From Birth to Burst: Neutron Star Diversity and Their Links to FRBs, GRBs, and Supernovae

• Nanda REA (ICE-CSIC UAB Barcelona)

Room: Seminar room Neutron stars represent one of the most diverse and dynamic populations in high-energy astrophysics, manifesting as radio pulsars, millisecond pulsars, magnetars, X-ray binaries, and other exotic subclasses. In recent years, time-domain surveys have revealed unexpected connections between these classes and some of the most energetic transients in the Universe, including fast radio bursts (FRBs), gamma-ray bursts (GRBs), and supernovae (SNe). This talk provides a comprehensive overview of the “neutron star zoo,” emphasizing the importance and distributions of physical parameters such as magnetic field, spin, age, and environment that drive their observational phenomenology. I will review how different neutron star classes emerge from distinct evolutionary pathways and how they can transition between states. Special focus will be placed on observational and theoretical links between young magnetars and FRBs, between compact object formation and GRBs, and between supernova explosion mechanisms and the birth properties of neutron stars.

Probing Dark Matter with Large Scale Structure

• Ennio SALVIONI (UAB & IFAE)

Room: Seminar room Precision cosmology offers opportunities to test the nature of dark matter independently of any interactions with the visible sector. I will discuss how data from galaxy surveys, including the ongoing DESI and Euclid projects, can be leveraged to probe new dynamics in the dark sector. For this purpose, I will show how to extend the Effective Field Theory of Large Scale Structure to include physics beyond the Standard Model, enabling perturbative computations of the power spectrum of galaxies. The scenarios I will discuss include long-range self-interactions of dark matter, and sub-components of dark matter exhibiting suppressed growth of structure, such as ultra-light axions or light thermal relics.

Tracing the Origin of the Nanohertz Gravitational Wave Background

• Andrea MITRIDATE (Imperial College, London)

Room: Seminar room By tracking the radio pulses from an array of millisecond pulsars, several pulsar timing array collaborations have found evidence for a stochastic background of gravitational waves permeating our Galaxy. In this talk, I will briefly review how this evidence was obtained, then discuss ongoing efforts to identify the origin of the signal and explore its implications for cosmology and astrophysics. I will focus in particular on the challenges of mapping the sky distribution of the gravitational-wave power and on searches for non-Gaussian features in the background.

Temperature-Dependent CPT Violation: Constraints from Big Bang Nucleosynthesis

• Anne-Katherine BURNS (Barcelona U)

Room: Seminar room In this talk, I will explore temperature-dependent CPT violation during Big Bang Nucleosynthesis (BBN) modeled as an electron–positron mass asymmetry controlled by a finite-temperature background. Using a modified version of the BBN code PRyMordial with dynamically-solved chemical potentials and appropriate finite-mass corrections, my collaborator and I have constrained electron-positron mass differences using the observed abundances of Helium-4, Deuterium, and Neff. We find no region of parameter space consistent with all three observables at 1σ, though pairwise combinations yield allowed bands that tightly bound the mass asymmetry. I will present three toy models demonstrating how the type of CPT violation can arise from field-theoretic mechanisms, including temperature-driven phase transitions. The results that I will discuss provide the most stringent constraints on early-universe CPT violation in this regime, probing parameter space inaccessible to laboratory experiments.