Vafa & Ooguri on String Landscape & Swampland

[marcus]

Vafa is chairman of the harvard physics department. Ooguri is also a strong admirable guy IMHO. These are among the best of the best of the string research fraternity. Maybe someone here would like to discuss this paper.

http://arxiv.org/abs/hep-th/0605264
On the Geometry of the String Landscape and the Swampland
Hirosi Ooguri, Cumrun Vafa
18 pages

"We make a number of conjectures about the geometry of continuous moduli parameterizing the string landscape. In particular we conjecture that such moduli are always given by expectation value of scalar fields and that moduli spaces with finite non-zero diameter belong to the swampland. We also conjecture that points at infinity in a moduli space correspond to points where an infinite tower of massless states appear, and that near these regions the moduli space is negatively curved. We also propose that there is no non-trivial 1-cycle of minimum length in the moduli space. This leads in particular to the prediction of the existence of a radially massive partner to the axion. These conjectures put strong constraints on inflaton potentials that can appear in a consistent quantum theory of gravity. Our conjectures are supported by a number of highly non-trivial examples from string theory. Moreover it is shown that these conditions can be violated if gravity is decoupled."

 

[marcus]

in case of further interest
http://arxiv.org/abs/hep-th/0605266
Domain walls, near-BPS bubbles, and probabilities in the landscape
Anna Ceresole, Gianguido Dall'Agata, Alexander Giryavets, Renata Kallosh, Andrei Linde
50 pages. 14 figures

"We develop a theory of static BPS domain walls in stringy landscape and present a large family of BPS walls interpolating between different supersymmetric vacua. Examples include KKLT models, STU models, type IIB multiple flux vacua, and models with several Minkowski and AdS vacua. After the uplifting, some of the vacua become dS, whereas some others remain AdS. The near-BPS walls separating these vacua may be seen as bubble walls in the theory of vacuum decay. As an outcome of our investigation of the BPS walls, we found that the decay rate of dS vacua to a collapsing space with a negative vacuum energy can be quite large. The parts of space that experience a decay to a collapsing space, or to a Minkowski vacuum, never return back to dS space. The channels of irreversible vacuum decay serve as sinks for the probability flow. The existence of such sinks is a distinguishing feature of the landscape. We show that it strongly affects the probability distributions in string cosmology."

Kallosh and Linde are co-authors the influential 2003 "KKLT" paper that informed us of the 10²⁰⁰ or 10⁵⁰⁰ string vacua helping to populate the string Landscape. They are among the stars of the Stanford physics department. Today is a good day for papers by prominent string people!

It could be we are seeing the run-up right before the Strings '06 conference in Beijing.
Maybe it is "season" for string papers.

 

[marcus]

wow all these eminent people posting in a single day. it must be CONFERENCE TIME!

http://arxiv.org/abs/hep-th/0605263
Holographic probabilities in eternal inflation
Raphael Bousso
14 pages, 3 figures.

"The problem of assigning probabilities to vacua is notoriously ambiguous in the global description of eternal inflation. The local point of view is preferred by holography, and it naturally picks out a simple probability measure. This requires no ambiguous choices, such as which time slices to use, or how to weight the volume occupied by a vacuum. The local viewpoint also cuts off the weight carried by exponentially large slow-roll expansion factors or lifetimes."

anybody who wants to discuss is welcome---have fun

 

[Chronos]

I have a different read, marcus - I think they are proposing a variable time model. I also think it is wrong because it does not conserve energy. It is impossible to conserve any quantity if you tweak the time factor.