Name: Generation, evolution, and observations of cosmological magnetic fields
Start: 2024-04-29T08:55:00+02:00
End: 2024-06-07T20:00:00+02:00
Location: Bernoulli Center

Monday, 29 April 2024

09:30 Welcome and registration
Welcome and registration
09:30 - 10:30
10:30 Sterile Neutrino Dark Matter and Magnetic Fields - Mikhail Shaposhnikov (EPFL)
Sterile Neutrino Dark Matter and Magnetic Fields
- Mikhail Shaposhnikov (EPFL)
10:30 - 11:30
I will discuss how the Abelian part of the electroweak anomaly can influence the generation of lepton asymmetry of the Universe and its impact on dark matter sterile neutrino.
11:30 Scenarios of inflationary magnetogenesis - Lorenzo Sorbo (Univesity of Massachusetts, Amherst)
Scenarios of inflationary magnetogenesis
- Lorenzo Sorbo (Univesity of Massachusetts, Amherst)
11:30 - 12:30
In this talk I will review the motivation behind the idea that the cosmic magnetic fields observed today were originated in some dynamics that occurred during inflation. I will then discuss the pros and cons of some of the most popular among these scenarios of inflationary magnetogenesis, with a particular focus on the role that might be played, in this context, by axionic degrees of freedom
12:30 Lunch
Lunch
12:30 - 14:00
14:00 Imprints of primordial curvature perturbations on inflationary magnetic fields - Rajeev Kumar Jain
Imprints of primordial curvature perturbations on inflationary magnetic fields
- Rajeev Kumar Jain
14:00 - 14:45
We examine the imprints of sharp departures from slow-roll inflation which lead to strong features in the scalar power spectra, on the spectra of the primordial electromagnetic fields generated during inflation. In particular, we find that an epoch of ultra-slow roll inflation leads to a severe suppression of the magnetic field spectrum over large scales. We also make use of the code magcamb to calculate the effects of the magnetic fields on the anisotropies in the cosmic microwave background and investigate if the magnetic field spectra with features are broadly consistent with the current observational constraints.
18:00 Welcome reception
Welcome reception
18:00 - 19:30
Tuesday, 30 April 2024
11:30 Symmetry breaking and magnetic fields - Tanmay Vachaspati (Arizona State University)
Symmetry breaking and magnetic fields
- Tanmay Vachaspati (Arizona State University)
11:30 - 12:30
TBA
12:30 Lunch
Lunch
12:30 - 14:00
14:00 Simulating the Early Universe - Paul Saffin (Nottingham University)
Simulating the Early Universe
- Paul Saffin (Nottingham University)
14:00 - 15:00
One approach to exploring the dynamical properties of systems is to use computer simulations, and these can take many different forms depending on the energy scales and length scales of interest. In this talk I shall give an overview of some techniques for real-time simulations of the underlying fields. This allows one to examine some of the microscopic processes underlying the development of physical phenomena.
15:00 Vacuum Energy of the Universe, Large scale magnetic field and nontrivial topology in QCD. - Ariel Zhitnitsky (University of British Columbia)
Vacuum Energy of the Universe, Large scale magnetic field and nontrivial topology in QCD.
