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Guilherme Leite Pimentel (University of Amsterdam)02/09/2019, 14:30Early UniverseTalk
I will describe an approach to compute correlation functions of primordial fluctuations that is based on symmetries and singularities. It borrows tools from other areas of theoretical physics, like the S-matrix program of particle physics, as well as the conformal bootstrap. Using this approach, I will present some new results for inflationary three and four-point functions of scalars and...
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Dr Krzysztof Turzynski (University of Warsaw)02/09/2019, 14:50Early UniverseTalk
We study the geometrical instability arising in multi-field models of inflation with negatively-curved field space. We analyse how the homogeneous background evolves in presence of geometrical destabilisation, and show that, in simple models, a kinematical backreaction effect takes place that shuts off the instability. We also follow the evolution of the unstable scalar fluctuations. We show...
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Mr Chris Pattison (Chris)02/09/2019, 15:10Early UniverseTalk
I will begin by introducing the stochastic formalism for inflation. I will give some motivation for using the stochastic approach and then explain why we may want to consider situations that violate slow roll. I will explain the requirements for stochastic inflation to be a valid approach and discuss whether they are still appropriate when we are away from slow roll. The two requirements that...
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Dr Jonathan Braden (CITA / University of Toronto)02/09/2019, 15:25Early UniverseTalk
Inflation provides a dynamical mechanism to produce the primordial density perturbations that seed the formation of structure in the Universe through gravitational collapse. However, during the inflationary phase, the Universe is in a nearly homogeneous and low-entropy state, which must eventually give rise to the dense thermal plasma of the standard hot big bang. This transition, known as...
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Dr Evangelos Sfakianakis (Nikhef & Leiden University)02/09/2019, 15:40Early UniverseTalk
I will discuss the post-inflation dynamics of multi-field models involving nonminimal couplings. In particular I will describe the results of lattice simulations used to capture significant nonlinear effects like backreaction and rescattering. I will show how we can we extract the effective equation of state and typical time-scales for the onset of thermalization, quantities that could affect...
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02/09/2019, 15:55Talk
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Sugumi Kanno02/09/2019, 16:40Early UniverseTalk
We consider possible detection of nonclassicality of primordial gravitational waves (PGWs) by applying Hanbury Brown - Twiss (HBT) interferometry to cosmology. We characterize the nonclassicality of PGWs in terms of sub-Poissonian statistics that can be measured by the HBT interferometry. We show that the presence of matter fields during inflation makes us possible to detect nonclassical PGWs...
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Ema Dimastrogiovanni02/09/2019, 17:00
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Dr Rajeev Kumar Jain (Dept. of Physics, Indian Institute of Science (IISc), Bangalore, India)02/09/2019, 17:20Early UniverseTalk
We study the formation of primordial black holes (PBH) in a single field inflection point model of inflation wherein the effective potential is expanded up to the sextic order and the inversion symmetry is imposed such that only even power terms are retained in the potential. By working with a near inflection point in the potential, we find that PBHs can be produced in our scenario in a very...
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Prof. Dietrich Bodeker (Bielefeld University)02/09/2019, 17:40Early UniverseTalk
In a first order electroweak phase transition bubbles of Higgs phase
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expand into the symmetric phase. Particles hitting a bubble wall
cause friction and slow down the expansion. In some models this can be
insufficient to compensate the pressure difference between the two
phases. Then the bubble wall would accelerate indefinitely, it would 'run
away'. However, particles crossing the... -
Spyros Sypsas (FCFM, Universidad de Chile)02/09/2019, 17:55Early UniverseTalk
We will discuss new probes of non-Gaussianity in the distribution of CMB temperature anisotropies as well as that of collapsed objects such as galaxies and clusters. Going beyond polyspectra, we will focus on CMB/LSS probability distribution functions and discuss how the structure of the pre-Big Bang era can be partially encoded in it.
