Konwersatorium CFT – CFT PAN – Centrum Fizyki Teoretycznej Polskiej Akademii Nauk

Why photons? A psychoanalytic portrait of a scientist as a mature man.

cft — Fri, 10 Apr 2026 07:54:57 +0000

Abstract: I will start with the origins: Maxwell theory, present five reasons to quantize, or maybe four? I will then discuss quantum theory of optical coherence, answering the question: How to reconcile Maxwell with photons? I will describe shortly coherent states and squeezed states. I will then turn to strong field physics, starting with a historical introduction and description of the present times, where semi-classical theory is sufficient. I will then mention the generation of Schrödinger cat states within atto-physics, answering the question: yes, we do need photons. At the end, I will discuss three mechanisms to exhibit quantumness of EM fields: i) Conditioning/post selection + applications; ii) Nonlinear effects induced by depletion/interband transitions, or dipole correlations; iii) Use quantum fields.

Zoom details

Zoom link: [LINK]

Meeting ID: 842 4891 1743

Passcode: 394021

Probing the early universe with gravitational waves.

cft — Wed, 11 Mar 2026 12:42:44 +0000

Abstract: This talk will focus on the phenomenon of cosmological phase transitions and the possibility of them sourcing an observable gravitational wave background. I will provide an overview of the field, highlighting the active areas of research, going from fundamental physics models, through the dynamics of the phase transition, to modelling gravitational-wave backgrounds. I will explore more closely the computation of the bubble nucleation rate during a first-order phase transition, introducing the theoretical tools needed for precise phenomenological predictions. I will comment on the prospects for future detection of a gravitational-wave background coming from a cosmological phase transition in future detectors, in particular, Laser Interferometer Space Antenna (LISA).

Zoom details

Zoom link: [LINK]

Meeting ID: 842 4891 1743

Passcode: 394021

Speaker: Bogumiła Świeżewska (Warsaw University)

Date & Time: Wednesday, 18th March at 14:00

Location: Aula of the Institute of Physics PAS, Al. Lotników 32/46

Asymptotics of quantum channels and quantum evolutions

cft — Wed, 07 Jan 2026 08:35:32 +0000

On 7 January 2026 we have planned a report talk by the recipient of the grant for projects implemented by young scientists at CFT 2025 instead of the regular colloquium. The speaker will be Arturo Konderak and he will talk about his project. Note that his talk will be held exclusively online.

Zoom details:

Zoom link: https://us06web.zoom.us/j/84421705396?pwd=CqrvIshGX3SWZDMzaJjhXaUG2dvQmW.1

Meeting ID: 844 2170 5396

Passcode: 691373

Configurations, Tessellations and Tone Networks

cft — Wed, 03 Dec 2025 12:43:22 +0000

Abstract: The Eulerian tonnetz, which associates three minor chords to each major chord and three major chords to each minor chord, can be represented by a bipartite graph with twelve white vertices signifying major chords and twelve black vertices signifying minor chords. This Levi graph uniquely determines a certain geometric configuration of twelve points and twelve lines in the Euclidean plane with the property that three points lie on each line and three lines pass through each point. Interesting features of the tonnetz, such as the existence of the four hexacycles and the three octacycles of Cohn-Waller, crucial for the understanding of nineteenth-century harmony and voice leading, can be read oﬀ rather directly as properties of this configuration. Analogous tone networks along with their associated Levi graphs and configurations can be constructed for pentatonic music and twelve-tone music, oﬀerring the promise of new methods of composition. When the voice leading constraints of the Eulerian tonnetz are relaxed in such a way as to allow movements between major and minor triads with variations at exactly two tones, the resulting bipartite graph has two components, each of which generates a remarkable tessellation of the plane, known to Kepler, based on hexagons, tetragons, and dodecagons. The talk will present a short survey of these and various related topics in the mathematical theory of music.

Zoom details

Zoom link: [LINK]

Meeting ID: 813 0444 2723

Passcode: 812303

Date & Time: Wednesday, 10th December at 14:00

Location: Aula of the Institute of Physics PAS, Al. Lotników 32/46

Nobel Prize in Physics 2025: The Schrödinger’s Cat gets bigger.

cft — Thu, 20 Nov 2025 12:33:59 +0000

Location: Aula of the Institute of Physics PAS, Al. Lotników 32/46

Abstract: Usually effects of quantum tunneling and energy quantization are associated with behavior of single atoms or molecules. Electrons occupy orbitals of definite energy and can change their state in the process of absorbing or emitting well-defined energy quanta – photons. In the Sun, two protons fuse by tunneling over the Coulomb barrier to form deuterium. But can we extend the direct applicability of quantum mechanics to macroscopic objects, i.e. objects visible with a bare eye? Yes, we can. This year the Nobel Prize has been awarded “for the discovery of macroscopic quantum tunneling and energy quantization in an electric circuit”. In their two seminal experiments (Phys.Rev.Lett. 55, 1908 (1985), Phys.Rev.Lett. 55, 1543 (1985)) laureates John Clarke, Michel Devoret and John Martinis showed that these two hallmarks of quantum mechanics can be observed also for macroscopic artificially-defined objects.

Full abstract is available here.

