Conveners
Contributed Talks
- Deanna C. Hooper (Helsinki Institute of Physics, University of Helsinki)
Contributed Talks
- Joshua Eby (Stockholm University)
Contributed Talks
- Aleksandr Chatrchyan (Stockholm University)
Contributed Talks
- Benjamin Wallisch (Stockholm University)
Contributed Talks
- Kyrylo Bondarenko
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Antonio Racioppi (NICPB, Tallinn, Estonia)23/10/2023, 14:00
Palatini F(R) gravity proved to be a powerful tool in order to realize asymptotically flat inflaton potentials. Unfortunately, it also inevitably implies higher-order inflaton kinetic terms in the Einstein frame that might jeopardize the evolution of the system out of the slow-roll regime. We prove that a F(R−X) gravity, where X is the inflaton kinetic term, solves the issue. Moreover, when F...
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Syksy Räsänen (University of Helsinki)23/10/2023, 14:15
Primordial black holes are a candidate for dark matter. Their seeds may be generated during inflation. I discuss the mechanism, why stochastic effects are expected to be important, and how they can be modelled consistently. I will also discuss new results on how stochastic fluctuations make the density profiles that collapse into black holes very choppy, unlike assumed so far.
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Øyvind Christiansen23/10/2023, 14:30
The asymmetron dark energy model is an extension of the symmetron that aspires to resolve some of the cosmological tensions by allowing for a late-time, stochastic and large-scale spatial variation of the effective gravitational constant, in addition to the environmental variation due to screening. Whether this model actually manages to do so is complicated as it relates to questions of...
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Benjamin Wallisch (Stockholm University)23/10/2023, 14:45
The primordial universe may provide a window to the highest energy densities accessible in nature. The observational detection of primordial non-Gaussianity and/or primordial features would therefore shed unique light on the laws of physics at scales far beyond those of any terrestrial experiment. In this talk, I will show how current and future large-scale structure (LSS) surveys can place...
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Jaakko Annala23/10/2023, 15:00
Electroweak sphaleron leads to non-conservation of baryon and lepton numbers. Thus, for many baryogenesis scenarios it is crucial to know how active the sphaleron transitions were through out the history of our universe. The Electroweak sphaleron has a magnetic dipole moment and in an external magnetic field the energy of the sphaleron can be lowered affecting the rate at which the transitions...
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Kyrylo Bondarenko23/10/2023, 15:15
Primordial magnetic field, when it is confidently discovered, will play an important role in cosmology as CMB or Large Scale Structure. However, its observation can be affected by the presence of the large-scale magnetic field of galactic origin, magnetic bubbles. In the series of works, we study the effects of galaxy formation physics on the magnetization of the intergalactic medium (IGM)...
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Jesús Franco Zavala23/10/2023, 16:00
One of the most relevant problems in Physics is to identify new particles beyond the Standard Model, which can fit the properties of the cosmological dark matter. Despite decades of searching for candidates, the nature of dark matter remains a mystery even though its role in explaining cosmic structure formation has become progressively more fundamental. Analysing the properties of the galaxy...
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Alexandre Adler23/10/2023, 16:15
Of the six ΛCDM parameters, five are constrained to percent level or lower by Planck data. The constraints on the optical depth to reionisation τ, are however ten times looser. Indeed, τ is almost fully degenerate with the primordial power spectrum amplitude As. Breaking the degeneracy between As and τ is important for several cosmological challenges, including measuring the sum of neutrino...
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Sambit Kumar Giri (Stockholm University, Nordita)23/10/2023, 16:30
The epoch of reionisation marks the emergence of the first galaxies that emit light into the intergalactic medium, leading to the ionisation and heating of the Universe. This phase is a forefront area in astrophysics. While our current understanding relies on theoretical models of early galaxy formation within the standard cold dark matter (CDM) cosmology, recent observations, including early...
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Pierluca Carenza (Stockholm University)23/10/2023, 16:45
I explore the possibility of dark matter being composed of stable scalar glueballs from a confining dark SU(N) gauge theory. The relic abundance of these glueballs is studied for the first time in a thermal effective theory, using an effective potential fitted by lattice simulations. The predicted relic abundance is smaller than previously believed. Moreover, this framework can be easily...
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Sveva Castello23/10/2023, 17:00
The distribution of galaxies provides an ideal laboratory to test deviations from General Relativity. In particular, constraints on gravity modifications are commonly obtained by measuring the growth of cosmic structures through redshift-space distortions. However, such constraints rely on the validity of the weak equivalence principle, which has never been tested for the dark matter...