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02/09/2019, 18:10
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Adrian Del Rio (IST-Universidade de Lisboa)03/09/2019, 14:30Early UniverseTalk
Hidden fields present during single-field inflation can affect CMB observables through quantum vacuum fluctuations. Besides the renormalization of background quantities, loop corrections of these fields induce Planck-suppressed logarithmic runnings in correlation functions of curvature and tensor perturbations. In this talk we consider the impact of a large number of such field degrees of...
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Yvette Welling (Deutsches Elektronen-Synchrotron DESY)03/09/2019, 14:50Early UniverseTalk
Recent swampland conjectures highlight again the importance of finding viable scenarios for inflation that are not strictly single-field. In particular, one may wonder whether there are multi-field inflationary scenarios that have a similar phenomenology to single field inflation. We present a family of exact models of inflation - dubbed Orbital Inflation - in which the multi-field effects are...
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Guadalupe Cañas Herrera03/09/2019, 15:10Early UniverseTalk
Observations of Planck's CMB favours a canonical slow-roll single-field scenario for inflation. However, simple multi-field extensions can also explain the current data, and on top some of the existing anomalies not accounted for by the canonical scenario. We present our search for multi-field-motivated extra degrees of freedom in the context of an effective single field theory with a varying...
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Bernardo Finelli (Utrecht University)03/09/2019, 15:25Early UniverseTalk
In this talk I will introduce tools for the construction of effective field theories (EFTs) that involve the breaking of spacetime symmetries. Nowadays, symmetry breakdown is part and parcel of the study of EFTs, with group theory allowing us to derive the most generic action for the Goldstone bosons—but only if the group is internal. When spacetime symmetries are broken, the game becomes much...
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Dr Jeff Kost (Institute of Basic Science)03/09/2019, 15:40Early UniverseTalk
The viability of a given model for inflation is determined not only by the form of the inflaton potential, but also by the initial inflaton field configuration. In many models, otherwise well-motivated inflaton field configurations fail to induce inflation, or fail to produce sufficient inflation to solve the horizon problem. In this talk, we propose a mechanism which enables inflation to...
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Dr Marjorie Schillo (Uppsala)03/09/2019, 15:55Early UniverseTalk
I will discuss a recent construction wherein an effective de Sitter spacetime appears as a non-supersymmetric AdS vacuum decays into the supersymmetric vacuum. Four-dimensional observers are localized on a spherical brane which nucleates to facilitate the decay. The expansion of the brane bubble then leads to an effective four-dimensional de Sitter space. This construction side-steps the...
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Dr Azadeh Maleknejad (Max Planck Institute for Astrophysics)03/09/2019, 16:40Early UniverseTalk
Primordial SU(2) gauge fields coupled to axions can contribute to the physics of inflation. Their rich phenomenology and unique observational features, e.g., chiral primordial gravitational waves, turned this class of models to a hot topic of study since their discovery in 2011. In this talk, I will briefly review the models in this class, which so far have been studied in the literature....
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Kyohei Mukaida (DESY)03/09/2019, 17:00Early UniverseTalk
The coupling of an axion-like particle driving inflation to the Standard Model particle content through a Chern-Simons term generically sources a dual production of massless helical gauge fields and chiral fermions. We demonstrate that the interplay of these two components results in a highly predictive baryogenesis model, which requires no further ingredients beyond the Standard Model. If the...
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Yuki Watanabe03/09/2019, 17:15Early UniverseTalk
In this talk I will consider an inflationary universe with non-Abelian gauge fields and axion fields that are in part identified with the standard model of particle physics.
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In particular I consider possibilities of an enlarged color group with extra heavy quarks that solves the strong CP problem. When the heavy quarks are integrated out below the Peccei-Quinn symmetry breaking scale, they... -
Early UniversePoster
The fate of the Higgs vacuum in the context of the cosmological history is usually studied
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by assuming no new physics between the Standard Model and the Planck scale. In this
work we show that even Planck suppressed operators can play a crucial role in determining
the fate of our vacuum during inflation. En passant, we notice that considering the time
dependence of the Hubble parameter during... -
Early UniversePoster
We study a class of models where inflation is driven by a self-gravitating
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adiabatic medium.
