this came out April 5, 2004 http://arxiv.org/hep-th/0404039 "String Scattering from Decaying Branes" Vijay Balasubramanian, Esko Keski-Vakkuri, Per Kraus, Asad Naqvi Abstract: "We develop the general formalism of string scattering from decaying D-branes in bosonic string theory. In worldsheet perturbation theory, amplitudes can be written as a sum of correlators in a grand canonical ensemble of unitary random matrix models, with time setting the fugacity. An approach employed in the past for computing amplitudes in this theory involves an unjustified analytic continuation from special integer momenta. We give an alternative formulation which is well-defined for general momenta. We study the emission of closed strings from a decaying D-brane with initial conditions perturbed by the addition of an open string vertex operator. Using an integral formula due to Selberg, the relevant amplitude is expressed in closed form in terms of zeta functions. Perturbing the initial state can suppress or enhance the emission of high energy closed strings for extended branes, but enhances it for D_{0}-branes. The closed string two point function is expressed as a sum of Toeplitz determinants of certain hypergeometric functions. A large N limit theorem due to Szego, and its extension due to Borodin and Okounkov, permits us to compute approximate results showing that previous naive analytic continuations amount to the large N approximation of the full result. We also give a free fermion formulation of scattering from decaying D-branes and describe the relation to a grand canonical ensemble for a 2d Coulomb gas." it has been a bit quiet here lately so I am offering the above for discussion in case anyone feels inclined to comment. I am relying somewhat on other poster's judgement and discretion in this matter. If this paper is not deemed worthy of comment then perhaps another will be offered instead.
The Extreme Elegance of Dirk Kreimer as it continues rather quiet at PF, I shall offer another paper for comment. This paper's style is so elegant that it practically levitates a few centimeters off the ground by the sheer force of its own elegance http://arxiv.org./hep-th/0404090 "The Residues of Quantum Field Theory--Numbers we should know" "Abstract: We discuss in an introductory manner structural similarities between the polylogarithm and Green functions in quantum field theory. 1. Introduction... It is a pleasure to report here on a connection between mathematics and physics through the study of Dysonâ€“Schwinger equations (DSE) which has been left mostly unexplored so far... " Regretably I can see no way in which the matters discussed here are relevant to quantum gravity. But I shall try to find out a little about Kreimer because of the civilized and elightened way he writes---this, by itself, is of value.
Spontaneous Decompactification this was posted recently the authors are at good places like Santa Barbara Kavli and/or have co-authored with good people like Marolf and Bousso and Lisa Randall http://arxiv.org/hep-th/0404220 what they are talking about is the "rolled up" dimensions being unstable and spontaneously unrolling in part the trouble is the positive cosmological constant, a kind of vacuum energy. things want to unroll because of dark energy Spontaneous decompactification Steven B. Giddings, Robert C. Myers 27 pages, 5 figures, "Positive vacuum energy together with extra dimensions of space imply that our four-dimensional Universe is unstable, generically to decompactification of the extra dimensions. Either quantum tunneling or thermal fluctuations carry one past a barrier into the decompactifying regime. We give an overview of this process, and examine the subsequent expansion into the higher- dimensional geometry..." It reminds me of some people in Kurt Vonnegut's Slaughterhouse Five who invented a spaceship but the first time they tried it their universe disappeared. Giddings and Myers are imagining a bubble of higherdimensional spacetime appearing in our 4D a kind of blister and its walls expand outwards at the speed of light and eventually all us 4D beings get gobbled up the blister starts by what Giddings and Myers call a quantum tunneling but I suppose someone trying out a new motor for his spaceship could cause a higherdimensional bubble to form as well that is, if string theory is correct. (Giddings is a string theorist and presumably knows how many extra dimensions there are rolled up and might suddenly come unrolled) this paper is offered for comment, depending, as always, on the judgement and discretion of those familiar with the topic
two more recent papers offered here in case anyone thinks it appropriate to comment: http://arxiv.org/hep-th/0405190 Catastrophic Decays of Compactified Space-Times Michael Dine, Patrick J. Fox, Elie Gorbatov 16 pages, 3 figures (may have some connection to the discussion of catastrophic spontaneous unrolling of curled up dimensions, mentioned earlier) http://arxiv.org/hep-th/0405189 Supersymmetry Breaking in the Anthropic Landscape Leonard Susskind 6 pages 'In this paper I attempt to address a serious criticism of the "Anthropic Landscape" and "Discretuum" approach to cosmology, leveled by Banks, Dine and Gorbatov. I argue that in this new and unfamiliar setting, the gauge Hierarchy may not favor low energy supersymmetry.' (the Susskind paper seems related to a talk Susskind gave a week or so ago in Davis, reported in Woit's blog)
Good papers Marcus! I recall Wittens BON(bubble of nothing)being one of the most interesting definations of Negative Energy(theorized), but I also recall Wittens paper of earlier this year relating the Proton Decay to many orders of magnitude greater than the expectant value? I will dig out the posts here on PF, if I recall correctly I estimated a large number of Stanford Theorists(Linde,Susskind to name but two) would be scrambling to get new Pre-Print papers following Wittens paper, I also stated that the Witten paper was fine-tuning the stability of Protons in order to combat obvious flaws with 'Super' string theory.
I must proclaim my admiration for those theorists mentioned, I am in no way criticizing , I mearly like the way Ed Witten appears to be able to forsee 'stormy-weather'.
And thus: http://arxiv.org/abs/astro-ph/0306304 http://arxiv.org/abs/astro-ph/0401313 http://arxiv.org/abs/astro-ph/0405397 Will be of paramount importance to the thread. Recent questioning post dealing with the very same thing! https://www.physicsforums.com/showthread.php?t=27128