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BEGIN:VEVENT
SUMMARY:Alexandre Baraviera (UFRGS)
DTSTART:20200812T170000Z
DTEND:20200812T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/1
DESCRIPTION:Title: Medidas estacionárias em grafos infinitos\nby Alexandre Bara
viera (UFRGS) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nGraf
os são objetos interessantes que aparecem naturalmente na modelagem de di
versos problemas\, como por exemplo a difusão de uma doença ou a eficiê
ncia da comunicação em uma certa rede de transmissão de dados\, dentre
muitos outros. A caracterização destes fenômenos em geral envolve conhe
cer o espectro associado ao grafo\, e por isso técnicas de obtenção des
se tipo de informação se fazem importantes. Nessa direção\, o mét
odo da redução isospectral desenvolvido por Bunimovich e Webb se mostra
uma ferramenta eficiente\, que permite trocar um grafo por subgrafos menor
es onde em principio a obtenção de autovalores pode ser uma tarefa mais
simples.\n\nNessa palestra pretendo contar de maneira relativamente elemen
tar uma parte da história acima (tentando ilustrar os conceitos envolvido
s) e falar sobre um trabalho escrito em colaboração com Joana Torres (Un
iversidade do Minho) e Pedro Duarte (Universidade de Lisboa) no qual uma e
xtensão dos métodos de Bunimovich-Webb para grafos infinitos é usada pa
ra obter estados estacionários de certos processos estocásticos numa cla
sse de grafos. Minha intenção é focalizar a exposição em exemplos de
forma a deixá-la acessível a um público amplo.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gonçalo Oliveira (UFF)
DTSTART:20200819T170000Z
DTEND:20200819T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/2
DESCRIPTION:Title: Sounding a Riemannian manifold with hard spheres\nby Gonçalo
Oliveira (UFF) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nGi
ven a Riemannian manifold M one may attempt at exploring its geometry by s
ounding it with hard spheres. Regarding these spheres as the atomic consti
tuents of a gas filling M\, one can compute an equation of state relating
its several macroscopic quantities such as pressure\, volume\, and tempera
ture. \n\nThis talk is an exercise in statistical mechanics where I shall
explain how the resulting equation depends on the underlying Riemannian ge
ometry.\n\nLink will appear shortly before the seminar.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alveri Alves Sant'Ana (UFRGS)
DTSTART:20200826T170000Z
DTEND:20200826T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/3
DESCRIPTION:Title: Extensões de Ore e álgebras de Hopf\nby Alveri Alves Sant'A
na (UFRGS) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nExtens
ões de Ore são anéis de polinômios nos quais os coeficientes não comu
tam necessariamente com a variável. Muitas álgebras bem conhecidas da li
teratura podem ser obtidas via extensões de Ore (ou por um quociente dela
s). Em particular\, M. Beattie\, S. Dascalescu e L. Grunenfelder construí
ram uma família infinita de álgebras de Hopf não isomorfas\, de uma cer
ta dimensão fixa\, via extensões de Ore de anéis de grupo\, dando uma r
esposta negativa à décima conjectura de Kaplansky. Posteriormente\, Pano
v deu uma caracterização das assim chamadas extensões Hopf-Ore (extens
ões de Ore de álgebras de Hopf que contém a álgebra base como uma sub
álgebra de Hopf)\, bem como classificou estas extensões das álgebras de
grupo. \n\nNesta palestra pretendemos abordar o enredo acima\, com ênfas
e nos resultados de Panov e finalizaremos com uma generalização do Teore
ma de Panov para o contexto das álgebras de Hopf fracas\, obtida num trab
alho em conjunto com C. Lomp (U. Porto) e R. Santos (FURG). Tentaremos evi
tar ao máximo as tecnicalidades para atingirmos uma audiência mais ampla
.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Juliana Fernandes (UFRJ)
DTSTART:20200902T170000Z
DTEND:20200902T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/4
DESCRIPTION:Title: Blow-up and grow-up for parabolic PDEs\nby Juliana Fernandes
(UFRJ) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nWe discuss
recent results on finite and infinite time blow-up solutions of parabolic
PDEs. We are mainly interested in the limiting dynamics as it approaches t
he maximal time of existence.\n\nLink will appear shortly before the talk.
