TBA

• Nanda REA (ICE-CSIC UAB Barcelona)

Room: Seminar room

TBA

• Ennio SALVIONI (UAB & IFAE)

Room: Seminar room

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.