Zoom details

Zoom link: [LINK]

Meeting ID: 813 0444 2723

Passcode: 812303

Quantum complexity and volumes in gravity

cft — Mon, 13 Oct 2025 07:46:45 +0000

Holography, also known as AdS/CFT, relates strongly-interacting quantum systems with gravitational theories in negatively curved universes. A lot of progress in quantum gravity over the course of the past 50 years, following foundational works by Bekenstein, Hawking and others, was devoted to understanding areas in gravitational systems in terms of microscopic entropy notions. In my colloquium, I will discuss in a pedagogical manner recent progress on viewing spacetime volume in gravity as representing hardness of microscopic quantum state preparation – quantum complexity. Based on 2412.17785 with Papalini and Schuhmann (PRL) and earlier results reviewed in 2503.10753 with Baiguera et al.

Aula of the Institute of Physics PAS, Al. Lotników 32/46

Zoom details

Zoom link: [LINK]

New insights on the structure formation of the Universe delivered by detailed properties of thousands of galaxy clusters

cft — Wed, 06 Aug 2025 20:49:09 +0000

The use of galaxy clusters as cosmological probes relies on a detailed understanding of their properties. They define cluster selection and ranking linked to a cosmologically significant cluster mass function. Previous studies have employed small samples of clusters, concentrating on achieving the first calibrations of cluster properties with mass, while the diversity of cluster properties has been revealed via detailed studies. The large spectroscopic follow-up on the CODEX cluster sample with SDSS and NOT enables a detailed study of hundreds of clusters, lifting the limitations of previous samples. We report on the scaling relations between richness, X-ray luminosity, and velocity dispersion for a complete sample of clusters with at least 15 members. Clusters with velocity substructure exhibit enhanced velocity dispersion for a given richness and are characterized by 2.5 times larger scatter. Clusters that have a strong offset in X-ray-to-optical centers have comparable scaling relations as clusters with substructure. We demonstrate that there is a consistency in the parameters of the scaling relations for the low- and high-richness galaxy clusters. Splitting the clusters by redshift, we note a decrease in scatter with redshift in all scaling relations. We localize the redshift range where a high scatter is observed to z < 0.15, which is in agreement with the literature results on the scatter. We note that the increase in scatter for both high- and low-luminosity clusters is z < 0.15, suggesting that both cooling and the resulting active galactic nucleus feedback are at the root of this scatter. We report a dependence of both the X-ray and optical luminosity of clusters on large-scale density, which we associate with the assembly bias. These results motivate an introduction of an additional characterization of galaxy clusters and shed light on the physical origin of anomalous clustering of galaxy clusters, found by the Dark Energy Survey (DES).

Quantum Coherence and an Unexpected Twist – Vortex Control in Optically Imprinted Polariton Landscapes

cft — Wed, 06 Aug 2025 20:47:56 +0000

Exciton-polaritons are mixed light-matter quasiparticles arising due to the strong coupling of photons and excitons inside a semiconductor microcavity. As they are composite bosons of low mass, they may form a macroscopically coherent non-equilibrium condensate at elevated temperatures [1], which led to fascinating demonstrations of superfluidity [2] and quantized vortices [3] in the solid state. The photons leaking from the cavity are a part of the polariton wave function. Thus, the properties of the polariton condensate, including its energy, spin, momentum and phase may be investigated by spectroscopic means. Under non-resonant excitation, polaritons form spontaneously from free carriers and form a condensate that interacts with them. As polaritons are several orders of magnitude lighter than these carriers, the latter effectively form a static repulsive potential for the condensed polaritons. Spatially shaping the excitation beam then enables us to investigate polariton condensates in optically imprinted potential landscapes. We show how to utilize these potentials to create and control quantized vortices in the polariton condensate [4], opening up new perspectives in polaritonics. Finally, we investigate quantitative means to characterize the resourcefulness of the condensate in terms of its quantum coherence [5] and demonstrate how to measure them using real-time spectroscopy for in-situ determination of photon correlations and density matrices of light fields. ‍

The light side of dark matter: waves vs. particles

cft — Wed, 06 Aug 2025 20:46:25 +0000

Cosmological observations on scales from galaxies to the cosmic microwave background indicate that most of the matter in the Universe is cold, dark, and non-baryonic. While searches for new massive particles have so far come up empty, QCD and string theory provide strong motivations for the existence of very light, weakly coupled, bosonic dark matter candidates: axions and axion-like particles (ALPs). As the de Broglie wavelength of these particles may reach galactic scales, structure formation with ALP dark matter predicts very distinctive signatures. Lower bounds on the particle mass have been obtained from different regimes of „waviness” involving diverse systematics. I will present an overview of the progress and challenges of exploring the low-mass frontier of the universe.

Galactic Winds accelerated by Cosmic Rays in Milky Way-like galaxies

cft — Wed, 06 Aug 2025 20:45:21 +0000

Cosmic rays are high-energy charged particles, primarily protons and electrons, that are produced and accelerated to relativistic speeds in the remnants of supernovae. These particles dynamically interact with the gas in the interstellar medium, transferring momentum and energy, which can accelerate vast amounts of gas and generate powerful galactic winds. While this mechanism is highly effective at driving large-scale outflows in massive galaxies, it is often overlooked in current galaxy models. In this colloquium, we will explore the role of cosmic rays in shaping galactic winds by employing magneto-hydrodynamical simulations of Milky Way-like galaxies. These simulations will include supernova feedback in the form of both thermal and cosmic ray energy injections. By comparing models with purely thermally-driven outflows to those incorporating cosmic rays, we will highlight the critical influence of cosmic rays on galactic winds. Additionally, we will discuss how this research could enhance our understanding of wind dynamics and composition in our own Galaxy.