\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Patrícia Gonçalves (Instituto Superior Técnico)
DTSTART:20200909T130000Z
DTEND:20200909T140000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/5
DESCRIPTION:Title: Symmetric exclusion with reservoirs\nby Patrícia Gonçalves
(Instituto Superior Técnico) as part of Webinários do PPGMat - UFRGS\n\n
\nAbstract\nIn this seminar I will describe the derivation of some partial
differential equations that rule the space-time evolution of the density
of some stochastic processes. The goal is to describe the connection betwe
en the macroscopic (continuous) equations and the microscopic (discrete) s
ystem of random particles. \n\nThe former can be either PDEs or stochastic
PDEs depending on whether one is looking at the law of large numbers or t
he central limit theorem scaling\; while the latter is a collection of par
ticles that move randomly according to a transition probability. \n\nI wil
l focus on a model for which we can obtain a collection of (fractional) re
action-diffusion equations given in terms of the regional fractional Lapla
cian with different types of boundary conditions. \n\nThis is a joint work
with Cédric Bernardin\, Byon Jiménez-Oviedo and Stefano Scotta.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Wagner de Oliveira Cortes (UFRGS)
DTSTART:20200916T170000Z
DTEND:20200916T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/6
DESCRIPTION:Title: Loops\, quasigrupos e temas relacionados\nby Wagner de Olivei
ra Cortes (UFRGS) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\n
Nesta palestra\, iremos falar de uma maneira introdutória sobre loops e q
uasigrupos que seriam uma versão não-associativa de grupo\, onde exibire
mos exemplos. Esta teoria é muito rica e amplamente explorada. Iremos exp
lanar também sobre grupoides e semigrupos inversos. Como quasigrupos são
“versões” não associativas de grupos\, o que seriam versões não a
ssociativas de grupoides e semigrupos inversos? Nesta direção\, iremos i
ntroduzir uma versão não-associativa de grupoide e uma versão não asso
ciativa de semigrupos inversos e exibir exemplos. Parte da teoria a ser ap
resentada nesta palestra foi obtida juntamente com a Professora Maria de L
ourdes Giuliani.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marcelo Muniz Alves (UFPR)
DTSTART:20200930T170000Z
DTEND:20200930T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/7
DESCRIPTION:Title: Teoria clássica de invariantes e códigos auto-duais\nby Mar
celo Muniz Alves (UFPR) as part of Webinários do PPGMat - UFRGS\n\n\nAbst
ract\nDada uma ação de um grupo $G$ em um conjunto $X$\, um invariante p
ara ação é um elemento que permanece inalterado pela aplicação de qua
lquer elemento de $G$. Invariantes fazem parte\, entre outros\, da Geometr
ia Analítica\, onde temos a classificação das cônicas por meio do disc
riminante\, que é um invariante sob os movimentos do plano\; na Álgebra
Linear\, em que o polinômio minimal\, o polinômio característico\, o de
terminante e o traço são invariantes da ação por conjugação do grupo
linear geral $GL(n\,K)$ no espaço das matrizes\; na Teoria de Galois\, c
ujo principal resultado é a correspondência entre subcorpos de $K$ e sub
grupos do grupo de Galois por meio de subcorpos invariantes\; e mesmo do e
studo de EDP's clássicas\, onde funções no círculo são identificadas
com funções periódicas da reta\, que são o mesmo que invariantes para
ação de um grupo de translações da reta. Nós apresentaremos detalhes
sobre o caso em que G é um subgrupo finito do grupo linear geral $GL(n\,K
)$ agindo em um anel de polinômios $K[x_1\,x_2\, ...\, x_n]$\, sendo que
esta ação é induzida da ação canônica de $GL(n\,K)$ em $K^n$. Neste
caso\, o conjunto de invariantes sob G forma um subanel do anel de polinô
mios e o problema de descrever este subanel foi um forte tema de pesquisa
entre o final do século XIX e as primeiras décadas do século XX. Nós v
eremos resultados fundamentais de Noether e Molien desta época sobre o an
el de invariantes. A teoria de invariantes "resssurgiu" novamente nos anos
1970 em Geometria Algébrica\, mas também na teoria de códigos corretor
es de erros. Estes códigos surgiram na década de 1950 com o objetivo de
implementar uma correção automática de erros de leitura em computadores
\, e tornaram-se a espinha dorsal de boa parte dos processos de comunicaç
ão e armazenamento de informação digital que temos hoje. Os problemas p
ráticos da teoria de códigos levam naturalmente a problemas de álgebra\
, geometria finita e combinatória\; um desses "spin-offs" é o estudo dos
códigos auto-duais e é aqui que aparecem aplicações da teoria clássi
ca de invariantes. Ao final falamos de um trabalho sobre códigos auto-dua
is feito por Welington Santos em sua tese defendida recentemente no PPGM-U
FPR.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jeovanny de Jesus Muentes Acevedo (Universidad Tecnológica de Bol
ívar)
DTSTART:20201007T170000Z
DTEND:20201007T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/8
DESCRIPTION:Title: Aplicações contínuas com dimensão métrica média positiva\nby Jeovanny de Jesus Muentes Acevedo (Universidad Tecnológica de Bolí
var) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nM. Gromov int
roduziu a dimensão média para uma aplicação contínua no final dos ano
s 1990\, o qual é um invariante sob conjugação topológica. Por outro l
ado\, a noção de dimensao métrica média para um sistema dinâmico foi
introduzida por Lindenstrauss e Weiss em 2000\, a qual refina a entropia t
opológica para sistemas dinâmicos com entropia topológica infinita. Nes
ta palestra\, mostraremos alguns resultados relacionados à existência de
aplicações contínuas com dimensao métrica média positiva.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Colin Adams (Williams College)
DTSTART:20201014T170000Z
DTEND:20201014T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/9
DESCRIPTION:Title: Volumes of Hyperbolic 3-Manifolds\nby Colin Adams (Williams C
ollege) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nGiven a li
nk in a 3-manifold that can be appropriately decomposed into tangles\, we
define certain types of hyperbolicity for the tangles and an associated vo
lume. Using results of Agol-Storm-Thurston\, we show that links obtained f
rom the tangles are themselves hyperbolic. Further\, we obtain surprisingl
y accurate lower bounds on the volumes of the links from the sum of the vo
lumes of the constituent tangles in various 3-manifolds.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Levon Nurbekyan (UCLA)
DTSTART:20201028T170000Z
DTEND:20201028T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/10
DESCRIPTION:Title: Spectral methods for nonlocal mean-field games\nby Levon Nur
bekyan (UCLA) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nMean
-field games (MFG) theory is a framework to model and study huge populatio
ns of agents that play non-cooperative differential games. I will discuss
some of the recent developments in applying spectral methods for a numeric
al and possibly theoretical resolution of MFG systems with nonlocal intera
ctions among agents. I will also draw connections with kernel methods in m
achine learning.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Paulo Varandas (UFBA & FCT-CMUP)
DTSTART:20201104T170000Z
DTEND:20201104T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/11
DESCRIPTION:Title: Phase transitions and appearance of ghost measures\nby Paulo
Varandas (UFBA & FCT-CMUP) as part of Webinários do PPGMat - UFRGS\n\n\n
Abstract\nThe thermodynamic formalism for transitive uniformly hyperbolic
dynamics is nowadays well understood and\, among other aspects\, it is wor
th mentioning that regular potentials (meaning Holder continuous) are so t
hat the pressure function is differentiable and admit unique equilibrium s
tates. The situation changes drastically in simple examples beyond uniform
hyperbolicity\, as the case of the Manneville-Pomeau maps\, where differe
nt kinds of phase transitions appear due to the phenomenon of intermittenc
y of an indifferent fixed point. In this talk I will focus on this family
and discuss a new aspect of the phase transitions\, namely the appearance
of finitely additive absolutely continuous invariant measures. This is par
t of a joint work with A. Castro (UFBA) and L. Cioletti (UnB).\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Luis Yapu
DTSTART:20201111T170000Z
DTEND:20201111T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/12
DESCRIPTION:Title: First integrals and hamiltonization of nonholonomic systems: the
example of a homogeneous ball on a convex surface of revolution\nby L
uis Yapu as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nUsing the
geometric approach to nonholonomic mechanical systems\, we will explain t
he utility of having special first integrals coming from symmetries (or h
orizontal gauge momenta) in order to obtain a hamiltonian formulation of t
he reduced dynamics (hamiltonization). The main result gives sufficient co
nditions on the horizontal gauge momenta in order to obtain a twisted-Pois
son (or sometimes Poisson) structure in the reduced space using the method
of gauge transformations by a 2-form\, which has explicit expressions. Th
e leaves of the reduced (twisted-)Poisson structure are given by the joint
level sets of casimirs coming from the first integrals. We will focus on
the example of a homogenous ball rolling on a convex surface of revolution
to illustrate the theory. This is a joint work with Paula Balseiro.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sérgio Romaña (UFRJ)
DTSTART:20201118T170000Z
DTEND:20201118T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/13
DESCRIPTION:Title: Como a dinâmica hiperbólica do fluxo geodésico pode controlar
a geometria\nby Sérgio Romaña (UFRJ) as part of Webinários do PPGM
at - UFRGS\n\n\nAbstract\nNeste seminário vamos tratar de relações entr
e geometria e dinâmica. Muitos de nós já ouvimos falar que variedades d
e curvatura negativa implica hiperbolicidade para a dinâmica do seu fluxo
geodésico\, isto é\, a geometria controla\, de certa forma\, a dinâmic
a. No entanto\, o que podemos dizer da recíproca? Quando a dinâmica cont
rola a geometria? Neste contexto\, vamos apresentar uma resposta razoável
a esta pergunta mostrado que\, em geral\, se o fluxo geodésico é hiper
bólico temos um controle sobre a curvatura da variedade e\, de certa form
