Présidents de session
Parallel session 2: Cosmology
- Ruth Durrer (Université de Genève)
Parallel session 2: Cosmology
- Camille Bonvin (Université de Genève)
Parallel session 2: Cosmology
- Eleonora Di Valentino (University of Sheffield)
Parallel session 2: Cosmology
- Eleonora Di Valentino (University of Sheffield)
Parallel session 2: Cosmology
- Pierre Vanhove (IPhT CEA-Saclay)
Parallel session 2: Cosmology
- Geraldine Servant (CERN)
Bubble nucleation is a key ingredient in a cosmological first order phase transition. The non-equilibrium bubble dynamics and the properties of the transition are controlled by the density perturbations in the hot plasma. We present, for the first time, the full solution of the linearized Boltzmann equation. Our approach, differently from the traditional one based on the fluid...
Gravitational waves o er a new way to understand the Higgs via the Electroweak phase transition. e signal from such a transition would, if observed, give crucial information of the underlying physics. Provided that the transition is first-order and proceeds through nucleating bubbles. Yet theoretical predictions of the gravitational-wave spectrum are rife with uncertainties. Large ones at...
I will describe how gravitational waves from a cosmological first-order phase transition can be cor- related with microlensing signals of Fermi balls (or gamma-ray signals of primordial black holes) produced during the phase transition. A measurable amount of dark radiation is also typically expected.
In this talk I will present a classically scale-invariant model in the context of a phase transition in the early Universe. The model consists of a scale-invariant version of the Standard Model augmented by a new SU(2) gauge group and a scalar eld which is a doublet under the new SU(2) group and a singlet of the Standard Model. Due to large supercooling, during the electroweak phase...
In our work we study the cosmological phase transition (PT) in a conformal extension of the Standard Model (SM). The model considered is called SU(2)cSM, it extends the SM gauge group by an additional hidden $SU(2)_X$ gauge group, and a scalar doublet (whilst singlet under SM gauge group).
Due to the large supercooling – a general feature of the conformal models – a strong gravitational...
Particle models beyond the Standard Model are o en accompanied by the spontaneous breaking of a new symmetry and thus by a phase transition. Arguably, the most interesting among them are first order phase transitions, in which bubbles of the low-temperature phase form and collide, leading to the generation of gravitational waves (GWs). These might be measurable as stochastic GW background...
To solve the hierarchy problem, the relaxion must remain trapped in the correct minimum, even if the electroweak symmetry is restored a er reheating. In this scenario, the relaxion starts rolling again until the backreaction potential, with its set of local minima, reappears. Depending on the time of barrier reappearance, Hubble friction alone may be insuffcient to retrap the relaxion in a...
Large and sharp turns in multi field inflation are attractive from the phenomenological point of view, but are difficult to obtain in supergravity and typically require a large field space curvature. In this talk, I will show that multiple sharp turns, aka, strong geodesic departures in the field space, are naturally realised due to transient violations of slow-roll without the requirement of...
Given the current discrepancy between early- and late- time measurements of the Hubble parameter (currently at around the 5sigma level) new models deviating from LambdaCDM have been proposed in the literature to address this so-called Hubble tension. Among the plethora of models out there, we focus particularly in the case of New Early Dark Energy (NEDE) (M Sloth and F. Niedermann) which...
Particle physics beyond the Standard Model can generate non-standard expansion histories which leave signatures in primordial stochastic backgrounds of gravitational waves (GW).
e detection of GW from cosmic strings in the next decades would tell about the presence of an early ma er-dominated era induced by a heavy unstable relic, about the presence of an early vacuum-dominated era induced...
Dark radiation (DR) appears as a new physics candidate in various scenarios beyond the Standard Model. While it is often assumed that perturbations in DR are adiabatic, they can easily have an isocurvature component if more than one eld was present during inflation, and whose decay products did not all thermalize with each other. In this talk, I will discuss the constraints on both...
e size and shape of stellar remnants are surprisingly sensitive to new light particles. We find large effects on the mass and radius of these astrophysical objects. In particular, we study light scalar fields coupled to SM ma er in spherically symmetric compact objects. Focusing on one baryon (the neutron) we show that a sourced scalar eld can induce a phase transition in nuclear ma er,...
