| Date |
Time |
Speaker |
Topic |
Room |
| April 18 |
12:00 |
Christina Koliofoti
|
Gravitationswellen und ihr direkter Nachweis (Bachelor colloquium)
|
Konferenzraum 1 (Neubau) |
Gravitationswellen und ihr direkter Nachweis (Bachelor colloquium)
Abstract:
"Ladies and gentleman, we have detected gravitational waves. We did it!"
Mit diesen Worten trat am 11. Februar 2016 David Reitze, der Direktor von LIGO vor
die Presse.
Durch diese bahnbrechende Entdeckung hat das Thema der Gravitationswellen neue
Bedeutung gewonnen. Als Albert Einstein ihre Existenz postulierte, zweifelte er selbst
noch an seiner Behauptung. Doch jetzt, fast einhundert Jahre später war LIGO in der
Lage, Gravitationswellen nachzuweisen.
Das Ziel dieser Bachelorarbeit ist es, einen Einblick in die Theorie der Gravitationswellen
zu verschaffen und die von LIGO veröffentlichten Ergebnis zu untersuchen. Dabei werde
ich zunächst auf die mathematischen und physikalischen Grundlagen eingehen, um anschlie
ÿend mithilfe der von LIGO bereitgestellten Daten die Chirp Masse zu bestimmen.
Mit der Chirp Masse kann man auf weitere Parameter des vermessenen Doppelsternsystems
schließen, welches die Gravitationswellen verursachte.
Close
| April 18 |
12:30 |
Manuel Krämer
|
Applications of the third quantization formalism
|
Konferenzraum 1 (Neubau) |
Applications of the third quantization formalism
Abstract: TBA
Close
| May 9 |
12:00 |
Marco De Cesare (King's College, London)
|
Bouncing cosmologies and accelerated expansion from group field
theory condensates
|
Konferenzraum 1 (Neubau) |
Bouncing cosmologies and accelerated expansion from group field
theory condensates
Abstract:
I will discuss the cosmological implications of the Group Field Theory
(GFT) approach to Quantum Gravity. The work I will present is part of a
programme which aims at understanding Early Universe Cosmology by studying
the dynamics of the emergent continuum spacetime, as obtained from a
fundamentally discrete microscopic theory of the gravitational field. In
particular, I will show how it is possible to achieve a bounce and an
early epoch of accelerated expansion in this approach.
Close
| May 16 |
12:00 |
Branislav Nikolic
|
Einstein gravity and functional Schrödinger equation from
the Weyl-Einstein canonical quantum gravity
|
Konferenzraum 1 (Neubau) |
Einstein gravity and functional Schrödinger equation from
the Weyl-Einstein canonical quantum gravity
Abstract:
In this talk I will discuss the semiclassical approximation to
the Weyl-Einstein-Wheeler-DeWitt (WEWDW) equation, an equation analogous
to the Weheler-DeWitt (WDW) equation appearing in quantum geometrodynamics of
Einstein-Hilbert (QEH) action. This equation is the dynamical equation
for the wave functional resulting from the canonical quantization
of the Weyl-squared action extended by the EH term
(and matter fields; in our particular case it will be non-minimally
coupled massless scalar field). I will present issues and possible work-arounds
of the Born-Oppenheimer type ansatz and WKB approximation related
to the role of the additional coupling constant (of the Weyl-squared term).
An approach which gives pure classical GR and modified functional
Schrödinger equation will be presented.
Close
| May 23 |
12:00 |
Friedrich Hehl
|
Gauge Theories of Gravitation: An external gauge group implies the
geometry of spacetime
|
Konferenzraum 1 (Neubau) |
Gauge Theories of Gravitation: An external gauge group implies the
geometry of spacetime
Abstract:
The advent of general relativity in 1915/1916 induced a paradigm shift:
since then, the theory of gravity had to be seen in the context of the
geometry of spacetime. An outgrowth of this new way of looking at
gravity is the gauge principle of Weyl (1929) and Yang–Mills–Utiyama
(1954/1956). It became manifest around the 1960s (Sciama–Kibble) that
gravity is closely related to the Poincaré group acting in Minkowski
space. The gauging of this external group induces a Riemann–Cartan
geometry on spacetime. If one generalizes the gauge group of gravity,
one discovers still more involved spacetime geometries. If one
specializes it to the translation group, one finds a specific
Riemann–Cartan geometry with teleparallelism (Weitzenböck geometry).
