Séminaire conjoint LSI+CPHT+PMC = M4S

mercredi 3 décembre à 11h

Salle de Conférence Louis Michel au CPHT (anciennement salle Jean Mandel, au RDC de l'aile 5, près de l'aile 3).

Yusuke Nomura
('Université de Tohoku au Japon)

"Electronic structure of nickelate superconductors"

The recent discovery of superconductivity in infinite-layer and bilayer nickelates has attracted significant attention. In this seminar, after briefly outlining the key differences between these two classes of nickelates, we will focus primarily on the electronic structure of infinite-layer nickelates, (R,Sr)NiO₂ (R = La, Nd) [1]. In particular, we will examine the similarities and shared features between nickelates and cuprates [2], and discuss the essential degrees of freedom relevant to superconductivity. We also disentangle the correlation effects in the multiband electronic structure of infinite-layer nickelates by comparing theoretical and experimental results for transport properties (Hall and Seebeck coefficients) [3].
 

[1] For a review, Y. Nomura and R. Arita, Rep. Prog. Phys. 85, 052501 (2022).
[2] Y. Nomura et al., Phys. Rev. B 100, 205138 (2019).
[3] Osada et al., Sci. Adv. 11, eadv6488 (2025).
[4] If you are interested in bilayer nickelates, see also, Phys. Rev. B 112, L020504 (2025).

Time:14 pm, Dec 3th Wednesday

Location: Salle de Conférence Louis Michel

Speaker: Francesco Bertucci (University of Mississippi) 

Title: Bootstrapping Euclidean latticese

Abstract: Using numerical bootstrap methods, we constrain the spectrum of the Laplacian operator in $d$-dimensional flat manifolds, as well as the triple integrals of its eigenmodes. We provide many examples of $d$-dimensional flat tori that populate these bounds. In certain dimensions, our bounds are saturated by some special lattices, including the $E_8$ lattice in 8d and the Leech lattice in 24d. These bounds admit an interpretation in the context of Kaluza-Klein theories and have connections with the sphere packing and kissing number problems.

Pierre Wang will defend his thesis on Friday December 5th, 2025 at 2:00 pm in room Louis Michel.

Titre :  "Perturbative and non-perturbative analysis of the renormalization group equations"
Advisor: Christoph Kopper

Time: 14 pm to 15 pm, Nov 26th, Wednesday  

Location: Salle de Conférence Louis Michel

Speaker: Dionysios Anninos (King’s College London)

Title: Features of the Partition Function of a Λ > 0 Universe

Abstract: We discuss properties of the gravitational path integral for rhetorics of gravity with Lambda>0. We consider the problem in various spacetime dimensions, and for various matter fields. Time permitting, we also comment on the two-dimensional case.

1st of December at 15:00-17:00

Salle Louis Michel,

CPHT, École Polytechnique.

The seminar will include two 45-minute talks followed by a discussion:

1) Sergei Popruzhenko (NRNU Moscow Engineering Physics Institute and Prokhorov General Physics Institute RAS, Moscow, Russia)

"On the theory of collective tunnelling ionisation"

2) Arseny Mironov (CPHT)

"Applications of strong-field ionisation in ultra-high-intensity laser fields: from in situ characterisation of the laser focus to investigating fundamental strong-field QED effects."

Organizers: Arseny Mironov and Mickael Grech

November 18 (Tuesday), 14:00, Room Louis Michel (CPHT) 

in the room Louis Michel (CPHT

Speaker: Álvaro Gómez León (Instituto de Física Fundamental, Madrid)

Title: Extrinsic topology in photonic lattices

Abstract: Topological phases give rise to edge states that can be used for technological applications. Among them, Floquet phases, which are obtained by periodically driving the system, have been shown to be exceptionally rich and externally tunable. In this talk, I will discuss extrinsic topology, which is a particular type of topology that emerges in Floquet systems that follow a discrete time evolution. Finally, I will show the existence of these topological phases in photonic lattices using a double fiber-ring setup and the manipulation of their edge states.

L'article « Couronne solaire : ses températures révèlent leur mystère » a été publié dans CNRS Le Journal.

Lire l'article : https://lejournal.cnrs.fr/articles/couronne-solaire-ses-temperatures-revelent-leur-mystere

Ces travaux sont publiés dans la revue The Astrophysical Journal Letters. Ils ont été conduits par des physiciens du Centre de physique théorique (CPHT, CNRS / École polytechnique), ainsi que de l’Institut d’Astrophysique Spatiale (IAS) et d’Astrophysique, Instrumentation Modélisation (AIM).

• Sariah Al Saati will defend his thesis on  Thursday, 13th of November, at 10:00 am, in Ecole polytechnique, Amphi Becquerel.

Our visitor Li Li (ITP Beijing) will give a seminar :

Time: 14 pm to 15 pm, Nov 5th, Wednesday  

Location: Salle de Conférence Louis Michel

Title: Dancing in the dark: interior structure and dynamics for hairy black holes

Abstract: 

Understanding the nature of black holes stands as a fundamental pillar of modern theoretical physics. While their external properties have been extensively mapped, the interior spacetime is an integral component of their complete causal structure. A comprehensive understanding of black holes therefore necessitates an exploration of their inner regions. In this talk, I will present our recent progress in this direction, covering the no-inner-horizon theorem, constraints on the number of horizons from energy conditions, and the rich interior dynamics of hairy black holes.

Mathematical Aspects of Flat-Space Holography, Black Holes and Condensed-Matter Physics II

Thematic one-day workshop funded by the Partenariat Hubert-Curien *
Organisers : Adrien Fiorucci, Marios Petropoulos, Junchen Rong (CPHT)

When? November 14, 2025. From 10:00 to 17:30.
Where? CPHT, École polytechnique. Salle Louis-Michel

Also streamed on ZOOM!
Link : https://ecolepolytechnique.zoom.us/j/8929497473?pwd=dvTzQhqhDFFetUMOmQ8Zn8ZROHx4eZ.1&omn=95067817516
Meeting ID : 892 949 7473
Password : curienhub

Scientific programme:

Blagoje Oblak (ICJ, Lyon) - Quantum Geometry in Conformal Field Theory
Olga Papadoulaki (CPHT, Palaiseau) - An inflationary cosmology from Anti-de-Sitter wormhole
Simon Pekar (SISSA, Trieste) - Flat from AdS in general dimension & for any spin: the Good, the Bad & the Ugly
Konstantinos Siampos (AUTH, Thessaloniki) - The geometric origin of the energy–momentum tensor improvement terms
Matthieu Vilatte (Université de Mons) - Hypermomentum & gravitational radiation

See the detailed programme in attachment.

For any question or remark concerning this event, please send an email to
adrien.fiorucci / marios.petropoulos / junchen.rong @polytechnique.edu

* Programme financé dans le cadre du Partenariat Hubert Curien France-Grèce
Symétries asymptotiques en gravitation, théories des champs conformes et holographie
Athènes-Lyon-Paris-Thessalonique