a\, sobre a geometria. Apresentaremos também de algumas consequências de
ste resultado.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Robin Neumayer (Northwestern University)
DTSTART:20201125T170000Z
DTEND:20201125T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/14
DESCRIPTION:Title: Quantitative stability for minimizing Yamabe metrics\nby Rob
in Neumayer (Northwestern University) as part of Webinários do PPGMat - U
FRGS\n\n\nAbstract\nThe Yamabe problem asks whether\, given a closed Riema
nnian manifold\, one can find a conformal metric of constant scalar curvat
ure (CSC). An affirmative answer was given by Schoen in 1984\, following c
ontributions from Yamabe\, Trudinger\, and Aubin\, by establishing the exi
stence of a function that minimizes the so-called Yamabe energy functional
\; the minimizing function corresponds to the conformal factor of the CSC
metric. \n\nWe address the quantitative stability of minimizing Yamabe met
rics. On any closed Riemannian manifold we show—in a quantitative sense
—that if a function nearly minimizes the Yamabe energy\, then the corres
ponding conformal metric is close to a CSC metric. Generically\, this clos
eness is controlled quadratically by the Yamabe energy deficit. However\,
we construct an example demonstrating that this quadratic estimate is fals
e in the general. This is joint work with Max Engelstein and Luca Spolaor
and will be accessible to a general graduate student audience.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dirceu Bagio (UFSM)
DTSTART:20201202T170000Z
DTEND:20201202T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/15
DESCRIPTION:Title: Representações de álgebras associativas\nby Dirceu Bagio
(UFSM) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nA ideia de
representar um objeto matemático complexo por algo mais simples é muito
antiga e tem sido muito utilizada em matemática. Por exemplo\, podemos re
presentar um número complexo $z=a+bi$ pelo par ordenado $(a\,b)\\in \\mat
hbb{R}^2$ ou um operador linear $T$ definido sobre um espaço vetorial de
dimensão finita $n$ por uma matriz $[T]$ de ordem $n\\times n$. \n\nNesta
palestra\, abordaremos sobre representações de álgebras associativas.
Veremos alguns dos principais problemas envolvidos\, bem como ferramentas
que são usadas para resolvê-los. Por fim\, as representações simples e
de dimensão finita de algumas álgebras associativas (dadas por geradore
s e relações) serão discutidas.\n\nTodos os conceitos necessários para
entender o que será abordado serão introduzidos. Os únicos pré-requis
itos exigidos são o conhecimento dos resultados clássicos de álgebra li
near e das definições das estruturas algébricas mais comuns (grupos\, a
néis e módulos).\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Franco Vargas Pallete (Yale University)
DTSTART:20201209T170000Z
DTEND:20201209T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/16
DESCRIPTION:Title: Perfis isoperimétricos para variedades quasi-Fuchsianas\nby
Franco Vargas Pallete (Yale University) as part of Webinários do PPGMat
- UFRGS\n\n\nAbstract\nUm perfil isoperimétrico para uma variedade Rieman
niana é uma função que associa a cada número V > 0 o menor perímetro
necessário para conter uma região de volume V. Nesta palestra veremos co
mo para variedades quasi-Fuchsianas em dimensão 3 este problema se relaci
ona com o Volume Renormalizado. Usaremos algumas ferramentas da Relativida
de Geral (Hawking mass) para obter resultados de comparação com variedad
es Fuchsianas. Trabalho em conjunto com Celso Viana (UFMG).\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Paolo Giulietti (Università di Pisa)
DTSTART:20210303T170000Z
DTEND:20210303T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/17
DESCRIPTION:Title: Parabolic Dynamics via Renormalization theory\nby Paolo Giul
ietti (Università di Pisa) as part of Webinários do PPGMat - UFRGS\n\n\n
Abstract\nWe will present an overview of parabolic dynamics via renormaliz
ation theory using transfer operators. I will present some results (and so
me work in progress) which highlight the relations between the distributio
ns appearing in the study of ergodic averages of parabolic flows and the o
nes appearing in the study of the statistical properties of hyperbolic dyn
amical systems.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giuseppe Tinaglia (King's College\, London)
DTSTART:20210324T130000Z
DTEND:20210324T140000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/18
DESCRIPTION:Title: Minimal surfaces and Plateau problem\nby Giuseppe Tinaglia (
King's College\, London) as part of Webinários do PPGMat - UFRGS\n\n\nAbs
tract\nIn calculus of variations\, Plateau problem is the problem of findi
ng the surface that minimises area among all surfaces spanning a given cur
ve. This was posed Lagrange in 1760 and solved independently by Douglas an
d Radó in 1930. In 1936 Douglas was awarded the Fields Medal for his effo
rts. After an introduction to the field of minimal surfaces\, I will talk
about the Plateau problem and its proof.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emanuel Indrei (Purdue University)
DTSTART:20210331T170000Z
