ICTP-SAIFR Activities

Abstract: In this chalktalk, I will delve into details of how I actually performed searches for, and set constraints on, continuous waves from neutron stars and dark matter. I will first focus on constraints on the millisecond pulsar hypothesis for the GeV excess and the existence of asteroid-mass primordial black holes using upper limits from all-sky searches for neutron stars. Then, I will detail the methods that I used to search for the direct detection of dark matter with gravitational-wave detectors, and how I developed a method, based on the Hough Transform, to search for planetary-mass primordial black holes in current-generation detectors, and binary neutron star inspirals in future ground-based detectors. I will show that these continuous-wave methods can easily apply to data from future ground- and space-based detectors, and inherently solve many specific problems that matched-filtering algorithms will face in the future (overlapping signals, non-stationarity of the noise, and gaps in data collection). I will also devote a portion of this chalktalk to future projects that could be undertaken at ICTP-SAIFR with Bachelors, Masters, and PhD students.

Uma nova cura do câncer, celulares que podem explodir postos de gasolina e um filtro quântico que cura doenças. Diariamente inúmeras notícias atingem a nossa sociedade, mas como separar o joio do trigo? Quais pessoas teriam a obrigação de se dirigir à sociedade para evitar a proliferação de notícias que fazem mau uso das ideias científicas? Falaremos nesse colóquio sobre como a comunidade científica pode, e deve, ajudar no letramento científico da sociedade e também influenciar os políticos na adoção de políticas públicas baseadas em fatos.

Abstract: The universe presents itself as a grand laboratory to explore and investigate a range of physical phenomena. High-energy cosmic messengers serve as unique tools to unravel some of the most energetic processes beyond the capabilities of current  human-made particle accelerators. These messengers are not only instrumental in providing cosmological insights by probing the medium they traverse, but also hold the potential to detect Planck-scale effects that accumulate over long distances.  In this talk, I will focus on the theory of cosmological particle propagation. I will then describe how they can be used to search for the elusive dark matter, in particular axion-like particles (ALPs). Finally, I will discuss some of the ways in which cosmic particles have been used to investigate quantum gravity phenomena at high and ultra-high energies.

The third observing run of advanced LIGO, Virgo and KAGRA brought unprecedented sensitivity towards a variety of quasi-monochromatic, persistent gravitational-wave signals. These signals, called continuous waves, allow us to probe not just the canonical asymmetrically rotating neutron stars, but also different forms of dark matter, thus showing the wide-ranging astrophysical implications of using a relatively simple signal model. In this colloquium, I will first describe the framework within which we try to detect continuous gravitational waves from asymmetrically rotating neutron stars, as well as how we can use these signals to constrain the millisecond pulsar hypothesis for the galactic-center GeV excess. I will then generalize continuous-wave methodologies to include the different forms of dark matter that we could detect using gravitational-wave detectors, specifically: (1) the direct interaction of dark matter with the gravitational-wave detectors themselves; (2) gravitational waves from planetary- or asteroid-mass primordial black hole inspirals and so-called "mini" extreme mass ratio inspirals, and (3) gravitational waves from annihilating boson clouds around spinning black holes.

The origins of the most energetic particles in the Universe have been a long-standing puzzle. In the quest to identify their sources, it is crucial to understand how these particles are accelerated, how they can escape their production sites, and which roads they can take on their journey to Earth. The multimessenger framework has proven to be a powerful tool for exploring the Universe at these extreme energies.  In this talk I will focus on the triad of (ultra-)high-energy messengers: cosmic rays, neutrinos, and gamma rays. I will begin with a summary of the state of affairs in this field, reviewing some key theoretical developments and recent experimental results. I will then delve into the essential components required for building theoretical models that explain these measurements. Particular emphasis will be placed on modelling the propagation of these messengers, including their interactions with matter and radiation fields, as well as with the poorly understood cosmic magnetic fields. Finally, I will discuss the prospects of building a unified and self-consistent model of the Universe at ultra-high energies and the implications such a model would have for astrophysics, cosmology, and fundamental physics.

