News: Institute of Physics

Cosmic strings are predicted in many particle physics models beyond the Standard Model. If such a model describes our universe, a network of strings inevitably forms in the early universe and persists to the present time. Cosmic strings lead to nonlinear density fluctuations at early times and will dominate the nonlinear structure at high redshifts. I will discuss how cosmic string loops dominate the halo mass function and can lead to early galaxy formation and to the formation of supermassive black holes at high redshifts. Long string segments lead to wakes which leave behind characteristic imprints in 21-cm redshift maps.

We invite you to the traditional HR coffee & talk meeting at Cukrovarnická.

We invite you to the traditional HR Coffee & Talk meeting at Slovanka.

The latest episode of the popular series Undistorted Science focuses on a key topic of our time – the photovoltaic harnessing of the Sun's energy.  

Abstract:  The Pierre Auger Observatory is the world's largest detector of ultrahigh-energy cosmic rays (UHECRs). The data, unrivaled in quality and statistics, collected by the observatory over nearly two decades greatly shaped the current state of UHECR physics. We review this impact using the most recent highlights from the Pierre Auger Observatory on the UHECR energy spectrum, mass composition, arrival directions, nuclear interactions, searches for neutral particles and multimessenger physics.  However, progress in our understanding of the UHECR properties has led to a complex picture with new challenges for discovering the UHECR origins. On this account, we discuss the nearly completed upgrade of the Pierre Auger Observatory (dubbed AugerPrime) and its potential to address these challenges during the next decade.   The seminar will be held in the main conference hall, Institute of Physics, Na Slovance 2, Prague 8. Location: https://goo.gl/maps/wEf7PsiLimSXMZhE9   For more details, see https://indico.fzu.cz/event/249/ 

The highest energy cosmic ray particles are likely to penetrate much deeper into the atmosphere than previously thought. The incoming particles are therefore likely to be much heavier. New and fundamental insights emerge from a method that generalises the approach to predicting models of cosmic particle collisions with the Earth's atmosphere. The accuracy of Jakub Vícha's method has been confirmed by hundreds of international scientists at the Pierre Auger Observatory, as shown in a study published these days in Physical Review D.

Deviations from General Relativity can be probed with black hole spectroscopy, as the quasi-normal mode (QNM) frequency spectrum of a black hole with additional ‘hair’ is expected to differ from that of a Kerr black hole. We construct an effective field theory scheme for QNMs to capture deviations from Kerr for black holes in theories with a coupling between a shift-symmetric scalar and the Gauss-Bonnet invariant. I will explain how our analysis, which is particularly suited for black holes in the LISA range, places limits on the prospects of detecting evidence of scalar hair in ringdown signals.

Dear colleagues, we would like to invite you to the seminar of Division of Elementary Particle Physics of Institute of Physics, presented by Viktor Pěč. For more info, please see invitation.

Theoretical interpretation often steps into the spotlight first once breakthrough experiments have been finished. A much more exciting situation, especially in the realm of spectral properties of magnetic materials, is when a theoretical prediction persuades researchers to undertake a specific measurement approach, and subsequently, the collected data align precisely with the prediction. Research that resulted in a paper published last week in Physical Review Letters, where an international team reported that the way light is absorbed by a magnetic substance varies according to its state of polarization, followed just this less common line of development.

We experienced another successful participation in career fairs. This year we started on 4th April at the FJFI CTU at the proven event "Ulov mě na Jaderce" and continued on 24th April at "Dny firem na Matfyzu". In both cases, a considerable number of students, especially students of physics and mathematics who are already looking for job opportunities during their studies, arrived at the FZU stand. Together we discussed the possibilities of professional employment and the offer of internships at FZU. Image

We are pleased to announce the 21st IUVSTA Summer School on Physics at Nanoscale 2024, continuing the tradition of successful summer schools on nanostructures, surfaces and thin films.

Love numbers describe the induced conservative response of an object subject to the action of an external gravitational field. They offer insight into the body's internal structure, and can be used to test gravity in the strong-field regime. In particular, Linear Love numbers are known to be zero for Schwarzschild black holes in four dimensions. In this talk I show how to extend this result to include nonlinear effects. I define these coefficients as Wilson couplings in the context of the point-particle effective field theory (EFT). After finding an explicit solution for the (static) response of a perturbed Schwarzschild black hole, I perform a matching with the aforementioned EFT, showing that: (i) the vanishing of the linear Love numbers is robust against nonlinear corrections and (ii) the quadratic Love number couplings also vanish.

Scientific Research has recently evolved by performing data-driven modeling via machine learning (ML) techniques. ML is used to make machines "intelligent" by allowing them to learn from data (i.e. experience). Integrating ML in astrophysics can open new frontiers, revolutionize data analysis, and improve our understanding. However, challenges persist in deploying ML in Astrophysics research, including the need for robust algorithms, data limitations, and the interpretability of AI-driven decisions in critical scenarios. As advancements continue, ML and astrophysics exploration synergy promises groundbreaking discoveries and enhanced capabilities for humanity's endeavors beyond Earth's boundaries. This talk will explore the multifaceted potential applications of ML in multiple domains of astrophysics, for example, gravitational wave detection, exoplanet studies, astrochemistry.

Abstract:  NA62 is a fixed-target experiment at the CERN Super Proton Synchrotron studying rare decays of kaons and pions. Its primary objective is to measure the branching ratio of the ultra-rare decay of a charged kaon into a charged pion and two neutrinos. Additionally, the NA62 undertakes a diverse physics program that includes searches for new physics and precision measurements of other kaon and pion decays. In this seminar, I will present the recent results of the experiment, with a focus on contributions from our research group.    The seminar will be held in the main conference hall, Institute of Physics, Na Slovance 2, Prague 8. Location: https://goo.gl/maps/wEf7PsiLimSXMZhE9 For more info, see : https://indico.fzu.cz/event/245/ 

Peter Ware Higgs, the British theoretical physicist known for his work on the Higgs boson and the Higgs mechanism, passed away on Tuesday 8 April at the age of 95.

When primordial inhomogeneities are produced with sufficiently large amplitude in the early universe, they may subsequently collapse into primordial black holes. I will explain why the effect of quantum diffusion during inflation needs to be taken into account in such a case, and how the statistics of cosmological fluctuations can be predicted within the formalism of stochastic inflation. Quantum diffusion leads to a peculiar type of non-Gaussianity that cannot be captured by perturbative parametrisations. This leaves specific imprints on the statistics of collapsed structures that I will discuss. In particular, I will present recent results on the clustering of primordial black holes, which conditions the rate at which they merge and emit gravitational waves.