DTEND:20210331T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/19
DESCRIPTION:Title: The equilibrium shape of a planar crystal in a convex coercive b
ackground is convex\nby Emanuel Indrei (Purdue University) as part of
Webinários do PPGMat - UFRGS\n\n\nAbstract\nI'll discuss my recent soluti
on to a long-standing open problem posed by Almgren: https://arxiv.org/abs
/2008.02238.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ramon Nunes (Federal University of Ceará)
DTSTART:20210526T170000Z
DTEND:20210526T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/20
DESCRIPTION:Title: Formas automorfas\, funções $L$ e o problema de subconvexidade
\nby Ramon Nunes (Federal University of Ceará) as part of Webinários
do PPGMat - UFRGS\n\n\nAbstract\nNesta palestra faremos uma introdução
ao conceito de formas automorfas e suas funções $L$. Estes últimos obje
tos são funções meromorofas do plano complexo que satisfazem propriedad
es similares àquelas da celebrada função zeta de Riemann. Em particular
\, temos aqui uma conjectura análoga à hipótese de Riemann. O problema
de subconvexidade consiste em provar estimativas não-triviais para a fun
ção $L$ que visam suprir nossa ignorância com respeito à hipótese de
Riemann. Por fim\, mostraremos uma aplicação do problema da subconvexida
de e descreveremos uma estratégia comumente utilizada para estudá-lo.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jaqueline Mesquita (University of Brasilia)
DTSTART:20210602T170000Z
DTEND:20210602T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/21
DESCRIPTION:Title: Correspondência entre EDOs generalizadas e outros tipos de equa
ções: resultados e aplicações\nby Jaqueline Mesquita (University o
f Brasilia) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nNesta
palestra\, iremos apresentar as EDOs generalizadas e mostraremos como pode
mos relacionar estas equações com outros tipos de equações. Vamos apre
sentar alguns resultados que podemos obter por meio destas correspondênci
as bem como algumas aplicações.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rodrigo Bissacot (University of São Paulo)
DTSTART:20210609T170000Z
DTEND:20210609T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/22
DESCRIPTION:Title: A natural compactification for a countable Markov shift and its
thermodynamic formalism\nby Rodrigo Bissacot (University of São Paulo
) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nIn 1999 Ruy Exel
and Marcelo Laca solved an important problem in operator algebras and con
structed the Cuntz-Krieger algebra with infinitely many symbols. Given a t
ransitive and infinite matrix $A$\, as a corollary of their arguments appe
ars for the first time what we call a generalized countable Markov shift $
X_A = \\Sigma_A \\cup Y_A$\, where $Y_A$ is a special set of finite admiss
ible words. For the most studied countable Markov shifts $\\Sigma_A$\, as
the full shift and renewal shift\, $X_A$ is a compactification of $\\Sigma
_A$. Differently from other proposals\, this compactification depends only
on the matrix $A$ and not on any extra structure.\n\nWe developed the the
rmodynamic formalism on the space $X_A$\, studying conformal and eigenmeas
ures on $X_A$ and its connections with standard measures on $\\Sigma_A$. N
ew phenomena appear\, a length-type phase transition\, when the eigenmeasu
re lives on $\\Sigma_A$ at high temperature and lives on $Y_A$ at low temp
erature. Using a pressure-point definition proposed by M. Denker and M. Yu
ri in the context of iterated function systems\, we able to prove that the
Gurevich pressure is the natural definition for the pressure function als
o in the generalized setting. The Gurevich entropy plays a role of a criti
cal temperature to the existence of new conformal measures (KMS states) li
ving on $Y_A$. We exhibit examples with infinitely (even uncountable) many
new extremal conformal measures\, which are undetectable in the usual for
malism. Based on "Thermodynamic Formalism for Generalized Markov Shifts on
Infinitely Many States" available at arXiv:1808.00765\n\nJoint work with
Ruy Exel (UFSC\, Brazil)\, Rodrigo Frausino (University of Wollongong\, Au
stralia) and Thiago Raszeja (AGH University of Science and Technology\, Po
land).\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniele Sepe (Fluminense Federal University)
DTSTART:20210616T170000Z
DTEND:20210616T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/23
DESCRIPTION:Title: Monotone vs Fano: an equivariant perspective\nby Daniele Sep
e (Fluminense Federal University) as part of Webinários do PPGMat - UFRGS
\n\n\nAbstract\nIntuitively speaking\, symplectic geometry studies spaces
on which the most fundamental quantity that can be measured is (oriented)
area. While all complex submanifolds of projective space are symplectic\,
the converse is false\, as first observed by Thurston. Nevertheless a natu
ral metaquestion in symplectic geometry is to understand the "difference"
between symplectic manifolds and smooth complex projective varieties. In t
his talk we concentrate on the relation between monotone symplectic manifo
lds and smooth Fano varieties: intuitively speaking\, both families can be
