-
Sébastien Renaux-Petel (IAP - CNRS)03/05/2023, 09:00
-
Giovanni Cabass (Institute for Advanced Study)03/05/2023, 09:35
-
Dr Matthieu TRISTRAM (CNRS)03/05/2023, 10:10
-
Kazuya Koyama03/05/2023, 11:15
-
Giovanni Tambalo03/05/2023, 11:50
Inflationary perturbations are mostly Gaussian, with non-Gaussian features usually calculated using in-in perturbation theory. However, for unlikely fluctuations, non-Gaussianities can be important and the probability distribution is then better characterized in a semi-classical approximation, which takes into account classical non-linearities at the non-perturbative level.
Go to contribution page
I will apply this... -
Guillermo Franco Abellán03/05/2023, 12:10
Although the CMB and galaxy surveys provide precise measurements of the primordial power spectrum at large scales, the small-scale power spectrum remains largely unconstrained. An enhancement in the small-scale primordial spectrum (such an spike) can lead to the formation of Ultra-Compact-Mini-Halos (UCMH) much earlier than standard halo can form. As a result, the DM annihilation signal...
Go to contribution page -
Denis Werth03/05/2023, 14:00
Correlation functions of primordial density fluctuations provide an exciting probe of the physics governing the earliest moments of our Universe. However, the standard approach to compute them is technically challenging. Theoretical predictions are therefore available only in restricted classes of theories, which can completely bias the interpretation of data.
In this talk, I will present...
Go to contribution page -
Guilherme Brando de Oliveira03/05/2023, 14:20
In this talk I will outline a fast and accurate approach to introduce modified gravity (MG) consistently in Cosmological N-Body simulations, using the COLA (COmoving Lagrangian Acceleration) method, a fast and approximate method to generate non-linear realizations of the density field. The matter power spectrum computed from these simulations is shown to be in agreement with known results in...
Go to contribution page -
Drew Backhouse03/05/2023, 14:40
I will present the results of arXiv:2301.02455 and arXiv:2301.08652 where it is shown that, for sufficiently low temperatures, a scalar field tunneling between two degenerate vacua on a flat FLRW background metric results in Null Energy Condition violation in the true vacuum state. The corresponding homogeneous fluid induces a cosmological bounce, after which it obtains a phantom-like equation...
Go to contribution page -
Eleanor Hall03/05/2023, 15:00
Gravitational waves from phase transitions in the early universe pose one of our most promising probes of beyond the standard model physics. However, existing perturbative methods for false vacuum decay rate calculations are limited to weakly coupled theories. Recently, we have proposed a new, non-perturbative quasi-stationary effective action for false vacuum decay rate calculations based on...
Go to contribution page -
Dr David Benisty (University of Cambridge)03/05/2023, 15:20
General Theory of Relativity needs at least one modification - the Cosmological Constant. Yet there are possibilities for other modified theories of gravity to explain the accelerated expansion. In this talk I'm going to discuss the impact of Modified Gravity on the two-body problem. In particular, with the latest observational constraints from the galactic center, binary pulsars and the Milky...
Go to contribution page -
Francesco Serra03/05/2023, 15:40
Gravitational waves emitted during a black-hole merger might differ from what General Relativity predicts due to the presence of yet unknown degrees of freedom coupled to gravity. A simple example is that of a scalar field that produces black hole hair, affecting both the inspiral and ringdown phases of black hole mergers.
Go to contribution page
We can constrain such scenarios from the point of view of fundamental... -
Claire Aude Laure Rigouzzo (King's College London)03/05/2023, 16:30
General relativity (GR) exists in different formulations. They are equivalent in pure gravity but generically lead to distinct predictions once matter is included. After a brief overview of various versions of GR, we focus on metric-affine gravity, which avoids any assumption about the vanishing of curvature, torsion, or nonmetricity. We use it to construct an action of a scalar field coupled...
Go to contribution page -
Dr Sukanta Panda (IISER Bhopal)03/05/2023, 16:50
We check quantum stability of the generalized Proca theories in curved spacetime by computing the quantum gravitational corrections using Vilkovisky- Dewitt formalism. First we consider a range of the coupling constants to maximize the predictability of EFT. We find that there exists a regime where classical nonlinearity dominates while quantum corrections are still suppressed protecting EFT...
Go to contribution page -
Ricardo Landim (University of Portsmouth)03/05/2023, 17:10
Holographic dark energy with the Hubble radius as infrared cutoff is considered as a candidate to explain the late-time cosmic acceleration for 20 years and it can solve the coincidence problem. However, a nonzero equation of state is only possible if there is an interaction between dark energy and cold dark matter. In this talk I show that the resulting matter power spectrum and cosmic...
Go to contribution page -
Vigneron Quentin (Copernicus University of Toruń)03/05/2023, 17:30
I will present a new cosmological model in which the expansion is no longer affected by spatial curvature (i.e. Ω = 1, ∀ Ω_k), while the measure of distances still requires this curvature. The model originates from a modification of Einstein's equation in a which a term related to the topology of the Universe is added. First, I will present the main motivation for this modification, which is...
Go to contribution page -
Ezgi Yilmaz (CASUS)03/05/2023, 17:50
Assuming nonnegligible relativistic component densities alongside the cold dark matter of the ΛCDM model, we reformulate cosmological perturbations within the framework of the cosmic screening approach. The scheme addresses all spatial scales, provided that gravitational interactions may be studied in the weak field limit to a good approximation. As a novel feature of the formulation,...
Go to contribution page -
Prof. Alexander Zhuk (Astronomical Observatory Odessa National University (UA), Center for Advanced Systems Understanding (Germany))03/05/2023, 18:10
We investigate the backreaction of nonlinear perturbations on the global evolution of the Universe within the cosmic screening approach. To this end, we have considered the second-order scalar perturbations. An analytical study of these perturbations followed by a numerical evaluation shows that, first, the corresponding average values have a negligible backreaction effect on the Friedmann...
Go to contribution page -
Prof. Bivudutta Mishra (BITS-Pilani, Hyderabad Campus)
To recreate the cosmological models, we employed the parametrization approach in modified teleparallel Gauss-Bonnet gravity. It has been interesting to apply the parametrization approach to investigate cosmological models. The real benefit of using this method is that the observational data may be incorporated to examine the cosmological models. Several cosmological parameters were examined,...
Go to contribution page
Choose timezone
Your profile timezone: