AQG 2015

Beginning next week, Advances in Quantum Gravity 2015 (AQG 2015) will begin.  Some of the most innovative young theorists in the world will gather to discuss the latest research in quantum gravity and unified field theory.  The conference is invitation only, with participants sharing the latest ideas from all major approaches to quantum gravity, in a formalism independent setting.

Turok on a Big Bounce

Neil Turok considers a bounce before the bang.

Hawking on Black Hole Information Loss (Again)

At a conference in Stockholm, famed physicist Stephen Hawking explains how he thinks information is stored in black holes - it is stored as supertranslations of the black hole event horizons. (KTH Royal Institute of Technology) For more information see: arXiv:1401.7026 [hep-th]

Algebras at the very Foundations of Space and Time

Excellent paper out today.  Revolutionary?  Maybe.

http://arxiv.org/abs/1506.08576

(Submitted on 29 Jun 2015)

While describing the results of our recent work on exceptional Lie and Jordan algebras, so tightly intertwined in their connection with elementary particles, we will try to stimulate a critical discussion on the nature of spacetime and indicate how these algebraic structures can inspire a new way of going beyond the current knowledge of fundamental physics.

Sporadic and Exceptional

So the mystery deepens and the plot thickens: http://arxiv.org/abs/1505.06742

Salam, Sciama, Witten (1990)

Shimura Varieties and Motives

Hermitian symmetric domains are complex manifolds isomorphic to bounded symmetric domains.  Every hermitian symmetric domain can be realized as a moduli space for Hodge structures plus tensors.  In general, hermitian symmetric domains are not algebraic varieties.  To obtain an algebraic variety one must pass to the quotient by an arithmetic group.  To obtain a moduli variety, one further assumes the arithmetic group is defined by congruence conditions.  The algebraic varities obtained this way are called connected Shimura varieties.

For all connected Shimura varieties except those of type E6, E7 and certain D types, the variety is a moduli variety for abelian motives with additional structure.  In the remaining cases, the connected Shimura variety is not a moduli variety for abelian motives and it is not know whether it is a moduli variety at all.

In supergravity applications, the hermitian symmetric domains of interest are E6/SO(10)xSO(2) and E7/E6xSO(2).  For real non-compact E6 and E7 quotients, such spaces are moduli for extremal black holes in D=5 and D=4 supergravity, with the real E6 and E7 groups acting as U-duality groups in compactified M-theory.  In the nonperturbative regime, due to charge quantization, it is quite natural to consider the quotients of the hermitian symmetric domains by an arithmetic group--which lives in a semisimple algebraic group over the rationals Q.

Further study of these exceptional Shimura varieties should lead to a deeper understanding of nonperturbative M-theory.

Alain Connes: Geometry and the Quantum

 

The lecture was held within the framework of the Hausdorff Trimester Program Non-commutative Geometry and its Applications. (17.12.2014)

Currently, Connes' approach is distinct from string theory; however, for some years the geometry of the worldvolume has been known to be described by C*-algebraic spectral triples.

See:

D-branes, Matrix Theory and K-homology
T. Asakawa, S. Sugimoto, S. Terashima

Hence, from an abstract perspective, Connes' approach is dual to the matrix model approach to M-theory.