thought of as satisfying certain positivity conditions. Again\, there are
compact monotone symplectic manifolds that are not Fano (as shown by Rezn
ikov\, Fine and Panov). After introducing all the above notions formally\,
the aim of this talk is to show that monotone symplectic manifolds are ne
cessarily equivalent to smooth Fano varieties in the presence of "almost m
aximal" toral symmetries. This is ongoing joint work with Isabelle Charton
and Silvia Sabatini.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Diego Moreira (UFC)
DTSTART:20210901T170000Z
DTEND:20210901T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/24
DESCRIPTION:Title: Supersolutions to Fully Nonlinear PDEs and Convexity\nby Die
go Moreira (UFC) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nI
n this talk\, we present some sharp regularity results related to supersol
utions to fully nonlinear equations that enjoy some kind of convexity prop
erty. If time allows\, ideas of the proof and some open problems will be
addressed. This is joint work with Alessio Figalli (ETH-Zurich) and J. Ede
rson Braga (UFC).\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pablo Lessa (UdelaR)
DTSTART:20210908T170000Z
DTEND:20210908T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/25
DESCRIPTION:Title: Geodesic random walks and fold maps\nby Pablo Lessa (UdelaR)
as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nWe will discuss r
ecent work with Lucas Oliveira on geodesic random walks. Our results yiel
d a geometric proof of old results of Tsujishita on the regularity of eige
nfunctions of the spherical mean operator on a compact manifold with non-p
ositive curvature.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rayssa Caju (UFPB & University of Chicago)
DTSTART:20210915T170000Z
DTEND:20210915T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/26
DESCRIPTION:Title: On the singular Q-curvature problem (lecture in Portuguese)\
nby Rayssa Caju (UFPB & University of Chicago) as part of Webinários do P
PGMat - UFRGS\n\n\nAbstract\nThe study of partial differential equations o
n manifolds has been extensively explored in the last few decades. In part
icular\, some problems arising in conformal geometry such as the classical
Yamabe problem\, can be reduced to the study of PDE’s with critical exp
onent on manifolds. More recently\, another class of conformal equations t
hat has drawn considerable attention is the so-called Q-curvature equation
\, which is a fourth-order elliptic PDE with critical exponent. \n\nIn thi
s talk\, I would like to discuss how to apply fixed point methods to under
stand the Q-curvature equation in a singular setting and discuss some inte
resting problems related to this topic. \n\nJoint work with J.H. Andrade\,
J. M do Ó\, J. Ratzkin and A. Silva Santos.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tertuliano Franco (UFBA)
DTSTART:20210929T170000Z
DTEND:20210929T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/27
DESCRIPTION:Title: Large Deviations in the Supremum Norm for a Reaction-Diffusion S
ystem\nby Tertuliano Franco (UFBA) as part of Webinários do PPGMat -
UFRGS\n\n\nAbstract\nWe present large deviations estimates for a system of
independent random walks superposed with a birth-and-death dynamics evolv
ing on the discrete torus whose density profiles converge in the supremum
norm. The scaling limit considered is the so-called high density limit whe
re space\, time\, and initial quantity of particles are rescaled\, and the
associated rate functional obtained is a semi-linearised version of the r
ate function of Vares/Landim/Jona-Lasinio'93 (in a different topology sett
ing). An ingredient in the proof of large deviations is to provide the lim
it for a suitable class of perturbations of the original process: this is
precisely one of the main contributions of this work\, a strategy to exten
d the original high density approach to weakly asymmetric systems. Talk ba
sed in a joint work with Luana Amaral and Bernardo de Lima.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Philippe Thieullen (Université de Bordeaux)
DTSTART:20211013T170000Z
DTEND:20211013T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/28
DESCRIPTION:Title: Calibrated subaction for Anosov maps and flows\nby Philippe
Thieullen (Université de Bordeaux) as part of Webinários do PPGMat - UFR
GS\n\n\nAbstract\nThe Livsic theorem for Anosov maps or flows says that a
Lipschitz observable that has zero average on every periodic orbit is nece
ssarily cohomologuous to a Lipschitz coboundary. The sub-Livsic theorem sa
ys that a Lipschitz observable that has non negative zero average on every
periodic orbit is necessarily bounded from below by a coboundary. In a pa
per with Artur Lopes we proved that in the invertible case (Anosov diffeom
orphism or flow) the coboundary may be chosen Holder. In a recent paper wi
th Xifeng Su we prove that the coboundary may be chosen Lipschitz. We intr
oduce a new Lax-Oleinik operator in the invertible case that could be used
in numerical experiments.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rodrigo Marinho (UFRGS)
DTSTART:20211020T170000Z
DTEND:20211020T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/29
