Conveners
Contributed talks
- Chair: Elisa Todarello
Contributed talks
- Chair: Swagat Mishra
Contributed talks
- Chair: Antonio Padilla
Contributed talks
- Chair: Oliver Gould
Contributed talks
- Chair: Sergio Sevillano Munoz
Contributed talks
- Stephen Green (University of Nottingham)
Contributed talks
- Chair: Miguel Bezares
Contributed talks
- Chair: Jorma Louko
Contributed talks
- There are no conveners in this block
Contributed talks
- There are no conveners in this block
Presentation materials
We analyze theories that do not have a de Sitter vacuum and cannot lead to slow-roll quintessence, but which nevertheless support a transient era of accelerated cosmological expansion due to interactions between a scalar ϕ and either a hidden sector thermal bath, which evolves as dark radiation, or an extremely light component of dark matter. We show that simple models can explain the...
Cosmological constraints on modified gravity typically need to assume parametrisations that heavily restrict the functional forms of the independent degrees of freedom. They are also subject to assumptions about the background expansion history, the speed of gravitational waves, and theoretical priors such as shift symmetry and stability in a gravitational wave background. I show the impact of...
Axion-dilaton models provide a well-motivated, minimal class of models
for which kinetic interactions between multiple scalar fields and their
predictions can be explored, in particular in late time cosmology. I will present the cosmological implications of these interactions when prescribing an axion and a dilaton field to describe dark matter and dark energy, respectively, including the...
The matter power spectrum,
A major challenge in the analysis of Cosmic Microwave Background (CMB) data is posed by the presence of Galactic foregrounds, especially thermal dust emission. Both the search for primordial B-modes and measurements of structure growth rely on foreground modelling, for which most works implicitly assume that all sky components follow Gaussian statistics. However, we know that this is a poor...
The discrepancy between local measurements of the Hubble constant and inferences from CMB and galaxy clustering data, known as the 'Hubble tension', has motivated numerous models introducing additional components active before recombination. While many such models have been proposed, none are currently strongly favoured by data. This highlights the critical role of upcoming CMB experiments,...
Understanding the accelerated expansion of the Universe remains as one of the key challenges in cosmology. The main candidates to explain this observation, which do not rely on a cosmological constant, are dark energy and modifications of General Relativity, but they require robust tests on cosmological scales. The Dark Energy Spectroscopic Instrument offers unprecedented precision in...
Accurate predictions of weak lensing observables are essential for understanding the large-scale structure of the Universe and probing the nature of gravity. In this talk, I will present a lightcone implementation to generate maps of the weak lensing convergence field using the COmoving Lagrangian Acceleration (COLA) method. The lightcone is constructed in spherical shells from the source to...
In this work, we introduce a numerical code that solves the Misner-Sharp formalism for a spherically symmetric cosmological model containing both a scalar field and a perfect fluid. While the code is capable of exploring general scenarios involving an uncoupled scalar field and perfect fluid, our current research focuses on the regime where the scalar field dominates the dynamics. As an...
Further bright sirens -- gravitational wave events with electromagnetic counterparts -- are keenly awaited, but proving elusive. The exceptional event GW170817 had a profound impact on the landscape of viable cosmological extensions of General Relativity (GR); can we expect this kind of shift to be repeated in the next decade? In this work we will assess the potential constraints from bright...
Recent Pulsar Timing Array (PTA) observations provide strong evidence for a stochastic gravitational wave background (SGWB), potentially originating from astrophysical sources or early universe phenomena. If the SGWB is cosmological, our relative motion with respect to the SGWB rest frame induces a kinematic anisotropy, which could dominate over intrinsic anisotropies, similar to the cosmic...
LISA and ET will operate in different frequency ranges but with comparable integrated sensitivities to a stochastic GW background (SGWB). We explore their synergies in detecting cosmological SGWBs with large amplitudes and broad frequency spectra, arising from sources such as cosmological phase transitions, cosmic strings, and primordial inflation. By combining measurements from both...
