(Back to
the menu - click here.)
|
Date: |
Download-files: |
Time: |
|
Thursday,
27 Feb 2025 |
Video-Recording for any system with MP4-support - Video.mp4 (ca. 414 Mb) |
15:15 – 16:17 |
"Primordial magnetic fields and relic gravitational waves:
messengers of the
first microseconds"
Speaker:
Prof. Axel Brandenburg
(Nordita)
Abstract:
Our detailed understanding of cosmology
rests on only a few firmly established observational probes. One of them
derives from the expansion history of the
universe and the clustering of galaxies
observed in the large-scale structure
of galaxies observed today. The other is
the measurement of temperature
anisotropies and polarization in the
cosmic microwave background that formed
when the universe was 400,000 years old.
Finally, there is the measurement of
the abundances of light elements in the
universe that constrain the physics within
the first three minutes. However, we lack
measurements of the first microseconds
when weak and electromagnetic forces
decoupled and particles attained their
masses and quarks got confined inside
nucleons. During these times, physics
beyond the standard model must have
determined the matter-antimatter
asymmetry, produced dark matter, and led
to the emergence of neutrinos.
We can probe these very first moments through
measurements of primordial
magnetic fields and relic gravitational
waves. The evolution of magnetic fields
can be traced in an evolutionary diagram
of magnetic field versus length scale
and it follows a characteristic path.
Relating the start- and endpoints to each
other is an important theoretical
accomplishment. At the same time,
observational constraints in radio and
gamma ray frequencies begin to narrow
down the allowed parameter space in the
evolutionary diagram.
In
this colloquium, I will discuss several of the theoretical and observational
discoveries that make primordial magnetic fields and gravitational waves
powerful probes of the first microseconds
of the universe.
About the Speaker:
Professor Axel Brandenburg received his
PhD at the University of Helsinki
in 1990 and held postdoc positions at
Nordita in Copenhagen and at the
National Center for Atmospheric Research
in Boulder/Colorado.
In 1996 became a full Professor of Applied
Mathematics to the University of
Newcastle upon Tyne. In 2000 he moved back
to Nordita as full professor and
has been a professor at the Department of
Astronomy in Stockholm since 2007.
Axel Brandenburg works in the field of
astrophysical fluid dynamics.
He is particularly interested in the
question of magnetic field generation from
turbulent motions with applications to the
Sun and stars, accretion discs,
galaxies, and the early Universe. His work
on accretion disc turbulence was
the first to show that the
magneto-rotational and dynamo instabilities lead to a sustained doubly-positive
feedback. Recently, he contributed to clarifying the
long-standing question of the suppression
of the dynamo effect in generating
large-scale fields. He is responsible for
the maintenance of the Pencil Code,
which is a public domain code
(pencil-code.googlecode.com) for astrophysical
fluid dynamics.