotients is not just a necessary co
ndition for positive spread\, but is also a sufficient one. Harper-Donoven
’s first question is therefore: is this the case for infinite groups? We
ll\, no. But that’s for the trivial reason that we have infinite simple
groups that are not 2-generated (and they point out that 3-generated examp
les are also known). But if we restrict ourselves to 2-generated groups\,
what happens? In this talk we’ll see the answer to this question. The ar
guments will be concrete (*) and accessible to a general audience.\n\n(*)
at the risk of ruining the punchline\, we will find a 2-generated group th
at has every proper quotient cyclic but that has spread zero.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nivedita Viswanathan (University of Edinburgh)
DTSTART;VALUE=DATE-TIME:20210318T150000Z
DTEND;VALUE=DATE-TIME:20210318T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/13
DESCRIPTION:Title: Understanding the notion of K-stability using 3-folds\nby Nivedita
Viswanathan (University of Edinburgh) as part of MESS (Mathematics Essex
Seminar Series)\n\n\nAbstract\nThe main objects of study in Algebraic geom
etry are ‘varieties’\, which are basically the geometric counterpart o
f solutions to polynomial equations. One of the most interesting questions
to ask about a variety\, is to determine whether it is ‘K-stable’. A
conjecture by Yau-Tian-Donaldson gives an algebro-geometric way of looking
at the notion of K-stability and many recent developments give very expli
cit ways of determining this property. In this talk\, my goal would be to
give you a rough idea of why this is very interesting to study\, by looki
ng at an explicit example of a Fano 3-fold. We will first look at the basi
c concepts that would be required to do this\, using some simple examples
and then take you through an example of a 3-fold slowly. We will look at
how best to describe the 3-fold using notions that are familiar to us and
then describe how one would determine the K-stability of the same. This
is joint work with Jesus Martinez Garcia\, Ivan Cheltsov\, Costya Shramov
\, Kento Fujita\, Carolina Araujo\, Ana-Maria Castravet\, Anne-Sophie Kalo
ghiros and Hendrick Suess.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mehmet Cihan (University of Essex)
DTSTART;VALUE=DATE-TIME:20210325T150000Z
DTEND;VALUE=DATE-TIME:20210325T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/14
DESCRIPTION:Title: Digraph groups and related groups\nby Mehmet Cihan (University of
Essex) as part of MESS (Mathematics Essex Seminar Series)\n\n\nAbstract\nG
roups can be expressed in terms of a ﬁnite a digraph which vertices cor
respond to the generators and arcs correspond to the relators. Cuno and
Williams investigated when the number of vertices is equal the number of a
rcs\, where the undirected graph is triangle free that means the girth is
at least 4\, and they proved that the corresponding group is either finite
cyclic or infinite. It is known that when the number of vertices is more
than the number of arcs\, then it is infinite. Therefore\, I investigated
when the number of vertices is less than or equal the number of arcs in m
y thesis. But it is more interesting when the undirected graph is with tri
angle and therefore the underlying graph is complete graph. When we direct
ed the complete graph\, then it is known as tournaments. All known example
s are done by Mennicke and Johnson for a strong tournament with 3 vertices
. In 1959\, Mennicke provided an example of a group defined by the present
ation M(a\, b\, c) =〈x\, y\, z | y^−1xy=x^a\, z^−1yz=y^b\, x^−1zx=
z^c〉\, which is finite in the case a=b=c ≥ 3. In 1997\, Johnson provi
ded another group needing exactly three generators with presentation J(a\,
b\, c) =〈x\, y\, z|x^y=y^(b−2)x^−1y^(b+2)\, y^z=z^(c−2)y^−1z^(c
+2)\,z^x=x^(a-2)z^−1x^(a+2)〉 and which is finite in the cases where a\
, b\, and c are non-zero even integers. These are important since they pr
ovide examples of finite groups needing exactly three generators. In this
talk\, I will talk about generalisation of their groups from 3 generators
to n generators for all strong tournaments.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Federica Armani (University of Essex)
DTSTART;VALUE=DATE-TIME:20210429T140000Z