Such class of media admits an effective description in terms of four
scalar fields related to the Goldstone bosons for the spontaneous
breaking of spacetime translations. Depending on the symmetry of the
effective action of the medium, one can have perfect barotropic or
non-barotropic fluids and... -
Early UniversePoster
Magnetogenesis in the early Universe can have strong impacts in cosmology since it can be responsible for the intergalactic magnetic fields suggested by blazar observations and for the baryogenesis. In this talk, I point out that the Affleck-Dine (AD) mechanism, which is one of the popular scenarios of baryogenesis, can also be the source of the magnetic field generation. By integrating out...
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Early UniversePoster
The self coupling $\lambda$ of the Higgs boson in the
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Standard Model may show critical behavior, i.e. the Higgs potential
may have a point at an energy scale $\sim 10^{17-18}$ GeV where both
the first and second derivatives (almost) vanish. Since $\lambda$ is
very small in this region, the Higgs boson can serve as inflaton
even if its nonminimal coupling to the curvature scalar is... -
Early UniversePoster
There has been considerable recent interest in a new class of non-slow roll inflationary solutions known as constant roll inflation. Constant roll solutions are a generalization of the ultra-slow roll (USR) solution, where the first Hubble slow roll parameter $\epsilon$ is small, but the second Hubble slow roll parameter $\eta$ is not. While it is known that the USR solutions represent...
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Early UniversePoster
It was recently shown that a coherent oscillation of an axion can cause an efficient parametric resonance, leading to a prominent emission of the gravitational waves (GWs). In this poster, conducting the Floquet analysis, we investigate the parametric resonance instability, which potentially triggers the emission of the GWs from axions. Such a resonance instability takes place, when the time...
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Early UniversePoster
Robust studies of the electroweak phase transition (EWPT) in scalar extensions of the Standard Model (SM) utilise dimensionally reduced effective field theories (EFT) and lattice studies to determine thermodynamic properties of the transition. We discuss multiple shortcomings of conventional perturbative approaches based on the resummed effective potential and demonstrate that greater accuracy...
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Early UniversePoster
In this talk we present some ongoing work on the entanglement in quantum field theories living on cosmological backgrounds. We focus in particular on primordial curvature fluctuations and the survival of the entanglement created during inflation in the radiation-dominated era.
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Early UniversePoster
Several recent proposals to embed inflation into high-energy physics rely on inflationary dynamics characterized by a strongly non-geodesic motion. This in turn relaxes the conditions of slow-roll to allow for potentials that are steep in Planck units, a welcome feature in view of the eta problem and the recently much discussed swampland conjectures.
In this talk I will present a general...
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Early UniversePoster
The robustness of inflation to inhomogeneous initial conditions for matter fields and the spacetime metric is under investigation. If inflationary expansion fails to begin under sufficiently inhomogeneous initial conditions, such that inflation requires fine-tuning of its initial state to occur, then its naturalness is challenged. I will present results for the range of initial conditions...
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Early UniversePoster
We determine the minimum value of the reheating temperature set by Big-Bang Nucleosynthesis by considering both radiative and hadronic decays of long-lived massive particles. In the current study, effects of neutrino oscillation and neutrino self-interaction are taken into account in the calculation of the neutrino thermalization. We adopt updated observational bounds on the primordial...
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Early UniversePoster
The mechanism of inflation is likely to be described in the context of theories beyond the standard model since it took place in the very early Universe, where the energy scale can be as large as $10^{15} GeV$. Thus, it is theoretically justified to consider more than one scalar field during inflation. Besides being well justified from a theoretical point of view, multifield models of...
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Early UniversePoster
Multi-field models of inflation with curved field space and non-geodesic motion have recently been under scrutiny as realistic realizations of high-energy physics in the Early Universe.
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Focusing on 2-field models, we present the covariant 3rd order action in terms of the adiabatic comoving curvature perturbation and the entropic field perturbation. We extend Maldacena’s calculation to such... -
Early UniversePoster
The spherically-symmetric soliton named oscillon emerges from the violent instability of the inflaton during the (p)reheating epoch, and has a potential to alter the cosmic expansion history in the epoch. For instance, if the oscillons decay soon after their formation, the (p)reheating epoch is terminated much earlier than expected, and therefore the e-fold number corresponding to the current...