In: D.Lehmkuhl, G.Schiemann, E. Scholz et al. (eds.), Towards a Theory
of Spacetime Theories, Einstein Studies Volume 13, pp 145-169,
Birkhauser-Springer (2017), arxiv:1204.3672v2
Close
| May 30 |
12:00 |
Claus Kiefer
|
Decoherence: From Schrödinger's Cat to the Classical World
|
Konferenzraum 1 (Neubau) |
Decoherence: From Schrödinger's Cat to the Classical World
Abstract:
How does the classical behaviour emerge in a world that is fundamentally
described by quantum theory? The key to the answer is given by a
process that was described for the first time 47 years ago
- decoherence. Decoherence is the irreversible
emergence of classical properties of a quantum system through the
unavoidable interaction with its environment. In my talk, I shall
give a general introduction into decoherence and present its most
important theoretical and experimental applications. These include,
in particular, the localization of objects. I shall then discuss
the relevance of decoherence for the interpretation of quantum theory
and end with an outlook on quantum cosmology and the origin of the
direction of time.
Close
| June 20 |
12:00 |
Discussion of a paper
|
How the huge energy of quantum vacuum gravitates to drive the
slow accelerating expansion of the Universe (Wang, Zhu, and Unruh)
|
Konferenzraum 1 (Neubau) |
| July 11 |
12:00 |
Erhard Scholz (Wuppertal)
|
The unexpected resurgence of Weyl geometry in late 20th century physics
|
Konferenzraum 1 (Neubau) |
The unexpected resurgence of Weyl geometry in late 20th century physics
Abstract:
Weyl's original scale geometry of 1918 (?purely infinitesimal geometry?) was
withdrawn by its author from physical theorizing in the early 1920s. It had
a comeback in the last third of the 20th century in different contexts:
scalar tensor theories of gravity, foundations of gravity, foundations of
quantum mechanics, elementary particle physics, and cosmology.
The talk will present the basic ideas of Weyl geometry and its application
to gravity. I will argue that even in its most simple form of an integrable
scale connections it may lead to at least methodologically interesting
modifications of Einstein gravity.
Close
| July 25 |
12:00 |
Sebastian Schuster (Wellington, New Zealand)
|
Effective metrics and a fully covariant description of constitutive
tensors in electrodynamics
|
Konferenzraum 1 (Neubau) |
Effective metrics and a fully covariant description of constitutive
tensors in electrodynamics
Abstract:
The idea behind analogue space-times is to gain additional testing
grounds for space-time physics. This, ideally, helps to get around many of
the experimental difficulties encountered in general relativity. Here, we
shall demonstrate how to approach macroscopic electrodynamics with this goal
in mind. In order to find media that lend themselves to an analogue of
vacuum electrodynamics on a curved space-time, we shall develop a fully
covariant, four-dimensional formulation of macroscopic electrodynamics.
Using this reformulation we shall regain and extend previous results. I
shall also contrast the perspective of analogue space-times to the goals
encountered in pre-metric electrodynamics.
Close
| September 26 |
12:00 |
David Wichmann (Master colloquium)
|
The Born-Oppenheimer Approach and the Semiclassical Limit of Canonical Quantum Gravity
|
Konferenzraum 1 (Neubau) |
The Born-Oppenheimer Approach and the Semiclassical Limit of Canonical Quantum Gravity
Abstract:
This thesis outlines and further develops the semiclassical approximation to quantum geometrodynamics.
Within a Born-Oppenheimer ansatz, the quantum gravitational corrections to quantum field theory in a
fixed curved background spacetime are derived within the functional Schrödinger picture.
It is demonstrated that the very choice of a product like / Born-Oppenheimer ansatz leads to arbitrary
gauge-like degrees of freedom which turn out to be important for the final result, in particular with
respect to unitarity violation. For the choice of a vacuum background, a closed expression containing
all quantum gravitational effects for the semiclassical matter Hamiltonian is derived. The formalism
is then adjusted such that the semiclassical limit has unitary time evolution and the lowest order
correction to the new Hamiltonian is calculated.
Close
