
Harold C. Steinacker Senior scientist & Privatdozent Fakultät für Physik




Email: harold.steinacker at univie.ac.at Phone: +43 1 4277
51503 Office: 5th floor Rm
3516 
Research Interests and perspectives
My primary research interest is the
theory of fundamental interactions, and to contribute to the
development of a quantum theory of fundamental interactions
including gravity. Specifically, I'm developing and following an
approach known as „Matrix Theory“, focusing on the IKKT or IIB matrix
model. This can be viewed as a constructive approach to
string theory, which avoids the "landscape" problem and its
inherent lack of predictivity.The model is extremely simple, and
leads naturally to a quantum structure of spacetime. A central
aspect of this programe is to establish a suitable notion of quantum
geometry, which is fairly well developed by now.
The basic idea of this approach is that 3+1dimensional
spacetime arises as a (branelike) solution or "vacuum
condensate" in the matrix model, and physics arises from
fluctuations on this brane. For YangMills gauge theories, this
works in a very nice and convincing way; the main challenge has
been to recover gravity. The 10dimensional (super)gravity
usually studied in string theory is not the answer here: it
merely leads to a weak shortrange interaction on the brane.
Rather, gravity is described through a dynamical frame, which
arises from the underlying noncommutative structure of the
spacetime brane.
A big step towards understanding
gravity in this framework is taken in a recent paper,
which demonstrates that the EinsteinHilbert action arises
indeed as quantum effect at one loop, in the presence of finite
or "fuzzy" extra dimensions. Hence the classical matrix model
defines a "pregravity theory" which is well suited for
quantization, and "real" gravity similar to Einstein's general
relativity arises as quantum effective action, which is
welldefined within this framework.
In plain words: you should not quantize gravity (it doesnt
work). Rather, gravity is already a quantum effect of the
underlying matrix theory!
(This realizes Sakharov's idea without the cosmological constant
problem. Also, there is no need for an unpredictive "landscape"
of string compactifications)
Of course it remains to be seen if all this can provide a
comprehensive and realistic physical theory. Some further steps
in this direction are as follows:
The goal in the next years is to
develop this theory further.
Apart from this longterm project,
I'm also interested in other topics in the context of the theory
of elementary particles and fundamental interactions, quantum
gravity, string theory, noncommutative geometry, random matrix
theory, quantum groups, etc.
Selected talks, providing an
introduction & overview of my recent work
Publications
InSPIRE HEPpreprint database: search
Research Project "Covariant Quantum
Spaces, Higher Spin, and Gravity"
supported
by the FWF, P
32086
This project focuses on the recently
discovered 3+1dimensional covariant quantum spacetimes, which
lead to higherspin gauge theories in the framework of YangMills
matrix models. The focus will be on the gravity sector, which
arises from spin 2 fluctuation modes on these spaces. This should
provide a promising framework for quantum gravity, and we will aim
to develop this as far as possible.
Members of this research group: Emmanuele Battista
(postdoc), Veronika Bachleitner (Master's student), Emil Broukal
(Master's student), Laurin Felder (Master's student), H.S.
(completed) Research Project "Squashed
Extra Dimensions in Gauge Theory and Matrix Models"
supported
by the FWF, P
28590
(completed) Project "Branes, Gauge Theory and Gravity in Matrix Models"
supported by the FWF, P24713, related press release
(completed) project "Matrix Models, Quantum
Spaces, and Gravity"
supported by FWF, P21610
Possible topics for a Master's thesis
COST network QSPACE
completed (I was member of the management committee & leader
of the working group on gravity models)
Current and recent teaching
Lecture notes:
related seminars & conferences
Workshop Matrix Models for Noncommutative Geometry and String Theory
international workshop on "Noncommutative Geometry, Duality and Quantum Gravity"
Training school Quantum Structure of Spacetime and Gravity 2016
Workshop on Noncommutative Field Theory and Gravity , Corfu, September 19  26, 2015