- Ariel Zhitnitsky (University of British Columbia)
15:00 - 15:45
We discuss a new scenario for early cosmology when the de Sitter phase emerges dynamically. This genuine quantum effect occurs as a result of dynamics of the topologically nontrivial sectors in a strongly coupled QCD in an expanding universe. We argue that the key element for this idea to work is the presence of nontrivial holonomy in strongly coupled gauge theories. The effect is global in nature and cannot be formulated in terms of a gradient expansion in an effective local field theory. We discuss some profound phenomenological consequences of this scenario as the dynamical generation of the Dark Energy (DE). The corresponding estimates lead to the dark energy magnitude which is expressed in terms of the dimensional QCD parameter and is amazingly close to the observed value, $\rho_{\rm DE}\sim H {\Lambda_{QCD}^3}\sim (10^{-3} eV)^4$. We argue that anomalous coupling of the dark energy emergent field with Maxwell electrodynamics generates the large cosmological magnetic field as a result of the helical instability. The generated magnetic field must be correlated on the scale of the visible Universe. The talk is based on recent paper: Ariel Zhitnitsky, "Cosmological Magnetic Field and Dark Energy", Phys.Rev.D 99 (2019) 10, 103518 e-Print: 1902.07737
Wednesday, 1 May 2024
10:30 The Non-linear early Universe - Daniel Figueroa (IFIC Valencia)
The Non-linear early Universe
- Daniel Figueroa (IFIC Valencia)
10:30 - 11:30
We review "Lattice Cosmology" techniques as a method to solve non-linear dynamics of interactive fields in an expanding Universe. As a demonstration we apply these ideas to solve two different problems of early Universe cosmology: i) the non-linear dynamics of axion inflation when backreaction of the produced gauge field becomes relevant, and ii) gravitational wave emission from (global and local) cosmic string loop dynamics
11:30 Statistical Mechanics of the Universe - Jürg Fröhlich (ETH Zurich)
Statistical Mechanics of the Universe
- Jürg Fröhlich (ETH Zurich)
11:30 - 12:30
To start with I summarize some key puzzles of cosmology to be clarified in the future. I then briefly sketch how to describe the geometry and the state of matter in the Universe after its inflationary era. The main part of my talk is devoted to describing possible mechanisms for the generation of primordial magnetic fields in the Universe. These mechanisms are based on the chiral magnetic effect and a generalization thereof involving an axion. Time permitting I sketch ideas of how to explain the accelerated expansion of the Universe and the Matter-Antimatter Asymmetry. Literature: Papers with A. Alekseev and V. Cheianov (chiral magentic effect, 1D quantum wires, particle jets from rotating stars) (90's) Paper with B. Pedrini (1999) (anomalies, chiral magnetic effect, axions, generation of magnetic fields) Papers with A. Boyarsky and O. Ruchayskii (anomalies, chiral magnetic effect, axions, generation of magnetic fields) (Papers with R. Brandenberger et al., Dark Matter & Dark Energy)
12:30 Lunch
Lunch
12:30 - 14:00
14:00 Particle production by axion-like particles - Valerie Domcke (CERN)
Particle production by axion-like particles
- Valerie Domcke (CERN)
14:00 - 15:00
Axion-like particles may play a key role in early universe cosmology. In this talk I discuss the dual production of gauge fields and fermions induced by axion-like particles, and its implications for magnetogenesis from axion inflation.
15:00 Magnetogenesis and baryogenesis in pseudoscalar inflation - Kohei Kamada (Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences)
Magnetogenesis and baryogenesis in pseudoscalar inflation
- Kohei Kamada (Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences)
15:00 - 16:00
Pseudoscalar inflation with Chern-Simons coupling to U(1) gauge fields generates helical magnetic field during inflation. If this U(1) gauge field is the Standard Model U(1) hypergauge interaction, the baryon (or B+L) asymmetry is generated at the same time through the chiral anomaly in a way that the total chirality vanishes. We could expect that it explains the present Baryon Asymmetry of the Universe (BAU). However, it is not trivial if the BAU remains until today since the sphaleron washout and/or the annihilation of magnetic helicity and baryon (chiral) asymmetry through the chiral magnetic effect may erase the baryon asymmetry. On the other hand, the baryogneesis from the hypermagnetic helicity decay at the electroweak symmetry break would also take place in this scenario. In this talk, I will explain all these ingredients and clarify how the present BAU can be explained in the pseudoscalar inflation. Implication on the intergalactic magnetic fields are also discussed.
