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DTSTART;TZID=Europe/Madrid:20260302T150000
DTEND;TZID=Europe/Madrid:20260302T160000
DTSTAMP:20260405T235928
CREATED:20251128T154934Z
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SUMMARY:Seminar: 'The tensions of LCDM: An update of observations and theoretical implications'
DESCRIPTION:Title: ‘The tensions of LCDM: An update of observations and theoretical implications’ \nSpeaker: Leandros Perivolaropoulos (Ioannina) \nVenue&Time: Red Room / 15:00 \nAbstract: The standard LCDM cosmological model\, despite its success in describing the large-scale structure of the Universe\, is currently challenged by statistically significant discrepancies between early and late-universe observations. In this talk\, I provide a comprehensive update on observational status and theoretical implications of three major tensions: the Hubble (H0) constant discrepancy\, the DESI DR2 Phantom-Crossing Anomaly\, and the S8 tension. First\, I re-examine the H0 tension by classifying 88 Sound-Horizon-Free measurements. This analysis reveals that the discrepancy is not merely an “Early vs. Late” issue but is fundamentally driven by a clash between the Distance Ladder and the majority of other probes (reaching a significance of ~ 6.5\sigma). I will further discuss why simple late-time modifications to the expansion history fail to solve this tension due to constraints from unanchored Type Ia Supernovae (Pantheon+)\, effectively establishing a “no-go” theorem for such solutions.\nSecond\, I address the implications of the recent DESI DR2 data\, which favors a dynamical dark energy equation of state crossing the phantom divide (w(z) < -1). While this behavior is forbidden in simple quintessence models within General Relativity\, I demonstrate how it can be naturally accommodated in reconstructed Scalar-Tensor theories. By allowing for an evolving effective gravitational constant (G_eff)\, these models can fit the phantom crossing while simultaneously alleviating the Hubble tension. Finally\, I review the current landscape of the S8 tension. I discuss the shift toward a “Combined CMB” baseline (Planck + ACT + SPT) which reduces uncertainties\, and analyze the dichotomy currently present in weak lensing surveys (e.g.\, DES Year 6 vs. KiDS Legacy). I conclude by summarizing which theoretical extensions of LCDM remain viable in the face of these combined precision constraints. (edited)
URL:https://www.ift.uam-csic.es/event/seminar-by-leandros-perivolaropoulos-ioannina/
LOCATION:IFT Seminar Room/Red Room\, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera\, 13-15\, Fuencarral-El Pardo\, Madrid\, 28049\,\, Spain
CATEGORIES:Scientific activities,Seminars
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