Author: petkou

1st Christmas Student Workshop, 20 Dec. 2018

Posted on by

The Institute of Theoretical Physics organises the 1st Christmas Student Workshop on 20th of  December 2018. For the first time we give the opportunity to our former undergraduate students, who are currently pursuing postgraduate or doctoral studies abroad, to present their work and academic progress. We hope that this will keep alive the crucial link between the Institute of Theoretical Physics and our young alumni.

Christos Anastasiou Petkou: 30/11/31-04/07/17

Posted on by

Us Christians, face up to the mystery of death reciting:

“Christ is risen from the dead, having beaten Death by his own death and having given the gift of life to those in the graves.”

My father faced up to life on Earth, and taught us to do the same, reciting:

“If you can keep your head when all about you
    Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you,
    But make allowance for their doubting too;
If you can wait and not be tired by waiting,
    Or being lied about, don’t deal in lies,
Or being hated, don’t give way to hating,
    And yet don’t look too good, nor talk too wise:
If you can dream—and not make dreams your master;
    If you can think—and not make thoughts your aim;
If you can meet with Triumph and Disaster
    And treat those two impostors just the same;
If you can bear to hear the truth you’ve spoken
    Twisted by knaves to make a trap for fools,
Or watch the things you gave your life to, broken,
    And stoop and build ’em up with worn-out tools:
If you can make one heap of all your winnings
    And risk it on one turn of pitch-and-toss,
And lose, and start again at your beginnings
    And never breathe a word about your loss;
If you can force your heart and nerve and sinew
    To serve your turn long after they are gone,
And so hold on when there is nothing in you
    Except the Will which says to them: ‘Hold on!’
If you can talk with crowds and keep your virtue,
    Or walk with Kings—nor lose the common touch,
If neither foes nor loving friends can hurt you,
    If all men count with you, but none too much;
If you can fill the unforgiving minute
    With sixty seconds’ worth of distance run,
Yours is the Earth and everything that’s in it,
    And—which is more—you’ll be a Man, my son!”
Au revoir, my Father, my Man…

 

Presentations of Undergraduate Diploma Theses

Posted on by

The final presentations for the undergraduate diploma thesis completed under my supervision for the academic year 2013-14 we done on the he 26 of June 2014. The students and the theses are:

  1. Alexander Tabler: “Hamiltonian Holography: The AdS/CFT Correspondence and the Inverted Time-dependent Oscillator”. Thesis. Presentation.
  2. Manthos Karydas: “The Black Hole Information Paradox”. Thesis. Presentation.
  3. Dimitris Krommydas: “Black hole information, rises”. Thesis. Presentation.
  4. George Katsianis: “Hawking radiation and the information paradox“. Thesis. Presentation.

Fotos from the presentations are here.

New research work: Instantons and the Hartle-Hawking-Maldacena proposal for dS/CFT

Posted on by

My newest work titled “Instantons and the Hartle-Hawking-Madacena proposal for dS/CFT” has appeared in http://arxiv.org/pdf/1406.6148.pdf.

Together with S. de Haro, we tested the Maldacena proposal for the Hartle-Hawking late time quantum state in an asymptotically de Sitter universe. In particular, we calculated the on-shell action for scalar instantons on the southern hemisphere of the four-sphere and compare the result with the renormalized on-shell action for scalar instantons in EAdS4. The two results agree provided the corresponding instanton moduli as well as the curvature radii are analytically continued.
The instanton solutions in de Sitter are novel and satisfy mixed boundary conditions. We also pointed out that instantons on S4 calculate the regularized volume of EAdS4, while instantons on EAdS4 calculate the volume of S4, where the boundary condition of the instanton in one space is identified with the radius of curvature of the other. We finally briefly discussed the implications of the above geometric property of instantons for higher-spin holography.

New research work: The Geroch group in Einstein spaces

Posted on by

My latest work titled “The Geroch group in Einstein spaces” has appeared in http://arxiv.org/pdf/1403.6511.pdf.

Together with R. G. Leigh, M. Petropoulos and P. Tripathy, we have studied how the presence of a cosmological constant modifies the well-known Geroch solution generating technique and its integrability properties. Remarkably, the cosmological constant enters as a constant shift in the Hamiltonian, hence it does not modify the equations of motion neither the integrability properties of the sigma model. It does break, however, the part of SL(2,R) that interchanges the mass and the nut charge. This means that these two constants of motion are not interchangeable under a canonical transformation and hence the the gravitational “electric-magnetic” duality is lost. Nevertheless, perhaps surprisingly our results show that the Schwarzchild-AdS and Taub-NUT-AdS  solutions emerge from the Geroch technique and hence they are related t each other.

 

Postdoc position

Posted on by

The ARISTEIA II grant “Aspects of Three-Dimensionsl CFTs” will fund a postdoc position starting as early as May 2014 and running until the end of the program. Interested candidates working in three-dimensional CFTs in the context of AdS/CFT, AdS/CMT and Higher-Spin Gauge Theories should send a CV and the names of  three referees to petkou@physics.auth.gr. The application deadline is 27th of April 2014.