Cosmological first-order phase transitions may have generated an observable gravitational wave background, offering a unique probe of beyond-Standard-Model physics. A crucial step in predicting this background is the reliable computation of bubble nucleation rates. In this talk, I will give an overview of recent advancements in perturbative high-temperature nucleation rate calculations. These...
We write a closed form expression for the metric perturbation around de Sitter that describes gravitational radiation from a compact and slowly varying source, in terms of a consistent multipolar expansion at quadrupolar order. We show that the corresponding displacement memory effect with both the even and odd parities is at a higher order in the radial expansion compared to their flat...
Primordial perturbations observed on the CMB are thought to come from cosmological correlators during inflation. While massive (spinning) fields lead to vanishing correlators, their interaction with massless ones can alter the massless field correlators. These changes can be used to infer existence of massive spinning fields during inflation. We will compare two main models of massive spinning...
A key step in the comparison between inflationary predictions and cosmological observations resides in the computation of primordial correlators.
Numerical methods have been developed, which allow to overcome some of the difficulties arising in analytical calculations when the models considered are complex.
The \texttt{PyTransport} package, which implements the transport formalism, allows...
Although ΛCDM has been a successful cosmological model, there is a 5σ tension between
Historically, studies of the merger stage of a black hole binary have centred on fully nonlinear numerical relativity simulations. However, nonlinear black hole perturbation theory provides powerful insights into the ringdown regime immediately following merger, and perturbative self-force theory has proved highly accurate in describing asymmetric binary inspirals even for mass ratios not too...
Gravitational self-force theory (GSF) has proved to be a viable method of solving the general relativistic 2-body problem for asymmetric binaries, with state-of-the-art GSF inspiral waveforms now exhibiting minimal phase error across all mass ratios smaller than ~1/10. Recent work has extended these GSF inspiral waveforms to include beyond-GR effects in a broad class of scalar-tensor theories....
In this talk, I will present recent developments aimed at simulating black hole binaries beyond general relativity in Spectre, an open-source numerical relativity code by the SXS Collaboration. For concreteness, I will focus on scalar Gauss-Bonnet (sGB) gravity. I describe results derived from a parameter space exploration of a model of sGB gravity using initial data sequences of equal-mass...
Black hole quasi-normal modes (QNMs) provide a powerful probe of deviations from General Relativity. We analyze the relative contributions of shifts in the QNM spectrum of Kerr black holes and the presence of additional modes sourced by extra fields in a theory-agnostic framework. By exploring different regimes, we identify when each effect dominates and propose suitable ansätze for the...
I will present a newly established, Nottingham-based experimental platform for simulating rotating curved spacetimes in superfluid helium - a quantum liquid with vanishing viscosity. The effective curved spacetime, induced by the most extensive quantum vortex flows ever created, is probed via micrometre-scale surface waves. These reveal intricate wave-vortex interactions, including the...
The inaccurate modeling of the gravitational wave templates that are used for analysing gravitational wave signals can lead to a systematic bias in the parameter estimation. This inaccuracy can be related to the lack of terms in the waveform coming from fundamental physics or astrophysical environments or to some truncation in perturbation theory. This issue is going to be more relevant for...
Black holes serve as key testing grounds for quantum gravity due to their singular nature and have been extensively studied in various quantum gravity approaches. In this talk, I apply the Henneaux-Teitelboim formulation of unimodular gravity to the symmetry-reduced Schwarzschild-(Anti-)de Sitter model. We perform a canonical quantization, leading to a Wheeler-DeWitt equation that takes the...
We present recent advancements in the 3+1 formalism within two reformulations of general relativity: the teleparallel equivalent of general relativity, and the symmetric teleparallel equivalent of general relativity. Both theories are based on the torsion and nonmetricity of a flat connection, respectively, and their Lagrangians are expressed in terms of the torsion scalar T and the...
