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19.02.2021

Σειρά Σεμιναρίων Εαρινού Εξαμήνου 2021

Τα σεμινάρια πραγματοποιούνται στις 5-6 μμ. Η σύνδεση σε αυτά γίνεται μέσω του αντίστοιχου link.

ΕΠΟΜΕΝΟ ΣΕΜΙΝΑΡΙΟ

 

14 Μαΐου 2021

Marc Mezard 
Ecole Normale Supérieure, Paris, France

Title: Statistical physics and statistical inference

Abstract: A major challenge of contemporary statistical inference is the large-scale limit, where one wants to discover the values of many hidden parameters, using large amount of data. In recent years, ideas from statistical physics of disordered systems, notably the cavity method, have helped to develop new algorithms for important inference problems, ranging from community detection to compressed sensing, machine learning (notably neural networks) and generalized linear regression. The talk will review these developments and explain how they can be used, together with the replica method, to identify phase transitions in benchmark statistical ensembles of inference problems. 

 https://uoa.webex.com/uoa/j.php?MTID=mc78b88555472720c3a6a2cf3a3cfb829

Οι διαφάνειες της ομιλίας του κ. M. Mezard , που ευγενικά παραχώρησε, βρίσκονται εδώ.

 

23 Ιουνίου 2021

 

John Pendry (Sir)
Imperial College, London, UK

 

Title: A new mechanism for gain in  time dependent media

 Abstract: Time dependent systems do not in general conserve energy invalidating much of the theory developed for static systems and turning our intuition on its head. This is particularly acute in luminal space time crystals where the structure moves at or close to the velocity of light. Conventional Bloch wave theory no longer applies, energy grows exponentially with time, and a new perspective is required to understand the phenomenology. In this letter we identify a new mechanism for amplification: the compression of lines of force  that are nevertheless conserved in number.

  https://uoa.webex.com/uoa/j.php?MTID=m5ba2af1166449ff3f43c316ab489633a


ΠΡΑΓΜΑΤΟΠΟΙΗΜΕΝΑ ΣΕΜΙΝΑΡΙΑ

 

5 Μαρτίου 2021

 Prof Reinhard Genzel  (Nobel PrizeLaureate 2020)

Max Plack Institute for Extraterrestrial Physics, Garching, Germany

 

 

 Title: A 40-Year Journey

Abstract:

More than one hundred years ago, Albert Einstein published his Theory of
General Relativity (GR). One year later, Karl Schwarzschild solved the GR
equations for a non-rotating, spherical mass distribution; if this mass is
sufficiently compact, even light cannot escape from within the so-called
event horizon, and there is a mass singularity at the center. The
theoretical concept of a 'black hole' was born, and was refined in the next
decades by work of Penrose, Wheeler, Kerr, Hawking and many others. First
indirect evidence for the existence of such black holes in our Universe came
from observations of compact X-ray binaries and distant luminous quasars. I
will discuss the forty  year journey, which my colleagues and I have been
undertaking to study  the mass distribution in the Center of our Milky Way
from ever more precise, long term studies of the motions of gas and stars as
test  particles of the space time. These studies show the existence of a
four million solar mass object, which must be a single massive black hole, beyond
any reasonable doubt.

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7 Απριλίου 2021

 Costas Bachas 

Ecole Normale Supérieure, Paris, France

 Title: Quantum + Gravity: the Unfinished Revolution

Abstract: A century after the discovery of General Relativity and Quantum Mechanics, their combination continues to challenge our understanding of both. I will discuss the current status of quantum gravity, a theory still under construction
that is guided by two main themes: String Theory, and the paradoxes raised by the Hawking evaporation of
black holes. 

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