2,106 research outputs found
Equilibration in low-dimensional quantum matrix models
Matrix models play an important role in studies of quantum gravity, being
candidates for a formulation of M-theory, but are notoriously difficult to
solve. In this work, we present a fresh approach by introducing a novel exact
model provably equivalent with low-dimensional bosonic matrix models. In this
equivalent model significant local structure becomes apparent and it can serve
as a simple toy model for analytical and precise numerical study. We derive a
substantial part of the low energy spectrum, find a conserved charge, and are
able to derive numerically the Regge trajectories. To exemplify the usefulness
of the approach, we address questions of equilibration starting from a
non-equilibrium situation, building upon an intuition from quantum information.
We finally discuss possible generalizations of the approach.Comment: 5+2 pages, 2 figures; v2: published versio
CMB Fluctuations and String Compactification Scales
We propose a mechanism for the generation of temperature fluctuations of
cosmic microwave background. We consider a large number of fields, such as
Kaluza-Klein modes and string excitations. Each field contributes to the
gravitational potential by a small amount, but an observable level of
temperature fluctuations is achieved by summing up the contribution of
typically of order 10^{14} fields. Tensor fluctuations are hardly affected by
these fields. Our mechanism is based on purely quantum effects, and is
different from the "slow-roll" or "curvaton" scenario. Using the observed data,
we find constraints on the parameters of this model, such as the size of the
extra dimensions and the string scale. Our model predicts a particular pattern
of non-gaussianity with a small magnitude.Comment: 4 pages, 2 figures; v2: Corrected a mistake in eq. (11), which does
not affect the subsequent context. Added a comment on inflaton fluctuations
at the end of the paper. Final version to appear in Phys. Lett.
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