[ABE-L] Seminar on Probability and Stochastic Processes - 30/09 - 14h

[Aline Duarte]

Prezados colegas,

na próxima sexta-feira, 30 de setembro, às 14h, acontecerá mais um
seminário híbrido do ciclo SPSP-IME-USP. O seminário será *presencial,
*no Auditório
Jacy Monteiro (IME-USP), e transmitido simultaneamente no YouTube, pelo
link

https://youtu.be/oYHUhoyQ-6k


Outras informações sobre os seminários passados e próximos seminários estão
disponíveis em  https://sites.google.com/usp.br/psps-ime-usp/in%C3%ADcio


Um abraço,

Aline Duarte

________________________________



*Seminar on Probability and Stochastic Processes*


Speaker: *Kádmo*  *de S. Laxa *(IME-USP)

Next Friday, *September 30th - 2pm*

Location: Auditório Jacy Monteiro (IME - USP)

Live on: https://youtu.be/oYHUhoyQ-6k



*Title*:  Fast Consensus and Metastability in a Highly Polarized Social
Network


*Abstract*: Discrepancy between the results of electoral intentions carried
out a few days before the actual voting and the electoral poll results
during the first round of the 2018 presidential elections in Brazil was
striking. At the time, it was conjectured that this discrepancy was the
result of social-media campaigning days before the elections. This
conjecture raises a question: is social-media campaigning enough to change
in a quite short period of time the voting intention of a significant
portion of voters? Providing an answer to this question was the initial
motivation to introduce a new stochastic model that mimics some important
features of real world social networks.

The model for a highly polarized social network is a system of interacting
marked point processes. Each point process indicates the successive times
in which a social actor expresses a “favorable” (+1) or “contrary” (-1)
opinion on a certain subject. The orientation and the rate at which an
actor expresses an opinion is influenced by the social pressure exerted on
them, modulated by a polarization coefficient. The polarization coefficient
of the network indicates the tendency of social actors to express an
opinion in the same direction of the social pressure exerted on them. The
social pressure on an actor is reset to 0, when they express an opinion,
and simultaneously the social pressures on all the other actors change by
one unit in the direction of the opinion that was just expressed.

We prove that when the polarization coefficient diverges, this social
network reaches consensus instantaneously. Moreover, this consensus has a
metastable behavior. This means that the direction of the social pressures
on the actors globally changes after a long and unpredictable random time.

This talk is based on a joint work with Antonio Galves.
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