DTEND;VALUE=DATE-TIME:20210429T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/15
DESCRIPTION:Title: Mathematics Anxiety: general overview\, what has been done and what we
need to do to help learners\nby Federica Armani (University of Essex)
as part of MESS (Mathematics Essex Seminar Series)\n\n\nAbstract\nMathema
tical competence is an important ability to master often accompanied by a
feeling of apprehension\, anxiety and fear which influence the achievement
s\, career choices or performance of an individual. This is called Math An
xiety\, a feeling of tension and anxiety that interferes with the manipula
tion of numbers and the solving of mathematical problems in ordinary life
and academic situations. In this seminar I will discuss this problem and s
how how tailored educational approaches in combination with motivational a
nd Mindset Theories can be used to mitigate the negative effects of Math A
nxiety. In the last part I will present the development and initial result
s obtained from a mathematical puzzle I am using in research which relies
on counting abilities\, spatial reasoning\, working memory and exploits ba
sic mathematical knowledge adapted and used in a different and more engagi
ng way in order to solve a series of puzzles.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marina Logares (Universidad Complutense de Madrid)
DTSTART;VALUE=DATE-TIME:20210520T140000Z
DTEND;VALUE=DATE-TIME:20210520T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/16
DESCRIPTION:by Marina Logares (Universidad Complutense de Madrid) as part
of MESS (Mathematics Essex Seminar Series)\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/EssexMaths/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sergey Dolgov (University of Bath)
DTSTART;VALUE=DATE-TIME:20210617T140000Z
DTEND;VALUE=DATE-TIME:20210617T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/17
DESCRIPTION:Title: Deep tensor decompositions for sampling from high-dimensional distribu
tions\nby Sergey Dolgov (University of Bath) as part of MESS (Mathemat
ics Essex Seminar Series)\n\nInteractive livestream: https://essex-univers
ity.zoom.us/j/96737423878\nPassword hint: Write to the organisers to obtai
n the password.\n\nAbstract\nCharacterising intractable high-dimensional r
andom variables is one of the fundamental challenges in stochastic computa
tion\, for example\, in the solution of Bayesian inverse problems. The rec
ent surge of transport maps offers a mathematical foundation and new insig
hts for tackling this challenge by coupling intractable random variables w
ith tractable reference random variables. In this talk I will present a ne
sted coordinate transformation framework inspired by deep neural networks
but driven by functional tensor-train approximation of tempered probabilit
y density functions instead. This bypasses slow gradient descent optimisat
ion by a direct inverse Rosenblatt transformation. The resulting deep inve
rse Rosenblatt transport significantly expands the capability of tensor ap
proximations and transport maps to random variables with complicated nonli
near interactions and concentrated density functions. We demonstrate the e
fficiency of the proposed approach on a range of applications in uncertain
ty quantification\, including parameter estimation for dynamical systems a
nd inverse problems constrained by partial differential equations.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/17/
URL:https://essex-university.zoom.us/j/96737423878
END:VEVENT
BEGIN:VEVENT
SUMMARY:Georgios Amanatidis (University of Essex)
DTSTART;VALUE=DATE-TIME:20201105T150000Z
DTEND;VALUE=DATE-TIME:20201105T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/18
DESCRIPTION:Title: Rapid mixing of the switch Markov chain for strongly stable degree seq
uences\nby Georgios Amanatidis (University of Essex) as part of MESS (
Mathematics Essex Seminar Series)\n\n\nAbstract\nThe switch Markov chain h
as been extensively studied as the most natural Markov Chain Monte Carlo a
pproach for sampling graphs with prescribed degree sequences. We show that
the switch chain for sampling simple undirected graphs with a given degre
e sequence is rapidly mixing when the degree sequence is so-called strongl
y stable. Strong stability is satisfied by all degree sequences for which