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Early UniversePoster
The next generation detectors will verify, or at least constraint high energy phenomena, predicted by the vast variety of inflationary scenarios. If a circularly polarized gravitational wave signal is detected, would point to the existence of parity breaking physics [1]. Here we consider, possible realizations of the effective field theory of scalar-tensor gravity [2], which could offer a rich...
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Early UniversePoster
In this presentation, I consider two case examples of
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Dirac-Born-Infeld (DBI) generalizations of canonical large-field
inflation models, characterized by a reduced sound speed, $c_{S} < 1$.
The reduced speed of sound lowers the tensor-scalar ratio, improving
the fit of the models to the data, but increases the equilateral-mode
non-Gaussianity, $f^\mathrm{equil.}_\mathrm{NL}$, which the... -
Early UniversePoster
We study the preheating process of the two-field inflationary model, namely the mixed Higgs-$R^2$ model. The characteristic potential shape leads to chaotic motion of the inflaton, which induces interesting decay channels. We numerically solve the full equations of motion to study the non-trivial behavior of the inflaton. We analyze the evolution of the background fields and find analytic...
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Early UniversePoster
ㅤNon-linear effects during inflation can generate primordial non-Gaussianities(PNG). Arkani-Hamed & Maldacena showed that an interaction between the inflaton and higher spin ($s\geq2$) fields, which may be predicted in string theory, can generate angular dependent PNG. Specifically, the search of the imprint of spin (s$\geq4$) fields can give us the evidences of string theory. As was argued by...
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Early UniversePoster
𝑆𝑈(2) gauge fields and axions can have a stable, isotropic and homogeneous configuration during inflation. However, couplings to other matter species lead to particle production, which in turn induces backreaction on background and can lead to destabilisation of the non-abelian and axion background.
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In this talk, I first discuss the particle production by a 𝑆𝑈(2) gauge field coupled to a... -
Early UniversePoster
For leptogenesis with heavy sterile neutrinos above the Casus-Ibarra bound, asymmetries produced by relativistic sterile neutrinos at early times can be relevant in the case of weak washout or if the asymmetry is partly protected from washout by being transferred to partially equilibrated spectator fields. We thus study the relevance of relativistic effects for leptogenesis in a minimal...
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Early UniversePoster
Multi-field inflation with a curved scalar geometry has been found to support background trajectories that violate the slow-roll, slow-turn conditions and thus have the potential to evade the swampland constraints. In order to understand how generic this novel behaviour is and what conditions lead to it, we perform a classification of dynamical attractors of two-field inflation that are of the...
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Early UniversePoster
In this talk I will discuss the generation of primordial non-Gaussianities in general multi-field inflation models where the primordial curvature perturbation is able to vigorously interact with an ultra-light isocurvature field. We identify an entire class of multi-field systems with a scaling symmetry that simultaneously acts on the fields and the spacetime coordinates. This transformation...
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Early UniversePoster
I will talk about our works (arXiv:1608.01213, arXiv:1710.06851, arXiv:1902.06736) in which we calculate the equation of state of the inflaton field after inflation and provide an upper bound on the duration before radiation domination by taking the nonlinear dynamics of the fragmented inflaton field into account. For the models considered, I will discuss how our work significantly reduces the...
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Early UniversePoster
Inflation has been widely accepted as one of the leading paradigms to describe the physics of the early universe. Nevertheless, it has also received its share of criticisms. In this talk, I shall present a brief outline of some of the issues raised against different aspects of inflation, and discuss how the advent of the recent Planck measurements of the cosmic microwave background has largely...
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Early UniversePoster
Multiple spectator fields are present during inflation, and thus they are expected to interact with the inflaton. We study time-dependent loop corrections to inflationary power spectrum, utilising the Schwinger-Keldysh formalism. We consider a generic interaction between heavy fields and the inflaton, calculate loop corrections to inflaton two-point correlation function, and discuss the...
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