Relativity and the Quantum

This page features an overview of all our spotlight texts dealing with the interplay of relativity and quantum theory - relativistic quantum theories as well as string theory, loop quantum gravity and other attempts to unify Einstein's theory of gravity with quantum theory. The spotlight texts already completed deal with General aspects of quantum gravity as well as with String theory, Loop quantum gravity as well as with Other approaches to the problem of quantum gravity. Physics in the background is the heading for texts providing background information that is helpful for a better understanding of the spotlight texts presented on this page.

Useful background information can be found in our introduction Elementary Einstein, especially in the chapter Relativity and the quantum.

General aspects of quantum gravity

Some aspects of quantum gravity that are independent of which of the possible approaches is chosen.

	Actors on a changing stage: quantum gravity and background independence The principle of background independence - space and time are no fixed structure, but take part in the dynamical evolution of the world - and its consequences for the problem of quantum gravity

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String theory

More about string theory - at present, mostly about the extra dimensions that play such a central role in that theory.

	Extra dimensions - and how to hide them Why our universe could possess dimensions beyond length, width and depth - and why those dimensions need not be noticeable in everyday life.
	The embedded universe Is our three-dimensional world embedded in a higher-dimensional space?
	The hunt for extra dimensions Ways of detecting extra dimensions - and why the fact that our earth orbits the sun is a relevant data point
	Simplicity in higher dimensions Why matters that seem rather complicated might be much more simple in higher dimensions
	Particle accelerators as black hole factories? (cf. Black holes & Co.) The intriguing possibility that the next generation of particle accelerators might produce - and allow the detection of - miniature black holes

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Loop quantum gravity

More about loop quantum gravity, in particular its cosmological applications.

	The fabric of space: spin networks The quantum structure of space according to loop quantum gravity
	Avoiding the big bang (also in Cosmology) The collapsing and then re-expanding quantum universe that loop quantum gravity offers as a replacement of the standard big bang models
	Taming infinity with loops (also in Cosmology) How loop quantum gravity could replace the absurd state of infinite density, the big bang with which, according to Einstein's relativity, the universe began.

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Other approaches to the problem of quantum gravity

While string theory and loop quantum gravity are the most prominent approaches to the problem of quantum gravity, they are not the only ones. Some other approaches are described in the following spotlights.

	Searching for the quantum beginning of the universe (also in Cosmology) About attempts to understand the beginning of our universe using different approaches to quantum gravity
	Geometry from order: causal sets An overview of the causal set approach to a theory of quantum gravity

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Physics in the background

Useful physics background information that may help with a better understanding of the other spotlight texts on this page.

	The sum over all possibilities About the path integral approach to quantum theory

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