the switch chain was known to be rapidly mixing based on Sinclair's multic
ommodity flow method up until a recent manuscript of Erd\\H{o}s et al. (20
19). Our approach relies on an embedding argument\, involving a Markov cha
in defined by Jerrum and Sinclair (1990). This results in a much shorter p
roof that unifies (almost) all the rapid mixing results for the switch cha
in in the literature\, and extends them up to sharp characterizations of P
-stable degree sequences. In particular\, our work resolves an open proble
m posed by Greenhill and Sfragara (2017).\n
LOCATION:https://researchseminars.org/talk/EssexMaths/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anouchah Latifi (University of Qom)
DTSTART;VALUE=DATE-TIME:20201029T150000Z
DTEND;VALUE=DATE-TIME:20201029T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/20
DESCRIPTION:Title: Labyrinth walk: A chaotic non Hamiltonian conservative system that doe
s not admit an energy function\nby Anouchah Latifi (University of Qom)
as part of MESS (Mathematics Essex Seminar Series)\n\n\nAbstract\nLabyrin
th Chaos and it conservative version\, Labyrinth walk are generic and mini
mal models of a dynamical system discovered by Otto Rossler and Rene Thoma
s in order to identify the necessary mathematical conditions for the appea
rance of chaotic and hyperchaotic motion in continuous flows. It turned ou
t that in spite of its extreme simplicity these systems are full of surpri
sing properties. Simple and elegant as it is\, it still holds great promis
e for elucidating aspects of chaotic dynamics that are not evident in othe
r systems. Our work highlights the incredible riches of this system in its
disconcerting simplicity and its importance in the context of dynamical s
ystems and in other fields. This is joint work with Chris G. Antonopoulos
and Vasileios Basios.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Simon Blackburn (Royal Holloway\, University of London)
DTSTART;VALUE=DATE-TIME:20201210T150000Z
DTEND;VALUE=DATE-TIME:20201210T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/21
DESCRIPTION:Title: How many finite rings are there?\nby Simon Blackburn (Royal Hollow
ay\, University of London) as part of MESS (Mathematics Essex Seminar Seri
es)\n\n\nAbstract\nFor a positive integer $n$\, write $f(n)$ for the numbe
r of isomorphism classes of rings of order $n$. What can we say about $f(n
)$? Determining $f(n)$ exactly for all $n$ looks unrealistic\, but in 1970
Kruse and Price (J LMS) stated an asymptotic result that gives the growth
rate of $f(n)$ as $n\\rightarrow\\infty$. Sadly\, there are problems wit
h their proof. I will talk about recent joint work with K. Robin McLean (U
niversity of Liverpool) in which we fix the problems\, and improve the err
or terms\, of the Kruse--Price result. No knowledge of ring theory above a
first undergraduate course will be assumed!\n
LOCATION:https://researchseminars.org/talk/EssexMaths/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Melissa Lee (University of Auckland)
DTSTART;VALUE=DATE-TIME:20201217T090000Z
DTEND;VALUE=DATE-TIME:20201217T100000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/22
DESCRIPTION:Title: The hunt for regular orbits of almost quasisimple groups\nby Melis
sa Lee (University of Auckland) as part of MESS (Mathematics Essex Seminar
Series)\n\n\nAbstract\nLet $G$ be a permutation group on $\\Omega$. We sa
y that $G$ has a regular orbit on $\\Omega$ if there exists $x \\in \\Omeg
a$ that is fixed only by the identity permutation. Regular orbits arise in
a number of applications including the study of Frobenius groups and the
proof of the celebrated $k(GV)$-theorem\, which gives an upper bound on th
e number of conjugacy classes of certain affine groups where $|G|$ and $|V
|$ are coprime. One of the major cases in the proof of the $k(GV)$-theore
m was a study of regular orbits of the so-called almost quasisimple groups
$G$ (i.e.\,$ G/F(G)$ is an almost simple group). In this talk\, after giv
ing some background and motivation\, I will discuss progress in my quest t
o finish classifying all pairs $(G\,V)$ where $G$ is an almost quasisimple
group with a regular orbit on its irreducible module $V$. By the proof of
the $k(GV)$-problem\, this boils down to the cases where $(|G|\,|V|) >1$.
