GGI workshop: Exploring New Frontiers in Cosmology

Session

Student Talks

10 juil. 2026, 14:00

Galileo Galilei Institute

141. Cosmology with Torsion and Nonmetricity

Ilaria Andrei

10/07/2026 14:00

Talk at the school (week 1)

Metric affine gravity (MAG) represents an extension of general relativity (GR) in which an independent connection other than the Levi-Civita one is present. In MAG there are three tensors describing the geometry of spacetime, curvature, torsion and nonmetricity. And two tensors related to matter's behaviour, the stress energy tensor and the hypermomentum. After reviewing the main features of...

150. Inverse non-metricity in f(Q) gravity: cosmology and observational constraints

Simão Marques Nunes (Institute of Astrophysics and Space Sciences (Lisbon Portugal))

10/07/2026 14:10

Talk at the school (week 1)

In this talk I will present a minimal modified gravity model within the symmetric teleparallel formulation, based on an inverse non-metricity term that introduces no additional free parameters with respect to $\Lambda$CDM. I will discuss its main cosmological signatures as well as observational constraints obtained from CMB data alone and in combination with BAO, RSD, SNIa, and DES data,...

146. Revisiting Quadratic Scalar Field (Fuzzy, Wave, Ultralight) Dark Matter in Light of DESI DR2 and Current Cosmological Observations

Hafiz Inam ullah (ESFM - Escuela Superior de Física y Matemáticas - IPN)

10/07/2026 14:20

Talk at the school (week 1)

We study the cosmological phenomenology of quadratic scalar field dark matter (SFDM) using an implementation in the Boltzmann code CLASS, in which dark matter is modeled as a single ultra-light scalar field with potential V (ϕ) = 12 m2ϕ ϕ2 . Adopting a dynamical-systems approach, we analyze the expansion of the homogeneous scalar field together with its linear perturbations, enabling stable...

164. Taming Instabilities in Mass-Varying Neutrino Cosmology

Vitor da Fonseca (Institute of Astrophysics and Space Siences (Lisbon, Portugal))

10/07/2026 14:30

Talk at the school (week 1)

Mass-varying neutrino models with strong scalar couplings are typically affected by late-time perturbative instabilities. In this talk, I present an inverse symmetron-like phase transition in which the neutrino nonrelativistic transition activates the fifth force, while the subsequent dilution of the neutrino density restores the symmetry and suppresses the coupling. This mechanism avoids...

134. On the potential of pseudo-scalar dark energy

Yunzhi Wu (UniTo and INFN)

10/07/2026 14:40

Talk at the school (week 1)

A cosmological pseudo-scalar field provides a compelling realization of dynamical dark energy (DE). If its coupling to photons is non-negligible, the cosmic microwave background acquires a rotation of its polarization plane, known as cosmic birefringence (CB). We present an extended analysis of several pseudo-scalar DE models and derive constraints on the parameters of their potentials by...

130. Constraining DDE Models with AdS-to-dS and Similar Late-Time Transitions

Mine Gökçen (Istanbul Technical University)

10/07/2026 14:50

Talk at the school (week 1)

With the release of DESI DR2, dynamical dark energy (DDE) models gained unprecedented attention as model candidates to release the current cosmological tensions. However, majority do not perform well in relaxing the H0 tension compared to some of the other novel theoretical and phenomenological DE models in the literature, such as the LsCDM model that can be explained by an AdS-to-dS...

168. Understandig the Dark Sector through reconstructions

David A López Magaña (Universidad Nacional Autónoma de México)

10/07/2026 15:00

Talk at the school (week 1)

Within the standard understanding of cosmology, the existence of Dark Matter and Dark Energy is considered. Together, these constitute approximately 95% of the Universe; however, their behavior is not fully understood. Through reconstructions, the phenomenological behavior of both Dark Energy and Dark Matter can be inferred from astronomical observations. This work addresses the interpolation...

173. Reconstructing dark energy with fewer assumptions

Daniel Kessler (University of Sheffield)

10/07/2026 15:10

Talk at the school (week 1)

We perform minimalistic reconstructions of the dark energy density and equation of state using late-time distance measurements. Our methodology avoids assumptions that correlate the values of these functions over time and instead yields their approximate average evolution within seven redshift bins from z=0 to z=4.2. Constraints are obtained using combinations of baryon acoustic oscillation...

163. Multi-field early dark energy and the Hubble tension

Marco Bella (University of Trento)

10/07/2026 15:20

Talk at the school (week 1)

Early dark energy (EDE) is a popular extension of the $\Lambda$CDM model, which alleviates the Hubble tension by reducing the sound horizon at recombination. The updated Planck high-$\ell$ likelihood (NPIPE), however, places strong constraints on such models.

In this talk, I will present a model with two non-interacting EDE fields active at different redshifts, inspired by the string...

151. Non-linear structure of interacting dark energy model

Yuejia Zhai (University of Sheffield)

10/07/2026 15:30

Talk at the school (week 1)

Following our previous work constraining interacting dark energy (IDE) models, which showed their potential to alleviate the Hubble tension, in this work we investigate the non-linear effects of the IDE scenario favoured by CMB and DESI observations. The implications of IDE for the $S_8$ tension remain unclear, since current weak-lensing and large-scale-structure analyses either exclude highly...