DESCRIPTION:Title: Sharp convergence to equilibrium of interacting particle systems
\nby Rodrigo Marinho (UFRGS) as part of Webinários do PPGMat - UFRGS\
n\n\nAbstract\nIn this seminar we will discuss the mixing times of Markov
chains. We will exhibit classical examples of card shuffles and use them t
o introduce some interesting particle systems. Furthermore\, we will show
some recent results and some open problems which may be of interest not on
ly for probability theory researchers but also for the ones who work with
analysis\, pdes or spectral graph theory.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:João Pedro Ramos (ETH Zürich)
DTSTART:20211027T170000Z
DTEND:20211027T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/30
DESCRIPTION:Title: Revisiting the subcritical case of Hardy’s uncertainty princip
le\nby João Pedro Ramos (ETH Zürich) as part of Webinários do PPGMa
t - UFRGS\n\n\nAbstract\nHardy's uncertainty principle is a pivotal result
in Fourier Analysis\, which states that if a function and its Fourier tra
nsform both decay at least as fast as the standard Gaussian\, then the fun
ction is either a Gaussian or identically zero. It seems\, however\, that
the subcritical case of this result has barely been explored so far: while
in the critical and supercritical cases one has explicit characterisation
s\, in the subcritical one only very recent results by Vemuri and Escauria
za\, Kenig\, Ponce and Vega shed new light onto the structure of functions
in the subcritical Hardy classes. \n\nIn this talk\, we will discuss thes
e recent contributions in connection to an interesting norm extrapolation
problem: if both $f$ and $\\widehat{f}$ are in $L^2(e^{2\\pi a |x|^2})\,$
for $a \\in (0\,1)$\, can one say that $e^{a \\pi |x|^2}f\, e^{a \\pi |x|^
2} \\widehat{f} \\in L^{\\infty}$? We will show that this almost holds in
general\, in the sense that $e^{b \\pi |x|^2}f\, e^{b \\pi |x|^2} \\wideha
t{f} \\in L^{\\infty}$\, for any $b < a.$ Further\, we will see that this
holds indeed in a class of generalised Laplace transforms of tempered dist
ributions. Finally\, time-allowing\, we shall see how this problem connect
s to a conjecture of Vemuri on decay of solutions to the time-dependent ha
rmonic oscillator problem and the sharp estimates of Escauriaza-Kenig-Ponc
e-Vega. \n\n\nJoint work with Lucas Oliveira.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Milton Jara (IMPA)
DTSTART:20211103T170000Z
DTEND:20211103T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/31
DESCRIPTION:Title: Mixing time of a stratified random walk on the hypercube\nby
Milton Jara (IMPA) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract
\nWe study the speed of convergence to its stationary state of a stratifie
d random walk on the hypercube. The dynamics is the following. At each ste
p\, two bits of a binary string of length $n$ are chosen\, and one adds th
e second bit to the first bit. Ben-Hamou and Peres showed that the mixing
time of this chain is equal to $\\frac{3}{2} n \\log n + \\mathcal{O}(n)$.
We will provide a more refined description of the convergence to the stat
ionary state of this chain\, which in particular allows us to compute the
mixing time of the chain\, up to an error of order $o(n)$ for every initia
l state of the chain\, and also to find the initial state for which the co
nvergence is fastest. Joint work with Freddy Hernández (Bogotá).\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chiara Franceschini (MSRI\, UC Berkeley)
DTSTART:20211110T170000Z
DTEND:20211110T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/32
DESCRIPTION:Title: Algebraic approach to stochastic duality for Markov processes wi
th some examples and applications\nby Chiara Franceschini (MSRI\, UC B
erkeley) as part of Webinários do PPGMat - UFRGS\n\n\nAbstract\nIn this t
alk I will introduce the concept of duality for Markov processes and expla
in how duality relations can be constructed starting from the description
of the infinitesimal generator of the process with generators of a suitabl
e Lie algebra: I will provide some classical examples as well as more rece
nt results which involves orthogonal polynomials. I conclude with some pos
sible applications in the context of interacting particle systems.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Henrique Borrin (UNICAMP)
DTSTART:20211117T170000Z
DTEND:20211117T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/33
DESCRIPTION:Title: Lagrangian structure of relativistic Vlasov systems\nby Henr
ique Borrin (UNICAMP) as part of Webinários do PPGMat - UFRGS\n\n\nAbstra
ct\nIn this work\, we studied the Lagrangian structure of relativistic Vla
sov systems in quasistatic limits of Maxwell's equations\, considering the
contribution of self-consistent electric and magnetic fields. As a result
\, we established the equivalence between renormalized and Lagrangian solu
tions\, i.e.\, solutions transported by an appropriately defined flow and
its global-in-time definition if finite energy conditions are imposed. We
also defined the notion of a generalized solution and proved its existence
. Furthermore\, assuming higher integrability on the initial data\, the ex