I will also briefly discuss techniques used for this classification\, whi
ch involve some algebraic group theory\, character theory and computationa
l methods.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Antonio Marcos Batista (State University of Ponta Grossa\, Paraná
\, Brazil)
DTSTART;VALUE=DATE-TIME:20210128T150000Z
DTEND;VALUE=DATE-TIME:20210128T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/23
DESCRIPTION:Title: Extreme events in nonlinear wave interactions (dragon king)\nby An
tonio Marcos Batista (State University of Ponta Grossa\, Paraná\, Brazil)
as part of MESS (Mathematics Essex Seminar Series)\n\n\nAbstract\nExtreme
events are by definition rare and exhibit unusual values of relevant ob
servables. In literature\, it is possible to find many studies about the p
redictability and suppression of extreme events. In this work\, we show
the existence of dragon-kings extreme events in nonlinear three-wave
interactions. Dragon-king extreme events\, identified by phase transi
tions\, tipping points and catastrophes\, affects fluctuating systems. We
show that these events can be avoided by adding a perturbing small ampli
tude wave to the system.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kelly Iarosz (Universidade Tecnológica Federal do Paraná UTFPR F
aculdade de Telêmaco Borba FATEB)
DTSTART;VALUE=DATE-TIME:20210218T150000Z
DTEND;VALUE=DATE-TIME:20210218T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/24
DESCRIPTION:Title: Our brain is not static\nby Kelly Iarosz (Universidade Tecnológic
a Federal do Paraná UTFPR Faculdade de Telêmaco Borba FATEB) as part of
MESS (Mathematics Essex Seminar Series)\n\n\nAbstract\nThe connections bet
ween brain neurons have the characteristic of being modified over time due
to several causes such as new experiences\, lesions\, brain pathologies\,
etc. This fenomenon is known as synaptic plasticity. We study the capacit
y of neurons in a network to change temporarily or permanently their conne
ctions and behavior\, as a function of their synchronous behavior. Specifi
cally\, an initial all-to-all topology evolves to a complex topology. More
over\, external perturbations can induce co-existence of clusters\, those
whose neurons are synchronous and those whose neurons are desynchronous. W
hen the delay is increased the network presents a non-trivial topology. Re
garding the synchronization\, only for small values of the synaptic delay
this phenomenon is observed.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jennifer Creaser (University of Exeter)
DTSTART;VALUE=DATE-TIME:20210311T150000Z
DTEND;VALUE=DATE-TIME:20210311T160000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/25
DESCRIPTION:Title: Domino effects on networks of bistable oscillatory nodes\nby Jenni
fer Creaser (University of Exeter) as part of MESS (Mathematics Essex Semi
nar Series)\n\n\nAbstract\nMultistability has been identified as a key mec
hanism in a diverse range of brain functions at different spatial scales.
It is well known that the addition of noise in a multistable system can in
duce random transitions between states. In a network\, the presence of cou
pling introduces dependence between nodes leading to sequences of noise-in
duced transitions in a so called domino effect. The timing and order of th
ese domino cascades are emergent properties of the network. Analysis of th
e transient dynamics responsible for these transitions is crucial to under
stand the drivers of neurological disorders such as epilepsy. We consider
a general model of coupled bi-stable oscillators. Each node has two stable
states\; oscillating (active) and non-oscillating (quiescent). Escape fro
m the quiescent state is driven by additive noise and we assume the timesc
ale of transitions back again is long enough to be ignored. Escapes are af
fected by changes in node dynamics\, coupling strength and synchronisation
. Using numerical and theoretical techniques we explore the interplay betw
een synchronisation and noise-induced escape. We consider amplitude and ph
ase-amplitude coupled motifs. In particular\, we find and investigate exam
ples of three node symmetric networks where sequences of noise-induced esc
apes are associated with various types of partial synchrony during the seq
uence.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kyle Wedgwood (University of Exeter)
DTSTART;VALUE=DATE-TIME:20210506T140000Z
DTEND;VALUE=DATE-TIME:20210506T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/26
DESCRIPTION:Title: The curious case of rapid entrainment after jet lag\, and\, how to get
a single neuron to remember\nby Kyle Wedgwood (University of Exeter)
as part of MESS (Mathematics Essex Seminar Series)\n\n\nAbstract\n"This ta
lk will cover two stories involving mathematical modelling (and some exper
iments) in neural systems.\n\nIn the first\, we will discuss the re-entrai
nment problem of how our bodies synchronise with the external environment
following travel across time zones or shift work. To do so\, we analyse a
two-dimensional variant of the Forgers-Jewett-Kronauer model\, which descr
ibes changes in core body temperature and neural activity in the brain reg
ion responsible for circadian rhythms\, forced by a 24-hour light/dark cyc
le. This model\, which has previously been used to explain the East-West a
symmetry in jet lag severity after travel\, predicts a counter-intuitive r
apid re-entrainment for sufficiently bright daylight. We explain this phen
omenon via continuation of invariant manifolds of fixed points of a 24-hou
r stroboscopic map and explore the consequence of the arrangement of such
manifolds on re-entrainment in a variety of scenarios.\n\nIn the second st
ory\, we will explore the capability of a neuron that is synaptically coup
led to itself\, to store and repeat patterns of precisely timed spikes\, w