170. Likelihood-Ratio Tests with Correlated Parameter Boundaries: Implications for CMB B-mode Searches

Georgia Kiddier (DAMTP, University of Cambridge)

10/07/2026 16:10

Talk at the school (week 1)

Likelihood-ratio statistics play a central role in assessing detection significance in cosmological analyses. Under regularity conditions, Wilks’ theorem predicts that these statistics follow a $\chi^2$ distribution in the asymptotic limit. When a parameter is restricted to a physical boundary, this result no longer holds, and Chernoff’s theorem provides the corresponding mixed distribution....

166. Cosmic birefringence from a stiff axion-like field

Andrea Minotti

10/07/2026 16:20

Talk at the school (week 1)

When polarized electromagnetic radiation propagates through a region of space permeated by a pseudo-scalar field, the plane of linear polarization undergoes a rotation. The rotation angle depends on the field's values when the radiation is emitted and when it is detected and does not depend on the frequency of the radiation. This phenomenon is called Cosmic Birefringence (CB) and is usually...

140. Cosmic Birefringence and Axion Dark Energy

Lena Stefanie Scheuchl (Max Planck Institute for Astrophysics)

10/07/2026 16:30

Talk at the school (week 1)

Recent analyses of Planck polarization data have reported a hint of cosmic birefringence at the level of a $~3.6\sigma$ deviation from the parity-conserving standard cosmological model. At the same time, tensions between CMB data and large-scale structure observations can be alleviated by replacing the cosmological constant with dynamical dark energy. Ultralight axion-like particles can...

129. CMB spectral distortion anisotropies from photon to dark photon conversions

Sara Evangelista (University of Manchester)

10/07/2026 16:40

Talk at the school (week 1)

Distortions of the CMB power spectrum have been proven to be a powerful probe for several cosmological and astrophysical processes. The energy distribution of the photons could provide complementary information to the well-studied temperature anisotropies, directly accessing pre-recombination physics. Each process releasing energy or changing the photon number density through the history of...

148. Constraining Primordial Magnetic Fields using Rayleigh Scattering of CMB

Kwanit Gangopadhyay (University of Groningen)

10/07/2026 16:50

Talk at the school (week 1)

The presence of magnetic fields has been inferred in extragalactic spaces like voids, and astrophysical mechanisms are unable to explain the magnitude of these fields. This hints towards cosmological magnetic fields of primordial origin, that are amplified by the astrophysical dynamo effect.

As future surveys and telescopes provide higher precision measurements of CMB, LSS and EoR; we are...

175. Exploring the Lyman-Alpha Forest in a Dynamical Dark Energy Cosmology using Cholla

Diego Garza (University of California, Santa Cruz)

10/07/2026 17:00

Talk at the school (week 1)

The Dark Energy Spectroscopic Instrument (DESI) Collaboration, when combining their baryonic acoustic oscillation observations with measurements of supernova surveys and cosmic microwave background data, inference of a best fit cosmology with a time-varying dark energy motivates independent observational tests of a departure from a cosmological constant dark energy. I will discuss the results...

133. Dark energy, spatial curvature, and star formation efficiency from JWST photometric and spectroscopic high-redshift galaxies

Leonardo Comini

10/07/2026 17:10

Talk at the school (week 1)

Early observations from the James Webb Space Telescope (JWST) have revealed an overabundance of massive high-redshift galaxies, raising the question of whether this points to new physics beyond ΛCDM, or an enhanced formation efficiency of massive stars. In this talk, I will present a Bayesian analysis of the most massive galaxies identified in recent JWST photometric and spectroscopic surveys,...

174. Measuring the Expansion Rate of the Universe with Strong Gravitational Lenses

Allan Gabriel Schweinfurth Pupo (Technical University of Munich / Max Planck Institute for Astrophysics)

10/07/2026 17:20

Talk at the school (week 1)

Strong gravitational lensing serves as a powerful, independent probe for measuring the Hubble constant (H0). We present the framework of time-delay cosmography and its relevance to the ongoing Hubble tension. We present the procedure for end-to-end cosmographical analysis. We then present ongoing mass-modelling efforts for two systems: the quadruply lensed quasar J1537-3010 and Supernova Winny...

165. Galaxy clusters as cosmic lenses for high frequency gravitational-waves

Tiziano Zanzarella

10/07/2026 17:30

Talk at the school (week 1)

High-frequency Gravitational Waves~(HFGW) ($f \gtrsim 1$ MHz) offer a distinctive probe of exotic physics and early-Universe cosmology. In the absence of dedicated detectors targeting this frequency range, indirect probes based on graviton–photon conversions in astrophysical magnetic fields become particularly relevant. In this talk we show that the extended magnetic fields permeating Galaxy...

147. Constraining the lensing dispersion from the angular clustering of binary black hole mergers

Fumihiro Chuman (Chiba Universitty)

10/07/2026 17:40

Talk at the school (week 1)

Gravitational waves from inspiraling compact binaries provide direct measurements of luminosity distances and serve as a powerful probe of the high-redshift Universe. In addition to their role as standard sirens, they offer an opportunity to constrain small-scale density fluctuations through the dispersion in the distance-redshift relation induced by gravitational lensing. In this talk, we...