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Marcus Högås (Stockholm University)24/10/2023, 14:45
Fifth forces are ubiquitous in modified theories of gravity. In this talk, I present our recent results investigating their effect on the Cepheid-calibrated cosmic distance ladder, specifically with respect to the inferred value of the Hubble constant (H0). We consider a variety of effective models where the strength of the fifth force is estimated using proxy fields related to the large-scale...
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Emil Brinch Holm24/10/2023, 15:00
In response to the current cosmological tensions, a multitude of proposed extensions to the cosmological concordance model, the LambdaCDM model, have been proposed. The analysis of these models has largely been made within the Bayesian statistical paradigm, which can be prone to undesired effects arising from the prior probability distributions. In this talk, I will discuss my recent work on...
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Jacob Osman Hjortlund24/10/2023, 15:15
Type Ia supernovae (SNe Ia) have played a significant role in measuring the acceleration of the Universe's expansion and the existence of dark energy. Correct characterization of systematics is crucial to accurately measuring cosmological parameters. An example of such a systematic is the potential presence of SN Ia progenitor-related sub-populations, the rates of which can change over cosmic...
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Rishav Roshan24/10/2023, 15:30
The EDGES anomaly and the ARCADE-2 excess are not explained within the standard cosmological model or by any astrophysical solution and so they might be an indication of new physics. The decays of relic neutrinos into sterile neutrinos provide intriguingly a simultaneous solution to both puzzles. We first build a simple model able to describe the correct values of the parameters, lifetime and...
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Lorenzo Giombi24/10/2023, 15:45
We use a full general relativistic framework to study the self-similar expansion of bubbles of the stable phase into a flat Friedmann-Lemaître-Robertson-Walker Universe in a first order phase transition in the early Universe. With a simple linear barotropic equation of state in both phases, and in the limit of a phase boundary of negligible width, we find that self-similar solutions exist,...
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Anna Kormu24/10/2023, 16:30
In the Standard Model the electroweak phase transition is a crossover, but in many beyond the Standard Model theories the transition is of first order. Strong first order phase transitions could produce gravitational waves that might be detectable by the Laser Interferometer Space Antenna (LISA). Perturbation theory is commonly used to estimate the parameters that enter the calculation of...
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Nicklas Ramberg24/10/2023, 16:45
In this talk, we demonstrate how to predict the gravitational wave spectra of Strongly coupled QFTs using holography and lattice data input for a pure SU(N) Yang-Mills theory with small uncertainties. We will elaborate on how we obtain an effective potential using holography with the free energy landscape approach and formulate an effective action. Once the effective action is in our grasp, we...
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Deanna C. Hooper24/10/2023, 17:00
A gravitational wave background from a first order phase transition at the electroweak scale may be observable with future detectors such as LISA. While the Standard Model does not predict a first order phase transition, these occur in many BSM scenarios. Therefore, detecting a stochastic gravitational wave background could point to new physics, while a null detection could constrain or even...
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Tuomas Tenkanen24/10/2023, 17:15
Gravitational waves (GW) from cosmological phase transitions bear huge discovery potential and can be probed by planned future space-based experiments. Complementary to current and future collider experiments, such GW signatures can offer a powerful probe for beyond the Standard Model physics. Predictions for stochastic GW spectrum of a cosmological origin are often plagued by large...
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Jorge Baeza-Ballesteros (University of Valencia/IFIC)25/10/2023, 11:30
Cosmic strings are one-dimensional topological defects expected to form in the early-universe by many extensions of the Standar Model. In the case of axion models, the resulting strings, called global strings, then decay via the emission of particles and gravitational waves. In this talk, I will present a recent work in which we studied the simultaneous decay of isolated global string loops...
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Johan Löfgren (Uppsala University)25/10/2023, 11:45
Standard approaches taken in theoretical calculations of phase transition quantities, such as the critical temperature or the bubble nucleation rate, suffer from a wide range of ambiguities: gauge dependence, strong renormalization scale dependence, IR divergences, imaginary potentials… Though a daunting list, these problems can be resolved with the proper methods. The issue is that phase...
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Andreas Ekstedt (Uppsala University)25/10/2023, 12:00
The discovery of gravitational waves by the LIGO-Virgo collaboration was a watershed moment for fundamental physics. Now, with the hint gravitational waves from pulsar timing arrays, and with the anticipated LISA experiment on the horizon, particle physics, too, turns to studying these waves. Nevertheless, a link between gravitational-waves and fundamental physics can not be formed without...
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Martin Sahlén (Uppsala universitet)
Observations of the neutral hydrogen (HI) 21-cm signal have the potential to map out the large-scale structures (LSS) of our Universe during the post-reionization era (z ≲ 6). Several present and future experiments will probe the signatures of the LSS inherent in the expected signal over a large redshift range. Predicting the expected signal demands a detailed modeling of the HI distribution....
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