hich we regard as single cell 'memories'. Drawing on analogies from semico
nductor lasers\, we append a delayed self-coupling term to the oft studied
Morris-Lecar model of neuronal excitability and use bifurcation analysis
to predict the number and type of memories the neuron can store. These res
ults highlight the delay period as an important period parameter controlli
ng the storage capacity of the cell. Finally\, we use the dynamic clamp pr
otocol to introduce self-coupling to a mammalian cell and confirm the exis
tence of the spiking patterns predicted by the model analysis."\n
LOCATION:https://researchseminars.org/talk/EssexMaths/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Constanza Rojas-Molina (CY Tech - Institut des Sciences et Techniq
ues - CY Cergy Paris Université)
DTSTART;VALUE=DATE-TIME:20210513T140000Z
DTEND;VALUE=DATE-TIME:20210513T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/27
DESCRIPTION:Title: Fractional random Schrödinger operators\, integrated density of state
s and localization\nby Constanza Rojas-Molina (CY Tech - Institut des
Sciences et Techniques - CY Cergy Paris Université) as part of MESS (Math
ematics Essex Seminar Series)\n\n\nAbstract\nIn this talk we will review s
ome recent results on the fractional Anderson model\, a random Schrödinge
r operator driven by a fractional laplacian. The interest on the latter li
es in their association to stable Levy processes\, random walks with long
jumps and anomalous diffusion. We discuss in this talk the interplay betwe
en the non-locality of the fractional laplacian and the localization prope
rties of the random potential in the fractional Anderson model\, in both t
he continuous and discrete settings. In the discrete setting we study the
integrated density of states and show a fractional version of Lifshitz tai
ls. This coincides with results obtained in the continuous setting by the
probability community. This is based on joint work with M. Gebert (LMU Mun
ich).\n
LOCATION:https://researchseminars.org/talk/EssexMaths/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Billy Woods (University of Essex)
DTSTART;VALUE=DATE-TIME:20210527T140000Z
DTEND;VALUE=DATE-TIME:20210527T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/28
DESCRIPTION:Title: Iwasawa algebras and skew power series rings\nby Billy Woods (Univ
ersity of Essex) as part of MESS (Mathematics Essex Seminar Series)\n\n\nA
bstract\nIn this talk\, beginning with a faulty proof of Fermat’s Last T
heorem from the 19th century\, I’ll attempt to provide some motivation
for the study of Iwasawa algebras\, which have now become a critical tool
in many significant number-theoretic problems. I’ll give a couple of way
s to think about them algebraically\, contrast them with similar algebraic
objects\, and outline some of what is known (and what is still unknown) a
bout them\, including my own research. This is a talk about noncommutative
algebra\, but I’ll try to keep the technical jargon to a minimum\, so t
hat much of this talk remains accessible even to those who haven’t thoug
ht about abstract algebra in some time!\n
LOCATION:https://researchseminars.org/talk/EssexMaths/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thanos Manos (CY Tech - Institut des Sciences et Techniques - CY C
ergy Paris Université)
DTSTART;VALUE=DATE-TIME:20210603T140000Z
DTEND;VALUE=DATE-TIME:20210603T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/29
DESCRIPTION:Title: Neural networks: desynchronization with synaptic and structural plasti
city\nby Thanos Manos (CY Tech - Institut des Sciences et Techniques -
CY Cergy Paris Université) as part of MESS (Mathematics Essex Seminar Se
ries)\n\n\nAbstract\n"Mathematical modelling is an important tool in under
standing the basic mechanisms of the human brain as well as determining it
s function and operation. In this talk\, I will discuss how such models\,
based on ordinary differential equations can capture and describe the unde
rlying dynamical evolution of interactions between a relatively small numb
er of neurons within some brain area. Several brain diseases are character
ized by abnormally strong neuronal synchrony. Coordinated Reset (CR) stimu
lation was computationally designed to specifically counteract abnormal ne
uronal synchronization processes by desynchronization. In the presence of
spike timing-dependent plasticity (STDP) this leads to a decrease of synap
tic weights and ultimately to an anti-kindling\, i.e.\, unlearning of abno
rmal synaptic connectivity and abnormal neuronal synchrony. The long-lasti
ng desynchronizing impact of CR stimulation has been verified in pre-clini
cal and clinical proof of concept studies. However\, as yet it is unclear
how to optimally choose the CR stimulation frequency\, i.e.\, the repetiti
on rate at which the CR stimuli are delivered.\nThe first part of the talk
is dedicated to systems with STDP and the design of optimal CR stimulatio
n protocols. Namely\, protocols that manage to induce global (for differen
t system initiations) desynchronization but also show very good robustness
among different signals and network dependent variations. These findings
can be implemented into stimulation protocols for first in man and proof o
f concept studies aiming at further improvement of CR stimulation.\nIn the
second part\, I will present a computational model which account for comb
ining different time scales with synaptic (STDP) and structural plasticity
. The latter one refers to a mechanism that deletes or generates synapses
in order to homeostatically adapt the firing rates of neurons to a set poi
nt-like target firing rate in the course of days to months. Such a model s
ucceeds to explain a clinically relevant dynamic phenomenon which could no
t be explained in the STDP-only models so far. It also provides a plausibl
e mechanism that explains why CR stimulation may become more effective (i.
e.\, require less stimulation duration) when repeatedly delivered (in the
course of the treatment). This aspect is crucial from a clinical standpoin
t to further optimize dosing (and hence treatment outcome) of CR stimulati
on."\n
LOCATION:https://researchseminars.org/talk/EssexMaths/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Helen Christodoulidi (University of Lincoln)
DTSTART;VALUE=DATE-TIME:20210610T140000Z
DTEND;VALUE=DATE-TIME:20210610T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/30
DESCRIPTION:Title: The role of KdV and Toda in the FPUT problem\nby Helen Christodoul
idi (University of Lincoln) as part of MESS (Mathematics Essex Seminar Ser
ies)\n\n\nAbstract\nThe celebrated Fermi-Pasta-Ulam-Tsingou model is a lon
g chain of coupled nonlinear oscillators representing the simplest one-dim
ensional analogue of atoms in a crystal. This system represents a benchmar
k in the history of nonlinear science: The FPUT problem sparked the birth
of both computational mathematics and integrable systems. Most notably\, i
t is the first dynamical system numerically integrated on a computer while
its enigmatic non-ergodic behaviour is puzzling the scientists for over 6
5 years\, with innumerable works published. In this talk I will focus on t
he role of two integrable models\, namely I) the Korteweg-de Vries equatio
n (KdV)\, which describes waves on shallow water surfaces\, and II) the To
da lattice\, in explaining FPUT's non-ergodic behaviour at low energies.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kirk McDermott (Slippery Rock University)
DTSTART;VALUE=DATE-TIME:20210624T140000Z
DTEND;VALUE=DATE-TIME:20210624T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/31
DESCRIPTION:Title: On the shift dynamics of groups of Fibonacci type\nby Kirk McDermo
tt (Slippery Rock University) as part of MESS (Mathematics Essex Seminar S
eries)\n\nInteractive livestream: https://essex-university.zoom.us/j/96737
423878\nPassword hint: Write to the organisers to obtain the password.\n\n
Abstract\nA group is said to be cyclically presented if it admits a presen
tation with a certain cyclic symmetry. Such a symmetry induces a periodic
automorphism of the group called the shift\, and its dynamics strongly imp
acts the structure of the group. In this talk\, we investigate the shift d
ynamics of the cyclically presented groups of Fibonacci type. These groups
have a rich history and have been studied from a variety of perspectives\
, from combinatorial group theory to 3-manifold topology. We use these per
spectives to study the shift dynamics and go on to introduce topological a
nd computational techniques for identifying fixed points.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/31/
URL:https://essex-university.zoom.us/j/96737423878
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ihechukwu Chinyere (University of Essex)
DTSTART;VALUE=DATE-TIME:20210701T140000Z
DTEND;VALUE=DATE-TIME:20210701T150000Z
DTSTAMP;VALUE=DATE-TIME:20210612T235129Z
UID:EssexMaths/32
DESCRIPTION:Title: Hyperbolicity of certain cyclically presented groups\nby Ihechukwu
Chinyere (University of Essex) as part of MESS (Mathematics Essex Seminar
Series)\n\nInteractive livestream: https://essex-university.zoom.us/j/967
37423878\nPassword hint: Write to the organisers to obtain the password.\n
\nAbstract\nIn his 1992 article titled “A funny property of sphere and e
quations over groups” Klyachko used the car-crash lemma to establish the
Kervaire conjecture for torsion-free groups. Inspired by this constructio
n we use ant-lane argument to prove that certain cyclically presented grou
ps are hyperbolic.\n
LOCATION:https://researchseminars.org/talk/EssexMaths/32/
URL:https://essex-university.zoom.us/j/96737423878
END:VEVENT
END:VCALENDAR