INFLATION 2025 - Josu Aurrekoetxea

The talk provides a clear and insightful overview of how numerical relativity can be applied to early universe cosmology, particularly to test inflationary models under inhomogeneous initial conditions. The speaker, Josu Aurrekoetxea, is a researcher actively using NR, and the content is grounded in a review he co-authored, lending credibility. The argumentation is solid: he logically motivates the need for NR by explaining the limitations of the FRW approximation and the importance of nonlinear effects. The lessons drawn from simulations (small-field models fragile, long-wavelength modes dangerous, concave potentials more dangerous) are presented with physical intuition and supported by analytical understanding. The talk also touches on reheating and PBHs, showing the breadth of NR applications. However, the presentation is a seminar, so it assumes prior knowledge of GR and cosmology; it is not a self-contained educational resource. The speaker does not provide detailed quantitative results or references to specific papers, but he mentions the review and the GRChombo code. The title ‘INFLATION 2025’ is somewhat generic but accurately reflects the focus. Overall, the content is scientifically rigorous and valuable for an audience familiar with the field, though it may be too technical for general viewers. The presence of a brief technical issue at the start does not affect the content quality.

The title 'INFLATION 2025' is broad but accurately reflects the focus on inflation research in 2025, with the speaker's name providing clarity.

8/10

The speaker is a researcher actively using numerical relativity, and the talk is based on a published review. The content is technically accurate and well-structured, though it is a seminar presentation rather than a peer-reviewed publication.

Markers derived by PSI from the transcript: the creator did not define chapters.

• 00:00Introduction and overview of numerical relativity in early universe cosmology.
• 02:00Explanation of numerical relativity: solving Einstein's equations on a computer using ADM/BSSN formalism.
• 05:00Example of NR: binary black hole merger and gravitational wave templates.
• 10:00Motivation for using NR in early universe: primordial black hole formation and nonlinear effects.
• 15:00Introduction to inflation and the problem of initial conditions.
• 20:00Using NR to test inflationary models with inhomogeneous initial data.
• 25:00Lesson 1: Small-field models are not robust to inhomogeneities.
• 30:00Lesson 2: Long-wavelength modes are more dangerous for inflation.
• 35:00Lesson 3: Concave potentials are more dangerous than convex ones.
• 40:00Discussion of reheating and ongoing work on primordial black holes.

• Review on numerical relativity in cosmology — Mentioned as a review written with Katy Clough and Eugene Lim earlier this year.
• GRChombo code — Mentioned as the code developed for adaptive mesh refinement simulations.

• Planck 2018 results — Mentioned as the source for the data favoring concave models.