The 4-metre Multi-Object Spectroscopic Telescope is currently being installed on the VISTA Telescope (Paranal) and will start observations of multiple science cases at the end of this year. One of the 18 experiments is the Cosmology Redshift Survey (CRS) which is composed of 4 samples: Bright Galaxies (BG, 0.15 < z < 0.4), Luminous Red Galaxies (LRG, 0.4 < z < 1.0), Quasars (QSO, 0.9 < z <...
I present a new gravity theory based on the Schouten and Codazzi tensors. Field equations are second order and generalize Einstein's equations with a well defined correspondence limit. Exact solutions with static spherical symmetry and with the Robertson-Walker metric contain extra terms with the potential to account for dark energy effects. The theory is still under development but it is...
Cosmological model selection, in the framework of Bayesian inference requires the calculation of the Bayesian evidence. This can often be quite challenging, especially if the underlying likelihood function is expensive to evaluate. I will show how a technique called Bayesian Optimisation, based on Gaussian Process regression, can be used to calculate this evidence in far fewer likelihood...
In this study, we explored the FLRW model within f(R,Lm) gravity, focusing on Strange Quark Matter and its role in cosmic evolution. Using 57 observational data points, we derived the best-fit H(z) curve with an impressive R^2 value of 0.9527, showing strong alignment with the ΛCDM model. The deceleration parameter q(z) highlights a smooth transition from deceleration to acceleration,...
In this study, we used the ( f(T) ) gravity framework with the energy-momentum tensor for a perfect fluid to derive key cosmological parameters, including the Hubble parameter ( H ), deceleration parameter ( q ) and Statefinder diagnostics. Model parameters were optimized using an ( R^2 ) test, resulting in ( \beta = 1.312^{+0.013}{-0.014} ), ( \xi = 1.273^{+0.0065}{-0.0071} ),...
Dark Matter (DM) is a cornerstone of the standard cosmological model, yet its fundamental nature remains elusive. Accurate numerical simulations are essential to test competing DM models against observational data. In this work, we propose a novel approach to DM simulations by replacing traditional N-body methods with Physics-Informed Kolmogorov-Arnold Networks (PIKANs). Specifically, we apply...
We assume that at a late stage of inflation, a scalar inflaton field, a thermal plasma, and a spacetime metric coexisted and interacted with each other. We expand them to the linear order around a homogeneous background and combine the perturbations into a set of gauge invariant variables. For the latter we derive evolution equations in the framework of smooth reheating. Having resolved some...
Scale hierarchies are required to reliably describe the thermodynamics of cosmological first-order phase transitions using perturbation theory. At finite temperature, such a hierarchy is provided naturally. One can then use this hierarchy to construct a three-dimensional effective field theory (EFT) that systematically includes thermal resummations to all orders.
Using this EFT framework, I...
QCD-like dark sectors may undergo a first-order chiral phase transition in the early Universe that may lead to production of stochastic gravitational wave background. We consider a class of such dark sectors that feature also dark pions as viable dark matter candidates and study the corresponding strength of the gravitational-wave signal. Importantly, the chiral phase transition is of first...
We investigate the generation of gravitational waves from scalar perturbations at second order in a matter-dominated Friedmann–Robertson–Walker (FRW) universe. Since the representation of gravitational waves in perturbation theory is gauge-dependent, identifying gauge-invariant quantities becomes essential for a physically meaningful interpretation. This leads us to define a new tensor...
Phase transitions are violent and interesting phenomena that could have occurred in the early stages of the universe. Possible perturbative techniques to study these phenomena and predict their gravitational wave background can be used in the presence of a hierarchy of scales, leading to the construction of Effective Field Theories at finite temperature by integrating out the heavier scales....
The large-scale structure of the universe provides valuable information on the fundamental
laws governing its evolution. This structure consists of a network of immense galaxy filaments,
separated by vast cosmic voids, forming an intricate pattern known as the cosmic web, which
is shaped by gravity. To study and better understand these phenomena, cosmologists employ
computational...
Motivated by analogies with the electrodynamics of media, we propose a non-local extension of Einstein’s theory of gravitation formulated within the framework of teleparallel gravity. Employing a specific localizing kernel, we analyze the local limit of the theory at both the background and linear perturbation levels, and confront it with cosmological observations. We demonstrate that the...
Combining measurements of the growth rate of cosmic structure with gravitational lensing is considered as the optimal way to test for deviations from General Relativity on cosmological scales. In my poster, I will demonstrate that this standard method suffers from an important limitation, since models of dark matter with additional interactions can lead to exactly the same signatures as...
Primordial black holes (PBHs) are a unique probe of the early Universe and offer a potential link between inflationary dynamics and dark matter. In this talk, I will present our recent work investigating PBH formation in the presence of local non-Gaussianities, exploiting a logarithmic duality relation to study a variety of inflationary mechanisms that locally deviate from slow-roll dynamics....
Scalar particles traveling faster than a subluminal gravitational wave generate gravitons via gravitational Cherenkov radiation. We investigated graviton production by the primordial plasma within the framework of modified gravity in the early Universe, generating a relic graviton background. By requiring the relic graviton background to remain consistent with the Big Bang Nucleosynthesis...
Physics-Informed Neural Networks (PINNs) have emerged as a powerful tool for solving differen-
tial equations by integrating physical laws into the learning process. This work leverages PINNs to
simulate gravitational collapse, a critical phenomenon in astrophysics and cosmology. We introduce
the Schr¨odinger-Poisson informed neural network (SPINN) which solve nonlinear...
The accelerated expansion of the Universe is canonically attributed to the Dark Energy (DE), encapsulated in the Lambda factor in the Einstein field equations of gravity, but its nature is still not understood. While observations supply strong evidence in favor of the standard model of cosmology Lambda-CDM, a plethora of different modified gravity models (MG) can still arise and describe...
In this work we reflect on the departure from the standard growth of structures induced by two seemingly different, yet comparable extensions to the standard cosmological model: modified gravity and massive neutrinos. Can current Cosmic Microwave Background anisotropy and lensing data tell the difference between a phenomenological modification in the growth of the large-scale structure,...
