Particle Production in the Early Universe

Session

Short Talks

10 Sept 2024, 09:30

4/3-006 - TH Conference Room (CERN)

Conveners

Short Talks

• Marco Drewes

Short Talks

• Yohei Ema

Short Talks

• Juraj Klaric (Universiteit van Amsterdam, Nikhef)

Short Talks

• Oleg Lebedev

33. Minimal Warm Inflation with the heavy QCD axion

Kim Berghaus (California Institute of Technology)

10/09/2024, 09:30

Slow-roll inflation is a successful paradigm. However, even small couplings of the inflaton to other light fields can dramatically alter the dynamics and predictions of inflation. As an example, the inflaton can generically have an axion-like coupling to gauge bosons. Even relatively small couplings will automatically induce a thermal bath during inflation. The thermal friction from this bath...

32. No Warm Inflation From a Vanilla Axion

Sebastian Zell (EPFL - Ecole Polytechnique Federale Lausanne (CH))

10/09/2024, 09:50

At finite temperature, the coupling of an axion to non-Abelian gauge fields causes dissipation due to sphaleron heating. This mechanism is ideally suited for realizing warm inflation since it can lead to large thermal friction while preserving the flatness of the potential. We show, however, that requiring standard properties of an axion − in particular a discrete shift symmetry and a...

3. The Open Effective Field Theory of Inflation

Santiago Agui Salcedo (University of Cambridge)

10/09/2024, 10:10

There is an increasing interest in the interplay between Open Quantum Systems and Inflationary Physics. A time-dependent background and limited access to the degrees of freedom invites the use of Open Quantum systems. It provides a more general framework than the unitary time evolution of a pure state. In this talk, we develop a local EFT for the scalar curvature perturbations subject to the...

5. Non-Gaussianity from preheating with scale dependence

Pulkit Ghoderao (Imperial College London)

10/09/2024, 10:25

Preheating involves the rapid production of daughter particles after the end of inflation. Combining lattice simulations with a non-perturbative delta N treatment, I will describe a general formalism to calculate the non-Gaussianity generated by preheating in the presence of a single light scalar field. When scale dependence during inflation is included, our results show that cosmic variance,...

34. Real dynamics of thermal false vacuum decay

Dr Andrey Shkerin (University of Minnesota)

10/09/2024, 11:25

We revisit false vacuum decay in relativistic field theory and with a heat bath. We find the decay rate due to classical thermal fluctuations of the field. We do this numerically, by performing real-time simulations of the field evolution from the initial state in thermal equilibrium. We compare our findings with predictions of the well-known Euclidean formalism. We find agreement at the level...

31. Excited bound states and their role in dark matter production

Tobias Binder

10/09/2024, 11:45

We explore the impact of highly excited bound states on the evolution of number densities of new physics particles, specifically dark matter, in the early Universe. Focusing on dipole transitions within perturbative, unbroken gauge theories, we develop an efficient method for including around a million bound state formation and bound-to-bound transition processes. This enables us to examine...

6. Open quantum system dynamics of non-relativistic dark matter pairs

Gramos Qerimi (Technical University of Munich (TUM))

10/09/2024, 12:05

For a quantitative investigation on the real-time evolution of heavy dark matter in the early universe, not only close-to-threshold effects but also key aspects such as decoherence and dissipation due to interactions with the thermal environment need to be taken into account. We employ the formalism of open quantum systems and determine the out-of-equilibrium evolution equations for...

26. Consistent EFTs in the Schwinger-Keldysh formalism

Edward Wang (Technical University of Munich (TUM))

10/09/2024, 12:20

We compare the evolution equations for a particle species in a thermal bath for a toy model obtained first by solving the full system and second by constructing an EFT in vacuum and solving the von Neumann equation for the subsystem. We find that the second approach clearly fails to account for particle production and decay due to the inability of the von Neumann equation to describe...

35. Gravitational production of dark particles

Andrew Long (Rice University)

10/09/2024, 14:00

The phenomenon of cosmological gravitational particle production (CGPP) occurs during and after inflation as quantum fields “feel” the cosmological expansion are excited out of their ground state. CGPP is a compelling and minimal explanation for the origin of dark matter, which might only interact gravitationally, as well as other cosmological relics. In this talk, I’ll discuss some recent...

36. On the anomalous gravitational fermion production in terms of level crossing

Kohei Kamada (Institute for Basic Science)

10/09/2024, 14:20

Gravitational chiral anomaly connects the topological charge of spacetime and the chirality of fermions. It has been known that the chirality is carried by the particles (or the excited states) and also by vacuum. However, in the study of gravitational leptogenesis, for example, lepton asymmetry associated with the chiral gravitational waves sourced during inflation is conventionally evaluated...

24. Adiabatic renormalization without infrared distortions in cosmological spacetimes

Dr Francisco Torrenti (ICCUB, U. Barcelona)

10/09/2024, 14:40

Particle creation in cosmological spacetimes leads to new ultraviolet divergences in the expectation values of field operators (such as the stress-energy tensor) not present in Minkowski spacetime. Adiabatic renormalization is an extensively used method to renormalize these, but it may lead to unwanted distortions at infrared scales. In my talk I will present a new renormalization method for...

4. Unitarity, holomorphic cuts, and thermal effects in zero-temperature calculations

Dr Peter Matak (Comenius University (SK))

10/09/2024, 14:55

When studying particle density evolution, within the classical Boltzmann approach, we must include all number-changing processes in which the particle participates, typically decays or scatterings. At higher orders, other types of reactions may become relevant as well. We formulate a diagrammatic unitarity-based algorithm to complete the set of contributing reactions. Initially, the particles...

7. Upper Bound on Thermal Gravitational Wave Backgrounds from Hidden Sectors

Yannis Georis

10/09/2024, 16:00

Hot viscous plasmas unavoidably emit a gravitational wave background, similar to the electromagnetic black body radiation. In this talk, based on arXiv:2312.13855, I will study the contribution from hidden particles to the GW background emitted by the early universe primordial plasma. While this contribution can easily dominate over that from Standard Model particles, we find that both...

17. Gravitational wave background from vacuum and thermal fluctuations during axion-like inflation

Philipp Klose (Universität Bielefeld)

10/09/2024, 16:15

We revisit the framework of axion-like inflation, considering a warm inflation scenario in which the inflaton couples to the topological charge density of non-Abelian gauge bosons whose self-interactions result in a rapidly thermalizing heat bath. Including both dispersive (mass) and absorptive (friction) effects, we find that the system remains in a weak regime of warm inflation (thermal...

23. Neutrino Decoupling at NLO: Methods and Rates

Miguel Escudero Abenza (CERN)

10/09/2024, 16:30

19. Exploring General Vector Mediators in Inelastic Dark Matter Models

Ana Luisa Foguel da Silva (Universidade de São Paulo)

10/09/2024, 16:45

Despite the robust cosmological and astrophysical evidence confirming the existence of a non-baryonic matter component in the Universe, the underlying nature of Dark Matter (DM) remains a mystery. Among the several possible scenarios, light DM candidates thermally produced in the early Universe are especially interesting, since their abundance could be set via the standard freeze-out...

9. CMB signature of non thermal dark matter production from self interacting dark sector

Mr Sk Jeesun (Indian Association for the Cultivation of Science)

10/09/2024, 17:00

The fundamental nature of dark matter (DM) and its production mechanism is yet unknown. Non thermal or freeze in DM scenarios are currently being widely explored. In this work we explore the production of non-thermal DM and its connection with Cosmic Microwave Background (CMB) via additional relativistic degrees of freedom which are simultaneously generated during the period $T_{\rm BBN}$ to...