istence of Lagrangian solutions with each energy bounded was shown.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Otávio Menezes (Purdue University)
DTSTART:20211124T170000Z
DTEND:20211124T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/34
DESCRIPTION:Title: Quenched CLT for a balanced random walk driven by the exclusion
process\nby Otávio Menezes (Purdue University) as part of Webinários
do PPGMat - UFRGS\n\n\nAbstract\nWe prove a quenched functional central l
imit theorem for a one-dimensional random walk driven by a simple symmetri
c exclusion process. This model can be viewed as a special case of the ran
dom walk in a balanced random environment\, for which the weak quenched li
mit is constructed as a function of the invariant measure of the environme
nt viewed from the walk. We bypass the need to show the existence of this
invariant measure. Instead\, we find the limit of the quadratic variation
of the walk and give an explicit formula for it. Joint with Jonathon Peter
son (Purdue University) and Yongjia Xie (Purdue University).\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sébastien Alvarez (UDELAR)
DTSTART:20211201T170000Z
DTEND:20211201T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/35
DESCRIPTION:Title: Earthquakes and graftings of hyperbolic surface laminations\
nby Sébastien Alvarez (UDELAR) as part of Webinários do PPGMat - UFRGS\n
\n\nAbstract\nWe study compact hyperbolic surface laminations. These are a
generalization of closed hyperbolic surfaces which appear to be more suit
ed to the study of Teichmüller theory than arbitrary non-compact surfaces
. We show that the Teichmüller space of any non-trivial hyperbolic surfac
e lamination is infinite dimensional. In order to prove this result\, we s
tudy the theory of deformations of hyperbolic surfaces\, and we derive wha
t we believe to be a new formula for the derivative of the length of a sim
ple closed geodesic with respect to the action of grafting. This formula c
omplements those derived by McMullen\, in terms of the Weil-Petersson metr
ic\, and by Wolpert for the case of earthquakes. This is joint work with G
raham Smith.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maria Eulália Vares (UFRJ)
DTSTART:20211208T170000Z
DTEND:20211208T180000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/36
DESCRIPTION:Title: Critical scaling for an anisotropic percolation system on $\\mat
hbb{Z}^2$\nby Maria Eulália Vares (UFRJ) as part of Webinários do PP
GMat - UFRGS\n\n\nAbstract\nMy basic goal in this talk is to discuss one f
urther example of the interplay between SPDEs and percolation methods. We
consider a highly anisotropic finite-range bond percolation on $\\mathbb{Z
}^2$: on horizontal lines we have edges connecting two vertices within dis
tance $N$ and vertical edges are only between nearest neighbor vertices.
On this graph we consider the following independent percolation model: hor
izontal edges are open with probability $1/(2N)$\, while vertical edges ar
e open with probability $\\epsilon$ to be suitably tuned as $N$ grows to i
nfinity. The main result tells that if $\\epsilon = \\kappa N^{-\\frac25}$
\, then we see a phase transition in $\\kappa$: there exist positive and f
inite constants $C_1\, C_2$ so that there is no percolation if $ \\kappa <
C_1$ while percolation occurs for $\\kappa >C_2$. The question is motivat
ed by a result on the analogously layered ferromagnetic Ising model at mea
n field critical temperature\, treated in [2]. The proof relies on the ana
lysis of the scaling limit of the growth process restricted to each horizo
ntal layer. This is inspired by works of Mueller and Tribe on the long ran
ge contact process (PTRF\, 1995). A renormalization scheme is used for the
percolative regime. The talk is based on a joint work with Thomas Mountfo
rd and Hao Xue [1].\n\n\n\n [1] T. S. Mountford\, M. E. Vares\, H. Xue. Cr
itical scaling for an anisotropic percolation system on $\\mathbb{Z}^2$ (E
lectronic Jr. in Probability\, 2020)\n\n [2]. L.R. Fontes\, D. H. Marchett
i\, I. Merola\, E. Presutti\, M.E. Vares. Layered systems at the\nmean fie
ld critical temperature. J. Stat. Phys. 161\, (2015)\, 91--122.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Renaud Leplaideur (Université de la Nouvelle-Calédonie)
DTSTART:20211215T190000Z
DTEND:20211215T200000Z
DTSTAMP:20260422T225719Z
UID:Web-PPGMat-UFRGS/37
DESCRIPTION:Title: Nonlinear Thermodynamical Formalism\nby Renaud Leplaideur (U
niversité de la Nouvelle-Calédonie) as part of Webinários do PPGMat - U
FRGS\n\n\nAbstract\nThe Thermodynamical Formalism aims to study equilibriu
m states\, that are measures maximizing the entropy plus the integral of s
ome observable (called a potential).\n\nWe will present a new formalism\,
called nonlinear\, as it aims to study maximizing measures for the entropy
+ some functional on the set of invariant measures.\n\nThis is a joint wo
rk with J. Buzzi and B. Kloeckner\, and extends previous results with F. W
atbled.\n\nThe main point is that classical mean field spin spaces (as Pot
ts or Curie-Weiss models) in Statistical Mechanics can be seen within this
formalism.\n
LOCATION:https://researchseminars.org/talk/Web-PPGMat-UFRGS/37/
END:VEVENT
END:VCALENDAR