Thursday, 2 May 2024
10:30 Primordial Magnetic Fields from Preheating at the Electroweak Scale - Juan Garcia-Bellido (Universidad Autonoma de Madrid)
Primordial Magnetic Fields from Preheating at the Electroweak Scale
- Juan Garcia-Bellido (Universidad Autonoma de Madrid)
10:30 - 11:30
TBA
11:30 Magnetic fields effects on particle interactions strength in the early universe - Gabriella Piccinelli (UNAM)
Magnetic fields effects on particle interactions strength in the early universe
- Gabriella Piccinelli (UNAM)
11:30 - 12:30
Motivated by our work on inflationary scenarios in presence of magnetic fields, we have focused on one of the puzzling features with which we have faced: the effect of magnetic fields on the particles’ interaction processes, which may be a relevant issue during inflation or in the subsequent stages of the Universe evolution. The importance of magnetic fields’ contribution comes from the fact that they are widespread in the Universe , at all scales. There is a vast literature on this topic, but the problem is that the results, in different situations, do not match. A vast assortment of physical situations and of analytical and numerical approaches can be found in the literature, making the comparison between them not straightforward. Our aim is to focus attention on differences and similarities between the different situations and approaches, looking for a systematization scheme that could be predictive, once the role played by each physical ingredient could be understood. The literature in this subject is so vast that the present work is far from being exhaustive. We mainly focus here on some seminal papers and on recent literature, both from our working group and from other research teams.
12:30 Lunch
Lunch
12:30 - 14:00
14:00 Magnetogenesis form axion-U(1) preheating - Evangelos Sfakianakis (Case Western Reserve U.)
Magnetogenesis form axion-U(1) preheating
- Evangelos Sfakianakis (Case Western Reserve U.)
14:00 - 15:00
I will review the numerical results that demonstrate efficient preheating of an axion-inflaton to photons and the prospects for magnetogenesis. I will also discuss possible correlated observables and possible connections to SM and BSM physics.
15:00 Backreaction from magnetic fields generated during inflation - Ruth Durrer (University of Geneva)
Backreaction from magnetic fields generated during inflation
- Ruth Durrer (University of Geneva)
15:00 - 16:00
In this talk I shall discuss how magnetic fields generated during inflation can back-react on the inflaton perturbation spectrum. I shall first outline the problem and present the generic form of the equations which have to be solved. I shall then discuss the effects which have been neglected in previous work. I can also outline an example which will be discussed in detail by another speaker (Deepen Garg).
Friday, 3 May 2024
10:30 Gravitational Waves from Chiral Plasma Instability in Standard Cosmology - Andrew Long (Rice University)
Gravitational Waves from Chiral Plasma Instability in Standard Cosmology
- Andrew Long (Rice University)
10:30 - 11:30
In the primordial plasma, at temperatures above the scale of electroweak symmetry breaking, the presence of chiral asymmetries is expected to induce the development of helical hypermagnetic fields through the phenomenon of chiral plasma instability. It results in magnetohydrodynamic turbulence due to the high conductivity and low viscosity and sources gravitational waves that survive in the universe today as a stochastic polarized gravitational wave background. In this article, we show that this scenario only relies on Standard Model physics, and therefore the observable signatures, namely the relic magnetic field and gravitational background, are linked to a single parameter controlling the initial chiral asymmetry. We estimate the magnetic field and gravitational wave spectra, and validate these estimates with 3D numerical simulations.
11:30 Charge transfer induced by chiral plasma instability - Kyohei Mukaida (KEK)
Charge transfer induced by chiral plasma instability
- Kyohei Mukaida (KEK)
11:30 - 12:30
It is well known that the weak sphaleron exchanges chemical potentials of left-handed fermions and plays important roles in baryogenesis. In this talk, we will focus on another source of $B+L$ violation, i.e., $U(1)_Y$ Chern-Pontryagin density. We discuss several examples where the charge transfer induced by this term plays a central role in the early Universe.
12:30 Lunch
Lunch
12:30 - 14:00
14:00 How's Schwinger effect affect primordial Magnetogenesis? - Tomohiro Fujita (Waseda University)
How's Schwinger effect affect primordial Magnetogenesis?
- Tomohiro Fujita (Waseda University)
14:00 - 15:00
The Schwinger effect is a non-perturbative phenomenon in QED in which an electric field stronger than a certain strength decays into charged particle pairs. In primordial magnetogenesis, especially in inflationary magnetogenesis, the Schwinger effect can drastically change the dynamics of the electromagnetic fields and significantly alter theoretical predictions. However, until recently this effect has been often neglected. Even now that its importance has been recognized, reliable computational methods for it is yet to be established. In this talk, I will introduce several prescriptions proposed so far, including my own work, and discuss what we can do to elucidate a realistic mechanism of magnetogenesis that incorporates the Schwinger effect.
Saturday, 4 May 2024
Sunday, 5 May 2024

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