Events
Astrophysics and Cosmology Seminar
Towards a multi-tracer cosmological measurement of neutrino masses.
Ms. Gali Shmueli
BGU
Wed, 03 Jul 2024, 11:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: Massive neutrinos modify the expansion history of the universe and suppress the structure formation below their free streaming scale. While neutrino oscillation experiments have provided only limited information, the quest to measure the sum of neutrino masses using cosmology has begun. Cosmic microwave background (CMB) observations at small angular scales can be used to constrain the total mass Σmν of the three neutrino flavors. However, at these scales, the CMB measured Σmν is degenerate with τ , the optical depth to reionization. To overcome this challenge, we utilize 21-cm power spectrum observations, enabling direct estimates for τ and breaking the degeneracy. Forecasting for the upcoming Hydrogen Epoch of Reionization Array (HERA) for a joint analysis of CMB and 21-cm data, we find that a ≲ O(10%) measurement of τ is achievable, which would enable a ≳ 5σ measurement of Σmν = 60 [meV]. Further work concerning the late universe explores the effect of massive neutrinos on the growth rate of structure. Here we wish to go beyond the analysis of density fluctuations and explore their impact on velocity fluctuations as well. To further refine our understanding, additional constraints on neutrino masses are derived through the reconstruction of the velocity field, achieved via cross-correlations with large-scale structure tracers, a technique known as velocity tomography. We utilize the kSZ and moving lens effects and forecast for future galaxy and LIM surveys, using Vera Rubin and the CII detector AtLAST as our study cases. We find that velocity tomography improvements are relevant in the case of galaxy surveys, lowering our forecasted uncertainties by 20 percent. On the other hand, LIM by itself has a stronger constraining power, regardless whether we include velocity tomography. We find lowest value of \sigma(\Sigma m_\nu)=70meV using the expected specs of AtLAST, reaching down to ~20meV adding data from CMB-S4, DESI-BAO and velocities.
Astrophysics and Cosmology Seminar
Machine learning based inference of EoR observations
Mr. Hovav Lazare
BGU
Wed, 03 Jul 2024, 11:45
Sacta-Rashi Building for Physics (54), room 207
Abstract: EoR observations, such as the 21cm signal, luminosity functions, etc., carries immense potential to probe the formation and properties of the first galaxies, and beyond $\Lambda \mathrm{CDM}$ Cosmology. However, a complete statistical analysis of such observation is limited by the time consuming nature of simulators. Using machine learning based emulators we can overcome this obstacle, and produce fast and accurate realizations of these observables. Here we present two applications of this approach: (i) reproducing HERA constraints on X-ray luminosity in the early universe from the 21cm power spectrum, and re-evaluating these bounds in the presence of PopIII stars. (ii) Achieving new constraints on Fuzzy Dark Matter using luminosity functions from EoR redshifts, the Thomson scattering optical depth of CMB photons, and upper bounds on the neutral fraction at $z\sim 6$.
Physics Colloquium
How to use plasmas to discover new particles
Dr. Andrea Caputo
CERN
Tue, 09 Jul 2024, 15:15
Ilse Katz Institute for Nanoscale Science & Technology (51), room 015
Abstract: Many theories of physics beyond the standard model predict the existence of new bosons, such as axions and dark photons, which mix with ordinary photons. In the presence of a dilute plasma, the probability of conversion between the photons and these new states is greatly enhanced by the presence of level crossings. In this Colloquium I will give a few examples of astrophysical systems, such as neutron stars and the ionosphere, which can be used to discover new physics in the near future.
Physics Colloquium
TBA
Prof. Ari Laor
Technion
Tue, 16 Jul 2024, 15:15
Ilse Katz Institute for Nanoscale Science & Technology (51), room 015
Abstract:
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