We point out that dark matter which is produced non-adiabatically in a supercooled phase transition receives a boost in velocity which leads to long free-streaming lengths. We find that this could be observed via the suppressed matter power spectrum for dark ma er masses around ∼ 10^8 − 10^9 GeV. We thus offer novel physics goals for galaxy surveys, Lyman-α, and weak lensing observations, and...
Cosmological relaxation of the electroweak scale provides an elegant solution to the Higgs mass hierarchy problem. In the simplest model, the Higgs mass is scanned during inflation by another scalar field, the relaxion, whose slow-roll dynamics selects a naturally small Higgs vev. In this work we investigate the mechanism in a less conventional regime where the relaxion is subject to large...
We study properties of Abrikosov-Nielsen-Olesen (ANO) cosmic strings with the Coleman-Weinberg (CW) potential, which we call CW-ANO strings. While the scale-invariant scalar potential has a topologically trivial vacuum admitting no strings at the classical level, quantum correction allows topologically nontrivial vacua and stable string solutions. We find that the system of two CW-ANO strings...
A large flux of axion-like particles can be produced in the solar core. While the majority of these particles will have high velocities and escape the Sun’s gravitational pull, a small fraction of low- velocity particles will become trapped on bound orbits. Over time, an appreciable density of slow- moving axions can accumulate in this “solar basin.” Their subsequent decay to two photons...
The QCD axion is one of the best motivated particles for physics beyond the Standard Model (SM) with a phenomenology mainly controlled by the unknown axion decay constant $f_a$ which determines its mass $m_a$ as well as its couplings to SM fields. The strongest bound on the mass of the axion is obtained by energy loss arguments from observation of the supernova SN1987A, where the dominant...
The explicit breaking of the PQ symmetry by higher dimensional operators can spoil the dynamical relaxation of the strong CP angle to its minimum of zero. One solution to this PQ “quality problem” is to introduce heavy QCD axions. While still solving the strong CP problem, such heavy axions acquire a mass from physics occurring far above the QCD scale. In this talk, I will discuss the...
Black holes are considered exceptional due to their time evolution and information processing. However, these properties are generic for objects, the so-called saturons, that attain the maximal entropy permitted by unitarity. We discuss the correspondence between black holes and saturons within a renormalizable SU(N) invariant theory.
The spectrum contains a tower of bubbles representing...
Warped throats have been used in countless works in the context of string theory compactifications, in particular for their ability to suppress high energy scales. The Klebanov-Strassler solution gives us an explicit description of the geometry of a warped throat which we can use to perform computations — my focus will be on the gravitational sector of the resulting 4d EFT, with its tower of...
General Relativity (GR) exists in different formulations. They are equivalent in pure gravity but lead to distinct predictions once matter is included. After a brief overview of various versions of GR, I will highlight metric-affine gravity, which avoids any assumption about the vanishing of curvature, torsion or non-metricity. Using the example of a scalar eld coupled non-minimally to GR, I...
Monomial inflationary models have been ruled out by latest B-mode experiments. In this talk, I will show that a simple and well motivated polynomial of degree four can nevertheless fit comfortably well current CMB data. The model predicts a running of the spectral index α ∼ −$10^{−3}$, which is testable by next generation CMB experiments. A full model parameter space was obtained by...
According to the current experimental data, the SM Higgs vacuum appears to be metastable due to the development of a second, lower ground state in the Higgs potential. Consequently, vacuum decay would induce the nucleation of true vacuum bubbles with catastrophic consequences for our false vacuum Universe. Since such an event would render our Universe incompatible with measurements, we are...
In the quest for unification of the Standard Model with gravity, classical scale invariance can be utilized to dynamically generate the Planck mass and the inflaton potential. However, the generation of the vastly separated electroweak scale requires further explanation. We use the Coleman- Weinberg mechanism in an additional scalar sector as a unified origin for dynamical generation of both...