Hawking evaporation offers a unique mechanism for particle production, unlike any other process involving fundamental interactions. Moreover, a black hole will emit all existing degrees of freedom in nature, including those which might not interact with the Standard Model sector. Thus, even a small primordial black hole population could have altered different processes in the Early Universe, such as the generation of dark matter, dark radiation, baryon asymmetry or a stochastic gravitational wave background. We will analyse the production of these cosmological observables assuming monochromatic and extended black hole mass and spin distributions, and give prospects on how future observables could test the existence of primordial black holes.

In this talk, I will give a brief introduction to the basis of mathematical modeling in biology, mainly in ecology and epidemiology.  I will then focus on recent works and challenges in the modeling of the dynamics of epidemics, discussing the difference between modeling past epidemics and ongoing outbreaks.  In the end, I will discuss the place of theoretical developments in this area.

While it is relatively widely accepted that cosmic inflation took place, the actual physics behind it are still elusive. One of the main open questions concerns the number of degrees of freedom active during inflation, which can be answered through searches for primordial non-Gaussianity and isocurvature perturbations. Analyses of cosmic microwave background (CMB) data could not provide definite answers, but future large-scale structure (LSS) surveys are expected to do so by piercing into the theoretically interesting parameter space regions. In this lecture I will describe how galaxy clustering data can be used to very efficiently probe primordial non-Gaussianity and isocurvature. I will focus in particular on the special role played by the phenomenon of "galaxy bias", which has been overlooked in the past, but which must be understood significantly better to let us both (i) robustly constrain inflation models and (ii) optimize our galaxy observations for tests of inflation.

The large-scale distribution of mass and energy in the Universe, called the large-scale structure (LSS), contains a wealth of information about fundamental physics and cosmology (dark energy, dark matter, gravity, inflation and particle physics). In this talk I will discuss both (i) the opportunities for fundamental discoveries from upcoming LSS observational surveys, as well as (ii) the two main challenges that need to be overcome. These challenges relate to the "invisibility" and the "non-Gaussianity" of the LSS: I will describe these and report on recent progress that has been made to address them

Neutrinos, proposed last century, have revolutionized particle physics by providing a unique window into the subatomic world. Initially proposed to preserve energy conservation in beta decays, it was later discovered that they come in three flavors and have a non-zero mass, fundamentally changing our understanding of the Standard Model.In this talk, we take an "epic poem" approach to review the historical development of neutrino physics. We start by presenting the current status of neutrino physics, then delve into the fascinating journey of how scientists discovered the properties of these elusive particles, with a particular focus on the groundbreaking discovery of neutrino oscillations. Finally, we explore exciting possibilities for future research, such as studying atmospheric, supernovae, and diffuse supernova neutrinos and neutrino scatterings, in order to deepen our understanding of the unique properties of these particles and their connections to broader topics in particle physics.

ChatGPT has spread like wildfire, and is now the face of the Artificial Intelligence revolution. However, this revolution, albeit in a quiter way, has been ongoing for some time. In the case of materials science and condensed matter physics, it has led to a paradigm change in the way we design and study novel materials. In this talk I will discuss some of the important advances in the field, and some of the issues that are yet to be tackled.

Quantum Chromodynamics (QCD) is 50 years old. It was born in an atmosphere of skepticism toward the possibility that a local quantum field theory could ever describe the strong interaction. The experimental discoveries of the J/Psi and high-energy hadron jets, the establishment of asymptotic freedom, and the formulation of lattice QCD and effective field theories, among other facts, have changed the original skepticism about such a possibility. By now, the evidence that QCD is indeed the fundamental theory of strong interaction is overwhelming. Yet, we are far from understanding how it actually works. In this talk, I will focus on a couple of problems that challenge our understanding of QCD and get me out of bed in the morning.